DESCRIPTION
Pharmaceutical Composition for Treating and/or Preventing Cancer
Technical Field
[0001]
The present invention relates to a novel pharmaceutical use of an antibody against
CAPRIN-1 or a fragment thereof, as an agent, for treating and/or preventing a cancer.
Background Art
[0002]
Cancer is the leading cause of death. Currently conducted therapy comprises
mainly surgical therapy in combination with radiation therapy and chemotherapy. In spite of
the development of new operative procedures and the discovery of new anticancer agents in
recent years, cancer treatment results have not been much improved recently, excluding that
for some types of cancer. Recent advances in molecular biology or cancer immunology lead
to identification of antibodies specifically reacting with cancer, cancer antigens to be
recognized by cytotoxic T cells, genes encoding cancer antigens, and the like. Demands on
specific cancer therapies targeting cancer antigens are increasing (Non-patent Literature 1).
[0003]
In cancer therapy, it is desirable that peptides, polypeptides, or proteins recognized as
antigens be almost absent in normal cells, but they be present specifically in cancer cells, in
order to alleviate side effects. In 1991, Boon et al., (Ludwig Institute for Cancer Research,
Belgium) isolated a human melanoma antigen MAGE1 recognized by CD8-positive T cells by
the cDNA expression cloning method using autologous cancer cell lines and cancer-reactive T
cells (Non-patent Literature 2). Thereafter, the SEREX (serological identification of
antigens by recombinant expression cloning) method that comprises identifying tumor
antigens recognized by antibodies that are produced in vivo in response to autologous cancer
of a cancer patient by gene expression cloning techniques was reported (Non-patent Literature
3 and Patent Literature 1). With the use of this method, some cancer antigens, which are
almost never expressed in normal cells but are specifically expressed in cancer cells, were
isolated (Non-patent Literatures 4-9). Furthermore, clinical trials were conducted with cell
therapies targeting some cancer antigens using imnrunocytes specifically reactive with cancer
antigens, or cancer-specific immunotherapies using vaccines or the like containing cancer
antigens.
[0004]
Meanwhile, in recent years, various antibody medicines which target antigenic
proteins on cancer cells for cancer treatment have appeared throughout the world. Antibody
medicines exhibit some pharmacological effects as cancer specific therapeutic agents and are
thus attracting attention. However, most antigen proteins to be targeted are also expressed in
normal cells, so that not only cancer cells, but also normal cells expressing antigens are also
damaged as a result of antibody administration. The resulting side effects cause for
concern. Therefore, it is expected that identification of cancer antigens that are specifically
expressed on the surface of a cancer cell and use of antibodies targeting the cancer antigens as
pharmaceuticals will realize treatment with antibody medicines with lower side effects.
[0005]
Cytoplasmic- and proliferation-associated protein 1 (CAPRIN-1) is expressed when
normal cells at the resting phase are activated or undergo cell division, and it is an
intracellular protein known to form intracellular stress granules with RNA within cells, so as
to be involved in mRNA transport and translational regulation. Meanwhile, many other
names that represent CAPRIN-1 exist, such as GPI-anchored membrane protein 1 or
membrane component surface marker 1 protein (M11S1), as if such proteins had been known
to be cell membrane proteins. These names originated from a report that the gene sequence
of CAPRIN-1 is a membrane protein having a GPI-binding region and expressed in colorectal
cancer cells (Non-patent Literature 10). However, the gene sequence of CAPRIN-1
provided in this report was later revealed to be wrong. The following has recently been
reported; i.e., deletion of a single nucleotide in the gene sequence of CAPRIN-1 registered at
GenBank or the like causes a frame shift, so that 80 amino acids are lost from the C-terminus,
resulting in generation of an artifact (74 amino acids) which corresponds to the GPI-binding
portion in the previous report, and additionally, another error is also present 5' of the gene
sequence, so that 53 amino acids were lost from the N-terminus (Non-patent Literature 11).
It has been also recently reported that the protein encoded by the gene sequence of CAPRIN-1
registered at GenBank or the like is not a cell membrane protein (Non-patent Literature 11).
[0006]
In addition, on the basis of the report of Non-patent Literature 10 that CAPRIN-1 is a
cell membrane protein, Patent Literatures 2 and 3 describe that CAPRIN-1 (as a cell
membrane protein) under the name of M11S1 can be used as a target of an antibody medicine
in cancer therapy, although working examples do not describe treatment using an antibody
against the protein. However, as reported in Non-patent Literature 11, it has been commonly
believed from the time of the filing of Patent Literature 2 to date that CAPRIN-1 is not
expressed on the surface of a cell. The contents of Patent Literatures 2 and 3 based only on
incorrect information that CAPRIN-1 is a cell membrane protein should not clearly be
understood as common general knowledge for persons skilled in the art.
Prior Art Literature
Patent Literature
[0007]
Patent Literature 1: U.S. Patent No. 5698396
Patent Literature 2: US2008/0075722
Patent Literature 3: WO2005/100998
Non-patent Literature
[0008]
Non-patent Literature 1: Tsuyoshi Akiyoshi, "Gan To Kagaku-Ryoho (Cancer and
Chemotherapy)," 1997, Vol. 24, p551-519 (Cancer and Chemotherapy Publishers, Inc., Japan)
Non-patent Literature 2: Bruggen P. et al., Science, 254: 1643-1647 (1991)
Non-patent Literature 3: Proc. Natl. Acad. Sci. U.S.A, 92: 11810-11813 (1995)
Non-patent Literature 4: Int. J. Cancer, 72: 965-971 (1997)
Non-patent Literature 5: Cancer Res., 58: 1034-1041 (1998)
Non-patent Literature 6: Int. J. Cancer, 29: 652-658 (1998)
Non-patent Literature 7: Int. J. Oncol., 14: 703-708 (1999)
Non-patent Literature 8: Cancer Res., 56: 4766-4772 (1996)
Non-patent Literature 9: Hum. Mol. Genet6: 33-39, 1997
Non-patent Literature 10: J. Biol. Chem., 270: 20717-20723, 1995
Non-patent Literature 11: J. Immunol., 172: 2389-2400, 2004
Summary of the Invention
Problem to be Solved by the Invention
[0009]
Objects of the present invention are to identify a cancer antigen protein specifically
expressed on the surface of a cancer cell and to provide the use of an antibody targeting the
cancer antigen protein as an agent for treating and/or preventing a cancer.
Means for Solving the Problem
[0010]
As a result of intensive studies, the present inventors have now obtained a cDNA
encoding a protein that binds to an antibody existing in sera from dogs with breast cancer by
the SEREX method using both cDNA libraries prepared from dog testis tissues and sera of
dogs with breast cancer. The present inventors have now further prepared CAPRIN-1
proteins having the even-numbered amino acid sequences of SEQ ID NOS: 2 to 30 and
antibodies against such CAPRIN-1 proteins based on the obtained dog gene and the
corresponding human, cattle, horse, mouse, and chicken homologous genes. Thus, the
present inventors have now found that CAPRIN-1 is specifically expressed in breast cancer,
brain tumor, leukemia, lymphoma, lung cancer, uterine cervix cancer, bladder cancer,
esophageal cancer, colorectal cancer, gastric cancer, and renal cancer cells, and that a portion
of the CAPRIN-1 protein is specifically expressed on the surface of each cancer cell. The
present inventors have thus now found that an antibody or antibodies against the portion of
CAPRIN-1 expressed on the surface of each cancer cell is/are cytotoxic to the
CAPRIN-1-expressing cancer cells. On the basis of these findings, the present invention as
described below was completed.
[0011]
The present invention has the following characteristics.
[0012]
The present invention provides a pharmaceutical composition for treating and/or
preventing a cancer, comprising an antibody that comprises a heavy chain variable region
comprising SEQ ID NO: 39, 40, and 41 and a light chain variable region comprising SEQ ID
NO: 43, 44, and 45 or a fragment thereof as an active ingredient and having immunological
reactivity with a CAPRIN-1 protein.
[0013]
In an embodiment, the above cancer is breast cancer, brain tumor, leukemia,
lymphoma, lung cancer, uterine cervix cancer, bladder cancer, esophageal cancer, colorectal
cancer, gastric cancer, or renal cancer.
[0014]
In another embodiment, the above antibody is a human antibody, humanized
antibody, chimeric antibody, single chain antibody, or bispecific antibody.
[0015]
This description includes part or all of the contents as disclosed in the description
and/or drawings of Japanese Patent Application No. 2010-023452, which is a priority
literature of the present application.
Effects of the Invention
[0016]
The antibody against CAPRIN-1 used in the present invention is cytotoxic to cancer
cells. As such, the antibody against CAPRJN-1 is useful for treating or preventing cancers.
Brief Description of the Drawings
[0017]
Fig. 1 shows the expression patterns of genes encoding CAPRIN-1 proteins in
normal tissues and tumor cell lines. Reference No. 1 indicates the expression patterns of
genes encoding CAPRIN-1 proteins, and Reference No. 2 indicates the expression patterns of
GAPDH genes.
Fig. 2 shows the cytotoxicity of an anti-CAPRIN-1 monoclonal antibody #1 (that is
reactive with the surfaces of the cancer cells) against the MDA-MB-157 breast cancer cell
line expressing CAPRIN-1. Reference No. 3 indicates the activity exhibited when the
anti-CAPRIN-1 monoclonal antibody #1 was added. Reference No. 4 indicates the activity
exhibited when PBS was added instead of the antibodies.
Fig. 3 shows the anti-tumor effects of the anti-CAPRIN-1 monoclonal antibody #1
(that is reactive with the surfaces of cancer cells) against Balb/c mice into which the 4T1
mouse breast cancer cell line expressing CAPRIN-1 was transplanted. Reference No. 5
indicates the tumor size of a mouse to which the anti-CAPRIN-1 monoclonal antibody #1 was
administered. Reference No. 6 indicates the tumor size of a mouse to which PBS was
administered instead of the antibodies.
Mode for Carrying Out the Invention
[0018]
The anti-tumor activity of an antibody against a polypeptide represented by any of
the even-numbered sequences of SEQ ID NOS: 2 to 30 used in the present invention can be
evaluated by examining in vivo suppression of tumor growth in animals with cancer, or,
examining whether or not the antibody exhibits cytotoxicity via immunocytes or complements
to tumor cells expressing the polypeptide in vitro, as described later.
[0019]
In the context, the nucleotide sequences of polynucleotides encoding proteins
comprising the even-numbered amino acid sequences (i.e., SEQ ID NOS: 2, , 4, , 6...28, 30)
of SEQ ID NOS: 2 to 30 are represented by the odd-numbered sequences (i.e., SEQ ID NOS:
1, 3, 5. ..27, 29) of SEQ ID NOS: 1 to 29.
[0020]
The amino acid sequences that are represented by SEQ ID NOS: 6, 8, 10, 12, and 14
in the Sequence Listing disclosed herein are the amino acid sequences of CAPRIN-1 isolated
as polypeptides, which bind to antibodies specifically existing in serum from a dog with
cancer, through the SEREX method using a cDNA library from dog testis tissue and the serum
of a dog with breast cancer. The amino acid sequences represented by SEQ ID NOS: 2 and
4 are the amino acid sequences of CAPRIN-1 isolated as human homologues. The amino
acid sequence represented by SEQ ID NO: 16 is the amino acid sequence of CAPRIN-1
isolated as a cattle homologue. The amino acid sequence represented by SEQ ID NO: 18 is
the amino acid sequence of CAPRIN-1 isolated as a horse homologue. The amino acid
sequences represented by SEQ ID NOS: 20 to 28 are the amino acid sequences of CAPRIN-1
isolated as mouse homologues. The amino acid sequence represented by SEQ ID NO: 30 is
the amino acid sequence of CAPRIN-1 isolated as a chicken homologue (see Example 1
described later). CAPRIN-1 is known to be expressed when normal cells in the resting
phase are activated or give rise to cell division.
[0021]
It was known that CAPRIN-1 was not expressed on cell surfaces. However, as a
result of the examination by the present inventors, it has now been revealed that a portion of
the CAPRIN-1 protein is expressed on the surfaces of various cancer cells. It has thus been
revealed that an antibody having immunological reactivity with a partial region of a
CAPRIN-1 protein that is expressed on cancer cell surfaces or specifically recognizing the
region (that is, specifically binding to the region) and comprising a heavy chain variable
region that comprises SEQ ID NO: 39, 40, and 41 and a light chain variable region that
comprises SEQ ID NO: 43, 44, and 45 exhibits anti-tumor activity
[0022]
The above-described anti-CAPRIN-1 antibody used in the present invention may be
any type of monoclonal antibody as long as it can exhibit anti-tumor activity. Examples of
such an antibody include recombinant antibodies, such as a synthetic antibody, a multispecific
antibody, a humanized antibody, a chimeric antibody, and a single chain antibody (scFv), a
human antibody, and antibody fragments thereof, such as Fab, F(ab')2, and Fv. These
antibodies and fragments thereof can be prepared by methods known by persons skilled in the
art. Also, when a subject is a human, human antibodies or humanized antibodies are desired
in order to avoid or suppress rejection.
[0023]
The term "specifically binding to a partial region of a CAPRIN-1 protein" as used
herein means that "the antibody specifically binds to a specific region of a CAPRIN-1 protein
without substantially binding to protein portions other than such a region."
[0024]
The anti-tumor activity of an antibody that can be used in the present invention can
be evaluated as described below by examining in vivo the suppression of the tumor growth in
animals with cancer, or, by examining whether or not it exhibits in vitro an activity of
cytotoxicity, which is mediated by immunocytes or complements, to tumor cells expressing
the polypeptide.
[0025]
Furthermore, examples of the subject for cancer treatment and/or prevention in the
present invention include mammals, such as humans, pet animals, domestic animals, and
animals for competition. A preferable subject is a human.
[0026]
Preparation of antigens and antibodies and pharmaceutical compositions relating to
the present invention are described below.
[0027]

Proteins or fragments thereof to be used as sensitizing antigens for obtaining
anti-CAPRIN-1 antibodies used in the present invention may be derived from any animal
species without particular limitation, such as humans, dogs, cattle, horses, mice, rats, and
chickens. However, proteins or fragments thereof are preferably selected in consideration of
compatibility with parent cells used for cell fusion. In general, mammal-derived proteins are
preferred and, in particular, human-derived protein is preferred. For example, when
CAPRIN-1 is human CAPRIN-1, the human CAPRIN-1 protein, a partial peptide thereof, or
cells expressing human CAPRIN-1 can be used.
[0028]
The nucleotide sequences and the amino acid sequences of human CAPRIN-1 and
homologues thereof can be obtained by accessing GenBank (NCBI, U.S.A.) and using an
algorithm such as BLAST or FASTA (Karlin and Altschul, Proc. Natl. Acad. Sci. U.S.A., 90:
5873-5877, 1993; Altschul et al., Nucleic Acids Res. 25: 3389-3402, 1997).
[0029]
In the present invention, on the basis of the nucleotide sequence (SEQ ID NO: 1 or
3) or the amino acid sequence (SEQ ID NO: 2 or 4) of human CAPRIN-1, a target nucleic
acid or a target protein comprises a sequence having 70% to 100%, preferably 80% to 100%,
more preferably 90% to 100%, even more preferably 95% to 100% (e.g., 97% to 100%, 98%
to 100%, 99% to 100%, or 99.5% to 100%) sequence identity with the nucleotide sequence or
the amino acid sequence of the ORF or the mature portion of human CAPRIN-1. As use
herein, the term "% sequence identity" refers to a percentage (%) of identical amino acids (or
nucleotides) relative to the total number of amino acids (or nucleotides), when two sequences
are aligned to achieve the highest similarity with or without introduction of gaps.
[0030]
The length of a fragment of CAPRIN-1 protein ranges from the amino acid length
of an epitope (antigenic determinant), which is the minimum unit recognized by an antibody,
to a length less than the full length of the protein. The term "epitope" refers to a polypeptide
fragment having antigenicity or immunogenicity in mammals, preferably in humans, and the
minimum unit of the epitope consists of about 7 to 12 amino acids (e.g., 8 to 11 amino acids).
[0031]
The polypeptides comprising the above-mentioned human CAPRIN-1 protein or
partial peptides of the protein, can be synthesized by a chemical synthesis method, such as the
Fmoc method (fluorenylmethyloxycarbonyl method) or the tBoc method (t-butyloxycarbonyl
method) (Edited by The Japanese Biochemical Society, Seikagaku Jikken Koza (Biochemical
Experimental Lecture Series) 1, Protein Chemistry IV, Chemical Modification and Peptide
Synthesis, TOKYO KAGAKU DOZIN (Japan), 1981). Alternatively, the above-mentioned
polypeptides may also be synthesized by conventional methods using various commercially
available peptide synthesizers. Furthermore, with the use of known genetic engineering
techniques (e.g., Sambrook et al., Molecular Cloning, 2nd Edition, Current Protocols in
Molecular Biology (1989), Cold Spring Harbor Laboratory Press, Ausubel et al., Short
Protocols in Molecular Biology, 3rd Edition, A compendium of Methods from Current
Protocols in Molecular Biology (1995), John Wiley & Sons), a polynucleotide encoding the
above polypeptide is prepared and then incorporated into an expression vector, which is
subsequently introduced into a host cell in order to produce a polypeptide of interest in the
host cell, and then recover it.
[0032]
The polynucleotides encoding the above polypeptides can be easily prepared by
known genetic engineering techniques or conventional techniques using a commercially
available nucleic acid synthesizer. For example, DNA comprising the nucleotide sequence
of SEQ ID NO: 1 can be prepared by PCR using a human chromosomal DNA or cDNA
library, as a template, and a pair of primers designed to be able to amplify the nucleotide
sequence represented by SEQ ID NO: 1. PCR conditions can be appropriately determined.
For example, PCR conditions comprise conducting 30 cycles of the reaction cycle of:
denaturation at 94°C for 30 seconds; annealing at 55°C for 30 seconds to 1 minute; and
extension at 72°C for 2 minutes, using a thermostable DNA polymerase (e.g., Taq polymerase
or Pfu polymerase) and PCR buffer containing Mg , followed by reacting at 72°C for 7
minutes. However, the PCR conditions are not limited to the above example. PCR
techniques, conditions, and the like are described in Ausubel et al., Short Protocols in
Molecular Biology, 3r Edition, A compendium of Methods from Current Protocols in
Molecular Biology (1995), John Wiley & Sons (particularly Chapter 15).
[0033]
Also, on the basis of the nucleotide sequence and amino acid sequence information
represented by SEQ ID NOS: 1 to 30 in the Sequence Listing described herein, appropriate
probes or primers are prepared, and then a cDNA library of a human or the like is screened
using them, so that desired DNA can be isolated. A cDNA library is preferably constructed
from cells, organs or tissues, which express proteins having even-numbered sequences of
SEQ ID NOS: 2 to 30. Examples of such cells or tissues include cells or tissues derived
from testis, and cancers or tumors, such as leukemia, breast cancer, lymphoma, brain tumor,
lung cancer, colorectal cancer, and the like. Procedures such as the preparation of probes or
primers, construction of a cDNA library, screening of a cDNA library, and cloning of target
genes are known by a person skilled in the art and can be carried out by the methods
described in Sambrook et al, Molecular Cloning, 2nd Edition, Current Protocols in Molecular
Biology (1989), Ausbel et al., (above), and the like. DNA encoding a human CAPRIN-1
protein or a partial peptide thereof can be obtained from the thus obtained DNA.
[0034]
The host cells may be any cells, as long as they can express the above-mentioned
polypeptide. Examples of prokaryotic cells include, but are not limited to, Escherichia coli
and the like. Examples of eukaryotic cells include, but are not limited to, mammalian cells,
such as monkey kidney cells (COS1) and Chinese hamster ovary cells (CHO), human fetal
kidney cell line (HEK293), fetal mouse skin cell line (NIH3T3), yeast cells such as budding
yeast and fission yeast, silkworm cells, and Xenopus oocyte.
[0035]
When prokaryotic cells are used as host cells, an expression vector used herein
contains an origin replicable within prokaryotic cells, a promoter, a ribosome-binding site, a
multiple cloning site, a terminator, a drug resistance gene, an auxotrophic complementary
gene, and the like. Examples of Escherichia coli expression vector include a pUC-based
vector, pBluescript II, a pET expression system, and a pGEX expression system. DNA
encoding the above polypeptide is incorporated into such an expression vector, prokaryotic
host cells are transformed with the vector, the thus obtained transformed cells are cultured,
and thus the polypeptide encoded by the DNA can be expressed in prokaryotic host cells. At
this time, the polypeptide can also be expressed as a fusion protein with another protein.
[0036]
When eukaryotic cells are used as host cells, an expression vector used herein is an
expression vector for eukaryotic cells, which contains a promoter, a splicing region, a poly(A)
addition site, and the like. Examples of such an expression vector include pKAl, pCDM8,
pSVK3, pMSG, pSVL, pBK-CMV, pBK-RSV, EBV vector, pRS, pcDNA3, and pYES2. In a
manner similar to the above, DNA encoding the above polypeptide is incorporated into such
an expression vector, eukaryotic host cells are transformed with the vector, the thus obtained
transformed cells are cultured, and thus the polypeptide encoded by the DNA can be
expressed in eukaryotic host cells. When pIND/V5-His, pFLAG-CMV-2, pEGFP-N1,
pEGFP-C1, or the like is used as an expression vector, the above polypeptide can be
expressed as a fusion protein to which a tag from among various tags such as a His tag (e.g.,
(His)6-(His)10), a FLAG tag, a myc tag, an HA tag, and GFP has been added.
[0037]
For introduction of an expression vector into host cells, a known method can be
employed, such as electroporation, a calcium phosphate method, a liposome method, a DEAE
dextran method, microinjection, viral infection, lipofection, and binding to a cell
membrane-permeable peptide.
[0038]
The polypeptide of interest can be isolated and purified from host cells by a
combination of known separation procedures. Examples of such procedures include, but are
not limited to, treatment with a denaturing agent such as urea or a surfactant, ultrasonication,
enzymatic digestion, salting-out or solvent fractionation and precipitation, dialysis,
centrifugation, ultrafiltration, gel filtration, SDS-PAGE, isoelectric focusing, ion exchange
chromatography, hydrophobic chromatography, affinity chromatography, and reverse phase
chromato graphy.
[0039]

An antibody is a heteromultimeric glycoprotein that generally contains at least two
heavy chains and two light chains. Antibodies other than IgM is an about 150-kDa hetero
tetramer glycoprotein composed of two identical light (L) chains and two identical heavy (H)
chains. Typically, each light chain is connected to a heavy chain via one disulfide covalent
bond, however, the number of disulfide bonds between heavy chains of various
immunoglobulin isotypes is varied. Each heavy chain or each light chain also has an
intrachain disulfide bond. Each heavy chain has a variable domain (VH region) on one end
followed by several constant regions. Each light chain has a variable domain (VL region)
and has one constant region on an end opposite to the other end. The constant region of a
light chain is aligned with the first constant region of a heavy chain, and a light chain variable
domain is aligned with a heavy chain variable domain. A specific region of an antibody
variable domain exhibits specific variability that is referred to as a complementarity
determining region (CDR), so that it imparts binding specificity to the antibody. A portion
of a variable region, which is relatively conserved, is referred to as a framework region (FR).
Complete heavy chain and light chain variable domains separately contains four FRs ligated
via three CDRs. The three CDRs in a heavy chain are referred to as CDRH1, CDRH2, and
CDRH3 in this order from the N-terminus. Similarly, in the case of a light chain, CDRLs are
referred to as CDRL1, CDRL2, and CDRL3. CDRH3 is most important for the binding
specificity of an antibody to an antigen. Also, the CDRs of each chain are retained together
in a state of being adjacent to each other due to the FR regions, contributing to the formation
of the antigen binding site of the antibody together with CDRs from the other chain. A
constant region does not directly contribute to the binding of an antibody to an antigen, but
exhibits various effector functions, such as involvement in antibody-dependent cell-mediated
cytotoxicity (ADCC), phagocytosis via binding to an Fey receptor, the rate of
half-life/clearance via a neonate Fc receptor (FcRn), and complement-dependent cytotoxicity
(CDC) via a Clq constituent of the complement cascade.
[0040]

The term "anti-CAPRIN-1 antibody" as used herein refers to an antibody having
immunological reactivity with a full-length CAPRIN-1 protein or a fragment thereof.
[0041]
As used herein, the term "immunological reactivity" refers to the property of in vivo
binding of an antibody to a CAPRIN-1 antigen. Through such an in vivo binding, the
function of damaging tumor (e.g., death, suppression, or degeneration) is exhibited.
Specifically, an antibody used in the present invention may be any type of antibody, as long as
it binds to a CAPRIN-l protein so as to be able to damage tumor, such as leukemia,
lymphoma, breast cancer, brain tumor, lung cancer, bladder cancer, uterine cervix cancer,
esophageal cancer, gastric cancer, renal cancer, or colorectal cancer.
[0042]
In the present invention, examples of an antibody include, but are not particularly
limited to, as long as it is a monoclonal antibody, a synthetic antibody, a multispecific
antibody, a human antibody, a humanized antibody, a chimeric antibody, a single chain
antibody, and an antibody fragment (e.g., Fab and F(ab')2). Also, an antibody may be an
immunoglobulin molecule of any class such as IgG, IgE, IgM, IgA, IgD, and IgY, or any
subclass such as IgGl, IgG2, IgG3, IgG4, IgA1, and IgA2.
[0043]
The antibody may further be modified by, in addition to glycosylation, acetylation,
formylation, amidation, phosphorylation, pegylation (PEG), or the like.
[0044]
Preparation examples of various monoclonal antibodies are as described below.
[0045]
When the antibody is a monoclonal antibody, for example, the breast cancer cell
line SK-BR-3 expressing CAPRIN-1 is administered to a mouse for immunization, the spleen
is removed from the mouse, cells are separated, and then the cells and mouse myeloma cells
are fused. From among the thus obtained fusion cells (hybridomas), a clone producing an
antibody having the effect of suppressing cancer cell proliferation is selected. A hybridoma
producing a monoclonal antibody that has the effect of suppressing cancer cell proliferation is
isolated, the hybridoma is cultured, and then an antibody is purified from the culture
supernatant by general affinity purification, so that the antibody can be prepared.
[0046]
The hybridoma producing a monoclonal antibody can also be prepared as described
below, for example. First, an animal is immunized with a sensitizing antigen according to a
known method. A general method is carried out by injecting a sensitizing antigen to a
mammal intraperitoneally or subcutaneously. Specifically, a sensitizing antigen is diluted
with PBS (Phosphate-Buffered Saline), saline, or the like to an appropriate amount, followed
by suspension. The resultant is then mixed with an appropriate amount of a general adjuvant
as necessary, such as Freund's complete adjuvant. After emulsification, the solution was
administered to a mammal several times every 4 to 21 days. Furthermore, an appropriate
carrier can also be used upon immunization with a sensitizing antigen.
[0047]
A mammal is immunized as described above. After confirmation of a rise in a
desired serum antibody level, immunized cells are collected from the mammal and then
subjected to cell fusion. Preferable immunized cells are particularly splenocytes.
[0048]
Mammalian myeloma cells are used as the other parent cells to be fused with the
immunized cells. As the myeloma cells, various known cell lines are preferably used, such
as P3U1 (P3-X63Ag8Ul), P3 (P3x63Ag8. 653) (J. Immunol. (1979) 123, 1548-1550),
P3x63Ag8U.l (Current Topics in Microbiology and Immunology (1978) 81, 1-7), NS-1
(Kohler. G. and Milstein, C. Eur. J. Immunol. (1976) 6, 511-519), MPC-11 (Margulies. D. H.
et al., Cell (1976) 8, 405-415), SP2/0 (Shulman, M. et al, Nature (1978) 276, 269-270), FO
(deSt. Groth, S. F. et al, J. Immunol. Methods (1980) 35, 1-21), S194 (Trowbridge, I. S. J.
Exp. Med. (1978) 148, 313-323), and R210 (Galfre, G. et al., Nature (1979) 277, 131-133).
[0049]
Fusion of the immunized cell and the myeloma cell can be carried out according to
basically a known method such as Kohler and Milstein's technique (Kohler, G and Milstein, C.
Methods Enzymol. (1981) 73, 3-46), for example.
[0050]
More specifically, the above cell fusion is carried out, for example, in the presence
of a cell fusion accelerator in a usual nutrient culture medium. As this fusion accelerator,
polyethyleneglycol (PEG), Sendai virus (HVJ), or the like is used. If desired, an auxiliary
agent such as dimethyl sulfoxide may be added and used in order to enhance fusion efficiency.
[0051]
The ratio of the immunized cells to the myeloma cells to be used herein can be
arbitrarily set. For example, the number of immunized cells that are preferably used is one
to ten times the number of myeloma cells. As a culture medium to be used for the
above-mentioned cell fusion, an RPMI1640 culture medium suitable for proliferation of the
above-mentioned myeloma cell line, an MEM culture medium, and other culture media
usually used for culturing this kind of cell can be used. Further, liquid that is supplemental
to serum such as fetal bovine serum (FCS) can be used together therewith.
[0052]
Cell fusion can be performed by thoroughly mixing the predetermined amounts of
the above immunized cells and the myeloma cells in the above culture medium, and a PEG
solution (for example, having an average molecular weight ranging from about 1000 to 6000)
prewarmed at about 37°C is added usually at a concentration of 30%-60% (w/v) and mixed,
thereby forming a culture containing hybridomas of interest. Next, a suitable culture
medium is successively added to the thus-obtained culture, which is then centrifiiged to
remove the supernatant, and this procedure is repeated to remove the cell fusion agent or the
like which is not preferable for the growth of hybridomas.
[0053]
The thus obtained hybridomas are cultured for selection in a usual selection culture
medium (e.g., a HAT culture medium containing hypoxanthine, aminopterin and thymidine).
Culturing in this HAT culture medium is continued for a sufficient period of time (usually
several days to several weeks) so that the cells (non-fused cells) other than the target
hybridomas die. Subsequently, screening and single cloning of the hybridoma which
produces an antibody of interest are performed using the general limiting dilution method.
[0054]
The above hybridomas are obtained by an immunizing non-human animal with an
antigen. In addition to this method, hybridomas that produce a human antibody having
desired activity (e.g., activity of suppressing cell proliferation) can also be obtained by in vitro
sensitizing human lymphocytes, such as human lymphocytes that have been infected with the
EB virus, with a protein, a protein-expressing cell, or a lysate thereof, followed by fusing of
the thus sensitized lymphocytes with human-derived myeloma cells having an ability to
permanently divide, such as U266 (Accession No. TIB196).
[0055]
The thus prepared hybridoma that produces a monoclonal antibody of interest can
be passaged in a general culture medium and can be stored in liquid nitrogen over a long
period of time.
[0056]
Specifically, a hybridoma can be prepared by immunizing by a general
immunization method using, as a sensitizing antigen, a desired antigen or a cell that expresses
the desired antigen, fusing the thus obtained immunized cell with a known parent cell by a
general cell fusion method, and then screening for a monoclonal antibody-producing cell (i.e.,
a hybridoma) by a general screening method.
[0057]
As a human antibody-producing mouse, a KM mouse (Kirin Pharma/Medarex)
and a Xeno mouse (Amgen) are known (e.g., International Patent Publications WO02/43478
and WO02/092812), for example. When such a mouse is immunized with a CAPRIN-1
protein or a fragment thereof, a complete human polyclonal antibody can be obtained from
blood. Also, splenocytes are collected from the immunized mouse and then a human-type
monoclonal antibody can be prepared by a method for fusion with myeloma cells.
[0058]
An antigen can be prepared according to a method using animal cells (JP Patent
Publication (Kohyo) No. 2007-530068) or baculovirus (e.g., International Patent Publication
W098/46777), for example. When an antigen has low immunogenicity, the antigen may be
bound to a macromolecule having immunogenicity, such as albumin, and then immunization
is carried out.
[0059]
Furthermore, an antibody gene is cloned from said hybridoma and then incorporated
into an appropriate vector. The vector is then introduced into a host, and then the genetically
recombined antibody produced using gene recombination techniques can be used (e.g., see
Carl, A. K. Borrebaeck, James, W. Larrick, THERAPEUTIC MONOCLONAL ANTIBODIES,
Published in the United Kingdom by MACMILLAN PUBLISHERS LTD, 1990).
Specifically, the cDNA of a variable region (V region) of an antibody is synthesized from the
mRNA of the hybridoma using reverse transcriptase. When DNA encoding the V region of
an antibody of interest can be obtained, this DNA is ligated to DNA encoding the constant
region (C region) of a desired antibody, and then the resultant fusion product is incorporated
into an expression vector. Alternatively, DNA encoding the V region of an antibody may be
incorporated into an expression vector containing the DNA for the C region of an antibody.
At this time, the DNA can be incorporated into an expression vector so that it is expressed
under the control of expression control regions, such as enhancer and promoter. Next, host
cells are transformed with the expression vector, so that the antibody can be expressed.
[0060]
The anti-CAPRIN-1 antibody of the present invention is characterized by being a
monoclonal antibody. Examples of a monoclonal antibody include human monoclonal
antibodies, non-human animal monoclonal antibodies (e.g., a mouse monoclonal antibody, a
rat monoclonal antibody, a rabbit monoclonal antibody, and a chicken monoclonal antibody),
and chimeric monoclonal antibodies. A monoclonal antibody can be prepared by culturing a
hybridoma obtained by cell fusion of a splenocyte from a non-human mammal (e.g., a mouse,
a human antibody-producing mouse, a chicken, or a rabbit) immunized with a CAPRIN-1
protein, with a myeloma cell. A chimeric antibody is prepared by combining sequences
from different animals, such as an antibody comprising heavy chain and light chain variable
regions of a mouse antibody and heavy chain and light chain constant regions of a human
antibody. A chimeric antibody can be prepared using a known method. For example, a
chimeric antibody can be obtained by ligating DNA encoding an antibody V region to DNA
encoding a human antibody C region, incorporating the resultant fusion product into an
expression vector, and then introducing the vector into a host for production of the chimeric
antibody. In Examples described later, human-chicken chimeric monoclonal antibodies were
prepared and thus its anti-tumor effects were confirmed. These monoclonal antibodies
comprise a heavy chain variable (VH) region comprising the amino acid sequence of SEQ ID
NO: 42 and a light chain variable (VL) region comprising the amino acid sequence of SEQ ID
NO: 46, wherein the VH region comprises CDR1 represented by the amino acid sequence of
SEQ ID NO: 39, CDR2 represented by the amino acid sequence of SEQ ID NO: 40, and
CDR3 represented by the amino acid sequence of SEQ ID NO: 41, and the VL region
comprises CDR1 represented by the amino acid sequence of SEQ ID NO: 43, CDR2
represented by the amino acid sequence of SEQ ID NO: 44, and CDR3 represented by the
amino acid sequence of SEQ ID NO: 45.
[0061]
A humanized antibody is a modified antibody that is also referred to as a reshaped
human antibody. A humanized antibody can be constructed by transplanting CDRs of an
antibody from an immunized animal into the complementarity determining regions of a
human antibody. General gene recombination techniques therefor are also known.
[0062]
Specifically, DNA sequences designed to have each of the CDRs of a mouse or
chicken antibody ligated to each of the framework regions (FRs) of a human antibody are
synthesized by the PCR method from several oligonucleotides, which are prepared so as to
have overlap portions at their terminal portions, for example. A humanized antibody can be
obtained by ligating the thus obtained DNA to DNA encoding the constant region of a human
antibody, incorporating the resultant fusion product into an expression vector, introducing the
vector into a host, and thus causing the host to produce the gene product (see European Patent
Publication No. 239400 and International Patent Publication WO96/02576). As the FRs of a
human antibody, which is ligated via CDRs, FRs that allow the formation of an
antigen-binding site with good complementarity determining regions are selected. If
necessary, for the formation of an antigen-binding site having the appropriate
complementarity determining regions of a reshaped human antibody, the amino acids of the
framework regions of an antibody variable region may be substituted (Sato, K. et al., Cancer
Research, 1993, 53: 851-856). Also, the amino acids of FRs may be substituted with those
of framework regions from various human antibodies (see International Patent Publication
W099/51743).
[0063]
As the framework regions (FRs) of a human antibody, which are ligated via CDRs,
FRs that allows the formation of an antigen-binding site with good complementarity
determining regions are selected. If necessary, for the formation of an antigen-binding site
having the appropriate complementarity determining regions of a reshaped human antibody,
the amino acids of the framework regions of an antibody variable region may be substituted
(Sato K. et al., Cancer Research 1993, 53: 851-856).
[0064]
After preparation of a chimeric antibody or a humanized antibody, amino acids in a
variable region (e.g., FR) or a constant region may be substituted with other amino acids.
[0065]
Amino acid substitution is a substitution of, for example, less than 15, less than 10,
8 or less, 7 or less, 6 or less, 5 or less, 4 or less, 3 or less, or 2 or less amino acids and is
preferably a substitution of 1 to 5 amino acids, and more preferably 1 or 2 amino acids. A
substituted antibody should be functionally equivalent to an unsubstituted antibody.
Substitution is desirably a substitution of a conservative amino acid(s) between amino acids
having analogous properties such as electric charge, side chain, polarity, and aromaticity.
Amino acids having analogous properties can be classified into basic amino acids (arginine,
lysine, and histidine), acidic amino acids (aspartic acid and glutamic acid), uncharged polar
amino acids (glycine, asparagine, glutamine, serine, threonine, cysteine, and tyrosine),
nonpolar amino acids (leucine, isoleucine, alanine, valine, proline, phenylalanine, tryptophan,
and methionine), branched-chain amino acids (threonine, valine, and isoleucine), and
aromatic amino acids (phenylalanine, tyrosine, tryptophan, and histidine), for example.
[0066]
Examples of a modified antibody product include antibodies bound to various
molecules such as polyethylene glycol (PEG). Substances to be bound in the modified
antibody product of the present invention are not limited. Such a modified antibody product
can be obtained by subjecting the thus obtained antibody to chemical modification. Methods
therefor have already been established in the art.
[0067]
As used herein, the term "functionally equivalent" refers to that a subject antibody
has biological or biochemical activity similar to that of the antibody of the present invention,
and specifically refers to that a subject antibody has the function of impairing tumor without
essentially causing rejection upon its application to a human, for example. An example of
such activity includes an activity to suppress cell proliferation or a binding activity.
[0068]
As a method well known by persons skilled in the art for preparation of a
polypeptide functionally equivalent to a polypeptide, a method for introducing a mutation into
a polypeptide is known. For example, persons skilled in the art can prepare an antibody
functionally equivalent to the antibody of the present invention by appropriately introducing a
mutation into the antibody using site-directed mutagenesis (Hashimoto-Gotoh, T. et al.,
(1995) Gene 152, 271-275; Zoller, MJ., and Smith, M. (1983) Methods Enzymol. 100,
468-500; Kramer, W. et al., (1984) Nucleic Acids Res. 12, 9441-9456; Kramer, W. and Fritz,
HJ., (1987) Methods Enzymol. 154, 350-367; Kunkel, TA., (1985) Proc. Natl. Acad. Sci.
U.S.A. 82, 488-492; Kunkel (1988) Methods Enzymol. 85, 2763-2766), for example.
[0069]
An antibody that recognizes an epitope of a CAPRIN-1 protein recognized by the
above anti-CAPRIN-1 antibody can be obtained by a method known by persons skilled in the
art. For example, such an antibody can be obtained by a method that involves determining
an epitope of a CAPRIN-1 protein recognized by an anti-CAPRIN-1 antibody, by a general
method (e.g., epitope mapping) and then preparing an antibody using a polypeptide having an
amino acid sequence contained in the epitope as an immunogen, or a method that involves
determining an epitope of such an antibody prepared by a general method, and then selecting
an antibody having the epitope identical with that of an anti-CAPRIN-1 antibody. As used
herein, the term "epitope" refers to, in a mammal and preferably a human, a polypeptide
fragment having antigenicity or immunogenicity. The minimum size unit thereof consists of
about 7 to 12 amino acids, and preferably 8 to 11 amino acids.
[0070]
The affinity constant Ka(kon/koff) of the antibody of the present invention is
preferably at least 107 M-1, at least 108 M-1, at least 5 x 108 M-1, at least 109 M-1, at least 5 x
109 M-1, at least 1010 M-1, at least 5 x 1010 M-1, at least 10l1 M-1, at least 5 x 1011 M-1, at least
l012M-1or at least 1013M-1.
[0071]
The antibody of the present invention can be conjugated with an antitumor agent.
Conjugation of the antibody with an antitumor agent can be carried out via a spacer having a
group reactive with an amino group, a carboxyl group, a hydroxy group, a thiol group or the
like (e.g., a succinimidyl succinate group, a formyl group, a 2-pyridyldithio group, a
maleimidyl group, an alkoxy carbonyl group, and a hydroxy group).
[0072]
Examples of the antitumor agent include the following known antitumor agents as in
prior art literatures and the like, such as paclitaxel, doxorubicin, daunorubicin,
cyclophosphamide, methotrexate, 5-fluorouracil, thiotepa, busulfan, improsulfan, piposulfan,
benzodopa, carboquone, meturedopa, uredopa, altretamine, triethylenemelamine,
triethylenephosphoramide, triethilenethiophosphoramide, trimethylolomelamine, bullatacin,
bullatacinone, camptothecin, bryostatin, callystatin, cryptophycinl, cryptophycin8, dolastatin,
duocarmycin, eleutherobin, pancrati statin, sarcodictyin, spongistatin, chlorambucil,
chlornaphazine, cholophosphamide, estramustine, ifosfamide, mechlorethamine,
rnechlorethamine oxide hydrochloride, melphalan, novembichin, phenesterine, prednimustine,
trofosfamide, uracil mustard, carmustine, chlorozotocin, fotemustine, lomustine, nimustine,
ranimustine, calicheamicin, dynemicin, clodronate, esperamicin, aclacinomycin, actinomycin,
authramycin, azaserine, bleomycin, cactinomycin, carabicin, carminomycin, carzinophilin,
chromomycin, dactinomycin, detorbicin, 6-diazo-5-oxo-L-norleucine, adriamycin, epirubicin,
esorubicin, idarubicin, marcellomycin, mitomycinC, mycophenolic acid, nogalamycin,
olivomycins, peplomycin, potfiromycin, puromycin, quelamycin, rodorubicin, streptonigrin,
streptozocin, tubercidin, ubenimex, zinostatin, zorubicin, denopterin, pteropterin, trimetrexate,
fludarabine, 6-mercaptopurine, thiamiprine, thioguanine, ancitabine, azacitidine, 6-azauridine,
carmofur, cytarabine, dideoxyuridine, doxifluridine, enocitabine, floxuridine, androgens (e.g.,
calusterone, dromostanolone propionate, epitiostanol, mepitiostane, and testolactone),
aminoglutethimide, mitotane, trilostane, frolinic acid, aceglatone, aldophosphamideglycoside,
aminolaevulinic acid, eniluracil, amsacrine, bestrabucil, bisantrene, edatraxate, defofamine,
demecolcine, diaziquone, elfornithine, elliptinium acetate, epothilone, etoglucid, lenthinan,
lonidamine, maytansine, ansamitocine, mitoguazone, mitoxantrone, mopidanmol, nitraerine,
pentostatin, phenamet, pirarubicin, losoxantrone, podophyllinic acid, 2-ethyl hydrazide,
procarbazine, razoxane, rhizoxin, schizophyllan, spirogermanium, tenuazonic acid,
triaziquone, roridine A, anguidine, urethane, vindesine, dacarbazine, mannomustine,
mitobronitol, mitolactol, pipobroman, gacytosine, docetaxel, chlorambucil, gemcitabine,
6-thioguanine, mercaptopurine, cisplatin, oxaliplatin, carboplatin, vinblastine, etoposide,
ifosfamide, mitoxanthrone, vincristine, vinorelbine, novantrone, teniposide, edatrexate,
daunomycin, aminopterin, xeloda, ibandronate, irinotecan, topoisomerase inhibitor,
difluoromethylolnitine (DMFO), retinoic acid, capecitabine, and pharmaceutically acceptable
salts or derivatives thereof.
[0073]
Through administration of the antibody of the present invention in combination
with an antitumor agent, even higher therapeutic effects can be obtained. This technique is
applicable to both before and after surgery of a cancer patient with the expression of
CAPRIN-1. Particularly after surgery, more effective prevention of cancer recurrences or
prolonged survival period can be obtained against cancer with the expression of CAPRIN-1,
which has been conventionally treated with an antitumor agent alone.
[0074]
Examples of the antitumor agent to be administered in combination with the
antibody of the present invention include the following known antitumor agents as in prior art
literatures or the like, such as paclitaxel, doxorubicin, daunorubicin, cyclophosphamide,
methotrexate, 5-fluorouracil, thiotepa, busulfan, improsulfan, piposulfan, benzodopa,
carboquone, meturedopa, uredopa, altretamine, triethylenenielamine,
triethylenephosphoramide, triethilenethiophosphoramide, trimethylolomelamine, bullatacin,
bullatacinone, camptothecin, bryostatin, callystatin, cryptophycinl, cryptophycin8, dolastatin,
duocarmycin, eleutherobin, pancratistatin, sarcodictyin, spongistatin, chlorambucil,
chlornaphazine, cholophosphamide, estramustine, ifosfamide, mechlorethamine,
mechlorethamine oxide hydrochloride, melphalan, novembichin, phenesterine, prednimustine,
trofosfamide, uracil mustard, carmustine, chlorozotocin, fotemustine, lomustine, nimustine,
ranimustine, calicheamicin, dynemicin, clodronate, esperamicin, aclacinomycin, actinomycin,
authramycin, azaserine, bleomycin, cactinomycin, carabicin, carminomycin, carzinophilin,
chromomycin, dactinomycin, detorbicin, 6-diazo-5-oxo-L-norleucine, adriamycin, epirubicin,
esorubicin, idarubicin, marcellomycin, mitomycinC, mycophenolic acid, nogalamycin,
olivomycins, peplomycin, potfiromycin, puromycin, quelamycin, rodorubicin, streptonigrin,
streptozocin, tubercidin, ubenimex, zinostatin, zorubicin, denopterin, pteropterin, trimetrexate,
fludarabine, 6-mercaptopurine, thiamiprine, thioguanine, ancitabine, azacitidine, 6-azauridine,
carmofur, cytarabine, dideoxyuridine, doxifluridine, enocitabine, floxuridine, calusterone,
dromostanolone propionate, epitiostanol, mepitiostane, testolactone, aminoglutethimide,
mitotane, trilostane, frolinic acid, aceglatone, aldophosphamideglycoside, aminolaevulinic
acid, eniluracil, amsacrine, bestrabucil, bisantrene, edatraxate, defofamine, demecolcine,
diaziquone, elfornithine, elliptinium acetate, epothilone, etoglucid, lenthinan, lonidamine,
maytansine, ansamitocine, mitoguazone, mitoxantrone, mopidanmol, nitraerine, pentostatin,
phenamet, pirarubicin, losoxantrone, podophyllinic acid, 2-ethyl hydrazide, procarbazine,
razoxane, rhizoxin, schizophyllan, spiro germanium, tenuazonic acid, triaziquone, roridine A,
anguidine, urethane, vindesine, dacarbazine, mannomustine, mitobronitol, mitolactol,
pipobroman, gacytosine, docetaxel, chlorambucil, gemcitabine, 6-thio guanine,
mercaptopurine, cisplatin, oxaliplatin, carboplatin, vinblastine, etoposide, ifosfamide,
mitoxanthrone, vincristine, vinorelbine, novantrone, teniposide, edatrexate, daunomycin,
aminopterin, xeloda, ibandronate, irinotecan, topoisomerase inhibitor, difluoromethylolnitine
(DMFO), retinoic acid, capecitabine, and pharmaceutically acceptable (known) salts or
(known) derivatives thereof. Of the above examples, particularly cyclophosphamide,
paclitaxel, docetaxel, and vinorelbine are preferably used.
[0075]
Alternatively, a known radio isotope as in prior art literatures or the like, such as
21IAt, 13iI, l25I, 90Y, 186Re, 188Re, I53Sm, 212Bi, 32P, 175Lu, or 176Lu can be bound to the antibody
of the present invention. A desired radio isotope is effective for treatment or diagnosis of
tumor.
[0076]
The antibody of the present invention is an antibody having immunological
reactivity with CAPRIN-1, or, an antibody specifically binding to CAPRIN-1, which exhibits
cytotoxic activity against cancer or the effect of suppressing tumor growth. The antibody
should have a structure such that rejection is almost or completely avoided in a subject animal
to which the antibody is administered. Examples of such an antibody include, when a
subject animal is a human, a human antibody, a humanized antibody, a chimeric antibody (e.g.,
a human-mouse chimeric antibody), a single chain antibody, and a bispecific antibody.
These antibodies are: recombinant antibodies in which heavy chain and light chain variable
regions are from a human antibody; recombinant antibodies in which heavy chain and light
chain variable regions comprise complementarity determining regions (CDRs) (CDR1, CDR2,
and CDR3) from a non-human animal antibody and framework regions from a human
antibody; or recombinant antibodies in which heavy chain and light chain variable regions are
from a non-human animal antibody, and, heavy chain and light chain constant regions are
from a human antibody. Preferable antibodies are the former two antibodies.
[0077]
These recombinant antibodies can be prepared as follows by cloning DNA
encoding an anti-human CAPRIN-1 monoclonal antibody (e.g., a human monoclonal antibody,
a mouse monoclonal antibody, a rat monoclonal antibody, a rabbit monoclonal antibody, or a
chicken monoclonal antibody) from an antibody-producing cell such as a hybridoma,
preparing DNA encoding a light chain variable region and a heavy chain variable region of
the antibody by an RT-PCR method using it as a template, and then determining the sequence
of each variable region of light chain and heavy chain or each sequence of CDR1, CDR2, and
CDR3 based on a Kabat EU numbering system (Kabat et al., Sequences of Proteins of
Immunological Interest, 5th Ed. Public Health Service, National Institute of Health, Bethesda,
Md. (1991)).
[0078]
Furthermore, DNA encoding each of these variable regions or DNA encoding each
CDR is prepared using gene recombination techniques (Sambrook et al., Molecular Cloning:
A Laboratory Manual, Cold Spring Harbor Laboratory Press (1989)) or a DNA synthesizer.
Here, the above human monoclonal antibody-producing hybridoma can be prepared by
immunizing a human antibody-producing animal (e.g., a mouse) with human CAPRIN-1 and
then fusing splenocytes excised from the immunized animal to myeloma cells. Alternatively,
DNAs encoding a light chain or heavy chain variable region and a constant region from a
human antibody are prepared as necessary using gene recombination techniques or a DNA
synthesizer.
[0079]
In the case of humanized antibody, DNA is prepared by substituting a CDR coding
sequence in DNA encoding a variable region of light chain or heavy chain derived from a
human antibody, with a CDR coding sequence corresponding thereto of an antibody derived
from a non-human animal (e.g., a mouse, a rat, or a chicken) and then ligating the DNA thus
obtained to DNA encoding a constant region of light chain or heavy chain derived from a
human antibody. Thus, DNA encoding humanized antibody can be prepared.
[0080]
In the case of chimeric antibody, DNA encoding a chimeric antibody can be
prepared by ligating DNA encoding a light chain or heavy chain variable region of an
antibody from a non-human animal (e.g., a mouse, a rat, and a chicken) to DNA encoding a
light chain or heavy chain constant region from a human antibody.
[0081]
In the case of single chain antibody, this antibody is an antibody prepared by
linearly ligating a heavy chain variable region to a light chain variable region via a linker.
Thus, DNA encoding a single chain antibody can be prepared by binding DNA encoding a
heavy chain variable region, DNA encoding a linker, and DNA encoding a light chain variable
region. Herein, a heavy chain variable region and a light chain variable region are both from
a human antibody, or, only CDRs are substituted with CDRs of an antibody from a
non-human animal (e.g., a mouse, a rat, and a chicken) although the other regions are from a
human antibody. Also, a linker comprises 12 to 19 amino acids, such as (G4S)3 of 15 amino
acids (G. -B. Kim et al., Protein Engineering Design and Selection 2007, 20 (9): 425-432).
[0082]
In the case of bispecific antibody (diabody), this antibody is capable of specifically
binding to two different epitopes. For example, DNA encoding a bispecific antibody can be
prepared by linking DNA encoding a heavy chain variable region A, DNA encoding a light
chain variable region B, DNA encoding a heavy chain variable region B, and DNA encoding a
light chain variable region A in this order (here, DNA encoding a light chain variable region B
is bound to DNA encoding a heavy chain variable region B via DNA encoding the above
linker). Here, a heavy chain variable region and a light chain variable region are both from a
human antibody, or, only CDRs are substituted with CDRs of an antibody from a non-human
animal (e.g., a mouse, a rat, or a chicken) although the other regions are from a human
antibody.
[0083]
The above-prepared recombinant DNA is incorporated into one or a plurality of
appropriate vectors, they are introduced into host cells (e.g., mammalian cells, yeast cells, or
insect cells), and then (co)expression is caused, so that a recombinant antibody can be
prepared (P. J. Delves., ANTIBODY PRODUCTION ESSENTIAL TECHNIQUES., 1997
WILEY, P. Shepherd and C. Dean., Monoclonal Antibodies., 2000 OXFORD UNIVERSITY
PRESS; J. W. Goding., Monoclonal Antibodies: principles and practice., 1993 ACADEMIC
PRESS).
[0084]
Examples of the antibody of the present invention prepared by the above method
include an antibody comprising a heavy chain variable region comprising SEQ ID NOS: 39,
40, and 41 and a light chain variable region comprising SEQ ID NOS: 43, 44, and 45 (e.g., the
antibody composed of the heavy chain variable region of SEQ ID NO: 42 and the light chain
variable region of SEQ ID NO: 46).
[0085]
The amino acid sequences represented by SEQ ID NOS: 39, 40, and 41 are CDR1,
CDR2, and CDR3 of a chicken antibody heavy chain variable region. Also, the amino acid
sequences represented by SEQ ID NOS: 43, 44, and 45 are CDRl, CDR2, and CDR3 of a
chicken antibody light chain variable region, respectively.
[0086]
Also, the humanized antibody, the chimeric antibody, the single chain antibody, or
the bispecific antibody of the present invention is the following antibody, for example:
[0087]
(i) an antibody wherein a heavy chain variable region comprises the amino acid sequences of
SEQ ID NOS: 39, 40, and 41 and the amino acid sequences of framework regions from a
human antibody, and, a light chain variable region comprises the amino acid sequences of
SEQ ID NOS: 43, 44, and 45 and the amino acid sequences of framework regions from a
human antibody (e.g., the antibody wherein the heavy chain variable region comprises the
amino acid sequence of SEQ ID NO: 42, and, the light chain variable region comprises the
amino acid sequence of SEQ ID NO: 46); and
[0088]
(ii) an antibody wherein a heavy chain variable region comprises the amino acid sequences of
SEQ ID NOS: 39, 40, and 41 and the amino acid sequences of framework regions from a
human antibody, and, a heavy chain constant region comprises an amino acid sequence from a
human antibody, and, a light chain variable region comprises the amino acid sequences of
SEQ ID NOS: 43, 44, and 45 and the amino acid sequences of framework regions from a
human antibody, and a light chain constant region comprises an amino acid sequence from a
human antibody (e.g., the antibody wherein a heavy chain variable region comprises the
amino acid sequence of SEQ ID NO: 42, and, a heavy chain constant region comprises an
amino acid sequence from a human antibody, as well as, a light chain variable region
comprises the amino acid sequence of SEQ ID NO: 46, and, a light chain constant region
comprises an amino acid sequence from a human antibody).
[0089]
In addition, the sequences of human antibody heavy chain and light chain constant
regions and variable regions can be obtained from NCBI (e.g., U.S.A.: GenBank, UniGene),
for example. For example, the sequence of Accession No. J00228 can be referred to as a
human IgGl heavy chain constant region, the sequence of Accession No. J00230 can be
referred to as a human IgG2 heavy chain constant region, the sequence of Accession No.
X03604 can be referred to as a human IgG3 heavy chain constant region, the sequence of
Accession No. K01316 can be referred to as a human IgG4 heavy chain constant region, the
sequences of Accession No. V00557, X64135, X64133, and the like can be referred to as
human light chain k constant regions, and the sequences of registration nos. X64132, X64134,
and the like can be referred to as human light chain X constant regions.
[0090]
The above antibodies preferably have cytotoxic activity and thus can exhibit
anti-tumor effects.
[0091]
Also, the specific sequences of heavy chain and light chain variable regions or
CDRs in the above antibodies are given simply for illustrative purposes, and thus are clearly
not limited to such specific sequences. A hybridoma capable of producing another human
antibody or non-human animal antibody (e.g., a mouse antibody) against human CAPRTN-1 is
prepared, a monoclonal antibody that is produced by the hybridoma is collected, and then
whether or not it is a target antibody is determined by immunological binding property with
human CAPRIN-1 and cytotoxic activity as indicators. After identification of a hybridoma
producing the target monoclonal antibody in this manner, DNA encoding heavy chain and
light chain variable regions of the target antibody is prepared from the hybridoma as
described above, sequencing is carried out, and then the DNA is used for preparation of
another antibody.
[0092]
Furthermore, the above antibody of the present invention, the sequence of each of
the above antibodies, particularly the sequence of the framework region and/or the sequence
of the constant region may have a substitution, a deletion, or an addition of one or several
(preferably, 1 or 2) amino acids, as long as it has specificity for specific recognition of
CAPRIN-1. Here the term "several" refers to 2 to 5, and preferably 2 or 3.
[0093]
The present invention further provides DNA encoding the above antibody of the
present invention, or, DNA encoding the above antibody heavy chain or light chain, or, DNA
encoding the above antibody heavy chain or light chain variable region. Examples of such
DNA include, DNA encoding a heavy chain variable region comprising the nucleotide
sequences encoding the amino acid sequences of SEQ ID NOS: 39, 40, and 41 and DNA
encoding a light chain variable region comprising the nucleotide sequences encoding the
amino acid sequences of SEQ ID NOS: 43, 44, and 45.
[0094]
Complementarity determining regions (CDRs) encoded by the sequences of DNA
are regions for determining the specificity of an antibody. Thus, sequences encoding regions
in an antibody other than CDRs (specifically, a constant region and a framework region) may
be from other antibodies. Here, examples of such "other antibodies" include antibodies from
non-human organisms, and are preferably from a human in view of reduction of side effects.
Thus, in the case of the above DNA, regions encoding each framework region and each
contact region of heavy chains and light chains preferably comprise nucleotide sequences
encoding corresponding amino acid sequences from a human antibody.
[0095]
Further alternative examples of DNA encoding the antibody of the present
invention include DNA encoding a heavy chain variable region comprising the nucleotide
sequence encoding the amino acid sequence of SEQ ID NO: 42 and DNA in which the region
encoding a light chain variable region comprises the nucleotide sequence encoding the amino
acid sequence of SEQ ID NO: 46. Here, an example of the nucleotide sequence encoding
the amino acid sequence of SEQ ID NO: 42 is the nucleotide sequence of SEQ ID NO: 49.
Also, an example of the nucleotide sequence encoding the amino acid sequence of SEQ ID
NO: 46 is the nucleotide sequence of SEQ ID NO: 50. In these DNAs, regions encoding
each constant region of heavy chains and light chains preferably comprise nucleotide
sequences encoding the corresponding amino acid sequences from a human antibody.
[0096]
The DNA of the present invention can be obtained by the above methods or the
following method, for example. First, total RNA is prepared from a hybridoma relating to
the antibody of the present invention using a commercially available RNA extraction kit, and
then cDNA is synthesized with reverse transcriptase using random primers, and the like.
Subsequently, cDNA encoding an antibody is amplified by a PCR method using as primers
the oligonucleotides of sequences conserved in each variable region of known mouse
antibody heavy chain and light chain genes. The sequence encoding a constant region can
be obtained by amplifying a known sequence by a PCR method. The nucleotide sequence of
DNA can be determined by a conventional method such as insertion of it into a plasmid or a
phage for sequencing.
[0097]
An anti-CAPRIN-1 antibody to be used in the present invention is considered to
exhibit the anti-tumor effects against CAPRIN-1-expressing cancer cells through the
following mechanism.
[0098]
Antibody-dependent cytotoxic activity (ADCC) of effector cells against
CAPRIN-1 -expressing cells, and the complement-dependent cytotoxicity (CDC) against
CAPRIN-1-expressing cells.
[0099]
Therefore, the activity of an anti-CAPRIN-1 antibody to be used in the present
invention can be evaluated by, as specifically described in Examples below, measuring ex vivo
the above ADCC activity or CDC activity against CAPRIN-1-expressing cancer cells.
[0100]
An anti-CAPRIN-1 antibody to be used in the present invention binds to a
CAPRIN-1 protein on a cancer cell and exhibits anti-tumor effects due to the above activity,
and thus it is useful for treating or preventing cancer. Specifically, the present invention
provides a pharmaceutical composition for treating and/or preventing a cancer, which
comprises an anti-CAPRIN-1 antibody as an active ingredient. When the anti-CAPRIN-1
antibody is used for administration thereof to a human body (antibody therapy), it is
preferably human antibody or humanized antibody in order to decrease immunogenicity.
[0101]
In addition, the higher the binding affinity between an anti-CAPRIN-1 antibody and
a CAPRIN-1 protein on the cancer cell surfaces, the stronger the anti-tumor activity of the
anti-CAPRIN-1 antibody that can be obtained. Therefore, when an anti-CAPRIN-1 antibody
having high binding affinity with a CAPRIN-1 protein can be acquired, stronger anti-tumor
effects can be expected and such antibody's application as a pharmaceutical composition for
the purpose of cancer treatment and/or prevention becomes possible. Such high binding
affinity is desirably as follows. As described above, binding constant (affinity constant) Ka
(Won/koff) is preferably at least 107 M-1, at least 108 M-1, at least 5 x 108 M-1, at least 109 M-1, at
least 5 x 109 M-1, at least 1010 M-1, at least 5 x 1010 M-1, at least 1011 M-1, at least 5 x 1011 M-1,
at least 1012 M-1, or, at least 1013 M-1.
[0102]

The capacity of an antibody to bind to CAPRIN-1 can be specified by binding assay
using ELISA, a Western blot method, immuno-fluorescence and flow cytometric analysis, or
the like as described in Examples.
[0103]

An antibody that recognizes CAPRIN-1 can be tested for reactivity to CAPRIN-1
by a method for immunohistochemistry known by persons skilled in the art using
paraformaldehyde- or acetone-fixed frozen sections or paraformaldehyde-fixed
paraffin-embedded tissue sections, which is prepared from tissue samples obtained from a
patient during surgery, or tissue samples obtained from an animal having heterotransplant
tissue inoculated with a cell line expressing CAPRIN-1, naturally or after transfection.
[0104]
An antibody reactive with CAPRIN-1 can be stained by various methods for
immunohistochemical staining. For example, a horseradish peroxidase-conjugated goat
anti-mouse antibody or goat anti-chicken antibody is caused to undergo reaction, a target
antibody can be visualized.
[0105]
Pharmaceutical composition>
A target of the pharmaceutical composition for treating and/or preventing a cancer
of the present invention is not particularly limited, as long as it is a cancer (cell) expressing a
CAPRIN-1 gene.
[0106]
The term "tumor" and "cancer" as used herein refers to malignant neoplasm and is
used interchangeably.
[0107]
Cancer to be subjected to the present invention is cancer expressing genes encoding
CAPRIN-1 proteins having amino acid sequences of even-numbered SEQ ID NOS: 2 to 30.
Examples of such cancer include preferably breast cancer, brain tumor, leukemia, lung cancer,
lymphoma, mastocytoma, renal cancer, uterine cervix cancer, bladder cancer, esophageal
cancer, gastric cancer, and colorectal cancer.
[0108]
Examples of such specific cancer include, but are not limited to, breast
adenocarcinoma, composite type breast adenocarcinoma, mammary gland malignant mixed
tumor, intraductal papillary adenocarcinoma, lung adenocarcinoma, squamous cell carcinoma,
small cell carcinoma, large cell carcinoma, glioma that is neural epithelial tissue tumor,
ependymoma, neurocytoma, fetal neuroectodermal tumor, schwannoma, neurofibroma,
meningioma, chronic lymphocytic leukemia, lymphoma, gastrointestinal lymphoma, digestive
lymphoma, small-cell to medium-cell lymphoma, cancer of cecum, ascending colon cancer,
descending colon cancer, transverse colon cancer, sigmoid colon cancer, and rectal cancer.
[0109]
Moreover, preferable subjects are mammals including primates, pet animals,
domestic animals, animals for race, and the like and are particularly preferably humans, dogs,
and cats.
[0110]
When an antibody to be used in the present invention is used as a pharmaceutical
composition, it can be formulated by a method known by persons skilled in the art. For
example, the antibody can be used parenterally in the form of an injection preparation such as
an aseptic solution or a suspension prepared with water or a pharmacologically acceptable
solution other than water. For example, it can be formulated by mixing in a unit dosage
form required by generally accepted pharmaceutical practice in appropriate combination with
a pharmacologically acceptable carrier or medium, specifically, sterile water or saline,
vegetable oil, an emulsifier, a suspension, a surfactant, a stabilizer, a flavoring compound, an
excipient, a vehicle, an antiseptic, a binder, and the like. The amounts of active ingredients
in these preparations are determined so that an appropriate dose within the indicated range can
be obtained.
[0111]
An aseptic composition for injection can be prescribed according to general
pharmaceutical practice using a vehicle such as distilled water for injection.
[0112]
Examples of an aqueous solution for injection include saline, an isotonic solution
containing dextrose or other adjuvants, such as D-sorbitol, D-mannose, D-mannitol, and
sodium chloride. These examples may be used in combination with an appropriate
solubilizing agent such as alcohol, specifically ethanol and polyalcohol (e.g., propylene glycol
and polyethylene glycol), and nonionic surfactant (e.g., polysorbate 80 (TM) and HCO-60).
[0113]
Examples of the oil include sesame oil and soybean oil, which can be used in
combination with a solubilizing agent such as benzyl benzoate or benzyl alcohol. Also, a
buffering agent such as phosphate buffer or sodium acetate buffer, a soothing agent such as
procaine hydrochloride, a stabilizer such as benzyl alcohol or phenol, and an antioxidant may
be combined therewith. An appropriate amplus is generally filled with the thus prepared
injection solution.
[0114]
Administration is peroral or perenteral administration and is preferably perenteral
administration. Specific examples of the route of administration include injection, transnasal
administration, pulmonary administration, and transdermal administration. Examples of
injection include intravenous injection, intramuscular injection, intraperitoneal injection, and
subcutaneous injection, so that systemic or local administration is possible.
[0115]
Also, administration methods can be appropriately selected depending on a patient's
age, body weight, gender, symptoms, and the like. The dosage per administration of a
pharmaceutical composition containing an antibody or a polynucleotide encoding the
antibody can be selected from the range between 0.0001 mg and 1000 mg per kg of body
weight, for example. Alternatively, for example, dosage can be selected from the range
between 0.001 mg/body and 100000 mg/body per patient. However, the dosage range is not
always limited to these numerical values. The dosage and administration method are varied
depending on a patient's body weight, age, gender, symptoms, and the like, but can be
appropriately selected by persons skilled in the art.
[0116]
The above pharmaceutical composition containing the antibody or a fragment
thereof of the present invention is administered to a subject, so that cancer, preferably, breast
cancer, brain tumor, leukemia, lung cancer, lymphoma, mastocytoma, renal cancer, uterine
cervix cancer, bladder cancer, esophageal cancer, gastric cancer, and colorectal cancer can be
treated and/or prevented.
[0117]
The present invention further encompasses a method for treating and/or preventing
a cancer, comprising administering to a subject the pharmaceutical composition of the present
invention in combination with the above exemplified antitumor agent or pharmaceutical
composition containing such antitumor agent. The antibody or a fragment thereof of the
present invention and an antitumor agent may be administered simultaneously or separately to
a subject. They can be separately administered regardless of the order of administration.
The administration intervals, dosage, the route of administration, and the frequency of
administration can be appropriately selected by a specialist. Examples of the other
pharmaceutical formulation to be administered simultaneously include pharmaceutical
compositions obtained by mixing the antibody or a fragment thereof of the present invention
with an antitumor agent in a pharmacologically acceptable carrier (or a medium) followed by
formulation. Furthermore, about either the above pharmaceutical composition containing an
antitumor agent and formulation, explanations concerning prescription, formulation, the route
of administration, dose, cancer, and the like for administering a pharmaceutical composition
containing the antibody of the present invention and formulation are applicable.
[0118]
Therefore, the present invention also provides a pharmaceutical combination for
treating and/or preventing a cancer, comprising the pharmaceutical composition of the present
invention, and the above exemplified pharmaceutical composition containing an antitumor
agent.
[0119]
Also, the present invention provides a pharmaceutical composition for treating
and/or preventing a cancer, comprising the antibody or a fragment thereof of the present
invention and an antitumor agent together with a pharmacologically acceptable carrier.
[0120]
Polypeptide and DNA>
The present invention further provides the following polypeptides and DNAs
relating to the above antibodies.
[0121]
(i) A polypeptide comprising the amino acid sequence of SEQ ID NO: 42 and DNA encoding
the polypeptide, wherein the DNA comprises the nucleotide sequence of SEQ ID NO: 49.
[0122]
(ii) A polypeptide comprising the amino acid sequence of SEQ ID NO: 46 and DNA encoding
the polypeptide, wherein the DNA comprises the nucleotide sequence of SEQ ID NO: 50.
[0123]
(iii) A heavy chain CDR polypeptide consisting of the amino acid sequences represented by
SEQ ID NOS: 39, 40, and 41, and DNA encoding the polypeptide.
[0124]
(iv) A light chain CDR polypeptide consisting of the amino acid sequences represented by
SEQ ID NOS: 43, 44, and 45, and DNA encoding the polypeptide.
[0125]
These polypeptides and DNAs can be prepared using gene recombination
techniques as described above.
[0126]

The above-explained present invention is as summarized as follows.
[0127]
(1) A pharmaceutical composition for treating and/or preventing a cancer, comprising an
antibody that comprises a heavy chain variable region comprising SEQ ID NOS: 39, 40, and
41 and a light chain variable region comprising SEQ ID NOS: 43, 44, and.45 or a fragment
thereof as an active ingredient and has immunological reactivity with a CAPRIN-1 protein.
[0128]
(2) The pharmaceutical composition according to (1) above, wherein the cancer is breast
cancer, brain tumor, leukemia, lymphoma, lung cancer, mastocytoma, renal cancer, uterine
cervix cancer, esophageal cancer, gastric cancer, bladder cancer, or colorectal cancer.
[0129]
(3) The pharmaceutical composition according to (1) or (2) above, wherein the antibody is a
human antibody, humanized antibody, chimeric antibody, single chain antibody, or bispecific
antibody.
[0130]
(4) An antibody, which comprises a heavy chain variable region comprising SEQ ID NOS: 39,
40, and 41 and a light chain variable region comprising SEQ ID NOS: 43, 44, and 45, and has
immunological reactivity with a CAPRIN-1 protein.
[0131]
(5) The antibody according to (4) above, which is a human antibody, humanized antibody,
chimeric antibody, single chain antibody, or bispecific antibody.
[0132]
(6) A pharmaceutical combination for treating and/or preventing a cancer, comprising the
pharmaceutical composition of any one of (1) to (3) above and a pharmaceutical composition
containing an antitumor agent.
[0133]
(7) A method for treating and/or preventing a cancer, comprising administering to a subject
the pharmaceutical composition according to any one of (1) to (3) above or the antibody of
any one of (3) to (5) above or a fragment thereof.
[0134]
(8) A method for treating and/or preventing a cancer, comprising using pharmaceutical
compositions of the pharmaceutical combination of (6) above in combination in a subject.
Examples
[0135]
The present invention is described more specifically based on Examples, but the
scope of the present invention is not limited by these specific examples.
[0136]
Example 1 Identification of novel cancer antigen protein by SEREX method
(1) Preparation of cDNA library
Total RNA was extracted from a testis tissue of a healthy dog by an acid
guanidium-phenol-chloroform method. PolyA RNA was purified according to protocols
included with an Oligotex-dT30 mRNA purification Kit (Takara Shuzo Co., Ltd.) using the
kit.
[0137]
A dog testis cDNA phage library was synthesized using the thus obtained mRNA (5
ug). For preparation of the cDNA phage library, a cDNA synthesis kit, a ZAP-cDNA
synthesis kit, and a ZAP-cDNA gigapack III gold cloning kit (STRATAGENE) were used and
the library was prepared according to protocols included with the kit. The size of the thus
prepared cDNA phage library was 7.73xl05pfu/ml.
[0138]
(2) Screening of cDNA library using serum
Immunoscreening was carried out using the above-prepared dog testis cDNA phage
library. Specifically, host Escherichia coli (XLl-Blue MRF) was infected with the phage so
that 2210 clones were present on a <|)90 x 15 mm NZY agarose plate. Cells were cultured at
42°C for 3 to 4 hours, so as to cause plaque formation. The plate was covered with a
nitrocellulose membrane (Hybond C Extra: GE HealthCare Bio-Sciences) impregnated with
IPTG (isopropyl-p-D-thiogalactoside) at 37°C for 4 hours. Proteins were induced, expressed,
and then transferred to the membrane. Subsequently, the membrane was recovered,
immersed, and shaken in TBS (10 raM Tris-HCl, 150 mM NaCl pH 7.5) containing 0.5%
powdered skim milk at 4°C overnight, so that nonspecific reaction was suppressed. The
filter was caused to react with 500-fold diluted sera of dogs with cancer at room temperature
for 2 to 3 hours.
[0139]
As the above sera from dogs with cancer, sera collected from dogs with breast
cancer were used. The sera were stored at -80°C and then subjected to pretreatment
immediately before use. Pretreatment for sera was performed by the following method.
Specifically, host Escherichia coli (XLl-Blure MRF) was infected with X ZAP Express
phage into which no foreign gene had been inserted, and then cultured on NZY plate medium
at 37°C overnight. Subsequently, a 0.2 M NaHC03 buffer (pH 8.3) containing 0.5 M NaCl
was added to the plate and then the plate was left to stand at 4°C for 15 hours. The
supernatants were collected as Escherichia co/z'/phage extracts. Next, the collected
Escherichia co/z/phage extract was passed through a NHS-coIumn (GE HealthCare
Bio-Sciences), so as to immobilize the Escherichia co/z-phage-derived protein. The serum
of a dog with cancer was passed through the column to which the protein had been
immobilized for reaction, thereby removing Escherichia coli and antibodies adsorbed to the
phage from the serum. Each serum fraction that had passed through the column was diluted
500-fold with TBS containing 0.5% powdered skim milk, and the resultant was used as an
immunoscreening material.
[0140]
A membrane, to which the thus treated serum and the fusion protein had been
blotted, was washed 4 times with TBS-T (0.05% Tween20/TBS). The membrane was
reacted with goat anti-dog IgG (Goat anti Dog IgG-h+I HRP conjugated: BETHYL
Laboratories) diluted 5000-fold as a secondary antibody with TBS containing 0.5% powdered
skim milk at room temperature for 1 hour. Detection was carried out by enzyme color
reaction using an NBT/BCIP reaction solution (Roche). Colonies corresponding to the color
reaction positive site were collected from the t|)90 x 15 mm NZY agarose plate, and then
dissolved in 500 ul of SM buffer (100 mM NaCl, 10 mM MgClS04, 50 mM Tris-HCl, 0.01%
gelatin, pH 7.5). Until unification of color reaction positive colonies, secondary screening
and tertiary screening were repeated by a method similar to the above. Thus, 30940 phage
clones that had reacted with serum IgG were screened so that 5 positive clones were isolated.
[0141]
(3) Homology search for isolated antigen gene
A procedure for conversion of phage vectors to plasmid vectors was performed for
the 5 positive clones isolated by the above method for the purpose of subjecting the clones to
nucleotide sequence analysis. Specifically, 200 ul of a solution of host Escherichia coli
(XLl-Blue MRF) prepared to give an absorbance ODg0o of 1.0, 250 ul of a purified phage
solution, and 1 ul of ExAssist helper phage (STRATAGENE) were mixed and allowed to
react at 37°C for 15 minutes. After that, 3 ml of LB medium was added, cells were cultured
at 37°C for 2.5 to 3 hours, and then the resultant was immediately put in water bath at 70°C
for incubation for 20 minutes. Centrifugation was carried out at 4°C, 1000 x g for 15
minutes, and then the supernatant was collected as a phagemid solution. Subsequently, 200
ul of a solution prepared from phagemid host Escherichia coli SOLR to give an absorbance
ODfioo of 1.0 and 10 ul of the purified phage solution were mixed, followed by 15 minutes of
reaction at 37°C. 50 ul of the resultant was plated on LB agar medium containing ampicillin
(at final concentration of 50 |^g/ml) and then cultured overnight at 37°C. A single colony of
transformed SOLR was collected and then cultured on LB medium containing ampicillin (at
final concentration of 50 ug/ml) at 37°C. After culture, plasmid DNA carrying an insert of
interest was purified using a QIAGEN plasmid Miniprep Kit (QIAGEN).
[0142]
The purified plasmid was subjected to the analysis of the entire sequence of the
insert by the primer walking method using the T3 primer of SEQ ID NO: 31 and the T7
primer of SEQ ID NO: 32. The gene sequences of SEQ ID NOS: 5, 7, 9, 11, and 13 were
obtained by the sequence analysis. With the use of the nucleotide sequences of the genes
and the amino acid sequences thereof (SEQ ID NOS: 6, 8, 10, 12, and 14), homology search
program BLAST search (http://www.ncbi.nlm.nih.gov/BLAST/) was conducted for searching
homology with known genes. As a result, it was revealed that all the five obtained genes
were genes encoding CAPRIN-1. The sequence identities among the five genes were 100%
at the nucleotide sequence level and 99% at the amino acid sequence level in the regions to be
translated into proteins. The sequence identities of these genes and the human
homologue-encoding gene were 94% at the nucleotide sequence level and 98% at the amino
acid sequence level in the regions to be translated into proteins. The nucleotide sequences of
the human homologues are represented by SEQ ID NOS: 1 and 3 and the amino acid
sequences of the same are represented by SEQ ID NOS: 2 and 4. Also, the sequence
identities of the obtained dog genes and the cattle homologue-encoding gene were 94% at the
nucleotide sequence level and 97% at the amino acid sequence level in the regions to be
translated into proteins. The nucleotide sequence of the cattle homologue is represented by
SEQ ID NO: 15 and the amino acid sequence of the same is represented by SEQ ID NO: 16.
In addition, the sequence identities of the human homologue-encoding genes and the cattle
homologue-encoding gene were 94% at the nucleotide sequence level and 93% to 97% at the
amino acid sequence level in the regions to be translated into proteins. Also, the sequence
identities of the obtained dog genes and the horse homologue-encoding gene were 93% at the
nucleotide sequence level and 97% at the amino acid sequence level in the regions to be
translated into proteins. The nucleotide sequence of the horse homologue is represented by
SEQ ID NO: 17 and the amino acid sequence of the same is represented by SEQ ID NO: 18.
In addition, the sequence identities of the human homologue-encoding genes and the horse
homologue-encoding gene were 93% at the nucleotide sequence level and 96% at the amino
acid sequence level in the regions to be translated into proteins. Also, the sequence
identities of the obtained dog genes and the mouse homologue-encoding genes were 87% to
89% at the nucleotide sequence level and 95% to 97% at the amino acid sequence level in the
regions to be translated into proteins. The nucleotide sequences of the mouse homologues
are represented by SEQ ID NOS: 19, 21, 23, 25, and 27 and the amino acid sequences of the
same are represented by SEQ ID NOS: 20, 22, 24, 26, and 28. In addition, the sequence
identities of the human homologue-encoding genes and the mouse homologue-encoding genes
were 89% to 91% at the nucleotide sequence level and were 95% to 96% at the amino acid
sequence level in the regions to be translated into proteins. Also, the sequence identities of
the obtained dog genes and the chicken homologue-encoding gene were 82% at the nucleotide
sequence level and 87% at the amino acid sequence level in the regions to be translated into
proteins. The nucleotide sequence of the chicken homologue is represented by SEQ ID NO:
29 and the amino acid sequence of the same is represented by SEQ ID NO: 30. In addition,
the sequence identities of the human homologue-encoding genes and the chicken
homo logue-enco ding gene were 81% to 82% at the nucleotide sequence level and 86% at the
amino acid sequence level in the regions to be translated into proteins.
[0143]
(4) Gene expression analysis in each tissue
The expression of genes obtained by the above method was examined in dog and
human normal tissues and various cell lines by an RT-PCR method. Reverse transcription
reaction was performed as follows. Specifically, total RNA was extracted from 50 mg to 100
mg of the tissue or 5 to 10 x 106 cells of the cell line using a TRIZOL reagent (Invitrogen)
according to the accompanying protocols. cDNA was synthesized with the total RNA using
a Superscript First-Strand Synthesis System for RT-PCR (Invitrogen) according to the
accompanying protocols. PCR was performed as follows using primers of SEQ ID NOS: 33
and 34 specific to the obtained genes. Specifically, reagents and an accompanying buffer
were added to 0.25 ul of the sample prepared by the reverse transcription reaction to a total
volume of 25 ul, so that the resultant contained the above primers of 2 uM each, dNTPs of 0.2
mM each, and 0.65 U ExTaq polymerase (Takara Shuzo Co., Ltd.). PCR was carried out by
repeating a cycle of 94°C for 30 seconds, 60°C for 30 seconds, and 72°C for 30 seconds 30
times using a Thermal Cycler (BIO RAD). The above gene-specific primers are capable of
amplifying the region ranging from nucleotides 206 to 632 in the nucleotide sequence of SEQ
ID NO: 5 (dog CAPRIN-1 gene) and the region ranging from nucleotides 698 to 1124 in the
nucleotide sequence of SEQ ID NO: 1 (human CAPRIN-1 gene). As a control for
comparison, GAPDH-specific primers of SEQ ID NOS: 35 and 36 were also used
concurrently. As a result, as shown in Fig. 1, strong expression was observed in testis
among normal dog tissues, while expression was observed in dog breast cancer and
adenocarcinoma tissues. Moreover, the observation of the expression of the human
homologues from the obtained genes was also carried out. As a result, similarly to the case
of the dog CAPRIN-1 gene, expression could be observed in only testis among normal
tissues. However, in the case of cancer cells, expression was detected in many types of
cancer cell lines, including breast cancer, brain tumor, leukemia, lung cancer, and esophageal
cancer cell lines. Expression was observed particularly in many breast cancer cell lines. It
was confirmed by the results that the expression of CAPRIN-1 is not observed in normal
tissues other than testis, while CAPRIN-1 was expressed in many cancer cells and particularly
in breast cancer cell lines.
[0144]
In Fig. 1, reference number 1 on each vertical axis indicates the expression patterns
of genes identified above and reference number 2 indicates the expression patterns of the
GAPDH gene as a control.
[0145]
(5) Immunohistochemical staining
(5)-l CAPRIN-1 expression in mouse and dog normal tissues
Mice (Balb/c, female) and dogs (beagles, female) were exsanguinated under ether
anesthesia and ketamine/isoflurane anesthesia. After laparotomy, each organ (stomach, liver,
eyeball, thymus gland, muscle, bone marrow, uterus, small bowel, esophagus, heart, kidney,
salivary gland, large bowel, mammary gland, brain, lung, skin, adrenal gland, ovary, pancreas,
spleen, and bladder) was transferred to a 10-cm dish containing PBS. Each organ was cut
open in PBS and then subjected to perfusion fixation overnight in 0.1 M phosphate buffer (pH
7.4) containing 4% paraformaldehyde (PFA). The perfusion solution was discarded, the
tissue surface of each organ was rinsed with PBS, a PBS solution containing 10% sucrose was
added to a 50-ml centrifuge tube, each tissue was added to the tube, and then the tube was
shaken using a rotor at 4°C for 2 hours. The solution was replaced by a PBS solution
containing 20% sucrose, and then left to stand at 4°C until the tissue sank. The solution was
replaced by a PBS solution containing 30% sucrose and then left to stand at 4°C until the
tissue sank. The tissue was removed and then needed portions were excised with a surgical
scalpel. Next, an OCT compound (Tissue Tek) was added to the tissue so that it was
thoroughly applied to the tissue surface, and then the tissue was placed in a cryomold. The
cryomold was placed on dry ice for quick freezing. Thereafter, the tissue was sliced to 10
urn to 20 urn using a cryostat (LEICA). Slices were air-dried on slide glasses using a hair
dryer for 30 minutes, to prepare the sliced tissue mounted on a slide glass. Next, each
sample was placed in a staining bottle filled with PBS-T (saline containing 0.05% Tween20)
and then subjected to replacement with PBS-T being repeated three times every 5 minutes.
Excess water around the sections was removed with Kimwipes, and then the sections were
circled using a DAKOPEN (DAKO). As blocking solutions, an MOM mouse Ig blocking
reagent (VECTASTAIN) and a PBS-T solution containing 10% FBS were overlaid on mouse
tissue and dog tissue, respectively, and then left to stand in a moist chamber at room
temperature for 1 hour. Next, a solution of the anti-CAPRIN-1 monoclonal antibody
(monoclonal antibody #1 prepared in Example 4) of 10 |ag/ml adjusted with a blocking
solution, which reacts with cancer cell surfaces and comprises the heavy chain variable region
of SEQ ID NO: 42 and the light chain variable region of SEQ ID NO: 46, was placed on and
then left to stand overnight in a moist chamber at 4°C. 10 minutes of washing with PBS-T
was performed 3 times, and then an MOM biotin-labeled anti-IgG antibody (VECTASTAIN)
diluted 250-fold with the blocking solution was placed and then left to stand at room
temperature for 1 hour in a moist chamber. After ten (10) minutes of washing with PBS-T
was performed 3 times, an avidin-biotin ABC reagent (VECTASTAIN) was placed on, and
then the sample was left to stand in a moist chamber at room temperature for 5 minutes.
After ten (10) minutes of washing with PBS-T was performed 3 times, a DAB coloring
solution (DAB 10 mg + 30% H202 10 uI/0.05 M Tris-HCl (pH 7.6) 50 ml) was placed on, and
then the sample was left to stand in a moist chamber at room temperature for 30 minutes.
After rinsing with distilled water, a hematoxylin reagent (DAKO) was placed on, the sample
was left to stand at room temperature for 1 minute, and then rinsed with distilled water. The
slide glass was immersed in 70%, 80%, 90%, 95%, and then 100% ethanol solutions in such
order for 1 minute each and then left to stand overnight in xylene. The slide glass was
removed, sealed in Glycergel Mounting Medium (DAKO), and then observed. As a result,
the expression of CAPRIN-1 was slightly observed within cells of each tissue of salivary
gland, kidney, colon, and stomach, but the expression of the same was not observed on cell
surfaces. Furthermore, no expression was observed in tissues from other organs.
[0146]
(5)-2 CAPRIN-1 expression in dog breast cancer tissue
Frozen section slides were prepared by a method similar to the above using 108
frozen breast cancer tissue specimens of dogs pathologically diagnosed as having malignant
breast cancer, and immunohistochemical staining was performed using the monoclonal
antibody #1 prepared in Example 4. As a result, the expression of CAPRIN-1 was observed
in 100 out of 108 specimens (92.5%) and CAPRIN-1 was strongly expressed on the surfaces
of cancer cells with a particularly high grade of atypism.
[0147]
(5)-3 CAPRIN-1 expression in human breast cancer tissues
Immunohistochemical staining was performed using 188 breast cancer tissue
specimens on a paraffin-embedded human breast cancer tissue array (BIOMAX). After 3
hours of treatment of the human breast cancer tissue array at 60°C, the array was placed in a
staining bottle filled with xylene, followed by xylene replacement being repeated three times
every 5 minutes. Next, a similar procedure was performed with ethanol and PBS-T instead
of xylene. The human breast cancer tissue array was placed in a staining bottle filled with
10 mM citrate buffer (pH 6.0) containing 0.05% Tween20. After 5 minutes of treatment at
125°C, the array was left to stand at room temperature for 40 minutes or more. Excess water
around the sections was removed with Kimwipes, the sections were circled with a
DAKOPEN, and Peroxidase Block (DAKO) was added dropwise in appropriate amounts.
After left to stand at room temperature for 5 minutes, the array was placed in a staining bottle
fdled with PBS-T, followed by PBS-T replacement being repeated three times every 5
minutes. As a blocking solution, a PBS-T solution containing 10% FBS was placed on the
array, and then the array was left to stand in a moist chamber at room temperature for 1 hour.
Next, a solution of the monoclonal antibody #1 of 10 |ig/ml adjusted with a PBS-T solution
containing 5% FBS, which reacts with cancer cell surfaces and had been prepared in Example
4, was placed on, and the array was left to stand overnight in a moist chamber at 4°C. After
ten (10) minutes of washing with PBS-T was performed 3 times, Peroxidase Labeled Polymer
Conjugated (DAKO) was added dropwise in appropriate amounts and then the array was left
to stand in a moist chamber at room temperature for 30 minutes. After ten (10) minutes of
washing with PBS-T was performed 3 times, a DAB coloring solution (DAKO) was placed on
and then it was left to stand at room temperature for about 10 minutes. The coloring solution
was discarded, 10 minutes of washing with PBS-T was performed 3 times, and then it was
rinsed with distilled water. The array was immersed in 70%, 80%, 90%, 95%, and then
100%. ethanol solutions in such order for 1 minute each, and then left to stand in xylene
overnight. The slide glass was removed, sealed in Glycergel Mounting Medium (DAKO),
and then observed. As a result, the strong expression of CAPRIN-1 was observed in 138 out
of a total of 188 breast cancer tissue specimens (73%).
[0148]
(5)-4 CAPRIN-1 expression in human malignant brain tumor
Immunohistochemical staining was performed according to a method similar to that
used in (5)-3 above with 247 malignant brain tumor tissue specimens on a paraffin-embedded
human malignant brain tumor tissue array (BIOMAX), using the monoclonal antibody #1
prepared in Example 4. As a result, the strong expression of CAPRIN-1 was observed in
227 out of a total of 247 malignant brain tumor tissue specimens (92%).
[0149]
(5)-5 CAPRIN-1 expression in human breast cancer metastasized lymph node
Immunohisto chemical staining was performed according to a method similar to that
in (5)-3 above with 150 breast cancer metastasized lymph node tissue specimens on a
paraffin-embedded human breast cancer metastasized lymph node tissue array (BIOMAX),
using the monoclonal antibody #1 prepared in Example 4. As a result, the strong expression
of CAPRIN-1 was observed in 136 out of a total of 150 breast cancer metastasized lymph
node tissue specimens (90%). Specifically, it was revealed that CAPRIN-1 was strongly
expressed also in cancer tissues that had metastasized from breast cancer.
[0150]
(5)-6 CAPRIN-1 expression in various human cancer tissues
Immunohistochemical staining was performed according to a method similar to the
above with specimens on various paraffin-embedded human cancer tissue arrays (BIOMAX),
using the monoclonal antibody #1 prepared in Example 4. As a result, the strong expression
of CAPRIN-1 was observed in esophageal cancer, colon cancer, rectal cancer, lung cancer,
renal cancer, bladder cancer, and uterine cervix cancer.
[0151]
Example 2 Preparation of novel human cancer antigen protein
(1) Preparation of recombinant protein
Based on the gene of SEQ ID NO: 1 obtained in Example 1, a recombinant protein
from the human homologous gene was prepared by the following method. PCR was
performed in a total volume of 50 |al with 1 ul of cDNA, two primers (SEQ ID NOS: 37 and
38 comprising Sac I and Xho I restriction enzyme cleavage sequences) of 0.4 uM each, 0.2
mM dNTP, and 1.25U PrimeSTAR HS polymerase (Takara Shuzo Co., Ltd.), prepared by
adding the reagents and an accompanying buffer. The expression had been confirmed by an
RT-PCR method for the cDNA used herein from among various tissue-or cell-derived cDNAs
prepared in Example 1. PCR was preformed by repeating a cycle of 98°C for 10 seconds
and 68°C for 2.5 minutes 30 times using a Thermal Cycler (BIO RAD). The above two
primers are capable of amplifying a region encoding the entire amino acid sequence of SEQ
ID NO: 2. After PCR, the thus amplified DNA was subjected to electrophoresis on 1%
agarose gel, and then an about 2.1 kbp DNA fragment was purified using a QIAquick Gel
Extraction Kit (QIAGEN).
[0152]
The thus purified DNA fragment was ligated to a cloning vector PCR-Blunt
(Invitrogen). After transformation of Escherichia coli with it, plasmid was collected. It
was verified by sequencing that the thus amplified gene fragment has the sequence of interest.
The plasmid having a matched sequence with the sequence of interest was treated with Sac I
and Xho I restriction enzymes and then purified with a QIAquick Gel Extraction Kit. The
gene sequence of interest was inserted into an Escherichia coli expression vector pET30a
(Novagen) treated with Sac I and Xho I restriction enzymes. A His-tag fused recombinant
protein can be produced using the vector. The plasmid was transformed into Escherichia
coli for expression, BL21(DE3), and then expression was induced with 1 mM IPTG, so that
the protein of interest was expressed in Escherichia coli.
(2) Purification of recombinant protein
The above-obtained recombinant Escherichia coli expressing the gene of SEQ ID
NO: 1 was cultured in LB medium containing 30 u-g/ml kanamycin at 37°C until absorbance
at 600 nm reached around 0.7, isopropyl-p-D-l~thiogalactopyranoside was added at a final
concentration of 1 mM, and then cells were cultured at 37°C for 4 hours. Subsequently,
centrifugation was performed at 4800 rpm for 10 minutes and then cells were collected. The
resulting cell pellet was suspended in phosphate buffered saline and centrifuged at 4800 rpm
for 10 minutes, and then cells were washed.
[0153]
The cells were suspended in phosphate buffered saline and then disrupted by
ultrasonication on ice. The resulting lysate of the ultrasonicated Escherichia coli was
subjected to centrifugation at 6000 rpm for 20 minutes, and then the resulting supernatant was
regarded as a soluble fraction and the precipitate was regarded as an insoluble fraction.
[0154]
The soluble fraction was added to a nickel chelate column adjusted according to a
conventional method (carrier: Chelating Sepharose™ Fast Flow (GE HealthCare); column
capacity of 5 ml; and equilibration buffer: 50 raM hydrochloride buffer (pH 8.0)).
Unadsorbed fractions were washed off with 50 mM hydrochloride buffer (pH 8.0) in an
amount 10 times the column capacity and 20 mM phosphate buffer (pH 8.0) containing 20
mM imidazole. Immediately after washing, 6 beds were eluted with 20 mM phosphate
buffer (pH 8.0) containing 100 mM imidazole. The elution of the protein of interest was
confirmed by Coomassie staining on the elution fraction with 20 mM phosphate buffer (pH
8.0) containing 100 mM imidazole, and then the elution fraction was added to a strong anion
exchange column (carrier: Q Sepharose™ Fast Flow (GE HealthCare); column capacity of5
ml; and 20 mM phosphate buffer (pH 8.0) as an equilibration buffer). An unadsorbed
fraction was washed off with 20 mM phosphate buffer (pH 7.0) in an amount 10 times the
column capacity and 20 mM phosphate buffer (pH 7.0) containing 200 mM sodium chloride.
Immediately after washing, 5 beds were eluted with 20 mM phosphate buffer (pH 7.0)
containing 400 mM sodium chloride, and thus the purified fraction of the protein having the
amino acid sequence represented by SEQ ID NO: 2 was obtained.
[0155]
200 \i\ of each purified sample obtained by the above method was dispensed into 1
ml of reaction buffer (20 mM Tris-Hcl, 50 mM, NaCl, 2 mM CaCl2'pH 7.4), followed by
addition of 2 ul of enterokinase (Novagen). After that, the resultant was left to stand
overnight at room temperature for reaction so that His-tag was cleaved off, and then
purification was performed using an Enterokinase Cleavage Capture Kit (Novagen) according
to the accompanying protocols. Next, 1.2 ml of the purified sample obtained by the above
method was subjected to the buffer replacement with physiological phosphate buffer (Nissui
Pharmaceutical Co., Ltd.) using an ultrafiltration NANOSEP 10K OMEGA (PALL).
Further, sterile filtration was performed using HT Tuffryn Acrodisc 0.22 pm (PALL) and then
the resultant was used for the following experiment.
[0156]
Example 3 Preparation of chicken monoclonal antibody against CAPRIN-1
300 ^g of the antigen protein (human CAPRIN-1) () shown by SEQ ID NO: 2
prepared in Example 2 was mixed with an equivalent amount of Freund's complete adjuvant,
and then this was used as an antigen solution for one chicken. The antigen solution was
intraperitoneally administered to 7-week-old chickens, and then the administration was
performed 7 times every 4 weeks, and thus immunization was completed. Each spleen was
excised on day 4 after the final immunization, and sandwiched between two sterilized slide
glasses and then crushed. The resultant was washed with PBS(-) (Nissui) and then
centrifuged at 1500 rpm for 10 minutes to remove the supernatant. This procedure was
repeated 3 times, so that splenocytes were obtained. The thus obtained splenocytes and
chicken myeloma cells deficient in light chain were mixed at a ratio of 5 : 1. The used
chicken myeloma cells had been established from a chicken by a transformation using an
avian reticuloendotheliosis virus. A PEG solution prepared by mixing 200 pi of IMDM
medium containing 10% FBS heated at 37°C and 800 pi of PEG1500 (Boehringer) was added
to the mixture, left to stand for 5 minutes for cell fusion, and then subjected to centrifugation
at 1700 rpm for 5 minutes. After removal of the supernatant, cells were suspended in 300 ml
of IMDM medium containing 10% FBS, supplemented with a HAT solution (Gibco) (2%
equivalent) (HAT selective medium), and then the cell suspension was plated on thirty
96-well plates (Nunc) at 100 pi per well. Cells were cultured for 7 days at 37°C under
conditions of 5% CO2, so that hybridoma prepared by fusion of splenocytes and chicken
myeloma cells were obtained.
[0157]
Hybridomas were selected using as a marker the binding affinity of the antibody
produced by the prepared hybridomas to the CAPRIN-1 protein. The CAPRIN-1 protein
solution (1 pg/ml) prepared in Example 2 was added to a 96-well plate at 100 pi per well and
then left to stand at 4°C for 18 hours. Each well was washed 3 times with PBS-T, 400 ul of
a 0.5% Bovine Serum Albumin (BSA) solution (Sigma) was added per well, and then the
plate was left to stand at room temperature for 3 hours. The solution was removed, and then
the wells were washed three times with 400 ul of PBS-T per well. The culture supernatant
of the above-obtained hybridomas was added at 100 ul per well, and then left to stand at room
temperature for 2 hours. After washing each well three times with PBS-T, an HRP-labeled
anti-chicken IgY antibody (SIGMA) diluted 5000-fold with PBS was added at 100 ul per well
and the resultant was then left to stand at room temperature for 1 hour. After washing the
wells three times with PBS-T, 100 ul of a TMB substrate solution (Thermo) was added per
well and then left to stand for 15 to 30 minutes for coloring reaction. After color
development, 100 ul of IN sulfuric acid was added per well to stop the reaction, and then
absorbances at 450 nm and 595 nm were measured using an absorption spectrometer. As a
result, several hybridomas producing antibodies with high absorbance values were selected.
[0158]
The thus selected hybridomas were added to a 96-well plate at 0.5 cells per well and
then cultured. After 1 week, hybridomas that had formed single colonies in wells were
observed. These cells in the wells were further cultured, and then hybridomas were selected
using as a marker the binding affinity of antibodies produced by the cloned hybridomas to the
CAPRIN-1 protein. The CAPRIN-1 protein solution (1 jig/ml) prepared in Example 2 was
added to a 96-well plate at 100 u.1 per well, and then left to stand at 4°C for 18 hours. Each
well was washed with PBS-T three times, 400 ul of a 0.5% BSA solution was added per well,
and then the resultant was left to stand at room temperature for 3 hours. The solution was
removed, and then the wells were washed three times with 400 ul of PBS-T per well. 100 ul
of each culture supernatant of the above-obtained hybridomas was added per well, and then
the plate was left to stand at room temperature for 2 hours. After washing each well three
times with PBS-T, 100 ul of an HRP-labeled anti-chicken IgY antibody (SIGMA) diluted
5000-fold with PBS was added per well and then left to stand at room temperature for 1 hour.
After washing the wells three times with PBS-T, 100 ul of a TMB substrate solution (Thermo)
was added per well, and then left to stand for 15 to 30 minutes for coloring reaction. After
color development, 100 ul of IN sulfuric acid was added per well to stop the reaction and
then absorbances at 450 nm and 595 nm were measured using an absorption spectrometer.
As a result, several hybridoma cell lines producing monoclonal antibodies reactive with the
CAPRIN-1 protein were obtained.
[0159]
Next, of those monoclonal antibodies, antibodies reactive with the cell surfaces of
breast cancer cells expressing CAPRIN-1 were selected. Specifically, 5 x 10 cells of the
human breast cancer cell line MDA-MB-231V were subjected to centrifugation in a 1.5-ml
microcentrifuge tube, and 100 ul of the culture supernatant of each of the above hybridomas
was added to the tube, and then the tube was left to stand on ice for 1 hour. After washing
with PBS, an FITC-labeled goat anti-chicken IgG (H+L) antibody (SouthernBiotech) diluted
30-fold with PBS containing 0.1% FBS was added, and then the resultant was left to stand on
ice for 1 hour. After washing with PBS, fluorescence intensity was measured using a FACS
caliber (Becton, Dickinson and Company). Meanwhile, procedures similar to the above
were performed for medium for culturing hybridomas, so that a control sample was obtained.
As a result, one monoclonal antibody (monoclonal antibody #1) that had exhibited
fluorescence intensity stronger than that of the control, and that is, that reacted with the cell
surfaces of CAPRIN-1-expressing breast cancer cells, was selected.
[0160]
Example 4 Characterization of selected antibody
(1) Cloning of genes of anti-CAPRIN-1 monoclonal antibody variable regions
mRNA was extracted from a chicken-derived hybridoma cell line producing
monoclonal antibodies (selected in Example 3) reactive with the surfaces of
CAPRIN-1-expressing breast cancer cells. An RT-PCR method using primers specific to the
chicken FR1-derived sequence and the chicken FR4-derived sequence was performed
therefor, and the gene of the heavy chain variable (VH) region and the gene of the light chain
variable (VL) region of the antibody were obtained. mRNA was also extracted from two
mouse-derived hybridoma cell lines producing monoclonal antibodies reactive with the
surfaces of CAPRIN-1-expressing breast cancer cells. An RT-PCR method using primers
specific to the mouse FR1-derived sequence and the mouse FR4-derived sequence was
performed therefor, and the gene of the heavy chain variable (VH) region and the gene of the
light chain variable (VL) region of each antibody were obtained. For sequence
determination, these genes were cloned into apCR2.1 vector (Invitrogen).
[0161]
(1)-1 RT-PCR
After extraction of total RNA from 106 cells of each hybridoma cell line using a
High Pure RNA Isolation Kit (Roche), cDNA was synthesized using a PrimeScriptll 1st
strand cDNA Synthesis Kit (Takara). These procedures were performed according to
protocols attached to each kit.
[0162]
The gene of the chicken antibody heavy chain variable region and the gene of the
chicken antibody light chain variable region, and the gene of the mouse antibody heavy chain
variable region and the gene of the mouse antibody light chain variable region were each
amplified by a PCR method according to a conventional method using the thus synthesized
cDNA as a template and KOD-Plus-DNA Polymerase (TOYOBO).
[0163]
To obtain the gene of the chicken antibody VH region, a primer specific to the
chicken heavy chain FR1 sequence and a primer specific to the chicken heavy chain FR4
sequence were used. Furthermore, to obtain the gene of the VL region, a primer specific to
the chicken light chain FR1 sequence and a primer specific to the chicken light chain FR4
were used. The genes of mouse antibody VH and VL regions were obtained in a manner
similar to the above. Specifically, a primer specific to the mouse heavy chain FR1 sequence, a
primer specific to the mouse heavy chain FR4 sequence, a primer specific to the mouse light
chain FR1 sequence, and a primer specific to the mouse light chain FR4 were used.
[0164]
The thus obtained PCR products were each subjected to agarose gel electrophoresis,
and DNA bands of the VH region and the VL region were excised. DNA fragments were
purified using a QIAquick Gel purification kit (QIAGEN) according to the accompanying
protocols. The purified DNA was cloned into a pCR2.1 vector using a TA cloning kit
(Invitrogen). The ligated vector was transformed into DH5 competent cells (TOYOBO)
according to a conventional method. 10 clones of each transformant were cultured overnight
in medium (100 ug/ml ampicillin) at 37°C, and then plasmid DNA was purified using a
Qiaspin Miniprep kit (QIAGEN).
[0165]
(l)-2 Sequence determination
The gene sequences of the VH region and the VL region in each plasmid obtained
above were analyzed with an M13 forward primer (SEQ ID NO: 47) and an M13 reverse
primer (SEQ ID NO: 48) on a fluorescence sequencer (DNA sequencer 3130XL; ABI), using
a Big Dye Terminator Ver3.1 Cycle Sequencing Kit (ABI) according to the accompanying
protocols. As a result, each gene sequence was determined. The sequences were identical
among the 10 clones.
[0166]
The thus obtained gene sequence encoding the heavy chain variable region of the
chicken-derived monoclonal antibody is represented by SEQ ID NO: 49 and the amino acid
sequence thereof is represented by SEQ ID NO: 42, and the thus obtained gene sequence
encoding the light chain variable region is represented by SEQ ID NO: 50 and the amino acid
sequence thereof is represented by SEQ ID NO: 46.
[0167]
Specifically, it was revealed that the monoclonal antibody #1 comprises the heavy
chain variable region of SEQ ID NO: 42 and the light chain variable region of SEQ ID NO:
46, wherein CDR1, CDR2, and CDR3 in the heavy chain variable region consist of the amino
acid sequences of SEQ ID NOS: 39, 40, and 41, respectively, and the CDR1, CDR2, and
CDR3 in the light chain variable region consist of the amino acid sequences of SEQ ID NOS:
43, 44, and 45, respectively.
[0168]
(2) Preparation of human-chicken chimeric recombinant antibody and mouse-chicken
chimeric antibody
An amplification fragment of the gene of the heavy chain variable region (SEQ ID
NO: 42) of the chicken monoclonal antibody #1 obtained in (1) above was treated at both
ends with restriction enzymes and then purified. The resulting fragment was inserted into a
pcDNA4/myc-His (Invitrogen) vector according to a conventional method, into which a
chicken antibody-derived leader sequence comprising SEQ ID NO: 51 and a human IgGl
H-chain constant region comprising SEQ ID NO: 52 had already been inserted.
Furthermore, an amplification fragment of the gene of the chicken monoclonal antibody #1
light chain variable region (SEQ ID NO: 46) was treated at both ends with restriction
enzymes and then purified. The resulting fragment was inserted into a pcDNA3.1/myc-His
(Invitrogen) vector according to a conventional method, into which a chicken
antibody-derived leader sequence comprising SEQ ID NO: 51 and a human IgGl L-chain
constant region comprising SEQ ID NO: 53 had already been inserted.
[0169]
Next, the above recombinant vector into which the heavy chain variable region
(SEQ ID NO: 42) of the chicken monoclonal antibody #1 had been inserted, and the above
recombinant vector into which the chicken monoclonal antibody #1 light chain variable
region (SEQ ID NO: 46) had been inserted, were introduced into CHO-K1 cells (obtained
from RIKEN Cell Bank). Specifically, 2 x 105 CHO-K1 cells cultured in 1 ml of Ham's F12
medium (Invitrogen) containing 10% FBS per well of a 12-well culture plate were washed
with PBS(-). 1 ml of Ham's F12 medium containing 10% FBS was further added per well
and then a mixture of 250 ng of each of the above vectors dissolved in 30 p.1 of OptiMEM
(Invitrogen) and 30 ul of a Poly feet transfection reagent (QIAGEN) was added to each well.
CHO-K1 cells into which the above recombinant vector had been introduced were cultured in
Ham's F12 medium containing 10% FBS, supplemented with 200 ug/ml Zeocin (Invitrogen)
and 200 p.g/ml geneticin (Roche). CHO-K1 cells into which the above recombinant vector
had been introduced were plated in a 96-well plate at 0.5 cells per well. Thus, a cell line
stably producing a human-chicken chimeric antibody #1 (also referred to as #1) having the
chicken monoclonal antibody #1 variable region was prepared. The thus prepared cell line
was cultured in a 150 cm flask containing 30 ml of serum-free OptiCHO medium
(Invitrogen) at 5 x 10 cells/ml for 5 days. Then, a culture supernatant containing #1 was
obtained.
[0170]
With a method similar to the above, an amplification fragment of the gene of the
heavy chain variable region (SEQ ID NO: 42) of the chicken monoclonal antibody #1 was
treated at both ends with restriction enzymes and then purified. The resultant was inserted
according to a conventional method into a pcDNA4/myc-His (Invitrogen) vector into which a
chicken antibody-derived leader sequence and a mouse IgGl H-chain constant region had
already been inserted. Furthermore, an amplification fragment of the gene of the light chain
variable region (SEQ ID NO: 46) of the chicken monoclonal antibody #1 was treated at both
ends with restriction enzymes and then purified. The resultant was then inserted according
to a conventional method into a pcDNA3.1/myc-His (Invitrogen) vector into which a chicken
antibody-derived leader sequence and the mouse IgGl L-chain constant region had already
been inserted. The resultant was introduced into CHO-K1 cells in a manner similar to the
above and thus a cell line stably producing a mouse-chicken chimeric antibody #1 comprising
the chicken monoclonal antibody #1 variable region was prepared. The cells were cultured
at 5 x 10 cells/ml using a 150cm flask and 30 ml of serum free OptiCHO medium
(Invitrogen) for 5 days, so that a culture supernatant containing the mouse-chicken chimeric
antibody #1 was obtained.
[0171]
(3) CAPRIN-1 expression on various cancer cell surfaces using anti-CAPRIN-1 antibody #1
Next, 7 breast cancer cell lines (MDA-MB-157, T47D, MRK-nu-1,
MDA-MB-231V, BT20, SK-BR-3, and DA-MB-231T) for which CAPRIN-1 gene expression
had been observed, and the other 3 breast cancer cell lines (MDA-MB-231C, MCF-7, and
ZR75-1), 5 glioma cell lines (T98G, SNB19, U251, U87MG, and U373), 4 renal cancer cell
lines (Caki-1, Caki-2, A498, and ACHN), 2 gastric cancer cell lines (MNK28 and MNK45), 5
colorectal cancer cell lines (HT29, LoVo, Caco2, SW480, and HCT116), 3 lung cancer cell
lines (A549, QG56, and PC8), 4 leukemia cell lines (AML5, Namalwa, BDCM, RPI1788),
one lymphoma cell line (Ramos), one uterine cervix cancer cell line (SW756), one bladder
cancer cell line (T24), and one esophageal cancer cell line (KYSE180) were examined for
CAPRIN-1 protein expression on the cell surfaces of each cell line using the culture
supernatants of CHO-K1 cells containing #1 obtained in (2) above. 106 cells of each cell
line were centrifuged in a 1.5 ml microcentrifuge tube. Each cell culture supernatant (100
µl) of CHO-K1 cells containing #1 obtained in (2) above was added and then left to stand on
ice for 1 hour. After washing with PBS, a FITC-labeled goat-anti human IgG (H+L)
antibody (SouthernBiotech) and a FITC-labeled anti-mouse IgG (H+L) antibody (Invitrogen)
diluted 500-fold with PBS containing 0.1% FBS were added and then left to stand on ice for 1
hour. After washing with PBS, fluorescence intensity was measured using a FACS Calibur
(Becton, Dickinson and Company). Meanwhile, procedures similar to the above were
performed using a culture supernatant of CHO-K1 cells into which no antibody gene had been
introduced and medium for culturing hybridomas, so that a negative control sample was
prepared. As a result, cells to which the antibody #1 had been added exhibited fluorescence
intensity stronger by 20% or more than that of the control. Specifically, fluorescence
intensity was enhanced to 4900% in the case of SK-BR-3 and 5000% in the case of
MDA-MB-231V. It was revealed by these results that the CAPRIN-1 protein was expressed
on the cell membrane surfaces of the above human cancer cell lines. The percentage of
enhancement in the above fluorescence intensity was expressed as percentage of increase in
mean fluorescence intensity (MFI level) in each type of cell and calculated by the following
formula.
[0172]
Percentage of increase in mean fluorescence intensity (percentage of enhancement in
fluorescence intensity)(%) = ((MFI level in cells having reacted with anti-human CAPRIN-1
antibody) - (MFI level of the control)) / (MFI level of control) x 100.
[0173]
(4) Anti-tumor effects (ADCC activity) of anti-CAPRIN-1 antibody #1 against cancer cells
Next, the anti-CAPRIN-1 antibody #1 was evaluated for the cytotoxic activity
(ADCC activity) against cancer cells. Each cell culture supernatant producing #1 obtained
in (2) above was purified using Hitrap ProteinA Sepharose FF (GE HealthCare), subjected to
buffer replacement with PBS(-), and then filtered with a 0.22 urn filter (Millipore). The
resultants were used as antibodies for activity measurement. 106 cells of MDA-MB-157
human breast cancer cell line were collected in a 50-ml centrifuge tube, 100 µCi
chromium-51 was added, and then incubation was performed at 37°C for 2 hours.
Subsequently, the resultant was washed three times with RPMI1640 medium containing 10%
FBS. Cells were added to a 96-well V-bottom plate at 5 x 103 cells per well for use as target
cells. The above purified antibodies were added to the cells at a final concentration of 1
jag/ml. 2.5 x 105 cells of lymphocytes separated from human peripheral blood according to a
conventional method were further added and then cultured for 4 hours at 37°C under
conditions of 5% CO2. After culture, the amount of chromium-51 released from damaged
cancer cells in a culture supernatant was measured, and the ADCC activity of each
anti-CAPRIN-1 antibody against cancer cells was calculated. As negative control samples, a
sample prepared by adding PBS instead of the anti-CAPRIN-1 antibodies and a sample
prepared by adding an isotype control antibody instead of anti-CAPRIN-1 antibodies were
used. As a result, the antibody #1 exhibited 30% or more cytotoxic activity against
MDA-MB-157 (see Fig. 2). In contrast, the activity in the sample prepared by adding PBS
as a negative control and the activity in the sample prepared by adding the isotype control
antibody as a negative control were 1.1% and 2.0%, respectively. Similarly, the antibody #1
was examined for the ADCC activity against other cancer cells including glioma cell lines
T98G and U373, lung cancer cell lines A549 and QG56, renal cancer cell lines Caki-1 and
ACHN, a uterine cervix cancer cell line SW756, a bladder cancer cell line T24, an esophageal
cancer cell line KYSE180, gastric cancer cell lines MNK28 and MNK45, a colorectal cancer
cell line SW480, a leukemia cell line AML5, and a lymphoma cell line Ramos. As a result,
the anti-CAPRIN-1 antibody #1 exhibited 16.4% activity against T98G (1.2% in the case of
the isotype control), 23.1% against U373 (3.2% in the case of the isotype control), 36.1%
against A549 (3.0% in the case of the isotype control), 33.5% against QG56 (0.5% in the case
of the isotype control), 28.3% against Caki-1 (2.6% in the case of the isotype control), 25.1%
against ACHN (1.6% in the case of the isotype control), 27.9% against SW756 (2.2% in the
case of the isotype control), 25.8% against T24 (2.0% in the case of the negative control),
26.7% against KYSE180 (3.0% in the case of the isotype control), 21.5% against MNK28
(1.9% in the case of the isotype control), 23.0% against MNK45 (3.0% in the case of the
isotype control), 24.0% against SW480 (1.8% in the case of the isotype control), 8.3% against
AML5 (1.8% in the case of the isotype control), and 8.0% against Ramos (2.2% in the case of
the isotype control). It was demonstrated by the above results that the thus obtained
anti-CAPRIN-1 antibody #1 damages various human cancer cells expressing CAPRIN-1.
[0174]
(5) Anti-tumor effects (CDC activity) of anti-CAPRIN-1 antibody #1 against cancer cell
Next, anti-CAPRIN-1 antibody #1 was evaluated for its cytotoxic activity (CDC
activity) against cancer cells. Blood collected from a rabbit was added to an Eppendorf tube,
left to stand at room temperature for 60 minutes, and then subjected to 5 minutes of
centrifugation at 3000 rpm. Thus, serum for measurement of CDC activity was prepared.
106 cells of human breast cancer cells MDA-MB-231V were collected in a 50-ml centrifuge
tube, 100 µCi chromium-51 was added, and then incubation was performed at 37°C for 2
hours. The resultant was washed three times with RPMI medium containing 10% FBS.
Subsequently, the cells were suspended in RPMI medium containing the above-prepared
rabbit serum (50%), and then added to a 96-well V-bottom plate at 5x103 cells per well. The
antibody #1 obtained in (5) above was added to the cells at a final concentration of 1 µg/ml
and then cells were cultured for 4 hours at 37°C under conditions of 5% CO2. After culture,
the amount of chromium-51 released from damaged tumor cells in a culture supernatant was
measured, and then the CDC activity against MDA-MB-231V was calculated. As a result,
the antibody #1 exhibited 25% or more CDC activity. Therefore, it was revealed that #1 can
damage cancer cells expressing CAPRIN-1 also by CDC activity.
[0175]
Example 5 In vivo anti-tumor effects of anti-CAPRIN-1 antibody #1 in mice
Next, the thus obtained anti-CAPRIN-1 antibody #1 was evaluated for its in vivo
anti-tumor effects in tumor-bearing mice. Antibodies used herein were prepared by column
purification of the culture supernatant of each cell producing #1 in the same manner as
described above.
[0176]
The anti-tumor effects of the antibody #1 was examined using tumor-bearing mice
into which a mouse-derived cancer cell line expressing CAPRIN-1 had been transplanted.
4T1 ceils (purchased from ATCC) were transplanted subcutaneously to the dorsal region of 20
Balb/c mice (Japan SLC Inc.) at 5 x 105 cells/mouse. Cancers were allowed to grow to reach
a size of about 5 mm in diameter. The antibody #1 was administered intraperitoneally to 10
tumor-bearing mice from among the 20 mice in an amount of 200 µg (in 200 µl) for one
mouse. Subsequently, the same amount of the antibody was administered intraperitoneally
to each tumor-bearing mouse 3 times in total within 2 days. Cancer sizes were measured
every day and anti-turnor effects were examined by observation. Meanwhile, as a control
group, PBS (-) was administered instead of the antibodies to the remaining 10 tumor-bearing
mice. As a result of the observation of the anti-tumor effects, in the test group to which the
anti-CAPRIN-1 antibody #1 had been administered, cancers were found to have regressed to
about 55% on day 4, about 32% on day 6, about 7% on day 8, and cancers were found to have
almost completely regressed before days 10 to 14, when the tumor volume at the initiation of
the antibody administration was designated 100% (see Fig. 3). In the control group to which
PBS(-) had been administered, the tumor size was increased to about 170%, 270%, 440%, and
670% on days 4, 6, 8, and 11, respectively (see Fig. 3). It was demonstrated by the results
that the obtained antibody #1 exhibits strong anti-tumor effects in vivo against cancer cells
expressing CAPRIN-1. The tumor (cancer) size was calculated as a volume using the
formula: length of major axis x length of minor axis x length of minor axis x 0.5.
Industrial Applicability
[0177]
The antibodies of the present invention are useful for treating and/or preventing a
cancer.
[0178]
All publications, patents, and patent applications cited herein are incorporated
herein by reference in their entirety.
Sequence Listing Free Text
[0179]
SEQ ID NOS: 31-38, 47, and 48: primers
We Claim:
1. A pharmaceutical composition for treating and/or preventing a cancer, comprising an
antibody or a fragment thereof as an active ingredient that has immunological reactivity with
a CAPRIN-1 protein, wherein the antibody comprises a heavy chain variable region
comprising SEQ ID NOS: 39, 40, and 41 and a light chain variable region comprising SEQ ID
NOS: 43, 44, and 45 or a fragment thereof.
2. The pharmaceutical composition according to claim 1, wherein the cancer is breast cancer,
brain tumor, leukemia, lymphoma, lung cancer, mastocytoma, renal cancer, uterine cervix
cancer, esophageal cancer, gastric cancer, bladder cancer, or colorectal cancer.
3. The pharmaceutical composition according to claim 1 or 2, wherein the antibody is a
human antibody, humanized antibody, chimeric antibody, single chain antibody, or bispecific
antibody.
4. An antibody, which comprises a heavy chain variable region comprising SEQ ID NOS: 39,
40, and 41 and a light chain variable region comprising SEQ ID NOS: 43, 44, and 45, and has
immunological reactivity with a CAPRIN-1 protein.
5. The antibody according to claim 4, which is a human antibody, humanized antibody,
chimeric antibody, single chain antibody, or bispecific antibody.
6. A pharmaceutical combination for treating and/or preventing a cancer, comprising the
pharmaceutical composition of any one of claims 1 to 3 and a pharmaceutical composition
containing an antitumor agent.
7. A method for treating and/or preventing a cancer, comprising administering to a subject the
pharmaceutical composition of any one of claims 1 to 3, or the antibody of any one of claims
3 to 5 or a fragment thereof.
8. A method for treating and/or preventing a cancer, comprising using pharmaceutical
compositions of the pharmaceutical combination of claim 6 in combination in a subject.