U.S. Pat. No. 5,650,291 ('291) incorporated herein by reference describes the isolation of a tumor-associated antigen, CA215, which is present on an ovarian tumor cell line, and is also displayed on many tumors in humans. Monoclonal antibodies were prepared to this antigen, including the monoclonal antibody RP215. The hybridoma cell line that produces this antibody was deposited at the American Type Culture Collection under the terms of the Budapest Treaty on 5 Apr. 1989 as ATCC HB10095. The current address of ATCC is P.O. Box 1549, Manassas, Va. 20108. The '291 patent describes CA215 as having a minimum molecular weight of 60 kD on SDS gels when identified with RP215. However, aggregates with molecular weights ranging from 100 kD to 2,000 kD were also shown to be present. CA215 was purified by immunoaffinity chromatographic procedures and could be purified either from an extract of cultured ovarian tumor cells (OC-3-VGH) or from the shed culture medium of these cells. The CA215 antigen is characterized as a “membrane associated” soluble antigen which can be detected by RP215 in sera of patients with ovarian or cervical cancer. The antigen could not be detected in any normal tissue. This antigen and the monoclonal antibody that recognizes it were also described in an article by Lee, C. Y. G., et al., Cancer Immunol. Immunother. (1992) 35:19-26. CA215 was denominated Cox-1 in that article
In a later paper, authored by the same group, Lee, G., et al., J. Clin. Ligand Assay (2006) 29:47-51, it was reported that treatment with periodate at neutral pH virtually eliminated the immunoreactivity of CA215 in a sandwich assay employing RP215. This led the authors to the conclusion that the epitope of CA215 reactive with RP215 may comprise carbohydrate.
It appears that the epitope of CA215 recognized by RP215 is present on approximately 60% of all cancers. Further information on its distribution is found in Lee, G., et al., J. Clin. Ligand Assay (2006) supra.
The '291 patent further describes a method to determine the location of tumors bearing the antigen CA215 by utilizing the antibodies immunoreactive against it to label cells that produce this antigen. Labeling the monoclonal antibodies with various radioisotopes was described as well as conjugating toxins to these antibodies and administration of the antibodies or immunotoxins for therapeutic use.
The present invention further refines the work described in these publications by demonstrating that the carbohydrate portion of the epitope is located at the variable region of immunoglobulin heavy chain-like molecules, thus making possible compositions which comprise only the relevant portions of CA215 for inclusion in vaccines or for generating and purifying antibodies useful in imaging of targeted cancer cells. This work also demonstrates that there are two forms of CA215—one membrane-bound and another that is secreted.