1.  Field of the Invention
The present invention is directed to methods of killing cancer cells, particularly cancer cells that express C35.  In one aspect, the method comprises administering at least one anti-C35 antibody and at least one anti-HER2 antibody.  In another aspect, the method comprises administering at least one anti-C35 antibody and at least one anti-EGFR antibody.  In some embodiments, a therapeutic agent is also administered in conjunction with the antibodies.  In another aspect, the invention is directed to methods of designing a treatment for C35-positive cancers comprising testing for the expression of receptor molecules such as HER2, EGFR, and IGFR. 
2.  Background Art
Cell growth is a carefully regulated process which responds to specific needs of the body.  Occasionally, the intricate and highly regulated controls dictating the rules for cellular division break down.  When this occurs, the cell begins to grow and divide independently of its homeostatic regulation resulting in a condition commonly referred to as cancer.  In fact, cancer is the second leading cause of death among Americans aged 25-44. 
Current therapies for cancer include chemotherapy and radiation therapy.  Chemotherapeutic drugs kill cancer cells mainly by inducing apoptosis (Fisher, D. E., Cell 78:539-542 (1994); Fung, C. Y., and D. E. Fisher, J. Clin.  Oncol.  13:801-807 (1995); Lowe, S. W., et al.,  Cell 74:957-967 (1993)).  Radiation therapy kills cancer cells by inducing apoptosis and by other mechanisms.  However, chemotherapy and radiation therapy do not kill all cells in a given tumor, and cells that survive such treatment continue to grow.  Thus, these treatments are often insufficient for eradicating an entire tumor.  There is therefore a need for improved therapeutic methods of treating cancer. 
Immunotherapeutic strategies for cancer have also been developed that target surface membrane markers differentially expressed in tumor cells using antibodies (e.g., U.S. Pat.  No.  5,770,195, “Monoclonal Antibodies to the HER2 Receptor”, Filed: May 23, 1995; Issued, Jun. 23, 1998).  Many antigens differentially expressed in tumors are, however, not exposed on the surface of tumor cells.  As a result, such intracellular antigens are not suitable as targets for antibody-based therapeutics.