ABSTRACT
Most cancer chemotherapeutic drugs currently in use are cytotoxic agents of limited selectivity against tumor cells. Many of these drugs are alkylating agents which damage DNA or antimetabolites which block essential processes, particularly in nucleic acid metabolism. Theories of cancer etiology suggest that malignancy may result from a failure of cells to differentiate appropriately or a reduced requirement for exogenous growth factors. The ablation of a hormone-secreting organ as a treatment of a hormone-dependent tumor, such as mammary carcinoma, is a well-established and effective procedure. Oophorectomy, for example, produces objective regression in about a third of breast cancer patients. Antagonists, which can bind to cell surface receptors without producing the effects of an agonist, are among the most useful classes of drugs and it is not surprising that there have been attempts to develop antagonists to the growth factors.
