Cancerous cells display overexpression or mutant expression of one or more of the genes normally used in cell proliferation. Such genes are called protoncogenes (1 ). The imphcation is that the targets that must be attacked in neoplastic cells are normal cellular genes that have sustained some activating lesion. Therasfamily of mammalian proto-oncogenes includes three members, termed Ha-ras, Ki-ras, and N-ras, that are found to be activated very often in human solid tumors and leukemias (2 ).
