Monoclonal Antibodies Generated to a Synthetic Peptide Define Ras Gene Expression at the Single Cell Level in Human Colon and Mammary Carcinomas

Ras oncogenes were first recognized as the transforming genes of two rat-derived viruses, the Harvey (Ha) and Kirsten (Ki) strains of murine sarcoma virus (MuSV) (1). Molecular cloning studies have identified Ha-ras, Ki-ras, and subsequently, N-ras, as members of a gene family present in a wide range of species including humans (2). At least two mechanisms have been identified by which ras activation can mediate transformation of NIH 3T3 cells: (a) a point mutation in the ras gene resulting in an alteration of a single amino acid in the 21,000 dalton (p21) ras gene product (3), or (b) increased expression of the normal cellular p21 ras gene product (1,4,5).