Mammalian ras genes encode a family of plasma membrane-bound proteins that function as intermediates in signal transduction pathways involved in cell growth and differentiation. Ras oncogene is frequently involved in neoplastic transformation of different cellular histotypes. In this study, we tested the ability of antisense oligodeoxyribonucleotides (AS-ODN) that have mixed phosphodiester/phosphorothioate backbone, targeted against human N-Ras, to inhibit N-ras gene expression and to specifically interfere with the Ras-dependent activity of mitogen-activated protein kinase (MAPK) in two human cell lines carrying an endogenous N-ras mutated allele at codon 61. Three AS-ODN that inhibit basal MAPK activity have been identified. Moreover, AS-ODN treatment resulted in potent antiproliferative effects in cell culture and great inhibition of N-ras mRNA levels in one of two cell lines. These studies suggest that antisense molecules, targeted against N-Ras, could be of considerable value as a tool to study the N-Ras-specific transduction pathway
