Interferon-induced modulation of human ras oncogene expression.

Abstract

Treatment of NIH 3T3 cells with interferon (IFN) after transfection with human bladder carcinoma EJ/T24 c-Ha-ras1 oncogene DNA caused inhibition of ras-induced cell transformation. Furthermore, the effect of IFN on oncogene expression in an established tumor line was studied. A tumor line of NIH 3T3 (RS485) was transformed by human c-Ha-ras1 activated by a viral long terminal repeat. Treatment of the tumor cells with IFN was associated with a progressive appearance of reverted, flat colonies which exhibited a normal phenotype with respect to morphology and growth. The revertants were well spread, contact inhibited cells; they did not grow in soft agar and were not tumorigenic in nude mice. Revertants retained their normal phenotype, although they contained transfecting human c-Ha-ras1 DNA; but, they produced significantly decreased levels of the onc-encoded protein p21 and c-Ha-ras1 mRNA as compared to RS485 cells.