Oncogene expression in differentiating F9 mouse embryonal carcinoma cells.

Differentiation of F9 mouse embryonal carcinoma cells in culture is accompanied by a decrease in growth rate and loss of tumorigenicity. Cells differentiating in monolayer culture (to parietal endoderm-type cells) or in aggregates (to visceral endoderm-type cells) show qualitatively similar changes in transcript levels from several c-oncogenes. In contrast with other studies with F9 cells, we find an early decrease in c-myb RNA but not in c-myc RNA. This and a later increase in c-src RNA may be associated with decreasing cell growth rate. Before differentiation, induction and maintenance of elevated c-abl RNA levels depend on the presence of retinoic acid in the medium. After differentiation c-abl RNA levels decline only partially when retinoic acid is removed. Increased RNA from c-fos is seen late in differentiation in monolayer cultures only, a change also seen with appearance of similar endoderm cell types in the developing mouse embryo.