Differentiation of F9 cells is independent of c-myc expression

The level of c-myc expression rapidly decreases during in vitro induced differentiation of mouse F9 embryonic teratocarcinoma to endoderm cells, raising the question of whether down regulation of c-myc expression is a part of the mechanism regulating differentiation. We have investigated the effect of enforced increases or decreases in c-myc RNA expression in F9 cells on growth and differentiation. The enforced expression of c-myc RNA in clones transfected with sense c-myc did not inhibit their terminal differentiation. Dramatically decreased c-myc RNA expression in antisense c-myc transfected clones also did not substantially alter the differentiation pathway, although the transformed cells withdraw from the cell cycle slightly earlier than control cells during the differentiation induction. These results suggest that the mechanism controlling differentiation operates independently of the level of c-myc RNA expression in F9 teratocarcinoma cells.