Cyclic-AMP-induced c- fos expression and its relevance to differentiation of a transformed mast cell line

Abstract

The effects of cyclic AMP on expression of the oncogenes c- myc, c- myb and c- fos in murine P815 mastocytoma cells were examined in relation to growth and differentiation. Induction of differentiation in mastocytoma cells by cyclic AMP was accompanied by a rapid increase in c- fos expression. Cyclic AMP induced stable expression of c- fos mRNA by increasing c- fos transcription 4–5-fold and slightly increasing the stability of c- fos mRNA. However, a high level of c- fos expression was not essential for differentiation of two temperature sensitive-mutant P815 cell lines, as c- fos mRNA did not increase in differentiating temperature-sensitive P815 cells. These results do not support an essential role for c- fos expression in the differentiation of mast cells. Although c- myc expression was lower after growth arrest by cyclic AMP, this decrease did not correlate with growth inhibition by cyclic AMP, since c- myc expression decreased only after cells had started to arrest in G1 phase.