Effect of tumor promoters on sarc gene expression in normal and transformed chick embryo fibroblasts.

The effects of 12-O-tetradecanoylphorbol-13-acetate (TPA) on the sarc protein kinase of normal chick embryo fibroblasts (CEF) and of the src kinase of cells transformed by a temperature-sensitive mutant of avian sarcoma virus (CEF-tsASV) were studied and compared with the known effects of TPA on cell morphology and plasminogen activator (PA) activity. One hr after the addition of TPA to normal CEF, there was a 3- to 8-fold stimulation of kinase activity when compared to control cultures; during the subsequent 24 hr, TPA produced less than a 2-fold stimulation. Although TPA induced levels of PA in CEF which were equivalent to those produced by cEF-tsASV grown at 36 degrees, the latter cells contained much higher levels of kinase activity than those of CEF plus TPA. In addition, TPA failed to enhance the kinase activity of CEF-tsASV at either 36 degrees or 40 degrees, even though at both temperatures TPA induced morphological changes and markedly enhanced PA activity. These results suggest that the effects of TPA on morphology and PA are not due to an effect on these protein kinases.