Differential EGF action on nuclear protooncogenes in human endometrial carcinoma RL95-2 cells.

Our aim was to analyze EGF action on nuclear protooncogenes in RL95-2 since it has not been documented so far. Synchronization and partial' growth arrest were obtained by maintaining cells for 15 hours in L-methionine-free medium. After this depletion, EGF transiently increased fos and jun mRNAs: the expression peaked at 45 minutes for c-fos (5.5 fold induction) and at 60 minutes for c-jun and jun-B (3 fold induction) and the mRNA levels returned to the basal value within 3 hours. Upon EGF addition, c-myc mRNAs peaked at 12 hours (7.6 fold induction) and surprisingly remained higher than the control up to 48 hours. Unlike fetal calf serum, EGF did not increase the cell number and this could be linked to steadily induced c-myc expression. These data provide evidence for a differential EGF action on fos/jun and c-myc in RL95-2 cells.