Fos expression and growth regulation in bovine corneal endothelial cells.

The authors evaluated the effects of stimulation (by serum, wounding, and three peptide growth factors: fibroblast growth factor [FGF], insulin, and transforming growth factor-beta [TGF-beta 1]) on the expression of the protein product of the immediate early gene, c-fos in bovine corneal endothelial (BCE) cells. These results were compared with those of cells which were made quiescent by serum starvation. They also examined the effect of these same growth factors or wounding on DNA synthesis. Quiescent cells expressed low levels of c-fos protein. Serum was the most potent stimulator, whereas FGF and insulin were modest stimulators. TGF-beta 1 did not significantly stimulate c-fos protein production. The results from DNA synthesis were different. Serum and FGF were still the most potent stimulators; insulin and TGF-beta 1 were weak stimulators. These data suggest that growth factors induce c-fos protein in BCE cells and that this may in part regulate the downstream event, cellular proliferation. Further investigation into the regulation of this and other protooncogene products may provide insight into the mechanisms which modulate corneal endothelial cell growth in humans.