title: The calcium signal for BALB/MK keratinocyte terminal differentiation counteracts epidermal growth factor (EGF) very early in the EGF-induced proliferative pathway.
abstract: BALB/MK mouse epidermal keratinocytes require epidermal growth factor (EGF) for proliferation and terminally differentiate in response to high calcium concentrations. We show that EGF is an extremely potent mitogen, causing BALB/MK cultures to enter the cell cycle in a synchronous manner associated with a greater than 100-fold increase in DNA synthesis. Analysis of the expression of proto-oncogenes which have been reported to be activated during the cascade of events following growth factor stimulation of fibroblasts or lymphoid cells revealed a very rapid but transient 100-fold increase in c-fos RNA but little or no effect on the other proto-oncogenes analyzed. Exposure of EGF-synchronized BALB/MK cells to high levels of calcium was associated with a striking decrease in the early burst of c-fos RNA as well as the subsequent peak of cell DNA synthesis. Since the inhibitory effect of high calcium on c-fos RNA expression was measurable within 30 min, our studies imply that the EGF proliferative and calcium differentiation signals must interact very early in the pathway of EGF-induced proliferation. Our results also establish that c-fos RNA modulation is an important early marker of cell proliferation in epithelial as well as mesenchymal cells.
mesh_terms: D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D002453:Cell Cycle / Q000187:drug effects; D002454:Cell Differentiation / Q000187:drug effects; D002478:Cells, Cultured; D004261:DNA Replication / Q000187:drug effects; D000078404:Epidermal Cells; D004815:Epidermal Growth Factor / Q000494:pharmacology*; D007633:Keratins / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D011519:Proto-Oncogenes / Q000187:drug effects*; D012333:RNA, Messenger / Q000235:genetics; D014158:Transcription, Genetic / Q000187:drug effects
chemical_list: D012333:RNA, Messenger; D004815:Epidermal Growth Factor; D007633:Keratins; D002118:Calcium