| The Effects of Epidermal Growth Factor on c-Fos mRNA Proto-Oncogene Expression in The Human Endometrial Cancer Cell Line , HEC-1-A. |
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J Y Park, Y K Park, J S Kang |
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| Abstract |
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Growth factors stimulate cell proliferation and differentiation through binding to specific high affinity receptors. Signalling pathway that mediate the normal functions of growth factors are commonly subverted in cancers. Proto-oncogenes are normal cellular genes whose alteration by mutation or deregulation has been implicated in the process of tumorigenesis and they play a role for control of normal cellular growth and differentiation. Epidermal growth factor is mitogenic in moderately differentiated endometrial adenocarcinoma cell line, HEC-1-A. These studies were performed to determine the effects of EGF on c-fos mRNA proto-oncogene expression, and whether EGF need new protein synthesis, and whether PKC pathway plays a role in the induction of c-fos mRNA expression in EGF treated cells. HEC-1-A cells were grown to confluency and maintained in a serum free media (0.3% BSA) 24 hours prior to treatment. The cells were treated with EGF (0, 0.01, 0.1, 1.0, 10, 100 ng/ml) and PMA (0, 0.001, 0.01, 0.1, 1, 10, 100 1000 nM) at varying times (0, 0.12, 0.25, 0.5, 1, 3, 6, 12, 24 h) and the expression of c-fos mRNA expression examined by northern blot analysis. The expession of c-fos mRNA induced by EGF and PMA was dose dependent and peak induction occurred at 1 hour, and decreased steadily after 1 hour. To determine whether PKC may mediate EGF effects on c-fos mRNA expression, the cells were preincubated without or with PMA (1000 nM) for 48 hours for down regulation of PKC, followed by EGF (100 ng/ml). Following 48 hours preincubation with PMA (1000 nM), EGF increased c-fos mRNA expression, while PMA failed to induce its expression, suggesting that EGF induces c-fos mRNA expression independent of PKC activation. To determine whether EGF need new protein synthesis in the induction of c-fos mRNA, the cells were preincubated with anisomycin, a stringent protein synthesis inhibitor, for 30 minutes followed by EGF(100 ng/ml). Anisomycin induced c-fos mRNA and augmented EGF effects on c-fos mRNA expression. These results suggest that EGF may induce c-fos mRNA expression through PKC independent pathway and the induction does not require new protein synthesis. |
| Key Words:
c-fos, EGF, Protein kinase-C, Endometrial carcinoma |
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