Expression of Cell Cycle Regulatory and Apoptosis-related Proteins in Etoposide-treated Human Skin Fibroblast

Abstract

Purpose: This study was designed to investigate effect of the etoposide on expression of cell cycle regulatory proteins and apoptosis-related proteins in human skin fibroblast (HSF). Materials and Methods: HSF cells were treated with etoposide. After treatment, expression patterns of cell cycle regulatory proteins and apoptosis-related proteins were analyzed by using Immunoprecipitation-Western blot method and RT-PCR. Results: Immediately after etoposide treatment, E2F-1 was up- regulated following MDM2 down-regulation. After E2F-1 up-regulation, p53 and p21WAF1 level was markedly increased without or with mRNA up-regulation, respectively. Consistent with these results, cell cycles arrested in mainly G1 phase 24 hr after etoposide treatment. However, HSF cells progressed into apoptosis 72 hr after etoposide treatment. In this process, caspase-3 activation and Bax up-regulation were observed. Conclusion: In early response of etoposide treatment, E2F-1 plays an important role in p53 accumulation through MDM2 down- regulation. The increased p53 induce an increase of p21WAF1 level through p21WAF1 mRNA up-regulation. However, after long term treatment of etoposide, HSF cells resulted in apoptotic cell death through caspase-3 activation and Bax up-regulation.