IER5 promotes irradiation- and cisplatin-induced apoptosis in human hepatocellular carcinoma cells.

Purpose: To elucidate the mechanisms of the immediate-early response gene 5 (IER5) effect on the apoptosis induced by irradiation and cisplatin (CDDP) in human hepatocellular carcinoma (HepG2) cells. Methods: We generated IER5 overexpression stable cells (HepG2/IER5) using Lipofectamine 2000 transfection HepG2 cells. Cell apoptosis was induced by irradiation and cisplatin treatments, and cell proliferation (viability) and apoptosis were evaluated by MTT and flow cytometry assays. Protein expression was determined by Western blot. Results: The growth of the IER5 overexpression cells was significantly inhibited after six days of 60Co γ-irradiation exposure (p<0.01) compared with the cell growth of vector control cells. Furthermore, the HepG2/IER5 cells were arrested at the G2/M phases. We also found that the expression of phospho-Akt was reduced, and the levels of cleaved caspase-3 and PARP were increased after the treatment of HepG2/IER5 cells with γ-irradiation and cisplatin. Conclusion: Our results suggest that the overexpression of IER5 can inhibit cell growth and enhance the cell apoptosis induced by exposure to radiation or cisplatin. The overexpression of IER5 can be utilized as a targeting strategy to improve the outcomes of radiotherapy used for the treatment of patients with liver cancer.