Overexpression of truncated AIF regulated by Egr1 promoter radiation-induced apoptosis on MCF-7 cells.

It has been demonstrated that gene-radiotherapy can improve the radiotherapy by selectively increasing cells' response to ionizing radiation. Apoptosis-inducing factor (AIF) is a mitochondrial flavoprotein, and its C-terminal domain is responsible for the proapoptotic activity. In the present study, we overexpressed truncated AIF on MCF-7 cells by transfection of pcDNA3.1-tAIF (pc-tAIF) and pcDNA3.1-Egr1-tAIF (pc-Egr1-tAIF) plasmids. After MCF-7-tAIF cells were exposed to X-rays, the AIF and tAIF expressions, cell proliferation, apoptosis, cell cycle invasion, cytochrome c (Cyt c) release and activation of caspase-9 were measured by using Western blot, MTT assay, flow cytometry and Matrigel transwell assay, respectively. Our results showed that tAIF expression increased on time- and dose-dependent manners. Both tAIF and radiation can synergistically enhance the apoptosis, cell proliferation inhibition, cell cycle arrest and cell-invasive inhibition. In addition, tAIF overexpression and irradiation increased Cyt c release. However, only irradiation increased caspase-9 activation. Our studies indicated that tAIF overexpression might enhance apoptosis induced by radiation in MCF-7 cells.