Inhibition of survivin reduces cell proliferation and induces apoptosis in human endometrial cancer

BACKGROUND. Endometrial cancer is a common gynecologic malignancy among women. The molecular mechanisms involved in the progression of endometrial cancer are unclear, which has hampered the development of an effective treatment. Survivin, a newly identified member of the inhibitor of apoptosis (LAP) family, regulates 2 critical processes in neoplastic transformation: cell proliferation and apoptosis. METHODS. Survivin mRNA and protein expression levels were analyzed in human normal cycling endometrium, atypical endometrium, and endometrial adenocarcinoma by immunohistochemical, reverse-transcriptase polymerase chain reaction (RT-PCR), and Western blot analyses. To study the biological function of survivin in endometrial cancer, RNA interference was applied to knock down survivin expression in the Ishikawa endometrial cancer cell line by recombinant plasmids producing survivin small hairpin RNA. Furthermore, the signal pathway that regulates survivin expression was investigated. RESULTS. Higher levels of survivin mRNA and protein expression were observed in endometrial adenocarcinomas than in atypical or normal endometrium. Immunohistochemical staining revealed that 83.3% (50 of 60) of endometrial adenocarcinoma samples, 55.0% (11 of 20) of atypical endometrium samples, and 25.0% (5 of 20) of normal endometrium samples were positive for survivin protein. Inhibition of survivin by RNA interference reduced cell proliferation and induced apoptosis in Ishikawa cells by down-regulating cyclin D1 and phosphorylated RB and activating caspase-3 and caspase-8. The authors also found that the MAPK pathway was a signal transduction pathway upstream of survivin. Epidermal growth factor (EGF) and transforming growth factor-alpha (TGF-alpha) upregulated survivin protein expression by activating the MAPK pathway in endometrial cancer cells. CONCLUSIONS. Survivin is an attractive target for endometrial cancer treatment. Growth factors could regulate survivin expression by activating the MAPK pathway.