Bifunctional roles of survivin-ΔEx3 and survivin-2B for susceptibility to apoptosis in endometrial carcinomas.

Abstract

Alternative splicing variants of survivin have different biological roles on cell kinetics. Here, we focused on the effects of different variants, including wild type (wt), survivin-ΔEx3, and survivin-2B, on apoptosis and cell proliferation in endometrial carcinomas (Em Cas). Expression of survivin-wt, survivin-ΔEx3, and survivin-2B with reference to cell death and proliferation was investigated, using Em Ca cell lines and its clinical tissues. Ishikawa cells stably overexpressing either survivin-ΔEx3 (Surv-ΔEx3#34) or survivin-2B (Surv-2B#17) demonstrated considerably lower proliferative activity, along with up-regulation of p21waf1. After TNF-α treatment, Surv-ΔEx3#34 cells showed an increase in apoptotic cells, while the effects were relatively minor in Surv-2B#17 cells. In contrast, doxorubicin treatment resulted in increased apoptotic cells in Surv-2B#17 but not Surv-ΔEx3#34 cells, along with decreased expression of bcl-2 relative to bax. Control Ishikawa cells also showed relatively higher endogenous mRNA expression of survivin-ΔEx3 and survivin-2B during treatment of TNF-α and doxorubicin, respectively. In addition, exogenous overexpression of each survivin variant resulted in inhibition of other endogenous isoforms, indicating that the relative proportion may contribute to regulation of the splicing machinery. In clinical samples, level of survivin-ΔEx3 relative to either survivin-wt or survivin-2B was significantly higher in Em Cas than non-neoplastic lesions. Moreover, survivin-ΔEx3 and survivin-wt were positively correlated with apoptosis and cell proliferation, respectively, in Em Cas. These findings provided evidence that the balance among expression level of survivin variants may contribute to modulation of cell kinetics in Em Ca cells.