Background Hyperinsulinemia, insulin-like growth factor （IGF）-I and -Ⅱ （IGF-Ⅱ） are associated with increased risk of endometrial carcinoma. Insulin receptor isoform A （IR-A） is more frequently expressed in endombtrial carcinoma than in normal endometrial tissues. To better understand their roles in endometrial carcinoma, we investigated the effects of insulin, IGF-I, and IGF-II in endometrial carcinomas cells with different IR-A expression levels. Methods To explore the role of IR-A in mediating the activity of IGF-I, IGF-II, and insulin, we investigate the cellular proliferation of endometrial carcinoma cell lines RL95-2 and RL95-2-1R-A by MTS assays. Then we examined the protein kinase Akt phosphorylation and extracellular signal-regulated kinase （ERK） 1/2 phosphorylation in both cell lines by Western blotting. The effect of IGF-II and AG1024 on cell cycle progression and apoptosis was assessed by fiowcytometry. To examine whether the effects of IGFs were mediated by IR-A, we blocked IGF-I receptor （IGF-IR） in both cell lines using AG1024, an IGF-IR-specific inhibitor. Results IGF-I and IGF-II significantly enhanced proliferation of both cell lines （P 〈0.05）. By contrast, insulin significantly increased proliferation of RL95-2-1R-A cells only （P 〈0.05）. IGF-I and IGF-II significantly increased pAkt levels in RL95-2 cells and pERK1/2 levels in RL95-2-1R-A cells （all, P 〈0.05）. Insulin increased pERK1/2 levels in RL95-2-1R-A cells only （P 〈0.05）. LY294002 and PD98059 inhibited the specific signaling activities and cellular proliferation. After AG1024 pretreatment, neither IGF-I nor IGF-II affected pAkt levels in RL95-2 cells. IGF-II, but not IGF-I, increased pERK1/2 levels in RL95-2-1R-A cells. After AG1024 pretreatment, the proliferation rate and DNA content corresponding to the S phase increased and apoptosis decreased significantly in IGF-II-treated RL95-2-1R-A cells only （P 〈0.05）. Conclusions The proliferation effect of insulin is mediated by IR-A. When I
WANG Chun-fang ZHANG Guo ZHAO Li-jun LI Xiao-ping QI Wen-juan WANG Jian-liu WEI Li-hui
