Analysis of the mechanism of estrogen-dependent proliferation of endometrial carcinoma cells via IGF-1/MAPK

点击翻译按钮获取中文摘要

To examine estrogen-induced growth mechanisms of endometrial carcinoma, we investigated the estrogen-induced activation of the mitogen-activated protein kinase (MAPK) pathway and cell cycle regulators. Estradiol (E2) treatment at concentrations of 10^8M and 10^6M to estrogen receptor (ER)-positive endometrial carcinoma Ishikawa cells for 24 hours resulted in increased cell proliferation by 20% and 28%, respectively. The E2-induced proliferation was associated with activation of extracellular signal-regulated kinase (ERK)1/2 and up-regulation of cyclin Dl and E, which were suppressed by the addition of a MEK inhibitor (U0126) or an ER antagonist (ICI182,780). Then, our screening for estrogen-inducible growth factors identified that insulin-like growth factor (IGF)-1 was up-regulated remarkably by E2. Immunoprecipitation using conditioned medium of Ishikawa cells after E2 treatment confirmed the E2-induced secretion of IGF-1 protein. Treatment with recombinant IGF-1 stimulated cell proliferation in a dose-dependent fashion, in association with ERK1/2 phosphorylation and up-regulation of cyclin D1 and E. These IGF-1-induced responses were suppressed by treatment with ER antagonist, MEK inhibitor, or anti-IGF-1 receptor antibody. Immunohistochemical staining confirmed the expression of activated ERK1/2 in normal proliferative phase endometria and endometrial carcinomas, indicating the involvement of this pathway in actively proliferating endometrial tissues in vivo. These findings suggest that E2-induced proliferation of endometrial carcinoma cells is mediated by the ERK1/2 pathway via autocrine stimulation of IGF- 1.