The effect of metformin on cell proliferation in patients with endometrial cancer.

Abstract

e15577 Background: Metformin, a widely used anti-diabetic drug, is thought to suppress oncogenesis and/or improve prognosis in a variety of malignancies. Diabetes-related metabolic disorders, obesity and insulin resistance are risk factors for endometrial cancer, and together form a potential target for metformin therapy. Thus, we assumed that metformin might have some impact on the prevention and treatment of endometrial cancer. We examined the influence of metformin on cell proliferation of human endometrial cancer cells in vitro and in vivo. Methods: The Ishikawa and HEC-IB endometrial cancer-cell lines were treated with metformin and cell-cycle progression was assessed by flow cytometry. Activation of the MAPK, AMPK and mTOR signalling pathways as well as cell-cycle proteins was evaluated by Western blotting. Changes in signalling pathways were also assessed in endometrial tissues obtained from 15 patients with stage I endometrial cancer who received metformin (1,500-2,250mg/day) for 21-28 days. Results: Metformin inhibited the growth of Ishikawa and HEC-IB cells in a dose- and time-dependent fashion. The cell cycle was arrested at G0/G1 phase, with decreased cyclin D1 and phospho-pRB levels and increased p27Kip1 levels. Addition of metformin induced phosphorylation of AMPKa and de-phosphorylation of S6K1 and ERK1/2. siRNA-mediated knockdown of AMPKα failed to completely prevent the anti-proliferative activity of metformin, suggesting that metformin has AMPK independent effect on cell cycle. Metformin activity was also determined in patient-derived endometrial tissues. In western blotting, pre-operative metformin therapy showed same effect on cell line. Metformin effect of reducing the S6K1 phosphorylation and ERK1/2 phosphorylation were also identified in immunohistochemistry. Conclusions: The anti-neoplastic activity of metformin was demonstrated by in vitro and in vivo experiments. This effect is thought mTOR inhibition via AMPK and cell cycle regulation via AMPK independent pathway. This work gives the possibility for clinical application of endometrial cancer treatment using metformin.