Metformin Has An Anticancer Effect By Repressing Twist/N-Cadherin Signaling

Introduction and Objective. Metformin, one of the most commonly used medications for treatment of type 2 diabetes, has emerged as a potential anticancer agent. The molecular mechanisms associated with the anti-cancer effect of metformin are poorly understood. We demonstrate, for the first time, that metformin inhibits prostate cancer proliferation through suppression of TWIST/N-cadherin signaling pathway. Methods. RT–PCR, Western blot, immunofluorescence assays and confocal microscopy were applied to evaluate protein expression level. MTS assay and FACS analysis were applied to determine cellular proliferation. N-cadherin and TWIST-1 expression vectors were transfected into PC3 prostate cancer cells to establish stable cells with over-expression of N-cadherin and TWIST-1, respectively. Metformin-resistant prostate cancer cells were established by exposure to higher concentrations (10mM) of metformin over 4 weeks. Results. Treatment with metformin (5mM) inhibited proliferation in three different types of cancer cells (PC3-prostate cancer cells; T24-bladder cancer cells and 786-O- kidney cancer cells). Metformin treatment suppressed expression of N-cadherin in all cell types. Similar findings were observed by confocal microscopy. In contrast to N-cadherin, expression of E-cadherin was not affected by metformin. Metformin-mediated repression of N-cadherin was dose and time- dependent in prostate cancer cells. PC3 prostate cancer cells with stable over-expression of N-cadherin became resistant to metformin-mediated inhibition. Stable PC3 prostate cancer cells, after selection for metformin, became resistant to metformin-mediated inhibition, and the metformin-resistant cancer cells had slightly higher baseline level of N-cadherin. In addition, in the metformin-resistant cells, N-cadherin levels were unchanged after treatment with metformin. The expression of AKT and AP-1, the downstream molecules of N-cadherin, closely correlated with expression of N-cadherin after treatment with metformin. Moreover, we also found that metformin inhibited expression of TWIST-1, a transcriptional activator of N-cadherin. Similar findings were observed by confocal microscopy. PC3 prostate cancer cells with stable over-expression of TWIST-1 became resistant to metformin-mediated inhibition. Conclusions. We demonstrate that Metformin9s anti-cancer therapeutic effect may be mediated through repression of the TWIST/N-cadherin signaling pathway. Citation Format: Ge Rongbin, Zongwei Wang, Aria F. Olumi. Metformin has an anticancer effect by repressing TWIST/N-cadherin signaling. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4965. doi:10.1158/1538-7445.AM2013-4965 Note: This abstract was not presented at the AACR Annual Meeting 2013 because the presenter was unable to attend.