Abstract 1313: Anti-tumorigenic effects of phenformin in human endometrial cancer cells

Abstract

Abstract Introduction: The anti-diabetic drugs, metformin and phenformin, are thought to have anti-tumorigenic benefits. Preclinical studies suggest that phenformin may be more potent for inhibiting tumor growth than metformin. Our objective was to assess the anti-tumorigenic effects of phenformin in endometrial cancer (EC) cell lines and primary cultures. Methods: The EC cell lines, ECC-1 and Ishikawa, were treated with phenformin under low glucose (2 mM), normal glucose (5.5 mM) and high glucose (25 mM) conditions. EC tumors were collected from consenting patients, at the time of surgical staging for primary culture. Cell proliferation was assessed by MTT assay. Apoptosis was analyzed by Annexin V-FITC assay. Cellometer evaluated cell cycle progression. Invasion was demonstrated by transwell invasion assay. Adhesion was assessed by ELISA. Western blotting was performed to determine expression of the downstream targets of phenformin. Results: Phenformin inhibited proliferation in a dose-dependent manner in both EC cell lines, within 48-72 hrs of exposure (IC50=1 mM, p=0.0004-0.009). Inhibition of proliferation was seen for all glucose concentrations, but greater potency was observed under low glucose conditions. Treatment with phenformin resulted in G1 arrest, induction of apoptosis (p=0.022-0.017) and inhibition of adhesion (p=0.0053-0.0144) and invasion (p=0.0063-0.05). Phenformin increased p21 and p27 and decreased cyclin D, cyclin E2, CDK4 and CDK 6, corresponding with G1 arrest. Phenformin significantly inhibited proliferation in 62% (8/13) of the EC primary cultures, within 48-72 hrs of exposure (IC50 0.1-5mM, p=0.00001-0.016). 3 additional EC samples (23%) were significantly inhibited by phenformin but did not reach an IC50 (p=0.0003-0.018), and 2/13 (15%) had no response to phenformin. Western blot analysis demonstrated that phenformin increased phosphorylation of AMPK and decreased phosphorylation of S6 coincident with inhibition of proliferation in the EC cell lines and primary cultures. Conclusion: Phenformin potently inhibited cell growth via G1 arrest and induced apoptosis in EC cell lines and the majority of primary cultures. Inhibition of adhesion/invasion was also seen with phenformin. Continued work is needed to explore whether phenformin has superior benefits over metformin. Citation Format: Amanda L. Jackson, Joshua E. Kilgore, Haifeng Qiu, Chunxiao Zhou, Paola A. Gehrig, Victoria L. Bae-Jump. Anti-tumorigenic effects of phenformin in human endometrial cancer cells. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1313. doi:10.1158/1538-7445.AM2014-1313