Increased efficacy of metformin corresponds to differential metabolic effects in the ovarian tumors from obese versus lean mice
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Jianjun Han1,2, Weiya Z. Wysham3, Yan Zhong2,4, Hui Guo2,5, Lu Zhang2,5, Kim M. Malloy6, Hallum K. Dickens2, Gene Huh7, Douglas Lee8, Liza Makowski9,10, Chunxiao Zhou2,10 and Victoria L. Bae-Jump2,10
1Department of Surgical Oncology, Shandong Cancer Hospital and Institute, Shandong Academy of Medical Sciences, Jinan, Postdoctoral Mobile Station of Tianjin Medical University, Tianjin, P.R. China
2Division of Gynecologic Oncology, Department of Obstetrics and Gynecology, University of North Carolina, Chapel Hill, NC, USA
3Legacy Medical Group, Gynecologic Oncology, Portland, OR, USA
4Department of Gynecologic Oncology, Linyi Cancer Hospital, Linyi, Shandong, P.R. China
5Department of Gynecologic Oncology, Shandong Cancer Hospital & Institute, Jinan, P.R. China
6Virginia Tech/Carilion Clinic, Department of Obstetrics and Gynecology, Blacksburg, VA, USA
7Seoul National University College of Medicine, Seoul, South Korea
8Omic Insight, Durham, NC, USA
9Department of Nutrition, University of North Carolina, Chapel Hill, NC, USA
10Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC, USA
Victoria L. Bae-Jump, email: email@example.com
Chunxiao Zhou, email: firstname.lastname@example.org
Keywords: metformin, metabolism, ovarian cancer, mTOR pathway, obesity
Received: June 03, 2017 Accepted: August 03, 2017 Published: September 08, 2017
Obesity is a significant risk factor for ovarian cancer (OC) and associated with worse outcomes for this disease. We assessed the anti-tumorigenic effects of metformin in human OC cell lines and a genetically engineered mouse model of high grade serous OC under obese and lean conditions. Metformin potently inhibited growth in a dose-dependent manner in all four human OC cell lines through AMPK/mTOR pathways. Treatment with metformin resulted in G1 arrest, induction of apoptosis, reduction of invasion and decreased hTERT expression. In the K18-gT121+/-; p53fl/ fl; Brca1fl/fl (KpB) mouse model, metformin inhibited tumor growth in both lean and obese mice. However, in the obese mice, metformin decreased tumor growth by 60%, whereas tumor growth was only decreased by 32% in the lean mice (p=0.003) compared to vehicle-treated mice. The ovarian tumors from obese mice had evidence of impaired mitochondrial complex 2 function and energy supplied by omega fatty acid oxidation rather than glycolysis as compared to lean mice, as assessed by metabolomic profiling. The improved efficacy of metformin in obesity corresponded with inhibition of mitochondrial complex 1 and fatty acid oxidation, and stimulation of glycolysis in only the OCs of obese versus lean mice. In conclusion, metformin had anti-tumorigenic effects in OC cell lines and the KpB OC pre-clinical mouse model, with increased efficacy in obese versus lean mice. Detected metabolic changes may underlie why ovarian tumors in obese mice have heightened susceptibility to metformin.
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