OBJECTIVE There is increasing pre-clinical evidence indicating that metformin, a medication commonly used for type 2 diabetes, may protect against cancer. Motivated by this emerging evidence we asked two questions: (a) can metformin prevent ovarian cancer growth by altering metabolism, and (b) will metformin increase sensitivity to chemotherapy. STUDY DESIGN The effect of metformin in ovarian cancer was tested in vitro and by using two different mouse models. In vitro, cell lines (n=6) were treated with metformin (10 to 40 mM) or PBS and cellular proliferation and metabolic alterations (AMP-activated protein kinase activity, glycolysis, lipid synthesis) were compared between the two groups. In mouse models, a prevention study was performed by treating mice with metformin (250 mg/kg/day intraperitoneal (i.p.)) or placebo for 2 weeks followed by i.p. injection of the SKOV3ip1 human ovarian cancer cell line and the mean number of tumor implants in each treatment group was compared. In a treatment study, the LSL-K-rasG12D/+/PTENfloxP/floxP genetic mouse model of ovarian cancer was used. Mice were treated with placebo, paclitaxel (3 mg/kg/week i.p. x 7 weeks), metformin (100 mg/kg/day in water x 7 weeks), or paclitaxel plus metformin and tumor volume was compared between treatment groups. RESULTS In vitro, metformin decreased proliferation of ovarian cancer cell lines and induced cell cycle arrest, but not apoptosis. Further analysis showed that metformin altered several aspects of metabolism including AMP-activated protein kinase activity, glycolysis, and lipid synthesis. In the prevention mouse model, mice pre-treated with metformin had 60 % fewer tumor implants compared to controls (p<0.005). In the treatment study, mice treated with paclitaxel plus metformin had a 60% reduction in tumor weight compared to controls (p=0.02); a level of tumor reduction greater than that resulting from either paclitaxel or metformin alone. CONCLUSION Based on these results, we conclude that metformin alters metabolism in ovarian cancer cells, prevents tumor growth, and increases sensitivity to chemotherapy in vitro and in mouse models. These pre-clinical findings suggest that metformin warrants further investigation for use as an ovarian cancer therapeutic.

Objective To test if estrogen promotes carcinogenesis in vitro and in a genetic mouse model of ovarian cancer and whether its effects can be inhibited by a novel selective estrogen receptor modulator (SERM), bazedoxifene. Methods Bazedoxifene was synthesized and it was confirmed that the drug abrogated the uterine stimulatory effect of 17β-estradiol in mice. To determine if hormones alter tumorigenesis in vivo LSL-K-rasG12D/+PtenloxP/loxP mice were treated with vehicle control, 17β-estradiol or bazedoxifene. Hormone receptor status of a cell line established from LSL-K-rasG12D/+PtenloxP/loxP mouse ovarian tumors was characterized using western blotting and immunohistochemistry. The cell line was treated with hormones and invasion assays were performed using Boyden chambers and proliferation was assessed using MTT assays. Results In vitro 17β-estradiol increased both the invasion and proliferation of ovarian cancer cells and bazedoxifene reversed these effects. However, in the genetic mouse model neither treatment with 17β-estradiol nor bazedoxifene changed mean tumor burden when compared to treatment with placebo. The mice in all treatment groups had similar tumor incidence, metastatic nodules and ascites. Conclusion While 17β-estradiol increases the invasion and proliferation of ovarian cancer cells, these effects do not translate into increased tumor burden in a genetic mouse model of endometrioid ovarian cancer. Likewise, while the SERM reversed the detrimental effects of estrogen in vitro, there was no change in tumor burden in mice treated with bazedoxifene. These findings demonstrate the complex interplay between hormones and ovarian carcinogenesis.