Effects of metformin on endometrial cancer cell growth in vivo: A preoperative prospective trial

BACKGROUND Metformin, an antidiabetic drug, decreases the incidence of various cancers in diabetic patients. Metformin‐induced inhibition of cancer cell proliferation has been confirmed in vitro but not in humans. Because endometrial cancer is associated with insulin resistance, the authors investigated whether a diabetes‐therapeutic metformin dose inhibits cancer cell growth in patients with endometrial cancer. METHODS A dose of metaformin was administered (1500‐2250 mg/day) to 31 patients with endometrial cancer preoperatively for 4 to 6 weeks. Cell proliferation was assessed in patient tissues using immunohistochemical and Western blot analyses and DNA synthesis was measured in serum using a thymidine uptake assay. All statistical tests were 2‐sided. P values of