Bateman NW, Teng PN, Hope E, et al. - In the current study, researchers identified proteomic alterations in tumor tissues harvested from endometrial cancer patients before and after daily metformin (850 mg) treatment for 4 weeks prior to surgical staging. Matched pre- and postmetformin-treated tumor tissues from a recently completed preoperative window trial of metformin in endometrioid endometrial cancer (EEC) patients have been analyzed by mass spectrometry (MS)-based proteomic and immunohistochemical analyses. Jupiter microtubule-associated homolog 1 (JPT1) was significantly raised in metformin responders compared with nonresponders and found to decline in abundance in metformin responders following treatment. Such findings indicate that JPT1 is a predictive and pharmacodynamic biomarker of metformin response that can enable preoperative EEC patient stratification for metformin treatment and the ability to monitor patient response if validated in larger populations.