Molecular and metabolic differences of treatment responders versus nonresponders in a phase 0 clinical trial of metformin in endometrial cancer

Abstract

Objectives: In a phase 0 clinical trial of metformin in endometrial cancer (EC) patients, we previously reported that metformin decreased proliferation in the tumors of the majority of patients enrolled. We aimed to determine molecular and metabolic differences between responders and nonresponders to metformin treatment. Methods: Obese women with endometrioid EC were enrolled. Patients took metformin (850 mg QD) for 1 to 4 weeks before surgical staging. Tissue microarrays (triplicate cores) were constructed from formalin-fixed, paraffin-embedded endometrial biopsy and hysterectomy specimens before and after metformin treatment. Expression of the metformin transporters (OCT1, OCT3, PMAT, MATE1, MATE2), phosphorylated (p)-insulinlike growth factor 1 receptor (IGF1R), p-insulin receptor substrate-1 (IRS1), LKB1, and PTEN were evaluated using immunohistochemistry. Global, untargeted metabolomics was performed on serum samples of EC patients before metformin treatment, using combined GC-MS and LC-MS/MS techniques. Results: Of 20 patients enrolled, 13 (65%) responded to metformin as defined by a significant decrease in Ki-67 staining. In responders, metformin decreased the expression of OCT1 (46%, P = .003), OCT3 (40%, P = .036), PMAT (66%, P = .0019), MATE2 (26%, P = .0017), p-IGF1R (24%, P = .035), LKB1 (36%, P = 0.0015), and PTEN (80%, P = .033) but was not associated with changes in MATE1 or p-IRS1. In nonresponders, metformin treatment was not associated with any changes in these molecular targets. Pretreatment MATE2 expression approached significance in predicting response to metformin (P = .0625). Metabolomic profiling revealed that responders had higher premetformin treatment levels of amino acids, dipeptides, glycolytic intermediates, arachidonic acid, monohydroxy fatty acids and lysolipids compared with nonresponders (P < .05). Conclusions: Treatment response to metformin was associated with decreased expression of OCT1, OCT3, PMAT, and MATE2 transporters as well as metabolically relevant proteins associated with obesity and EC. Baseline metabolic differences were found between responders and nonresponders to metformin that may serve as biomarkers for ongoing clinical trials of metformin in this obesity-driven disease.