Measuring the biological effect of presurgical metformin treatment in endometrial cancer

Abstract

Background: Preclinical studies in endometrial cancer (EC) show that metformin reduces cellular proliferation by PI3K-AKT-mTOR inhibition. We tested the hypothesis that short-term presurgical metformin reduces cellular proliferation in atypical endometrial hyperplasia (AEH) and endometrioid EC, and assessed the feasibility of using phosphorylated PI3K-AKT-mTOR proteins as tissue end points.

Methods: Women with AEH or EC received metformin 850 mg twice a day or no drug in the presurgical window between diagnosis and hysterectomy. Before and after the window, tissue samples were obtained; serum markers of insulin resistance (e.g. homeostasis model of assessment of insulin resistance index) were determined; and anthropometrics measured (e.g. BMI). Cell proliferation (Ki-67) and PI3K-AKT-mTOR phosphostatus were assessed by immunohistochemistry and scored blinded to treatment.

Results: Twenty-eight metformin-treated and 12 untreated patients, well matched for age and BMI, completed the study. Metformin treatment (median 20 days, range 7-34) was associated with a 17.2% reduction in tumour Ki-67 (95% CI -27.4, -7.0, P=0.002), in a dose-dependent manner. Tumour PI3K-AKT-mTOR protein phosphostatus varied but the effects were not significant after adjusting for changes in controls.

Conclusions: Short-term metformin was associated with reduced Ki-67 expression in EC. Changes in tumour PI3K-AKT-mTOR protein phosphostatus were seen in both groups. Future studies should address the variability attributed to different sampling techniques including devascularisation of the uterus at hysterectomy.

Figure 1

Flow chart showing study enrolment, withdrawals and exclusions. Concerns about starting a new drug with potential gastrointestinal side effects, inability to adhere to strict follow-up procedures and psychological distress at their recent cancer diagnosis were the most common reasons given for declining participation in the study.

Figure 2

(A) Line graph showing the adjusted mean difference in Ki-67 proliferation index in paired pre- and postintervention endometrial tumours from metformin-treated and control patients. (B and C) Endometrial tumour stained for Ki-67 before (B) and after (C) treatment with metformin at × 20 magnification.

Figure 3

Phosphorylation changes in (A) AKT, (B) ACC, (C) S6 and (D) 4EBP1 using box and whisker plots representing the median modified H-score (middle line) and the first and third quartile from paired pre- and postintervention endometrial biopsies for metformin-treated and control patients. The whiskers represent the maximum and minimum values.