Metformin effects on head and neck squamous carcinoma microenvironment: Window of opportunity trial

Abstract

Objective The tumor microenvironment frequently displays abnormal cellular metabolism, which contributes to aggressive behavior. Metformin inhibits mitochondrial oxidative phosphorylation, altering metabolism. Though the mechanism is unclear, epidemiologic studies show an association between metformin use and improved outcomes in HNSCC. We sought to determine if metformin alters metabolism and apoptosis in HNSCC tumors. Study Design Window of opportunity trial of metformin between diagnostic biopsy and resection. Participants were patients with newly diagnosed HNSCC. 50 patients were enrolled, and 39 completed a full treatment course. Metformin was titrated to standard diabetic dose (2000 mg/day) for a course of 9 or more days prior to surgery. Level of Evidence 4 Methods Immunohistochemistry (IHC) for the metabolic markers caveolin-1 (CAV1), B-galactosidase (GALB) and monocarboxylate transporter 4 (MCT4) as well as the TUNEL apoptosis assay and Ki-67 IHC were performed in pre- and post-metformin specimens. Exploratory mass spectroscopy imaging (MSI) to assess lactate levels was also performed in three subjects. Results Metformin was well tolerated. The average treatment course was 13.6 days. Post-treatment specimens showed a significant increase in stromal CAV1 (p<0.001) and GALB (p<0.005) and tumor cell apoptosis by TUNEL assay (p<0.001). There was no significant change in stromal MCT4 expression or proliferation measured by Ki67. Lactate levels in carcinoma cells were increased 2.4-fold post-metformin (p<0.05) as measured by MSI. Conclusions Metformin increases markers of reduced catabolism and increased senescence in stromal cells and increased carcinoma cell apoptosis. This study demonstrates that metformin modulates metabolism in the HNSCC microenvironment. Trial Registration ClinicalTrials.gov Identifier NCT02083692.

Metabolic coupling and the Reverse Warburg Effect in cancer: Implications for novel biomarker and anticancer agent development

“…No difference was seen in MCT4 expression [82]. Metformin induced carcinoma cell apoptosis 2.8 fold by TUNEL staining in this trial, which was not seen in control patients and increased lactate levels 2.4 fold in carcinoma cells [82]. This can be viewed as proof of principle that metformin can be used to modify the metabolic milieu of tumor stroma.…”

“…Patients who received metformin were found to have increased stromal CAV1 staining intensity, from 25.7% pre-treatment to 62.8% post-treatment; control patients showed no difference in staining. No difference was seen in MCT4 expression [82]. Metformin induced carcinoma cell apoptosis 2.8 fold by TUNEL staining in this trial, which was not seen in control patients and increased lactate levels 2.4 fold in carcinoma cells [82].…”

Pilot study demonstrating metabolic and anti-proliferative effects of in vivo anti-oxidant supplementation with N-Acetylcysteine in Breast Cancer

“…Apoptotic cells were identified using the TUNEL-based ApopTag Peroxidase In Situ Apoptosis Detection Kit (MilliporeSigma, Burlington, MA) as previously described 30 .…”

Repurposing metformin for the prevention of cancer and cancer recurrence

“…A single study has examined the role of metformin in head and neck squamous cell carcinoma (HNSCC) prior to surgery, with change in stromal caveolin-1 (CAV1) and monocarboxylate transporter 4 (MCT4) as the primary endpoint, with the rationale that metformin targets cells with altered glycolysis, which has been shown in cancer-associated fibroblasts particularly in HNSCC [59]. Low CAV1 and increased MCT4 levels are associated with aggressive disease in HNSCC.…”

“…Low CAV1 and increased MCT4 levels are associated with aggressive disease in HNSCC. The study showed a significant increase in CAV1 but no change in MCT4 in 33 evaluable participants between baseline biopsy and surgical specimen [59]. …”