Metformin Clinical Trial in HPV+ and HPV– Head and Neck Squamous Cell Carcinoma: Impact on Cancer Cell Apoptosis and Immune Infiltrate

Abstract

Background: Metformin, an oral anti-hyperglycemic drug which inhibits mitochondrial complex I and oxidative phosphorylation has been reported to correlate with improved outcomes in head and neck squamous cell carcinoma (HNSCC) and other cancers. This effect is postulated to occur through disruption of tumor-driven metabolic and immune dysregulation in the tumor microenvironment (TME). We report new findings on the impact of metformin on the tumor and immune elements of the TME from a clinical trial of metformin in HNSCC.Methods: Human papilloma virus—(HPV–) tobacco+ mucosal HNSCC samples (n = 12) were compared to HPV+ oropharyngeal squamous cell carcinoma (OPSCC) samples (n = 17) from patients enrolled in a clinical trial. Apoptosis in tumor samples pre- and post-treatment with metformin was compared by deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay. Metastatic lymph nodes with extra-capsular extension (ECE) in metformin-treated patients (n = 7) were compared to archival lymph node samples with ECE (n = 11) for differences in immune markers quantified by digital image analysis using co-localization and nuclear algorithms (PD-L1, FoxP3, CD163, CD8).Results: HPV–, tobacco + HNSCC (mean Δ 13.7/high power field) specimens had a significantly higher increase in apoptosis compared to HPV+ OPSCC specimens (mean Δ 5.7/high power field) (p < 0.001). Analysis of the stroma at the invasive front in ECE nodal specimens from both HPV—HNSCC and HPV+ OPSCC metformin treated specimens showed increased CD8+ effector T cell infiltrate (mean 22.8%) compared to archival specimens (mean 10.7%) (p = 0.006). Similarly, metformin treated specimens showed an increased FoxP3+ regulatory T cell infiltrate (mean 9%) compared to non-treated archival specimens (mean 5%) (p = 0.019).Conclusions: This study presents novel data demonstrating that metformin differentially impacts HNSCC subtypes with greater apoptosis in HPV—HNSCC compared to HPV+ OPSCC. Moreover, we present the first in vivo human evidence that metformin may also trigger increased CD8+ Teff and FoxP3+ Tregs in the TME, suggesting an immunomodulatory effect in HNSCC. Further research is necessary to assess the effect of metformin on the TME of HNSCC.

Dissecting the Anticancer Mechanism of Trifluoperazine on Pancreatic Ductal Adenocarcinoma

“…Mitochondria and energy metabolism disruption play an important role in cell death. This is a hot topic, and nowadays, several therapeutic approaches are exploiting and targeting it, as is the case of metformin, currently under clinical trials [16,17]. In this regard, TFP-treatment demonstrates a great anticancer effect because it is able to target mitochondria and induce metabolic-driven cell death.…”

Metformin alters signaling induced crosstalk and homeostasis in the carcinogenesis paradigm “Epistemology of the origin of cancer”

“…In a small study of head and neck squamous cell carcinomas (HNSCC), Metformin was shown to differentially impact HNSCC subtypes with greater apoptosis in human papilloma virus negative (HPVÀ) HNSCC compared to human papilloma virus positive (HPV+) oropharyngeal squamous cell carcinoma. Moreover, the study presented the first in vivo human evidence that Metformin also triggers increased CD8 + Teff and FoxP3 + Tregs in the tumor microenvironment, suggesting an immunomodulatory effect in HNSCC [165]. In a double-blind, randomized, placebo controlled, multicenter study design, metformin in a daily dosage of 2,000 mg in Barrett's esophagus reduced serum levels of insulin and insulin resistance but were not associated with decrease of a biomarker of insulin pathway activation, phosphorylated S6 kinase (pS6K1), or alter epithelial proliferation or apoptosis in esophageal tissues [166].…”

Metformin as an archetype immuno-metabolic adjuvant for cancer immunotherapy

“…86 An analysis of the immunomodulatory effects of metformin in a clinical trial of head and neck squamous cell carcinoma revealed its ability to increase both CD8 + effector T-cells and FoxP3 + T reg cell infiltrates in the TME. 87 A retrospective descriptive analysis carried out in the randomized phase III OAK trial for treatment of advanced or metastatic previously-treated non-small cell lung cancer revealed an encouraging improvement of overall response rate in patients receiving concomitant metformin treatment with the anti-PD -L1 antibody atezolizumab. 88 Not surprisingly, large prospective clinical trials are currently underway to study the synergistic effect of metformin in combination with immune-checkpoint inhibitors before its recommendation as routine additive to cancer immunotherapy.…”