Metformin Effects on FOXP3⁺ and CD8⁺ T Cell Infiltrates of Head and Neck Squamous Cell Carcinoma

Abstract

ObjectivesAlterations of cellular metabolism have been implicated in immune dysfunction in the tumor microenvironment (TME) of head and neck squamous cell carcinoma (HNSCC). Metformin has recently emerged as a candidate of interest for combination with immunotherapy in HNSCC. This study investigated the effect of metformin on immune cell infiltrates of HNSCC.MethodsRetrospective analysis of T cell infiltrates in primary tumor specimens from patients enrolled in a clinical window of opportunity trial of presurgical metformin. Metformin was titrated to a standard diabetic dose (2000 mg/day) for a minimum of 9 days (mean 13.6 days) prior to surgical resection. Pre and posttreatment surgical specimens from 36 patients (16 HPV+, 20 HPV−) were comparatively analyzed. FOXP3+ and CD8+ immune cell infiltrates in the tumor and peritumoral stroma of pre and posttreatment HNSCC specimens were quantified by digital image analysis using Visiopharm software.ResultsMetformin treatment was associated with a 41.4% decrease in FOXP3+ T cells in intratumor regions of interest (P = .004) and a 66.5% increase in stromal CD8+ T cells at the leading edge of the tumor (P = .021) when compared to pretreatment biopsies. This was reflected in increased CD8+/FOXP3+ cell ratios within the tumor (P < .001) and stromal compartments (P < .001). The effects of metformin occurred independently of HPV status.ConclusionMetformin treatment may favorably alter the immune TME in HNSCC independent of HPV status.Level of Evidence1b. This study is most accurately described as a non‐randomized controlled trial and therefore may reflect a level of evidence below 1b but above 2a from the provided “levels of evidence” chart. Laryngoscope, 130:E490–E498, 2020

Metformin changes the immune microenvironment of colorectal cancer in patients with type 2 diabetes mellitus

“…Eikawa et al demonstrated that metformin increases the number of CD8(+) TILs and enhances the efficacy of T‐cell‐mediated tumor cell lysis in a murine model 17 . Recent studies have shown that the number of CD8(+) TILs in human head and neck squamous cell carcinoma tumors (HNSCC) 33 and non‐small‐cell lung cell tumors 34 are increased in metformin‐treated patients, and is consistent with these results.…”

The Tumor Microenvironment and Immunotherapy of Oropharyngeal Squamous Cell Carcinoma

“…Another potential mechanism is the effect of metformin on Tregs, as it also inhibits mammalian target of rapamycin (mTOR). Metformin treatment for a minimum of 9 days before surgery of HNSCC, more than half being OPSCC, resulted in a strong decrease of intratumoral Foxp3+ Tregs and increase of stromal CD8+ T cells between pre-and post-treatment samples (n=16 HPV+ and n=20 HPV-negative), independent of HPV status (139). Potentially, metformin treatment may be interesting for HPV+ OPSCC patients with ongoing tumor immunity.…”

Comparative Multiomic Analysis Reveals Low T Cell Infiltration as the Primary Feature of Tobacco Use in HPV(+) Oropharyngeal Cancer

“…The images were evaluated using digital analysis software (Visiopharm; Hoersholm, Denmark), which has been used previously for identifying T cells in the HNSCC TIME. 17 Red-Blue-Green color filters were set which reliably distinguished 3,3’-diaminobenzidine (DAB) stained and hematoxylin stained cells without detecting unstained negative space. Areas of artifact or damage were manually excluded.…”

“…The images were evaluated using digital analysis software (Visiopharm; Hoersholm, Denmark), which has been used previously for identifying T cells in the HNSCC TIME. 17 Red-Blue-Green color filters were set which reliably distinguished 3,…”