HMGB1 is overexpressed in tumor cells and promotes activity of regulatory T cells in patients with head and neck cancer.

HMGB1 has gained a prominent role in cancer development and is implicated in tumor escape phenomena. To date, only few data are available on effects of HMGB1 on regulatory T cells (Treg) in cancer patients. This study evaluates the prevalence of HMGB1 and its effects on Treg in patients with head and neck squamous cell carcinoma (HNSCC). Sixty-seven patients with HNSCC and seventeen healthy donors were included in this study. Tumor tissues of patients were analyzed for expression of HMGB1 employing immunofluorescence and qRT-PCR. HMGB1 serum levels were assessed using ELISA. Tumor-infiltration and Treg from peripheral blood were phenotyped with flow cytometry and immunofluorescence microscopy. Migration and suppressive function of Treg upon HMGB1 stimulation was analyzed in chemotaxis assays and CFSE assays. HMGB1 is overexpressed in tumor cells of HNSCC, and serum levels are significantly elevated. Tumor-infiltrating Treg express HMGB1-recognizing receptors, TLR4 and RAGE. HMGB1 is a chemoattractant for Treg and promotes their suppressive function. Our data provide new aspects how the HMGB1 tumor-derived danger signal augments function of Treg in patients with HNSCC.