Inflammation-induced myeloid-derived suppressor cells associated with squamous cell carcinoma of the head and neck

Background: The purpose of this study was to present our assessment of the significance of myeloid-derived suppressor cells (MDSCs) in head and neck squamous cell carcinoma (HNSCC). Methods: We examined the percentage of MDSCs in the peripheral blood of patients with HNSCC. The relationship among MDSC recruitment, tumor progression, and cyclooxygenase (COX)-2 inhibition was also evaluated by animal models. Results: Circulating MDSCs were significantly increased in patients with HNSCC compared with healthy people, and this was associated with the clinical tumor burden. In immunocompetent 4-nitroquinoline-1-oxide (4-NQO)-induced oral tumor and immunocompromised tumor implantation animal models, MDSC recruitment was associated with the duration of 4-NQO treatment and tumor progression. The responsible mechanisms included the suppressive ability of T-cell proliferation and augmenting angiogenesis by MDSC. Blockade of COX-2 attenuated the induction and function of MDSCs and subsequently inhibited tumor growth. Conclusion: The levels of MDSC are linked with tumor progression in HNSCC. Moreover, targeting COX-2 could be a promising strategy for the treatment of HNSCC.