CXCR2 and head and neck squamous cell carcinoma: In vivo treatment of a murine syngeneic model of HNSCC with SX-682 plus docetaxel led to potent anti-tumor efficacy through a simultaneous decrease in suppressive CXCR2+ polymorphonuclear, myeloid-derived suppressor cells and an increase in cytotoxic CD8+ T cells in the combination therapy treated tumors compared to controls.