Inhibition of MDSC Trafficking with SX 682, a CXCR1/2 Inhibitor, Enhances NK Cell Immunotherapy in Head and Neck Cancer Models
Purpose: Natural killer (NK) cell based immunotherapy may overcome obstacles to effective T cell based immunotherapy such as the presence of genomic alterations in IFN response genes and antigen presentation machinery. All immunotherapy approaches may be abrogated by the presence of an immunosuppressive tumor microenvironment present in many solid tumor types, including head and neck squamous cell carcinoma (HNSCC) Here, we studied the role of myeloid derived suppressor cells (MDSC) in suppressing NK cell function in HNSCC. Experimental Design: The ability of peripheral and tumor infiltrating MDSC from mice bearing murine oral cancer 2 (MOC2) non T cell inflamed tumors and from patients with HNSCC to suppress NK cell function was studied with real time impedance and ELISpot assays. The therapeutic efficacy of SX 682, a small molecule inhibitor of CXCR1 and CXCR2, was assessed in combination with adoptively transferred NK cells. Results: Mice bearing MOC2 tumors pathologically accumulate peripheral CXCR2+ neutrophilic MDSC (PMN MDSC) that traffic into tumors and suppress NK cell function through TGFb and production of H2O2. Inhibition of MDSC trafficking with orally bioavailable SX 682 significantly abrogated tumor MDSC accumulation and enhanced the tumor infiltration, activation, and therapeutic efficacy of adoptively transferred murine NK cells. Patients with HNSCC harbor significant levels of circulating and tumor infiltrating CXCR1/2+ CD15+ PMN MDSC and CD14+ monocytic MDSC. Tumor MDSC exhibited greater immunosuppression than those in circulation. HNSCC tumor MDSC immunosuppression was mediated by multiple, independent, cell specific mechanisms including TGFb and nitric oxide. Conclusions: The clinical study of CXCR1/2 inhibitors in combination with adoptively transferred NK cells is warranted.
Clinical Cancer Research