Inhibition of MDSC Trafficking with SX-682, a CXCR1/2 Inhibitor, Enhances NK-Cell Immunotherapy in Head and Neck Cancer Models

Clin Cancer Res. 2020 Mar 15;26(6):1420-1431. doi: 10.1158/1078-0432.CCR-19-2625. Epub 2019 Dec 17.


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 TGFβ 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 TGFβ and nitric oxide.

Conclusions: The clinical study of CXCR1/2 inhibitors in combination with adoptively transferred NK cells is warranted.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, N.I.H., Intramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antineoplastic Agents, Immunological / pharmacology*
  • Cell Line, Tumor
  • Disease Models, Animal
  • Head and Neck Neoplasms / immunology
  • Head and Neck Neoplasms / metabolism
  • Head and Neck Neoplasms / therapy*
  • Humans
  • Immunotherapy / methods
  • Killer Cells, Natural / drug effects
  • Killer Cells, Natural / immunology*
  • Leukocytes, Mononuclear
  • Mice
  • Mice, Inbred C57BL
  • Mouth Neoplasms / immunology
  • Mouth Neoplasms / metabolism
  • Mouth Neoplasms / therapy*
  • Myeloid-Derived Suppressor Cells / drug effects
  • Myeloid-Derived Suppressor Cells / immunology
  • Myeloid-Derived Suppressor Cells / metabolism*
  • Receptors, Interleukin-8A / antagonists & inhibitors*
  • Receptors, Interleukin-8B / antagonists & inhibitors*
  • Transforming Growth Factor beta / immunology
  • Transforming Growth Factor beta / metabolism
  • Tumor Microenvironment


  • Antineoplastic Agents, Immunological
  • Receptors, Interleukin-8A
  • Receptors, Interleukin-8B
  • Transforming Growth Factor beta