CXCR1 and head and neck squamous cell carcinoma: To determine the effect of SX-682 treatment on HPV-negative HNSCC tumors in vivo, xenografts of UM-SCC-11B and UM-SCC-74B tumor cells growing in NSG-MHC I/II KO mice were first evaluated for the expression of IL-8, CXCR1, and CXCR2 via RNA in situ hybridization.