XCL1 and head and neck squamous cell carcinoma: The functional roles of XCL1 and XCL2 remain unclear; however, increased production of XCL1/2 by NK cells in head and neck squamous cell carcinoma, melanoma, and triple-negative breast cancer has been associated with improved patient survival, likely through the recruitment of conventional type 1 dendritic cells (cDC1) [115].