XCL1 and head and neck squamous cell carcinoma: When analyzing TCGA datasets for skin cutaneous melanoma (SKCM, n = 470 patients), breast invasive carcinoma (BRCA, n = 1098), head and neck squamous cell carcinoma (HNSC, n = 528), and lung adenocarcinoma (LUAD, n = 585), we observed a positive correlation between the three chemokines XCL1, XCL2, and CCL5 that was highly significant in each dataset (Figures 6B and S6A), consistent with the notion that they might all be produced by the same intratumoral cell type.