First, we investigated the mRNA expression levels of XCL2 in 21 different tumor tissues and adjacent normal tissues from TCGA database (Figure 1A), which indicated that XCL2 expression was significantly different in 11 cancer types, including BRCA, COAD, GBM, HNSC, KIRC, KIRP, LUAD, LUSC, READ, THCA, and UCEC, and that it was significantly lower in most of the cancer tissues than in normal tissues. This evidence concerns the gene XCL2 and neoplasm.