XRCC4 and cancer: Among the 48 immune checkpoint genes, strong correlations (≥ 5 genes) with XRCC4 expression were found in 33 human cancers, including LIHC, PRAD, SARC, THCA, BLCA, LGG, SKCM, UVM, KIRC, THYM, HNSC, TGCT, UCEC, LUAD, LUSC, PCPG, COAD, LAML, BRCA, STAD, DLBC, PAAD, READ, GBM, KIRP, CESC, OV and KICH (FDR < 0.1).