PDCD1 and cancer: The expression of six Tex marker genes was initially investigated across pan-cancer types, revealing higher mRNA levels of CXCL13 in LUAD, HNSC, and KIRC; HAVCR2 in KIRP, STAD, and KIRC; LAG3 in LUAD, BRCA, HNSC, and KIRC; LAYN in LIHC, HNSC, and KIRC; PDCD1 in LUAD, BRCA, and KIRC; and TIGIT in STAD, ESCA, LUAD, BRCA, HNSC and KIRC compared to their corresponding normal tissues (Figure 1A).