GSEA results showed that hallmarks of malignant tumors (including allograft rejection, apical junction, apoptosis, coagulation, complement, epithelial-mesenchymal transition, late estrogen response, hypoxia, IL2/STAT5 signaling, IL6/JAK/STAT3 signaling, inflammatory response, interferon gamma response, KRAS signaling, mTORC1 signaling, P53 pathway and TNFA signaling via NFKB) were significantly enriched in cluster 2, in which the IL6/JAK/STAT3 signaling pathway was shown to induce the expression of PD-1 and/or PD-L1 (29, 30). Here, STAT3 is linked to cancer.