XCL1 and neoplasm: Marker genes in tumor-infiltrating CD8+ T cells could be mainly classified into three types: (1) T-cell receptor-associated genes, such as TRDV1, TRGV2, TRGV8, and TRBV20-1; (2) chemokines and cytokines, such as CXCL13, XCL1, and XCL2; and (3) stressful stimuli genes, such as BAG3, HSPA6, and HPPA1A.