PDCD1 and melanoma: In mice bearing the solid tumor CT26 colon carcinoma, it shows that among CD8+ TILs, cells that coexpress Tim-3 and PD-1 comprise the major population (∼50%) with cells expressing PD-1 alone or neither Tim-3 nor PD-1 comprising smaller populations (∼30% and ∼20%, respectively) (59).This phenomena was also observed in mice bearing two other solid tumors: 4T1 mammary adenocarcinoma and B16F10 melanoma (59).