PDCD1 and melanoma: LAG-3 and PD-1 induced T cell function inhibition through different signaling pathways, which may synergistically lead to exhaustion of T cells. Studies have shown that co-blockade of PD1 and LAG3 expressed on CD8+ and CD4+ TILs exhibited enhanced antitumor responses in some preclinical mouse models of ovarian cancer, colon adenocarcinoma, and melanoma (52, 56, 57).