PDCD1 and melanoma: Combinations involving blockade of leucine-rich repeat-containing G-protein-coupled receptor 4 (Lgr4) in lung cancer (Tan et al., 2018), inhibition of IL-6 in melanoma-bearing mice (Tsukamoto et al., 2018), dietary protein restriction (Orillion et al., 2018), inhibition of casein kinase 2 (Hashimoto et al., 2018), and blockade of receptor-interacting serine/threonine protein kinase 1 (RIP1) in PDAC mouse model (Wang W. et al., 2018) in myeloid cells; and ICB (anti-PD-1, anti-PD-L1, anti-CTLA-4) therapy, synergistically enhanced the antitumor immune response.