PDCD1 and melanoma: The signaling pathway—programmed death receptor 1 (PD-1)/programmed cell death ligand 1 (PD-L1)—led to melanoma, non-small cell lung cancer (NSCLC), colorectal cancers (CRCs), bladder cancer, and renal-cell cancer if it was activated (Ott et al., 2020; O'Neil et al., 2017; Topalian et al., 2012; Stein et al., 2021; and Yi and Li, 2016).