PDCD1 and melanoma: As melanoma tumors evade antitumor immune responses by employing tolerance mechanisms such as IC molecules, immune checkpoint inhibitors (ICIs), including anti-PD-1 (nivolumab and pembrolizumab) and anti-PD-L1 (atezolizumab), have been widely used as a single agent or in combination with BRAF/MEK inhibitors to treat melanoma patients [31,32,33].