PDCD1 and melanoma: By counteracting the negative activity of melanoma cells on the immune system, monoclonal antibodies anti cytotoxic-T-lymphocyte-associated antigen 4 (CTLA-4), such as ipilimumab, and anti programmed cell death-1 (PD-1), such as nivolumab and pembrolizumab, were introduced in the clinics for the treatment of advanced melanomas41,42.