PDCD1 and melanoma: Antibody blockade of immune checkpoints Cytotoxic T Lymphocyte Antigen 4 (CTLA-4) and Programmed cell Death 1 (PD1)/PD1 ligand 1 (PD-L1) have been shown to restore antitumor immunity in multiple tumor types such as melanoma [1,2], renal cell carcinoma [3,4], non-small cell lung carcinoma [5,6] and Hodgkin’s lymphoma [7,8].