PDCD1 and cancer: Immune-checkpoint blockade is the basis for the clinical antitumor activity of the most promising currently approved antibodies targeting the checkpoint molecules CTLA4 (Cytotoxic T-Lymphocyte Antigen 4) , PD1 (Programmed Cell Death 1) and PD-L1 (Programmed cell death ligand 1).Nevertheless, there are heterogeneous response rates to immune checkpoint inhibitors (ICI) [4,5,6] among the different cancer types, and also in the context of patients affected by a specific cancer.