Programmed cell death-1 (PD1) has become a significant target for cancer immunotherapy. by which PD1-targeted therapies rescue T cell functions still remain elusive. Therefore, it is a key issue to uncover the molecular pathways by which these therapies exert its function in T cells. A profound knowledge of PDL1/PD1 mechanisms will surely uncover a new array of targets susceptible of therapeutic intervention.Here, we provide an overview of the molecular events underlying PD1-dependent T cell suppression in cancer.