PDCD1 and melanoma: PTEN regulates cell proliferation, migration, survival, genomic stability and metabolism by phosphatase-dependent and phosphatase-independent activities.3 Loss of PTEN was associated with immunoresistance and worse response to programmed cell death protein 1 (PD-1) inhibitors in preclinical murine models of melanoma, by decreasing T cell trafficking into the tumours and T cell-mediated cell death in the tumour.