PDCD1 and cancer: CAR (chimeric antigen receptor)-T cells have been game changer in cancer therapeutic field, and in 2016, it has been observed that Programmed cell death protein 1 (PD-1) blockage through antibody or knocking down the PDCD1 gene that encodes PD-1, enhances the antitumour activity of CAR-T cells [21, 22].