PDCD1 and neoplasm: Moreover, recent evidence has reported that histone deacetylases 2 (HDAC2) blockade can regulate the level of T lymphocyte subsets, inhibit tumor immune suppression and, consequently, enhance the efficacy of PD-1/PD-L1 inhibitors by regulating the progress of membranal PD-L1 nuclear translocation, improving anti-cancer immunity [143,166,167].