EZH2 and neoplasm: Evidence has shown that the PARP inhibition effect is dependent on the infiltration degree of T cells (Pantelidou et al., 2019; Sen et al., 2019); however, EZH2 downregulates the degree of T-cell infiltration in the tumor microenvironment (Peng et al., 2015), which hurdles the effect of PARP inhibitors.