EZH2 and neoplasm: The following issues should be resolved (1): how EZH2 can be targeted in specific subgroups or differentiation stages of T lymphocytes (2); how the functional pattern of EZH2 on both tumor cells and T cells changes with tumor progression (3); how combination therapy strategies can be used to eliminate or weaken the adverse effects of EZH2 targeting; and (4) whether targeting EZH2 in combination with immunotherapy could be a new strategy for antitumor therapy.