CD4 and neoplasm: Downregulation of G9a retarded tumor growth and extended survival in an immunocompetent glioma mouse model, promoted the filtration of IFN‐γ + CD4+ and CD8+ T lymphocytes, and suppressed the filtration of PD‐1+ CD4+ and CD8+ T lymphocytes, myeloid‐derived suppressor cells (MDSCs) and M2‐like macrophages in TME.