miR‐34a has an important role in regulating the production and activation of various immune cells, including the tumor‐infiltrating lymphocytes (TILs), CD8+ cytotoxic T lymphocytes, regulatory T cells (Tregs), tumor‐associated macrophages (TAMs), and the myeloid‐derived suppressor cells (MDSCs). The gene discussed is CD8A; the disease is neoplasm.