CTLA4 and neoplasm: Intratumoral Tregs are involved in tumor progression by inhibiting the function or maturation of antigen-presenting cells, destroying target cells, impeding the proliferation or activation of natural killer cells and effector T cells, causing metabolic disruption, secreting the immunosuppressive cytokines transforming growth factor beta (TGF-β) and IL-10, and expressing T lymphocyte–associated antigen 4 (CTLA-4) protein [45–48].