T lymphocytes, like tumor cells, express immune inhibitory programmed cell death receptor-1 (PD-1), its ligand programmed death ligand-1 (PD-L1), and cytotoxic T-lymphocyte-associated protein 4 (CTLA-4), which is responsible for suppressing immune activity (He and Xu, 2020). Here, CTLA4 is linked to neoplasm.