Research has shown that tumor infiltrated lymphocytes (TILs) tend to be hypofunctional due to the hypoxic conditions and upregulation of immune inhibitory molecules, such as PD-1 and CTLA-4, as well as suppression from the myeloid-derived suppressor cells (MDSCs) and regulatory T cells (Tregs) [35–37]. Here, CTLA4 is linked to neoplasm.