CTLA4 and neoplasm: For example, CD8+T cells often show a dysfunctional state and change into depleted T cells, which cannot effectively eliminate tumor cells and promote the occurrence of immune escape reaction of tumors; In addition, depleted T cells also express multiple inhibitory receptors such as programmed death protein 1 (PD1) and cytotoxic T-lymphocyte associated protein 4 (CTLA4), which drive the progression of liver cancer (7).