Tumor cells use inhibitory signaling pathways in the immune system, such as the PD-1/PD-L1, CTLA-4, LAG-3, Tim-3, and CD160 signaling pathways, to inhibit the function of TILs in the TME, resulting in tumor immunosuppression (Wherry, 2011; Chen and Flies, 2013). Here, CTLA4 is linked to neoplasm.