Notably, cytotoxic T-lymphocyte-associated protein 4 (CTLA4) and PD-1 (PDCD1) genes serve as exemplars of immune checkpoint genes, and the application of antibody therapy to inhibit the CTLA4 or PD-1 checkpoints has been shown to unleash T-cells for tumor eradication 46. This evidence concerns the gene PDCD1 and neoplasm.