They selectively block PD-1/PD-L1 or CTLA-4/CD80 or CD86 interactions and subsequently enhance the ability of immune cells to attack cancer cells and establish long-lasting anti-tumor immunity, whereas traditional cytotoxic chemotherapeutic agents directly disturb cancer cell activity or viability regardless of the genetic or epigenetic background of the tumor or tumor microenvironment (TME) [4,5,6,7]. The gene discussed is PDCD1; the disease is cancer.