Additionally, the expression of PD-L1 on tumor cells is related to the exhaustion of T cells; therefore, blocking the PD-1 pathway has been demonstrated to be a successful approach for the treatment of different types of cancers including non-small cell lung cancer (NSCLC), melanoma, breast, RCC, and CRC [70,72,73,74,75]. The gene discussed is PDCD1; the disease is cancer.