Most immune checkpoint molecules include programmed cell death protein-1 (PD-1), T cell immunoglobulin domain and mucin domain-3 (TIM-3), lymphocyte-activation gene 3 (LAG-3) and T cell immune receptor with Ig and ITIM domains (TIGIT) have shown immunosuppressive activity, which can suppress T cell responses and mediate T cell exhaustion, cancer cells can evade immune surveillance by upregulating ligands for inhibitory checkpoint molecules (20–23). The gene discussed is PDCD1; the disease is cancer.