CD274 and cancer: The binding of PD-1 and PD-L1 leads to the suppression of T cell activity and T cell mediated cytotoxicity, resulting in driving the plethora inflammation to a reasonable range, keeping the immune homeostasis, maintaining self-tolerance and protecting tissues from damage caused by the immune system [1,4]; or dampening of the anti-cancer immune response and facilitating immune escape of cancer cells [1,2,5,6].