One of the mechanisms of immune suppression is to upregulate the expression of immune suppressive molecules or their ligands or receptors, for example LAG‐3, galectin‐9/TIM‐3, CTLA4, and programmed death‐1 (PD‐1), inhibiting the activation of effector T cells, thus leading to poor response by the immune system to the cancer [6]. Here, PDCD1 is linked to cancer.