PDCD1 and cancer: Its ligand programmed death ligand 1 (PD-L1), also known as B7-H11 is commonly expressed in many cell types, including T cells, B cells, monocytes, antigen process cells (APCs), and epithelial cells.2,3 The PD-1/PD-L1 interaction limits the development of T cells response, thereby ensuring the activation of immune system appropriately.2,3 Cancer cells can exploit various immune checkpoints to evade immune detection and elimination.