PDCD1 and neoplasm: The past decade has witnessed the evolving progress of biological molecular therapies for diverse tumors and multiple biomarkers and biological targets have been found, several of which have been successfully applied in clinical tumor treatment, such as trastuzumab which is an antibody of human epidermal growth factor receptor type 2 (HER2) and nivolumab which is an antibody of the programmed cell death-1 (PD-1) [12–16].