PDCD1 and cancer: The paper has also shown the promising result of anti-PD-1/PD-L1 drug in various cancer types and several kinds of strategies improving efficacy of anti-PD-1/PD-L1 drug have been mentioned in the paper, including developing companion PD-L1 test, searching for biomarkers, and discovering small molecule PD-1/PD-L1 inhibitors.