Dear Editor,PD-L1,also known as CD274,plays a vital role in tumor cell related immune escape.It can be expressed on the cell surface of many solid tumors (Brahmer et al.,2012) and inhibits T cell proliferation and cytokine production by binding to the Tcell surface receptor programmed death 1 (PD-1) or B7-1 (McClanahan et al.,2015).In 2013,targeting PD-1/ PD-L1 signaling for cancer immunotherapy was selected as the No.1 scientific breakthrough of the year by the editors of Science.