YAP regulates PD-L1 expression in human NSCLC cells

// Jinbai Miao 1, 2, * , Ping-Chih Hsu 1, 3, * , Yi-Lin Yang 1 , Zhidong Xu 1 , Yuyuan Dai 1 , Yucheng Wang 1 , Geraldine Chan 1, 5 , Zhen Huang 1, 4 , Bin Hu 2 , Hui Li 2 , David M. Jablons 1 and Liang You 1 1 Thoracic Oncology Laboratory, Department of Surgery, Comprehensive Cancer Center, University of California, San Francisco, CA, USA 2 Department of Thoracic Surgery, Beijing Chao-Yang Hospital, Affiliated with Capital Medical University, Beijing, People’s Republic of China 3 Department of Thoracic Medicine, Chang Gung Memorial Hospital, Linkou, Taoyuan, Taiwan 4 Department of Hepatobiliary Surgery, National Cancer Center/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China 5 Class of 2020, Medical College of Wisconsin, Milwaukee, WI, USA * These authors contributed equally to this work Correspondence to: Liang You, email: Liang.You@ucsf.edu Keywords: programmed death-ligand 1; yes-associated protein; non-small cell lung cancer; hippo pathway Received: July 26, 2017      Accepted: November 13, 2017      Published: December 09, 2017 ABSTRACT Programmed death-ligand 1 (PD-L1) is a membrane protein on tumor cells that binds to the PD-1 receptor expressed on immune cells, leading to the immune escape of tumor cells. Yes-associated protein (YAP) is a main effector of the Hippo/YAP signaling pathway, which plays important roles in cancer development. Here we show that YAP regulates PD-L1 expression in human non-small cell lung cancer (NSCLC) cells. First, we investigated YAP and PD-L1 expression at the protein level in 142 NSCLC samples and 15 normal lung samples. In tumor tissue, immunohistochemistry showed positive staining for YAP and PD-L1, which correlated significantly ( n = 142, r = 0.514, P < 0.001). Second, in cell lines that express high levels of PD-L1 (H460, SKLU-1, and H1299), the ratio of p-YAP/YAP was lower and GTIIC reporter activity of the Hippo pathway was higher than those in three cell lines expressing low levels of PD-L1 (A549, H2030, and PC9) ( P < 0.05). Third, in the same three cell lines, inhibition of YAP by two small interfering RNAs (siRNAs) decreased the mRNA and protein level of PD-L1 ( P < 0.05). Fourth, forced overexpression of the YAP gene rescued the PD-L1 mRNA and protein level after siRNA knockdown targeting 3’UTR of the endogenous YAP gene. Finally, chromatin immunoprecipitation (ChIP) assays using a YAP-specific monoclonal antibody resulted in the precipitation of PD-L1 enhancer region encompassing two putative TEAD binding sites. Our results indicate that YAP regulates the transcription of PD-L1 in NSCLC.