YAP regulates PD-L1 expression in human NSCLC cells
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Jinbai Miao1,2,*, Ping-Chih Hsu1,3,*, Yi-Lin Yang1, Zhidong Xu1, Yuyuan Dai1, Yucheng Wang1, Geraldine Chan1,5, Zhen Huang1,4, Bin Hu2, Hui Li2, David M. Jablons1 and Liang You1
1Thoracic Oncology Laboratory, Department of Surgery, Comprehensive Cancer Center, University of California, San Francisco, CA, USA
2Department of Thoracic Surgery, Beijing Chao-Yang Hospital, Affiliated with Capital Medical University, Beijing, People’s Republic of China
3Department of Thoracic Medicine, Chang Gung Memorial Hospital, Linkou, Taoyuan, Taiwan
4Department of Hepatobiliary Surgery, National Cancer Center/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
5Class of 2020, Medical College of Wisconsin, Milwaukee, WI, USA
*These authors contributed equally to this work
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
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.
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