Inhibition of ERK1/2 down-regulates the Hippo/YAP signaling pathway in human NSCLC cells.

// Bin You 1, 2, * , Yi-Lin Yang 1, * , Zhidong Xu 1 , Yuyuan Dai 1 , Shu Liu 1 , Jian-Hua Mao 3 , Osamu Tetsu 4 , Hui Li 2 , David M. Jablons 1 , Liang You 1 1 Department of Surgery, Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, CA, USA 2 Department of Thoracic Surgery, Beijing Chao-Yang Hospital, Affiliated with Capital University of Medical Science, Beijing, People's Republic of China 3 Life Sciences Division, Lawrence Berkeley National Laboratory, University of California, Berkeley, CA, USA 4 Department of Otolaryngology–Head and Neck Surgery, University of California, San Francisco, CA, USA * These authors have contributed equally to this work Correspondence to: Liang You, e-mail: liang.you@ucsfmedctr.org Keywords: non-small cell lung cancer, extracellular signal regulated kinases, Hippo pathway, yes-associated protein, inhibition Received: June 17, 2014      Accepted: December 20, 2014      Published: January 23, 2015 ABSTRACT Alterations of the EGFR/ERK and Hippo/YAP pathway have been found in non-small cell lung cancer (NSCLC). Herein, we show that ERK1 and ERK2 have an effect on the Hippo/YAP pathway in human NSCLC cells. Firstly, inhibition of ERK1/2 by siRNA or small-molecular inhibitors decreased the YAP protein level, the reporter activity of the Hippo pathway, and the mRNA levels of the Hippo downstream genes, CTGF , Gli2 , and BIRC5 . Secondly, degradation of YAP protein was accelerated after ERK1/2 depletion in NSCLC cell lines, in which YAP mRNA level was not decreased. Thirdly, forced over-expression of the ERK2 gene rescued the YAP protein level and Hippo reporter activity after siRNA knockdown targeting 3'UTR of the ERK2 gene in NSCLC cells. Fourthly, depletion of ERK1/2 reduced the migration and invasion of NSCLC cells. Combined depletion of ERK1/2 had a greater effect on cell migration than depletion of either one separately. Finally, the MEK1/2 inhibitor Trametinib decreased YAP protein level and transcriptional activity of the Hippo pathway in NSCLC cell lines. Our results suggest that ERK1/2 inhibition participates in reducing YAP protein level, which in turn down-regulates expression of the downstream genes of the Hippo pathway to suppress migration and invasion of NSCLC cells.