ABSTRACT
Yes-associated protein (YAP) is a main mediator of the Hippo pathway and promotes cancer development and progression in human lung cancer. We sought to determine whether inhibition of YAP suppresses metastasis of human lung adenocarcinoma in a murine model. We found that metastatic NSCLC cell lines H2030-BrM3(K-rasG12C mutation) and PC9-BrM3 (EGFRΔexon19 mutation) had a significantly decreased p-YAP(S127)/YAP ratio compared to parental H2030 (K-rasG12C mutation) and PC9 (EGFRΔexon19 mutation) cells (P < .05). H2030-BrM3 cells had significantly increased YAP mRNA and expression of Hippo downstream genes CTGF and CYR61 compared to parental H2030 cells (P < .05). Inhibition of YAP by short hairpin RNA (shRNA) and small interfering RNA (siRNA) significantly decreased mRNA expression in downstream genes CTGF and CYR61 in H2030-BrM3 cells (P < .05). In addition, inhibiting YAP by YAP shRNA significantly decreased migration and invasion abilities of H2030-BrM3 cells (P < .05). We are first to show that mice inoculated with YAP shRNA-transfected H2030-BrM3 cells had significantly decreased metastatic tumour burden and survived longer than control mice (P < .05). Collectively, our results suggest that YAP plays an important role in promoting lung adenocarcinoma brain metastasis and that direct inhibition of YAP by shRNA suppresses H2030-BrM3 cell brain metastasis in a murine model.
Subject(s)
Adaptor Proteins, Signal Transducing/genetics , Adenocarcinoma of Lung/genetics , Brain Neoplasms/genetics , Carcinogenesis/genetics , Phosphoproteins/genetics , Adaptor Proteins, Signal Transducing/antagonists & inhibitors , Adenocarcinoma of Lung/pathology , Adenocarcinoma of Lung/therapy , Animals , Brain Neoplasms/pathology , Brain Neoplasms/secondary , Brain Neoplasms/therapy , Cell Line, Tumor , Connective Tissue Growth Factor/genetics , Disease Models, Animal , Drug Resistance, Neoplasm/genetics , ErbB Receptors/genetics , Gene Expression Regulation, Neoplastic/genetics , Humans , Mice , Mutation , Phosphoproteins/antagonists & inhibitors , Proto-Oncogene Proteins p21(ras)/genetics , RNA, Small Interfering/administration & dosage , Signal Transduction , Transcription Factors , Xenograft Model Antitumor Assays , YAP-Signaling ProteinsABSTRACT
Although tumour PD-L1 (CD274) expression had been used as a predictive biomarker in checkpoint immunotherapy targeting the PD1/PD-L1 axis in various cancers, the regulation of PD-L1 (CD274) expression is unclear. Yes-associated protein (YAP), an important oncogenic protein in Hippo signalling pathway, reportedly promotes cancer development. We investigated whether inhibition of YAP down-regulates PD-L1 (CD274) in human malignant pleural mesothelioma (MPM). Western blotting showed that 2 human MPM cell lines (H2052 and 211H) had increased PD-L1 protein expression compared to H290, MS-1 and H28 cells. In H2052 and 211H cells, PD-L1 mRNA expression was significantly increased compared to other MPM cell lines; YAP knockdown by small interfering RNA decreased PD-L1 protein and mRNA expression. Forced overexpression of the YAP gene increased PD-L1 protein expression in H2452 cells. Chromatin immunoprecipitation (ChIP) assay showed the precipitation of PD-L1 enhancer region encompassing 2 putative YAP-TEAD-binding sites in H2052 cells. We found that, in human MPM tissue microarray samples, YAP and PD-L1 concurrently expressed in immunohistochemistry stain (n = 70, P < .05, chi-square). We conclude that PD-L1 is correlated with YAP expression, and inhibition of YAP down-regulates PD-L1 expression in human MPM. Further study of how YAP regulates PD-L1 in MPM is warranted.