Loss of BRMS1 Promotes a Mesenchymal Phenotype through NF-κB-Dependent Regulation ofTwist1

Abstract

Breast cancer metastasis suppressor 1 (BRMS1) is downregulated in non-small cell lung cancer (NSCLC), and its reduction correlates with disease progression. Herein, we investigate the mechanisms through which loss of theBRMS1gene contributes to epithelial-to-mesenchymal transition (EMT). Using a short hairpin RNA (shRNA) system, we show that loss of BRMS1 promotes basal and transforming growth factor beta-induced EMT in NSCLC cells. NSCLC cells expressingBRMS1shRNAs (BRMS1knockdown [BRMS1KD]) display mesenchymal characteristics, including enhanced cell migration and differential regulation of the EMT markers. Mesenchymal phenotypes observed inBRMS1KDcells are dependent on RelA/p65, the transcriptionally active subunit of nuclear factor kappa B (NF-κB). In addition, chromatin immunoprecipitation analysis demonstrates that loss ofBRMS1increasesTwist1promoter occupancy of RelA/p65 K310—a key histone modification associated with increased transcription. Knockdown ofTwist1results in reversal ofBRMS1KD-mediated EMT phenotypic changes. Moreover, in our animal model,BRMS1KD/Twist1KDdouble knockdown cells were less efficient in establishing lung tumors thanBRMS1KDcells. Collectively, this study demonstrates that loss of BRMS1 promotes malignant phenotypes that are dependent on NF-κB-dependent regulation ofTwist1. These observations offer fresh insight into the mechanisms through which BRMS1 regulates the development of metastases in NSCLC.