Abstract 1299: KEAP1-NRF2-ARE signaling interacts with the SWI/SNF chromatin remodeling complex in non-small cell lung cancer.

Abstract

Abstract NF-E2-related factor 2 (NRF2), negatively regulated by KEAP1, modulates induction of a battery of cytoprotective genes against oxidative stress via binding to the antioxidant responsive element (ARE) sequence. Recent NGS studies have shown a significant number of mutations in the KEAP1-NRF2-ARE signaling pathway, implicating aberrant activation of this pathway in lung cancer carcinogenesis and chemoresistance. The SWI/SNF chromatin-remodeling complex, employing either BRG1 or BRM as a catalytic subunit, regulates gene expression and alters chromatin structures in an ATP-dependent manner. Loss of complex function often occurs in lung cancers, via mutations in complex subunits. Since KEAP1/NRF2 mutations and BRG1/BRM loss occur frequently in non-small cell lung cancers (NSCLCs) in a mutually exclusive fashion, we hypothesized that BRG1 and/or BRM play(s) a role in the regulation of NRF2 target genes. To test this hypothesis, we developed a series of isogenic H358 NSCLC lines with reduced BRG1 and/or BRM expression using shRNA technology. We observed a significant increase in the levels of HMOX1 (heme oxygenase1) and GSTM4 (Glutathione S-transferase Mu 4) with a concomitant decrease in NQO1 (NAD(P)H dehydrogenase, quinone 1) in the BRG1-deficient H358 cell lines. However, GCLM (Glutamate–cysteine ligase regulatory subunit) was elevated only in the BRM-reduced H358 cells. Interestingly, BRG1 loss, either alone or combined with BRM loss, promoted SDS-resistant KEAP1 dimerization. We are currently examining whether BRG1 and/or BRM loss increases ROS levels. Chromatin immunoprecipitation (ChIP) showed that NRF2 were enriched at NRF2 downstream genes in both H358 parental and vector control cells, whereas BRG1 knockdown led to a moderate increase (HMOX1) or decrease (NQO1) in NRF2 binding. These results provide evidence that loss of SWI/SNF chromatin remodeling complex activity alters the NRF2 pathway in NSCLC. Furthermore, novel drugs targeting NRF2 downstream genes might provide a therapeutic approach for BRG1 deficient NSCLC patients. Citation Format: Shujie Song, Tess Orvis, Yanfang Zheng, Michael B. Major, Bernard E. Weissman. KEAP1-NRF2-ARE signaling interacts with the SWI/SNF chromatin remodeling complex in non-small cell lung cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1299. doi:10.1158/1538-7445.AM2013-1299