Project description:KEAP1 overexpressed and NRF2 siRNA knockdown A549 NSCLC cells were used to identify downstream genes of NRF2 pathway separately and by combinatorial analysis. We used triplicate microarrays of transfected A549 cells with mKeap1-GFP for overexpression, siRNAs targeting NRF2 for knockdown and siGFP as control respectively. As a result, we identified several genes which are involved in cancer metabolic functions in these cells. We used microarrays to identify the gene downregulated in both KEAP1 overexpressed and NRF2 siRNA knockdown A549 NSCLC cells and found a subset of downregulated genes which are involved in metabolic functions.
Project description:Multiple cancers regulate oxidative stress by activating the transcription factor NRF2 through mutation of its negative regulator KEAP1. NRF2 has been studied extensively in KEAP1-mutant cancers, however the role of this pathway in cancers with wildtype KEAP1 remains poorly understood. To answer this question, we induced NRF2 via pharmacological inactivation of KEAP1 in a panel of 50+ non-small cell lung cancer cell lines. Unexpectedly, marked decreases in viability were observed in >13% of the cell lines—an effect that was rescued by NRF2 ablation. Genome-wide and targeted CRISPR screens revealed that NRF2 induces NADH-reductive stress, through the upregulation of the NAD+-consuming enzyme ALDH3A1. Leveraging these findings, we show that cells treated with KEAP1 inhibitors or those with endogenous KEAP1 mutations are selectively vulnerable to Complex I inhibition, which impairs NADH oxidation capacity and potentiates reductive stress. Thus, we identify reductive stress as a metabolic vulnerability in NRF2-activated lung cancers.
Project description:Considerable advances have been made in lung cancer therapies, but there is still an unmet clinical need to improve survival for lung cancer patients. Immunotherapies have improved survival, although only 20-30% of patients respond to these treatments. Interestingly, cancers with mutations in KEAP1, the negative regulator of the NRF2 cytoprotective pathway, are resistant to immune checkpoint inhibition and correlate with decreased immune cell infiltration. NRF2 is known for promoting an anti-inflammatory phenotype when activated in immune cells, but the study of NRF2 activation in cancer cells has not been adequately assessed. The objective of this study was to determine how lung cancer cells with constitutive NRF2 activity interact with the immune microenvironment to promote cancer progression. To assess this, we generated CRISPR-edited mouse lung cancer cell lines by knocking out KEAP1 or NFE2L2 genes. We also utilized publicly available single cell data through the Gene Expression Omnibus to investigate tumor/immune cell interactions. We show here that KEAP1-mutant cancers promote immunosuppression of the tumor microenvironment. Our data suggests KEAP1-deletion is sufficient to alter the secretion of cytokines, increase expression of immune checkpoint markers on cancer cells, and alter recruitment and differential polarization of immunosuppressive macrophages that ultimately lead to T cell suppression.
Project description:We identified RNA binding motif protein 47 (RBM47) as a target gene of transforming growth factor (TGF)-beta in mammary gland epithelial cells (NMuMG cells) that have undergone the epithelial-to-mesenchymal transition (EMT). TGF-beta repressed RBM47 expression in NMuMG cells and lung cancer cell lines. Expression of RBM47 correlated with good prognosis in patients with lung, breast, and gastric cancer. RBM47 suppressed the expression of cell metabolism-related genes, which were the direct targets of nuclear factor erythroid 2-related factor 2 (Nrf2; also known as NFE2L2). RBM47 bound to KEAP1 and Cullin3 mRNAs, and knockdown of RBM47 inhibited their protein expression, which led to enhanced binding of Nrf2 to target genomic regions. Knockdown of RBM47 also enhanced the expression of some Nrf2 activators, p21/CDKN1A and MafK induced by TGF-beta. Both mitochondrial respiration rates and the side population cells in lung cancer cells increased in the absence of RBM47. Our findings, together with the enhanced tumor formation and metastasis of xenografted mice by knockdown of the RBM47 expression, suggested tumor suppressive roles for RBM47 through the inhibition of Nrf2 activity. Effect of shRNA for RBM47 and TGF-beta on gene expression was evaluated by RNA-seq and RBM47-bound RNAs were identified by RIP-seq in A549 cells.
Project description:Cancer-derived loss-of-function mutations in the KEAP1 tumor suppressor gene stabilize the NRF2 transcription factor, resulting in a pro-survival gene expression program that alters cellular metabolism and neutralizes oxidative stress. In a previous study of KEAP1 mutations observed in lung cancer, we classified 40% of the mutations as ‘superbinders’ (superbinders). These mutants bind and ubiquitylate NRF2 but do not promote NRF2 degradation. Here, we further investigated the molecular mechanism(s) driving the superbinder phenotype. BioID-based quantitative proteomic analysis of the R320Q and R470C superbinder mutations revealed increased co-complexed NRF2 without significant alteration to other KEAP1-associated proteins, including CUL3, VCP, and several ubiquitin receptors within the proteasome lid. Dynamic simulation modeling and limited proteolysis analyses suggest that superbinder mutations stabilize residues in KEAP1 that contact NRF2. In cells, KEAP1 R320Q and R470C mutants co-localize with NRF2, p62/SQSTM1 and polyubiquitin in spherical clusters that rapidly fuse and dissolve; KEAP1-NRF2 localization to these clusters requires p62. Expression of R320Q and R470C in lung cancer cells provided resistance to the reactive oxygen species-inducing drug bleomycin. We present a model wherein superbinder mutations alter the conformational dynamics of the KEAP1-NRF2 complex to alter the cycling of KEAP1 between open and closed conformations, thus inhibiting NRF2 degradation.
Project description:HCC515 lung cells with dox-inducible KEAP1 knockdown and/or STK11 re-addition, under two different metabolic stress conditions, baseline vs. suspension, were transcriptionally profiled to investigate whether KEAP1 knockdown can rescue metabolic defects in STK11-null cancer cells and how the regulation of the transcriptome by KEAP1 knockdown is affected by STK11 status and different metabolic stress conditions. In lung adenocarcinoma (LUAD), stabilization of the transcription factor NRF2 through genomic alterations in KEAP1 and NFE2L2 occurs in roughly a quarter of patients, often in the context of STK11 tumor suppressor loss. In this study, we demonstrate that NRF2 activation in the context of concurrent KRAS mutation and STK11 loss promotes aggressive LUAD tumor behavior in both human and mouse preclinical models. This phenotype is associated with metabolic rewiring and rescue by NRF2 of redox stress, high in STK11 null tumors. Applying a novel, pan-lung cancer, diagnostic NRF2 activation gene expression signature that is independent of frequently co-occurring mutations, we dissect the independent contributions of the three most frequent genetic events in human LUAD (NRF2 activation, STK11 loss and KRAS mutations) on patient prognosis and clinical responses in a dataset of second-line LUAD patients treated with immunotherapy or chemotherapy (OAK trial). Our findings underscore that both individual effects and epistatic relationships among oncogenic and tumor suppressor pathways influence tumor biology, immune contexture and patient clinical outcomes. Our work also highlights the value of lung cancer disease sub-classification based on genetic and expression profiling as part of patient clinical management.