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Project description:Approximately 15% of all lung cancer cases are small cell lung cancer (SCLC), which originates from neuroendocrine cells lining the airways (bronchi) of the lung. SCLC is known for its aggressive nature and swift growth, resulting in a five-year survival rate of around 6%. Understanding the genetic pathways that drive tumor development remains an ongoing challenge. In our study, we employed an in vivo multiplexed approach, known as Tuba-seq, to investigate the impact of the functional loss of 18 putative tumor suppressors. Our screening unveiled Pten and Keap1 as top candidates; knocking out either one promoted both tumor initiation and progression. We identified the Keap1/Cul3/Nrf2 pathway as a pivotal regulator for SCLC development, particularly in regulating the susceptibility of SCLC to ferroptosis. Our work not only established an in vivo multiplexed approach for assessing the role of tumor suppressors in SCLC but also uncovers a previously unappreciated role of Keap1 in SCLC.
2024-01-26 | GSE239440 | GEO
Project description:Approximately 15% of all lung cancer cases are small cell lung cancer (SCLC), which originates from neuroendocrine cells lining the airways (bronchi) of the lung. SCLC is known for its aggressive nature and swift growth, resulting in a five-year survival rate of around 6%. Understanding the genetic pathways that drive tumor development remains an ongoing challenge. In our study, we employed an in vivo multiplexed approach, known as Tuba-seq, to investigate the impact of the functional loss of 18 putative tumor suppressors. Our screening unveiled Pten and Keap1 as top candidates; knocking out either one promoted both tumor initiation and progression. We identified the Keap1/Cul3/Nrf2 pathway as a pivotal regulator for SCLC development, particularly in regulating the susceptibility of SCLC to ferroptosis. Our work not only established an in vivo multiplexed approach for assessing the role of tumor suppressors in SCLC but also uncovers a previously unappreciated role of Keap1 in SCLC.
2024-01-26 | GSE239436 | GEO
Project description:Nuclear factor erythroid 2-related factor 2 (Nrf2) is a transcription factor that induces a battery of cytoprotective genes involved in antioxidant defense through binding to Antioxidant Response Elements (ARE) located in the promoter regions of these genes. To identify Nrf2 activators for the treatment of oxidative/electrophilic stress-induced diseases, the present study developed a high-throughput assay to evaluate Nrf2 activation using AREc32 cells that contain a luciferase gene under the control of ARE promoters. Of the 47,000 compounds screened, 238 (top 0.5% hits) of the chemicals increased the luminescent signal more than 14.4-fold and were re-tested at eleven concentrations in a range of 0.01-30 µM. Of these 238 compounds, 231 (96%) increased the luminescence signal in a concentration-dependent manner. Chemical structure relationship analysis of these 231 compounds indicated enrichment of four chemical scaffolds (diaryl amides and diaryl ureas, oxazoles and thiazoles, pyranones and thiapyranones, and pyridinones and pyridazinones). In addition, 30 of these 231 compounds were highly effective and/or potent in activating Nrf2, with a greater than 80-fold increase in luminescence, or an EC50 lower than 1.6 µM. These top 30 compounds were also screened in Hepa1c1c7 cells for an increase in Nqo1 mRNA, the prototypical Nrf2-target gene. Of these 30 compounds, 17 increased Nqo1 mRNA in a concentration-dependent manner. In conclusion, the present study documents the development, implementation, and validation of a high-throughput screen to identify activators of the Keap1-Nrf2-ARE pathway. Results from this screening identified Nrf2 activators, and provide novel insights into chemical scaffolds that might prevent oxidative/electrophilic stress-induced toxicity and carcinogenesis.
| S-EPMC3466241 | biostudies-literature
Project description:BackgroundNuclear factor erythroid-2 related factor 2 (NRF2) is a redox-sensitive transcription factor that positively regulates the expression of genes encoding antioxidants, xenobiotic detoxification enzymes, and drug efflux pumps, and confers cytoprotection against oxidative stress and xenobiotics in normal cells. Kelch-like ECH-associated protein 1 (KEAP1) negatively regulates NRF2 activity by targeting it to proteasomal degradation. Increased expression of cellular antioxidants and xenobiotic detoxification enzymes has been implicated in resistance of tumor cells against chemotherapeutic drugs.Methods and findingsHere we report a systematic analysis of the KEAP1 genomic locus in lung cancer patients and cell lines that revealed deletion, insertion, and missense mutations in functionally important domains of KEAP1 and a very high percentage of loss of heterozygosity at 19p13.2, suggesting that biallelic inactivation of KEAP1 in lung cancer is a common event. Sequencing of KEAP1 in 12 cell lines and 54 non-small-cell lung cancer (NSCLC) samples revealed somatic mutations in KEAP1 in a total of six cell lines and ten tumors at a frequency of 50% and 19%, respectively. All the mutations were within highly conserved amino acid residues located in the Kelch or intervening region domain of the KEAP1 protein, suggesting that these mutations would likely abolish KEAP1 repressor activity. Evaluation of loss of heterozygosity at 19p13.2 revealed allelic losses in 61% of the NSCLC cell lines and 41% of the tumor samples. Decreased KEAP1 activity in cancer cells induced greater nuclear accumulation of NRF2, causing enhanced transcriptional induction of antioxidants, xenobiotic metabolism enzymes, and drug efflux pumps.ConclusionsThis is the first study to our knowledge to demonstrate that biallelic inactivation of KEAP1 is a frequent genetic alteration in NSCLC. Loss of KEAP1 function leading to constitutive activation of NRF2-mediated gene expression in cancer suggests that tumor cells manipulate the NRF2 pathway for their survival against chemotherapeutic agents.
| S-EPMC1584412 | biostudies-literature
Project description:Background and purposeTargeted therapy and immunotherapy have led to dramatic change in the treatment of lung cancer, however, the overall 5-year survival rate of lung cancer patients is still suboptimal. It is important to exploit new potential of molecularly targeted therapies. High-frequency somatic mutations in KEAP1/NRF2 (27.9%) have been identified in lung squamous cell carcinoma. In this research, we explored the role of KEAP1 somatic mutations in the development of LSCC and whether a nuclear factor erythroid 2-related factor 2(NRF2) inhibitor be potential to target lung cancer carrying KEAP1/NRF2 mutations.MethodsLung cancer cell lines A549 and H460 with loss-of-function mutations in KEAP1 stably transfected with wild-type (WT) KEAP1 or somatic mutations in KEAP1 were used to investigate the functions of somatic mutations in KEAP1. Flow cytometry, plate clone formation experiments, and scratch tests were used to examine reactive oxygen species, proliferation, and migration of these cell lines.ResultsThe expression of NRF2 and its target genes increased, and tumor cell proliferation, migration, and tumor growth were accelerated in A549 and H460 cells stably transfected with KEAP1 mutants compared to control cells with a loss-of-function KEAP1 mutation and stably transfected with WT KEAP1 in both in vitro and in vivo studies. The proliferation of A549 cell line trasfected with the R320Q KEAP1 mutant was inhibited more apparent than that of the A549 cell line trasfected with WT KEAP1 after treatment with NRF2 inhibitor ML385.ConclusionSomatic mutations of KEAP1 identified from patients with LSCC likely promote tumorigenesis mediated by activation of the KEAP1/NRF2 antioxidant stress response pathway. NRF2 inhibition with ML385 could inhibit the proliferation of tumor cells with KEAP1 mutation. Video abstract.
| S-EPMC7310414 | biostudies-literature
Project description:The Nrf2 (nuclear factor erythroid 2 [NF-E2]-related factor 2 [Nrf2])-Keap1 (Kelch-like erythroid cell-derived protein with CNC homology [ECH]-associated protein 1) signaling pathway is one of the most important cell defense and survival pathways. Nrf2 can protect cells and tissues from a variety of toxicants and carcinogens by increasing the expression of a number of cytoprotective genes. As a result, several Nrf2 activators are currently being tested as chemopreventive compounds in clinical trials. Just as Nrf2 protects normal cells, studies have shown that Nrf2 may also protect cancer cells from chemotherapeutic agents and facilitate cancer progression. Nrf2 is aberrantly accumulated in many types of cancer, and its expression is associated with a poor prognosis in patients. In addition, Nrf2 expression is induced during the course of drug resistance. Collectively, these studies suggest that Nrf2 contributes to both intrinsic and acquired chemoresistance. This discovery has opened up a broad spectrum of research geared toward a better understanding of the role of Nrf2 in cancer. This review provides an overview of (1) the Nrf2-Keap1 signaling pathway, (2) the dual role of Nrf2 in cancer, (3) the molecular basis of Nrf2 activation in cancer cells, and (4) the challenges in the development of Nrf2-based drugs for chemoprevention and chemotherapy.
| S-EPMC3814639 | biostudies-literature
Project description:OBJECTIVES:Drugs for targeted therapy have become a new strategy of adjuvant therapy for treatment of lung cancer. The Keap1 (kelch-like ECH-associated protein 1)-Nrf2 (nuclear factor erythroid 2-related factor 2) pathway is recognized to be critical in regulating genes related to the cellular protective response and protecting cells from oxidative damages and toxic insult. METHODS:Pubmed, Embase, OVID, and the Cochrane Library databases were searched from the beginning of each database without any limitations to the date of publication. Search terms were "Nrf2" or "Keap1" and "Lung cancer". RESULTS:The upregulation of Nrf2 had been closely related to tumor protection and drug resistance. The aberrant state of Keap1 or Nrf2 that were frequently found in lung cancer conferred a poor prognosis. Nrf2 could prevent cells from undergoing oncogenesis as a tumor suppressor, while it could also promote cancer progression and resistance to chemotherapeutic drugs as an oncogene, depending on the different stages of tumor progression. Target Nrf2 signaling by specific chemicals showed it could prevent tumor growth or combat chemoresistance. CONCLUSIONS:Increasing evidence has demonstrated the dual roles of the Keap1-Nrf2 pathway in tumor initiation and progression. In this paper, we provide a comprehensive overview of the potency of the Keap1-Nrf2 pathway as an antitumor target, and the current status of Nrf2 activators or inhibitors for therapeutic approaches. Further studies are required to clarify the role of Nrf2 in lung cancer at different tumor stages, in order to maximize the efficacy of Keap1-Nrf2 targeting agents.
| S-EPMC5643752 | biostudies-literature
Project description:The nuclear factor-E2-related factor 2 (NRF2) serves as a master regulator in cellular defense against oxidative stress and chemical detoxification. However, persistent activation of NRF2 resulting from mutations in NRF2 and/or downregulation of or mutations in its suppressor, Kelch-like ECH-associated protein 1 (KEAP1), is associated with tumorigenicity and chemoresistance of non-small-cell lung carcinomas (NSCLCs). Thus, inhibiting the NRF2-mediated adaptive antioxidant response is widely considered a promising strategy to prevent tumor growth and reverse chemoresistance in NSCLCs. Unexpectedly, stable knockdown of KEAP1 by lentiviral shRNA sensitized three independent NSCLC cell lines (A549, HTB-178, and HTB-182) to multiple chemotherapeutic agents, including arsenic trioxide (As(2)O(3)), etoposide, and doxorubicin, despite moderately increased NRF2 levels. In lung adenocarcinoma epithelial A549 cells, silencing of KEAP1 augmented the expression of peroxisome proliferator-activated receptor γ (PPARγ) and genes associated with cell differentiation, including E-cadherin and gelsolin. In addition, KEAP1-knockdown A549 cells displayed attenuated expression of the proto-oncogene cyclin D1 and markers for cancer stem cells (CSCs) and reduced nonadherent sphere formation. Moreover, deficiency of KEAP1 led to elevated induction of PPARγ in response to As(2)O(3). Pretreatment of A549 cells with PPARγ agonists activated PPARγ and augmented the cytotoxicity of As(2)O(3). A mathematical model was formulated to advance a hypothesis that differential regulation of PPARγ and detoxification enzymes by KEAP1 and NRF2 may underpin the observed landscape changes in chemosensitivity. Collectively, suppression of KEAP1 expression in human NSCLC cells resulted in sensitization to chemotherapeutic agents, which may be attributed to activation of PPARγ and subsequent alterations in cell differentiation and CSC abundance.
| S-EPMC3418425 | biostudies-literature
Project description:Keratinization is a tissue adaptation, but aberrant keratinization is associated with skin disorders such as ichthyoses, atopic dermatitis, psoriasis, and acne. The disease phenotype stems from the interaction between genes and the environment; therefore, an understanding of the adaptation machinery may lead to a new appreciation of pathomechanisms. The KEAP1/NRF2 signaling pathway mediates the environmental responses of squamous epithelial tissue. The unpredicted outcome of the Keap1-null mutation in mice allowed us to revisit the basic principle of the biological process of keratinization: sulfur metabolism establishes unparalleled cytoprotection in the body wall of terrestrial mammals. We summarize the recent understanding of the KEAP1/NRF2 signaling pathway, which is a thiol-based sensor-effector apparatus, with particular focuses on epidermal differentiation in the context of the gene-environment interaction, the structure/function principles involved in KEAP1/NRF2 signaling, lessons from mouse models, and their pathological implications. This synthesis may provide insights into keratinization, which provides physical insulation and constitutes an essential innate integumentary defense system.
| S-EPMC7465315 | biostudies-literature
Project description:Kelch-like ECH-associated protein 1 (Keap1)-nuclear factor erythroid 2-related factor 2 (Nrf2)-antioxidant response elements (ARE) pathway represents one of the most important cellular defense mechanisms against oxidative stress and xenobiotic damage. Activation of Nrf2 signaling induces the transcriptional regulation of ARE-dependent expression of various detoxifying and antioxidant defense enzymes and proteins. Keap1-Nrf2-ARE signaling has become an attractive target for the prevention and treatment of oxidative stress-related diseases and conditions including cancer, neurodegenerative, cardiovascular, metabolic, and inflammatory diseases. Over the last few decades, numerous Nrf2 inducers have been developed and some of them are currently undergoing clinical trials. Recently, overactivation of Nrf2 has been implicated in cancer progression as well as in drug resistance to cancer chemotherapy. Thus, Nrf2 inhibitors could potentially be used to improve the effectiveness of cancer therapy. Herein, we review the signaling mechanism of Keap1-Nrf2-ARE pathway, its disease relevance, and currently known classes of small molecule modulators. We also discuss several aspects of Keap1-Nrf2 interaction, Nrf2-based peptide inhibitor design, and the screening assays currently used for the discovery of direct inhibitors of Keap1-Nrf2 interaction.
| S-EPMC3393814 | biostudies-literature