Targeting antioxidant vulnerabilities in KEAP1/NRF2 mutant NSCLC

The transcription factor NRF2 is a central regulator of cellular redox balance. Mutations in NRF2 and its negative regulator KEAP1 are found in 15-34% of non-small cell lung cancer (NSCLC). The result of these mutations is constitutive NRF2 activation and chronic induction of a battery of NRF2 target genes, which confers resistance

to chemo/radiation therapy. While targeting NRF2 holds great therapeutic potential, there is no effective strategy to inhibit the consequences of pathogenic KEAP1/NRF2 signaling. It is therefore critical to identify and understand vulnerabilities of KEAP1/NRF2 mutant NSCLC to develop effective therapies for patients harboring

these mutations. NRF2 controls the transcription of many antioxidant enzymes, thereby regulating the detoxification of reactive oxygen species. However, it remains largely unknown which specific antioxidant enzymes can be therapeutically targeted to reverse the profound resistance of NRF2/KEAP1 mutations to

oxidative stress, the key mediator of chemo/radiation therapy. Glutathione (GSH)/GSH reductase (GSR) and thioredoxin (TXN)/thioredoxin reductase (TXNRD) are two parallel, compensating thiol-dependent antioxidant pathways that critically regulate and maintain cellular thiol redox homeostasis and protein dithiol/disulfide

balance. My preliminary results indicate that both GSR and TXNRD1 are strongly induced by NRF2 activation and contribute to the intrinsic resistance to the pro-oxidant therapies. However, they play unique roles in different cellular compartments. Specifically, NRF2 induced GSR acts to protect mitochondria from oxidation, while

TXNRD1 protects the cytosol. Further, TXNRD1 upregulation is associated with the suppression of other selenoproteins, suggesting that NRF2 activation causes an imbalance in selenium distribution. Given the key role of selenoprotein in redox biology, the switch in the production of the different selenoproteins induced by

NRF2 activation may create novel vulnerabilities of NRF2 active NSCLC with therapeutic potential. This proposal is designed to further strengthen these observations by defining the mechanistic basis of how GSR contributes to NRF2-mediated resistance to oxidative stress, and to leverage the imbalanced selenoprotein translation to

develop potent therapeutic strategies for KEAP1/NRF2 mutant NSCLC. The following specific aims are pursued in this application: Aim 1. Investigate the role of GSR in NRF2-mediated resistance to oxidative stress. Aim 2. Define the role of NRF2 as a modulator of the selenoproteome in NSCLC. The knowledge and scientific expertise

that I acquire from these proposed studies will facilitate my transition to an independent position. My long-term goal is to study the antioxidant enzymes in cancer, with a major focus on selenoproteins. In addition to the scientific goal, I have outlined a detailed career development plan to obtain skillsets that are key for leading a

research laboratory and establishing a strong research program. I will conduct the proposed research and carry out the training plan under the guidance of my mentoring committee. I will embark on the excellent academic environment provided by Moffitt Cancer Center to achieve these goals and transition to an independent position.