Graduation Year

2023

Document Type

Dissertation

Degree

Ph.D.

Degree Name

Doctor of Philosophy (Ph.D.)

Degree Granting Department

Biology (Cell Biology, Microbiology, Molecular Biology)

Major Professor

Gina M. DeNicola, Ph.D.

Committee Member

Joseph L. Kissil, Ph.D.

Committee Member

Ana P. Gomes, Ph.D.

Committee Member

Elsa Flores, Ph.D.

Committee Member

Amer Beg, Ph.D.

Committee Member

Marcus Cooke, Ph.D.

Keywords

Kelch-like ECH-associated protein 1 (KEAP1), Cancer, Genetically engineered mouse model (GEMM)

Abstract

NRF2 is a redox-responsive transcription factor the directs the antioxidant program and several critical metabolic processes. Mutations in NRF2 or its negative regulator KEAP1 occur in up to one third of non-small cell lung cancers (NSCLCs) and are often associated with resistance to therapy and poor outcomes. In the present studies, murine alleles of the Keap1 and Nrf2 mutations found in human NSCLC were developed and I comprehensively investigated their impact on tumor initiation and progression. I observed that chronic Nrf2 stabilization by Keap1 loss-of-function or Nrf2 activating mutation was not sufficient to cause lung tumor initiation, even when p53 or Lkb1 were deleted. In the context of oncogenic KrasG12D/+, constitutive Nrf2 activation via Keap1/ Nrf2 mutation promoted lung tumor initiation and early progression of hyperplasia to low-grade tumors. When KrasG12D/+ was combined with p53 deletion, I observed an impairment in progression to advanced-grade tumors with Keap1R554Q/R554Q mutation, which caused the most robust Nrf2 activation. I discovered that this progression block was reversed by NRF2 deletion, indicating that the effects of Keap1 mutation in this model were Nrf2-dependent. I also interrogated the effect of Nrf2 hyperactivation in another mutational background, the KrasG12D/+; Lkb1fl/fl model. Interestingly, Nrf2D29H/+ mutation, which was the most activating towards Nrf2 in this model, blocked progression to high-grade tumors, suggesting that excess levels of Nrf2 are detrimental to lung tumor progression. Finally, I observed that NRF2 overexpression in KEAP1 mutant human NSCLC cell lines impaired cell proliferation, viability, and anchorage-independent colony formation. Collectively, these results establish the context-dependence and activity threshold for NRF2 during the lung tumorigenic process.

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