Exploring The Intersection Of Rev1 Inhibition And Autophagy: Implications For Cancer Radioresistance
Date of Award
2024
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Cellular, Molecular and Biomedical Sciences
First Advisor
Nimrat Chatterjee
Abstract
The development of therapeutic resistance during cancer management remains a significant obstacle to ideal therapeutic outcomes. The ability of cancer cells to utilize the Translesion Synthesis (TLS) pathway to tolerate and bypass DNA damage induced by genotoxic therapy has been implicated as a mechanism for developing therapeutic resistance. TLS is a DNA damage bypass process that tolerates damage and contributes to mutagenesis, unlike the DNA repair pathway that fixes and repairs DNA damage. Mutagenesis is the cornerstone of cancer resistance to therapy, where newly mutagenized pathways perpetuate the survival of treated cells. As such, inhibition of TLS has garnered interest in solving the therapeutic resistance crisis. Small molecule inhibitors of REV1, a crucial TLS polymerase, effectively sensitize cancer cells to chemotherapy.
First, using small molecule inhibitors of REV1 and mouse REV1 knockdown cell models, we delineated an extensive array of combination treatment modules of strand-breakage agents and REV1 inhibition. In this published work, we showed that despite the prevalence of double-strand breaks from ionizing radiation (IR) or etoposide treatment, the limitation of REV1 was cytoprotective to cells. We found that REV1 inhibition in IR-treated cells triggers an autophagy response with a cytoprotective effect and that REV1 polymerase is associated with a novel function of autophagy. In addition, we determined that autophagy inhibitors provided a narrow window of therapeutic sensitization.
Second, we elucidated the mechanistic link between REV1, a TLS polymerase proposed to be involved in DNA damage bypass primarily in the nucleus, to its newly uncovered cytoplasmic functional regulation of autophagy. We employed high throughput RNA and proteomic analysis to capture gene and pathway enrichments to fully uncover all newer associations of REV1 with other cellular pathways specific to autophagy. Our results confirmed upregulation of the mTOR signaling pathway in REV1-inhibited cells, including associations with distinct energy metabolisms perturbations, such as engagement of glycolysis, endoplasmic stress responses, and unique DNA damage responses in the tested conditions. Mechanistically, REV1 inhibition activates the AMPK/mTOR signaling pathway, a coping mechanism for energy stress that activates autophagy. This pathway specifically relies on genotoxic stress, particularly activation of Chk1, which is known to activate the metabolic stress response with induction of autophagy as a coping mechanism. Further, by targeting the Chk1 signaling pathway through a commercial inhibitor, we rescued REV1-inhibition-induced autophagy, suggesting a significant leap in our understanding of new functional and synthetic lethal treatment model for cancer resistance.
Collectively, this project uncovered new functional attributes of the DNA damage tolerance pathway via REV1 and its mechanistic implications. The results of this dissertation not only significantly add to our understanding of the cancer resistance problem, including clinical decision-making for cancer drug combinations, but most importantly, shed light on fundamental mechanisms of TLS-dependent genome instability programs.
Language
en
Number of Pages
176 p.
Recommended Citation
Ikeh, Kanayo Eugene, "Exploring The Intersection Of Rev1 Inhibition And Autophagy: Implications For Cancer Radioresistance" (2024). Graduate College Dissertations and Theses. 1950.
https://scholarworks.uvm.edu/graddis/1950