Understanding Vulnerabilities in Metabolism and DNA Repair in Oncometabolite-producing Cancers
Date of Award
Spring 2023
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Molecular Biophysics and Biochemistry
First Advisor
Bindra, Ranjit
Abstract
Cancer associated mutations in citric acid cycle enzymes cause overproduction of2-hydroxyglutarate (2HG), fumarate, or succinate, commonly referred to as oncometabolites. These oncometabolite-producing mutations are prevalent in 70% of gliomas, >75% of hereditary leiomyomatosis and renal cell carcinoma, and >25% of paraganglioma and pheochromocytomas, respectively, and contribute to their progression. These oncometabolites can competitively inhibit alpha ketoglutarate dependent dioxygenases, which includes lysine demethylases (KDMs) and ten eleven translocation (TET) enzymes. As a result, both histone methylation and DNA methylation is increased in oncometabolite-producing cancers. Previous work has established that the histone hypermethylation results in the suppression of homologous recombination, and therefore DNA double strand break (DSB) repair. This phenomenon and potential vulnerabilities conferred by the DNA hypermethylation phenotype requires further investigation to ultimately design more targeted therapeutic strategies. Here, I demonstrate that DNA hypermethylation in oncometaboliteproducing cancers results in silencing of nicotinate phosphoribosyl transferase (NAPRT) in cell line models and patient samples, a vital enzyme for NAD+ biosynthesis via the Preiss Handler pathway. The hypermethylation of the NAPRT promoter and subsequent silencing confers sensitivity to nicotinamide phosphoribosyl transferase (NAMPT) inhibitors, which further prevents NAD+ biosynthesis by inhibiting the NAM Salvage Pathway. As NAD+ is used to synthesize poly-ADP-ribose (PAR) chains by Poly (ADP-ribose) Polymerases (PARPs), I find that NAMPTis and PARPis synergize and have profiled the downstream effects of these inhibitors on DNA repair in cell line models of FH-deficient RCC. To further understand DSB repair in oncometabolite-producing cancers, I also profile the role of Pol theta, an enzyme involved in another mode of DSB repair, in genomic stability in HR-deficient IDH1R132H cells. Overall, my findings indicate that oncometabolite induced hypermethylation leads to novel vulnerabilities in NAD+ metabolism and DSB repair, which can be exploited for further therapeutic gain in combination with other DNA repair inhibitors. This underscores the interconnected nature of impact diverse cellular processes from epigenetics to metabolism and DNA repair.
Recommended Citation
Noronha, Katelyn, "Understanding Vulnerabilities in Metabolism and DNA Repair in Oncometabolite-producing Cancers" (2023). Yale Graduate School of Arts and Sciences Dissertations. 1372.
https://elischolar.library.yale.edu/gsas_dissertations/1372
