Dissertation
Targeting NAD metabolism in cancer therapy
University of Iowa
Doctor of Philosophy (PhD), University of Iowa
Spring 2021
DOI: 10.17077/etd.005773
Abstract
Nicotinamide adenine dinucleotide (NAD) is fundamental to electron movement and metabolism in all living organisms. Tumor cells exhibit NAD metabolic dependencies that may be amenable to targeting with available agents. Two primary means by which cells synthesize NAD+ are driven by nicotinic acid phosphoribosyltransferase (NAPRT) and nicotinamide phosphoribosyltransferase (NAMPT). Multiple potent and selective NAMPT inhibitors (NAMPTi’s; GMX-1778, FK866) have been developed and demonstrate robust anti-tumor activity in pre-clinical models in vitro and in vivo. First, we tested the hypothesis that specific inhibition of NAMPT would deplete NAD(P)(H) and selectively induce metabolic oxidative stress in non-small cell lung cancer (NSCLC) cells, and that this effect would be augmented by radiation, chemotherapies, and pharmacological ascorbate (P-AscH-). We found that physiologically-relevant doses of NAMPTi’s induce NAD(P)(H) depletion and clonogenic cell death that is prevented by nicotinic acid (NA) supplementation. Furthermore, NAMPTi’s induce metabolic oxidative stress characterized by glutathione depletion and/or oxidation, increased mitochondrial pro-oxidant production and significant sensitization to agents that modulate steady-state levels of hydroperoxides. In addition, NAMPTi’s sensitize tumor cells, but not normal human fibroblasts (NHFs) to temozolomide (TMZ) and cisplatin and serve as effective radiosensitizers. Second, we characterized NAPRT expression as a biomarker for NAMPTi sensitivity utilizing publicly available data from the Cancer Dependency Map (DepMap). We found that rhabdomyosarcoma (RMS) and glioma cell lines exhibit high degrees of NAPRT promoter methylation accompanied by low NAPRT mRNA and protein levels relative to other cancer types. Clonogenic survival assays showed that NAPRT-silenced RMS cells are highly sensitive to GMX-1778 (GMX) and that this toxicity is not rescued by NA-supplementation, confirming that functional NAPRT is not expressed by these cells. Finally, we found that GMX exhibited potent sensitization toward TMZ and P-AscH- in NAPRT-silenced sarcoma cell lines. Overall, these results suggest that NAMPTi’s may serve as promising adjuvants for cancer therapy and designate RMS and gliomas as potential targets for NAMPTi’s.
Details
- Title: Subtitle
- Targeting NAD metabolism in cancer therapy
- Creators
- Collin David Heer
- Contributors
- Douglas R. Spitz (Advisor)Garry R. Buettner (Committee Member)Eric B. Taylor (Committee Member)Bryan G. Allen (Committee Member)Prabhat C. Goswami (Committee Member)
- Resource Type
- Dissertation
- Degree Awarded
- Doctor of Philosophy (PhD), University of Iowa
- Degree in
- Biochemistry
- Date degree season
- Spring 2021
- DOI
- 10.17077/etd.005773
- Publisher
- University of Iowa
- Number of pages
- xvii, 140 pages
- Copyright
- Copyright 2021 Collin David Heer
- Language
- English
- Description illustrations
- color illustrations
- Description bibliographic
- Includes bibligraphical references (pages 107-140)
- Public Abstract (ETD)
The goal of this work is to increase the efficacy of existing cancer therapies by combining them with agents that target fundamental differences in NAD metabolism between tumor and normal cells. NAD represents a group of four molecules essential for electron movement in biological organisms. There are two primary means by which cells synthesize NAD that are governed by two enzymes called nicotinamide phosphoribosyltransferase (NAMPT) and nicotinic acid phosphoribosyltransferase (NAPRT). Small molecules have been developed that inhibit the activity of NAMPT (NAMPTi’s). Our studies show that NAMPTi’s induce oxidative stress in tumor cells and sensitize them to current cancer therapies such as radiation and chemotherapies. Crucially, these NAMPTi’s do not chemo-sensitize normal cells. Furthermore, we have characterized NAPRT expression as a biomarker for sensitivity to NAMPTi’s that can assist physicians in identifying which patient tumors are more likely to respond to treatment with NAMPTi’s. Overall, these findings are significant, as they have the potential to illuminate specific differences in NAD metabolism in cancer that can be exploited to improve patient outcomes.
- Academic Unit
- Biochemistry and Molecular Biology
- Record Identifier
- 9984097075902771
Metrics
8 File views/ downloads
209 Record Views