Nicotinamide adenine dinucleotide (NAD) is a key regulator of several metabolic and signaling pathways that are relevant in cancer cell survival. Cancer cells have an increased energy demand associated with an increased NAD turnover. Nicotinamide phosphoribosyltransferase (NAMPT), a key enzyme of the NAD salvage pathway, plays a crucial role in maintaining the intracellular NAD levels and in regulating the activity of NAD-dependent enzymes, such as sirtuins (SIRTs). The inhibition of NAMPT activity and the use of phytochemicals, such as resveratrol, represent novel therapeutic approaches in cancer therapy. Based on these facts, this thesis aimed to investigate (1) the chemotherapeutic potential and molecular mechanisms of FK866, a specific NAMPT inhibitor, and resveratrol on hepatocarcinoma cells and to find out whether there are differences compared to primary human hepatocytes; (2) to address the impact of NAMPT inhibition on the energy metabolism in cancer cells; and (3) to investigate the roles of NAMPT and SIRT1 in resveratrol´s mode of action and chemotherapeutic effects. This work demonstrates that FK866 and resveratrol possess potent chemotherapeutic effects in hepatocarcinoma cells which were absent in human hepatocytes. Hepatocarcinoma cells display a dysregulation in the AMP-activated kinase (AMPK)/mammalian target of rapamycin (mTOR) signaling as well as in the NAMPT-mediated NAD salvage pathway compared to human hepatocytes. FK866-induced NAMPT inhibition induces ATP depletion associated with AMPK activation and mTOR inhibition whereas resveratrol induces caspase3-mediated apoptosis that is not dependent on NAMPT and SIRT1 function. NAMPT and SIRT1 are differentially regulated by resveratrol in hepatocarcinoma cells and human hepatocytes. This work also reveals that resveratrol activates p53-induced cell cycle arrest in hepatocarcinoma cells which is partly mediated by SIRT1 inhibition. In summary, this thesis provides new insight into the role of the NAMPT-mediated NAD salvage pathway in energy metabolism and characterized FK866 and resveratrol as promising potential chemotherapeutic agents for treatment of hepatocellular carcinoma.
| Identifer | oai:union.ndltd.org:DRESDEN/oai:qucosa:de:qucosa:13395 |
| Date | 03 July 2015 |
| Creators | Schuster, Susanne |
| Contributors | Beck-Sickinger, Annette G., Kiess, Wieland, Universität Leipzig |
| Source Sets | Hochschulschriftenserver (HSSS) der SLUB Dresden |
| Language | English |
| Detected Language | English |
| Type | doc-type:doctoralThesis, info:eu-repo/semantics/doctoralThesis, doc-type:Text |
| Rights | info:eu-repo/semantics/openAccess |
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