NAD+ salvage pathway in cancer metabolism and therapy

Nicotinamide adenine dinucleotide (NAD(+)) is an essential coenzyme for various physiological processes including energy metabolism, DNA repair, cell growth, and cell death. Many of these pathways are typically dysregulated in cancer cells, making NAD(+) an intriguing target for cancer therapeutics. NAD(+) is mainly synthesized by the NAD(+) salvage pathway in cancer cells, and not surprisingly, the pharmacological targeting of the NAD(+) salvage pathway causes cancer cell cytotoxicity in vitro and in vivo. Several studies have described the precise consequences of NAD(+) depletion on cancer biology, and have demonstrated that NAD(+) depletion results in depletion of energy levels through lowered rates of glycolysis, reduced citric acid cycle activity, and decreased oxidative phosphorylation. Additionally, depletion of NAD(+) causes sensitization of cancer cells to oxidative damage by disruption of the anti-oxidant defense system, decreased cell proliferation, and initiation of cell death through manipulation of cell signaling pathways (e.g., SIRT1 and p53). Recently, studies have explored the effect of well-known cancer therapeutics in combination with pharmacological depletion of NAD(+) levels, and found in many cases a synergistic effect on cancer cell cytotoxicity. In this context, we will discuss the effects of NAD(+) salvage pathway inhibition on cancer cell biology and provide insight on this pathway as a novel anti-cancer therapeutic target. (C) 2016 Elsevier Ltd. All rights reserved.