Nicotinamide phosphoribosyltransferase (Nampt) inhibitors such as FK866 are potent inhibitors of NAD+ synthesis that show promise for the treatment of different forms of cancer. Based on Nampt upregulation in activated T lymphocytes and on preliminary reports of lymphopenia in FK866 treated patients, we have investigated FK866 for its capacity to interfere with T lymphocyte function and survival. Intracellular pyridine nucleotides, ATP, mitochondrial function, viability, proliferation, activation markers and cytokine secretion were assessed in resting and in activated human T lymphocytes. In addition, we used experimental autoimmune encephalomyelitis (EAE) as a model of T-cell mediated autoimmune disease to assess FK866 efficacy in vivo. We show that activated, but not resting, T lymphocytes undergo massive NAD+ depletion upon FK866-mediated Nampt inhibition. As a consequence, impaired proliferation, reduced IFN-γ and TNF-α production, and finally autophagic cell demise result. We demonstrate that upregulation of the NAD+-degrading enzyme poly-(ADP-ribose)-polymerase (PARP) by activated T cells enhances their susceptibility to NAD+ depletion. In addition, we relate defective IFN-γ and TNF-α production in response to FK866 to impaired Sirt6 activity. Finally, we show that FK866 strikingly reduces the neurological damage and the clinical manifestations of EAE. In conclusion, Nampt inhibitors (and possibly Sirt6 inhibitors) could be used to modulate T cell-mediated immune responses and thereby be beneficial in immune-mediated disorders.

Background:Cytokine secretion has unwanted consequences in malignant and in inflammatory disorders. The deacetylase SIRT6 has pro-inflammatory activity, but the underlying mechanisms and its biological significance remain unclear. The relationship between inflammation and carcinogenesis has been known for many years (1). Chronic inflammation is a risk factor for cancer development. In addition, even in those cancers that do not develop in inflamed tissues, an inflammatory component is usually observed, and it is now known to be an essential part of the malignant microenvironment (2, 3). Inflammation contributes to tumorigenesis and cancer progression by supplying growth factors that sustain cancer cell proliferation and/or survival, proangiogenic factors, extracellular matrix-modifying enzymes that promote invasion and metastasis, and signals that lead to epithelial-mesenchymal transition (2, 4, 5). Moreover, increased circulating levels of pro-inflammatory cytokines are responsible for systemic manifestations of disease, such as cachexia, fever, and sweats (6 -9). Among other forms of cancer, pancreatic ductal adenocarcinoma (PDAC) 2 is well known for its propensity to secrete high levels of pro-inflammatory factors that contribute to its clinical aggressiveness and to its metastatic potential (10). The mechanisms controlling cyto-/chemokine production by inflammatory and cancer cells are only partially understood. A more detailed understanding of the molecular pathways leading to cancer-associated inflammation may lead to new therapeutic strategies with a strong impact on patient quality of life.Previous studies showed that intracellular nicotinamide adenine dinucleotide (NAD ϩ ) levels influence the capacity of inflammatory cells to secrete cytokines, such as tumor necrosis factor ␣ (TNF), interleukin 6 (IL6), IL1␤, interferon ␥ (IFN-␥), * This work was supported in part by the Associazione Italiana per la Ricerca sul Cancro (AIRC, Code 6108) (to A. N.), by the European Seventh Framework Program (Project 256986, PANACREAS) (to A. N.), by Ministero della Salute Grant GR-2008-1135635 (to A. N.)

Background: NAMPT inhibitors showed antitumor activity in preclinical cancer models, but no tumor remission occurred in clinical studies. Results: Cells treated with a NAMPT inhibitor are rescued by low NAD

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Background: Nicotinamide phosphoribosyltransferase (NAMPT) acts both as an enzyme in the production of the coenzyme NAD ϩ and as a secreted cytokine.

Nicotinamide adenine dinucleotide (NAD+) biosynthesis from nicotinamide is used by mammalian cells to replenish their NAD+ stores and to avoid unwanted nicotinamide accumulation. Pharmacological inhibition of nicotinamide phosphoribosyltransferase (NAMPT), the key enzyme in this biosynthetic pathway, almost invariably leads to intracellular NAD+ depletion and, when protracted, to ATP shortage and cell demise. Cancer cells and activated immune cells express high levels of NAMPT and are highly susceptible to NAMPT inhibitors, as shown by the activity of these agents in models of malignant and inflammatory disorders. As the spectrum of conditions which could benefit from pharmacological NAMPT inhibition becomes broader, the mechanisms accounting for their activity are also eventually becoming apparent, including the induction of autophagy and the impairment of Ca2+--and NF-κB-dependent signaling. Here, we discuss the rationales for exploiting NAMPT inhibitors in cancer and inflammatory diseases and provide an overview of the preclinical and clinical studies in which these agents have been evaluated.

Genomic instability plays a pathological role in various malignancies, including acute myeloid leukemia (AML), and thus represents a potential therapeutic target. Recent studies demonstrate that SIRT6, a NAD+-dependent nuclear deacetylase, functions as genome-guardian by preserving DNA integrity in different tumor cells. Here, we demonstrate that also CD34+ blasts from AML patients show ongoing DNA damage and SIRT6 overexpression. Indeed, we identified a poor-prognostic subset of patients, with widespread instability, which relies on SIRT6 to compensate for DNA-replication stress. As a result, SIRT6 depletion compromises the ability of leukemia cells to repair DNA double-strand breaks that, in turn, increases their sensitivity to daunorubicin and Ara-C, both in vitro and in vivo. In contrast, low SIRT6 levels observed in normal CD34+ hematopoietic progenitors explain their weaker sensitivity to genotoxic stress. Intriguingly, we have identified DNA-PKcs and CtIP deacetylation as crucial for SIRT6-mediated DNA repair. Together, our data suggest that inactivation of SIRT6 in leukemia cells leads to disruption of DNA-repair mechanisms, genomic instability and aggressive AML. This synthetic lethal approach, enhancing DNA damage while concomitantly blocking repair responses, provides the rationale for the clinical evaluation of SIRT6 modulators in the treatment of leukemia.

Chemokines trigger leukocyte trafficking and are implicated in cardiovascular disease pathophysiology. Chemokine-binding proteins, called "Evasins" have been shown to inhibit both CC and CXC chemokine-mediated bioactivities. Here, we investigated whether treatment with Evasin-3 (CXC chemokine inhibitor) and Evasin-4 (CC chemokine inhibitor) could influence post-infarction myocardial injury and remodelling. C57Bl/6 mice were submitted in vivo to left coronary artery permanent ligature and followed up for different times (up to 21 days). After coronary occlusion, three intraperitoneal injections of 10 μg Evasin-3, 1 μg Evasin-4 or equal volume of vehicle (PBS) were performed at 5 minutes, 24 hours (h) and 48 h after ischaemia onset. Both anti-chemokine treatments were associated with the beneficial reduction in infarct size as compared to controls. This effect was accompanied by a decrease in post-infarction myocardial leukocyte infiltration, reactive oxygen species release, and circulating levels of CXCL1 and CCL2. Treatment with Evasin-4 induced a more potent effect, abrogating the inflammation already at one day after ischaemia onset. At days 1 and 21 after ischaemia onset, both anti-chemokine treatments failed to significantly improve cardiac function, remodelling and scar formation. At 21-day follow-up, mouse survival was exclusively improved by Evasin-4 treatment when compared to control vehicle. In conclusion, we showed that the selective inhibition of CC chemokines (i.e. CCL5) with Evasin-4 reduced cardiac injury/inflammation and improved survival. Despite the inhibition of CXC chemokine bioactivities, Evasin-3 did not affect mouse survival. Therefore, early inhibition of CC chemokines might represent a promising therapeutic approach to reduce the development of post-infarction heart failure in mice.