Overexpression of Nampt in gastric cancer and chemopotentiating effects of the Nampt inhibitor FK866 in combination with fluorouracil

Abstract

Abstract. Nicotinamide phosphoribosyltransferase (Nampt), an enzyme involved in the NAD + salvage pathway, is overexpressed and important in the carcinogenesis in several types of cancers. The expression of Nampt and its role in gastric cancer remain largely unknown. In this study, using real-time PCR and Western blotting we found that Nampt was overexpressed at the mRNA and protein levels, respectively, in established gastric cancer cells and human gastric cancer tissues. The specific Nampt inhibitor FK866 repressed gastric cancer cell proliferation, as assessed by MTT assay. Using transwell and soft agar clonogenic assays, we also found that FK866 suppressed gastric cancer cell migration and anchorageindependent growth, respectively. These inhibitory effects of FK866 were accompanied by significantly decreased expression of VEGF, MMP2, MMP9 and NF-κB. As determined by MTT assay and flow cytometry, FK866 also increased the chemosensitivity of gastric cancer cells to fluorouracil by greater inhibition of cell proliferation and the induction of apoptosis. Our findings indicate that Nampt may be a new therapeutic target for gastric cancer. IntroductionGastric cancer is the fourth most common malignancy in the world and causes ~800,000 deaths annually worldwide (1). For patients with recurrent, metastatic, or advanced gastric cancer, fluorouracil (5-FU) is a commonly used chemotherapeutic drug (2). However, the toxic side effects associated with 5-FU remain a significant challenge to its use. The development of more effective therapeutic drugs with minimal side effects is crucial, and is dependent on a better understanding of the molecular mechanism underlying gastric carcinogenesis.Nicotinamide adenine dinucleotide (NAD) is an essential cofactor found in all cells and plays key roles as a carrier of electrons during redox reactions. The rate-limiting enzyme involved in the biosynthesis of NAD from the nicotinamide precursor is nicotinamide phosphoribosyltransferase (Nampt) (3). Increasing evidence demonstrates that Nampt is a multifunctional enzyme and is important in metabolism and immune response as well as cancer (4). Nampt is also known as pre-B-cell colony enhancing factor (PBEF1), a presumptive cytokine (5), and as visfatin, an insulin-mimetic adipocytokine secreted by visceral fat (6) that is also encoded by the PBEF1 gene (5).Cross-talk between the two NAD-dependent enzymes SIRT1 (also known as sirtuin 1 or NAD-dependent deacetylase sirtuins-1) deacetylase and poly(ADP-ribose) polymerase 1 (PARP1) plays a major role in cell viability under stress (7). By binding to and thereby causing the deacetylation of PARP1, SIRT1 protects cells from PARP1-mediated cell death. SIRT1 has also been shown to control PARP1 at the transcriptional level by negatively regulating the PARP1 gene promoter. The activity of SIRT1 can be positively regulated by Nampt, making Nampt a player in promoting cell survival under stress (8).Nampt was first reported to be overexpressed in colorectal cancer (9,10). It is also overexpressed i...

NAD+ Metabolism and the Control of Energy Homeostasis: A Balancing Act between Mitochondria and the Nucleus

“…NAMPT has been found to be overexpressed in several types of tumors and its expression is associated to tumor progression (Bi et al, 2011; Hasmann and Schemainda, 2003; Van Beijnum et al, 2002; Wang et al, 2011). Consequently, several studies showed that the NAD + depletion triggered by the down-regulation of NAMPT activity can reduce tumor cell growth and sensitize cells to chemotoxic agents (Bi et al, 2011; Hasmann and Schemainda, 2003; Wang et al, 2011; Watson et al, 2009). One must keep in mind that in most cancer cells, PARPs are activated due to DNA damage and genome instability, leading to NAD + depletion in cancer cells (Garten et al, 2009).…”

Inhibitor of Nicotinamide Phosphoribosyltransferase Sensitizes Glioblastoma Cells to Temozolomide via Activating ROS/JNK Signaling Pathway

“…More importantly, NAMPT has a crucial role in cancer cell metabolism [7]. NAMPT expression was found to be increased in numerous types of tumors, including colorectal cancer [8], breast cancer [9], gastric cancer [10], ovarian cancer [11], prostate cancer [12]. In these tumors, inhibition of NAMPT had a profound antitumor effect [8–12].…”

Visfatin is involved in promotion of colorectal carcinoma malignancy through an inducing EMT mechanism

“…Higher visfatin levels in breast cancer are correlated with overall survival and disease-free survival [8]. Literatures also reported that visfatin overexpression can predict poor response of the patients to doxorubicin [9] or fluorouracil [10] based chemotherapy. Visfatin is closely associated with the pathogenesis of colon cancer, therefore it is considered as a novel and promising biomarker of CRC [11].…”