Nicotinamide Affects The Biological Behavior Of Pancreatic Carcinoma Through Deregulating SIRT1and Ras/Akt Pathways

Objective: Nicotinamide (NAM), the precursor of nicotinamide adenine dinuclotide,has been found to inhibit some carcinomas such as liver cancer, bladder cancer, andmelanoma. But the effect on pancreatic cancer is rare. Our research is aimed toexplore the function of NAM on pancreatic cancer as well as the potentialmechanisms, which provide a novel chemotherapy strategy for pancreatic cancer.Methods: Pancreatic cancer cell lines PANC-1and BXPC-3were exposed to serialconcentrations of NAM (0,1.25,2.5,5,10,20,40and80mM) for48hours. CellSIRT1colorimetry evaluated SIRT1activity, and MTT evaluated the viability. Then,after both cell lines exposed to NAM at the concentration of5mM, colony formationassay detected cell proliferation, flow cytometry method examined cell apoptosis andcell cycle, Western Blot examined proteins associated with apoptosis and cellcycle(Bcl-2/Bax, cyclinD1and P53), transwell assay tested invasion ability, WesternBlot examined proteins associated with invision (MMP2and MMP9), MTT detectedchemosensitivity to5-FU, Gemcitabine(GEM) and Dichlorodiamineplatinum(DDP),Western Blot deteceted the expressions of SIRT1, K-Ras, phosphorylate-Akt(P-Akt,Ser-473) and total Akt. AT last, PANC-1cells silenced SIRT1by SIRT1-siRNAtransfection or combination with NAM (5mM)，Western Blot detected the expressionof SIRT1, K-Ras, P-Akt and total Akt.Results: The SIRT1activity and viability of PANC-1and BXPC-3were inhibited byNAM, which showed a dose-dependent manner. NAM (5mM) inhibited cellproliferation, induced apotosis and arrested cell cycle, both the ratio of Bcl-2/Bax andcyclinD1were downregulation, but the level of P53showed no statistical significance.NAM also inhibited cell invasion, the MMP2and MMP9were decresed. NAMenhanced the chemosensitivity of cells to5-FU, GEM and DDP. NAM alsodownregulated expressions of SIRT1, K-Ras and P-Akt, but no impact on Akt. Aftercell transfected with SIRT1-siRNA, SIRT1was decreased but K-Ras and P-Akt just increased when combination with NAM (5mM).Conclusions: NAM can inhibit the SIRT1activity of PANC-1and BXPC-3, and haveeffects on inhibiting proliferation, inducing apoptosis, arresting cell cycle, restraininginvasion and enhancing chemosensitivity through downregulation SIRT1as well asRas/Akt signal pathways. NAM shows a potential chemotherapy strategy forpancreatic cancer.