Schuster Susanne, Penke Melanie, Gorski Theresa, Gebhardt Rolf, Weiss Thomas S, Kiess Wieland, Garten Antje
Center for Pediatric Research Leipzig, University Hospital for Children and Adolescents, Faculty of Medicine, University of Leipzig, Liebigstr. 21, 04103 Leipzig, Germany.
Center for Pediatric Research Leipzig, University Hospital for Children and Adolescents, Faculty of Medicine, University of Leipzig, Liebigstr. 21, 04103 Leipzig, Germany.
Biochem Biophys Res Commun. 2015 Mar 6;458(2):334-40. doi: 10.1016/j.bbrc.2015.01.111. Epub 2015 Feb 3.
Nicotinamide phosphoribosyltransferase (NAMPT) is the key enzyme of the NAD salvage pathway starting from nicotinamide. Cancer cells have an increased demand for NAD due to their high proliferation and DNA repair rate. Consequently, NAMPT is considered as a putative target for anti-cancer therapies. There is evidence that AMP-activated protein kinase (AMPK) and mammalian target of rapamycin (mTOR) become dysregulated during the development of hepatocellular carcinoma (HCC). Here, we investigated the effects of NAMPT inhibition by its specific inhibitor FK866 on the viability of hepatocarcinoma cells and analyzed the effects of FK866 on the nutrient sensor AMPK and mTOR complex1 (mTORC1) signaling.
FK866 markedly decreased NAMPT activity and NAD content in hepatocarcinoma cells (Huh7 cells, Hep3B cells) and led to delayed ATP reduction which was associated with increased cell death. These effects could be abrogated by administration of nicotinamide mononucleotide (NMN), the enzyme product of NAMPT. Our results demonstrated a dysregulation of the AMPK/mTOR pathway in hepatocarcinoma cells compared to non-cancerous hepatocytes with a higher expression of mTOR and a lower AMPKα activation in hepatocarcinoma cells. We found that NAMPT inhibition by FK866 significantly activated AMPKα and inhibited the activation of mTOR and its downstream targets p70S6 kinase and 4E-BP1 in hepatocarcinoma cells. Non-cancerous hepatocytes were less sensitive to FK866 and did not show changes in AMPK/mTOR signaling after FK866 treatment.
Taken together, these findings reveal an important role of the NAMPT-mediated NAD salvage pathway in the energy homeostasis of hepatocarcinoma cells and suggest NAMPT inhibition as a potential treatment option for HCC.
烟酰胺磷酸核糖转移酶（NAMPT）是从烟酰胺开始的NAD补救途径的关键酶。由于癌细胞具有高增殖率和DNA修复率，因此对NAD的需求增加。因此，NAMPT被认为是抗癌治疗的一个假定靶点。有证据表明，在肝细胞癌（HCC）发生过程中，AMP激活的蛋白激酶（AMPK）和雷帕霉素哺乳动物靶蛋白（mTOR）会失调。在此，我们研究了其特异性抑制剂FK866抑制NAMPT对肝癌细胞活力的影响，并分析了FK866对营养传感器AMPK和mTOR复合物1（mTORC1）信号传导的影响。
FK866显著降低了肝癌细胞（Huh7细胞、Hep3B细胞）中的NAMPT活性和NAD含量，并导致ATP减少延迟，这与细胞死亡增加有关。烟酰胺单核苷酸（NMN），即NAMPT的酶产物，可以消除这些影响。我们的结果表明，与非癌性肝细胞相比，肝癌细胞中AMPK/mTOR途径失调，肝癌细胞中mTOR表达较高，AMPKα激活较低。我们发现，FK866抑制NAMPT可显著激活肝癌细胞中的AMPKα，并抑制mTOR及其下游靶点p70S6激酶和4E-BP1的激活。非癌性肝细胞对FK866不太敏感，FK866处理后AMPK/mTOR信号没有变化。
综上所述，这些发现揭示了NAMPT介导的NAD补救途径在肝癌细胞能量稳态中的重要作用，并表明抑制NAMPT是HCC的一种潜在治疗选择。
