BACKGROUND The role and mechanism of the nicotinamide adenine dinucleotide (NAD+) salvage pathway in cancer cell proliferation is poorly understood. Nicotinamide phosphoribosyltransferase (NAMPT), which converts nicotinamide into NAD+, is the rate-limiting enzyme in the NAD+ salvage pathway. Here, we assessed the role of NAMPT in the proliferation of colorectal cancer. METHODS Real-time PCR, immunohistochemistry, western blotting, and analyses of datasets from Oncomine and Gene Expression Omnibus were conducted to assess the expression of NAMPT at the mRNA and protein levels in colorectal cancer. The Kaplan Meier plotter online tool was used to evaluate the prognostic role of NAMPT. Knockdown of NAMPT was performed to assess the role of NAMPT in colorectal cancer cell proliferation and tumorigenesis both in vitro and in vivo. Overexpression of NAMPT was used to evaluate impact of NAMPT on colorectal cancer cell proliferation in vitro. NAD+ quantitation, immunofluorescence, dual luciferase assay and western blot were used to explore the mechanism of colorectal cancer proliferation. Transwell migration and invasion assays were conducted to assess the role of NAMPT in cell migration and invasion abilities of colorectal cancer cells. RESULTS Our study indicated that the inhibition of NAMPT decreased proliferation capacity of colorectal cancer cells both in vitro and in vivo. Conversely, overexpression of NAMPT could promote cell proliferation in vitro. NAMPT inhibition induced β-catenin degradation by increasing Axin expression levels; this resulted in the inhibition of Wnt/β-catenin signaling and cell proliferation in colorectal cancer. The addition of nicotinamide mononucleotide, the enzymatic product of NAMPT, effectively reversed β-catenin protein degradation and inhibited growth. Similarly, the knockdown of Axin also decreased the cell death induced by the inhibition of NAMPT. In addition, we showed that colorectal cancer tissues harbored significantly higher levels of NAMPT than the levels harbored by paired normal tissues, especially in colorectal cancer stages I and II. And the overexpression of NAMPT was associated with unfavorable survival results. CONCLUSIONS Our findings reveal that NAMPT plays an important role in colorectal cancer proliferation via Wnt/β-catenin pathway, which could have vital implications for the diagnosis, prognosis and treatment of colorectal cancer.

中文翻译：

---

靶向NAD +抢救途径可通过增加Axin水平来抑制APC突变驱动的结直肠癌生长和Wnt /β-catenin信号传导。

背景技术对烟酰胺腺嘌呤二核苷酸（NAD +）挽救途径在癌细胞增殖中的作用和机制了解甚少。将烟酰胺转换为NAD +的烟酰胺磷酸核糖基转移酶（NAMPT）是NAD +挽救途径中的限速酶。在这里，我们评估了NAMPT在结直肠癌增殖中的作用。方法采用实时荧光定量PCR，免疫组织化学，蛋白质印迹以及Oncomine和Gene Expression Omnibus的数据集分析，以评估NAMPT在大肠癌的mRNA和蛋白质水平上的表达。使用Kaplan Meier绘图仪在线工具评估NAMPT的预后作用。进行了NAMPT的基因敲除，以评估NAMPT在体外和体内在大肠癌细胞增殖和肿瘤发生中的作用。NAMPT的过表达用于评估NAMPT对体外结直肠癌细胞增殖的影响。NAD +定量，免疫荧光，双重荧光素酶测定和蛋白质印迹被用来探讨结直肠癌增殖的机制。进行Transwell迁移和侵袭分析以评估NAMPT在结肠直肠癌细胞的细胞迁移和侵袭能力中的作用。结果我们的研究表明，对NAMPT的抑制可降低体内和体外结直肠癌细胞的增殖能力。相反，NAMPT的过表达可促进体外细胞增殖。NAMPT抑制通过增加Axin表达水平诱导β-catenin降解；这导致了Wnt /β-catenin信号传导的抑制和大肠癌中细胞的增殖。NAMPT的酶促产物烟酰胺单核苷酸的添加可有效逆转β-catenin蛋白的降解并抑制其生长。类似地，Axin的敲低也减少了由NAMPT抑制引起的细胞死亡。此外，我们发现结直肠癌组织的NAMPT水平明显高于配对正常组织的水平，尤其是在大肠癌I和II期。NAMPT的过表达与不良的生存结果有关。结论我们的发现表明NAMPT通过Wnt /β-catenin途径在结直肠癌的增殖中起着重要作用，这可能对结直肠癌的诊断，预后和治疗具有重要意义。有效逆转β-catenin蛋白质降解并抑制生长。类似地，Axin的敲低也减少了由NAMPT抑制引起的细胞死亡。此外，我们发现结直肠癌组织的NAMPT水平明显高于配对正常组织的水平，尤其是在大肠癌I和II期。NAMPT的过表达与不良的生存结果有关。结论我们的发现表明NAMPT通过Wnt /β-catenin途径在结直肠癌的增殖中起着重要作用，这可能对结直肠癌的诊断，预后和治疗具有重要意义。有效逆转β-catenin蛋白质降解并抑制生长。类似地，Axin的敲低也减少了由NAMPT抑制引起的细胞死亡。此外，我们发现结直肠癌组织的NAMPT水平明显高于配对正常组织的水平，尤其是在大肠癌I和II期。NAMPT的过表达与不良的生存结果有关。结论我们的发现表明NAMPT通过Wnt /β-catenin途径在结直肠癌的增殖中起着重要作用，这可能对结直肠癌的诊断，预后和治疗具有重要意义。我们发现，结直肠癌组织的NAMPT水平明显高于配对正常组织的水平，尤其是在大肠癌I和II期。NAMPT的过表达与不良的生存结果有关。结论我们的发现表明NAMPT通过Wnt /β-catenin途径在结直肠癌的增殖中起着重要作用，这可能对结直肠癌的诊断，预后和治疗具有重要意义。我们发现，结直肠癌组织的NAMPT水平明显高于配对正常组织的水平，尤其是在大肠癌I和II期。NAMPT的过表达与不良的生存结果有关。结论我们的发现表明NAMPT通过Wnt /β-catenin途径在结直肠癌的增殖中起着重要作用，这可能对结直肠癌的诊断，预后和治疗具有重要意义。