Cancer Institute (Key Laboratory of Cancer Prevention and Intervention, China National Ministry of Education), the Second Affiliated Hospital, School of Medicine, Zhejiang University, Zhejiang, 310009, Hangzhou, China.
Department of Abdominal Oncology, West China Hospital, Sichuan University, Chengdu, Sichuan, China.
Cell Commun Signal. 2020 Jan 31;18(1):16. doi: 10.1186/s12964-020-0513-5.
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.
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.
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.
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.
烟酰胺腺嘌呤二核苷酸（NAD）补救途径在癌细胞增殖中的作用和机制尚未完全阐明。烟酰胺磷酸核糖转移酶（NAMPT）将烟酰胺转化为 NAD，是 NAD 补救途径中的限速酶。在这里，我们评估了 NAMPT 在结直肠癌增殖中的作用。
实时 PCR、免疫组织化学、Western blot 以及 Oncomine 和基因表达综合数据库的数据集分析用于评估结直肠癌中 NAMPT 的 mRNA 和蛋白水平的表达。Kaplan Meier plotter 在线工具用于评估 NAMPT 的预后作用。通过体外和体内实验评估 NAMPT 敲低在结直肠癌细胞增殖和肿瘤发生中的作用。过表达 NAMPT 用于评估 NAMPT 对结直肠癌细胞体外增殖的影响。NAD 定量、免疫荧光、双荧光素酶测定和 Western blot 用于探索结直肠癌增殖的机制。Transwell 迁移和侵袭实验用于评估 NAMPT 在结直肠癌细胞迁移和侵袭能力中的作用。
我们的研究表明，抑制 NAMPT 可降低结直肠癌细胞的体外和体内增殖能力。相反，过表达 NAMPT 可促进体外细胞增殖。NAMPT 抑制通过增加 Axin 表达水平诱导 β-连环蛋白降解；这导致 Wnt/β-连环蛋白信号通路的抑制和结直肠癌细胞的增殖。NAMPT 的酶产物烟酰胺单核苷酸的添加可有效逆转 β-连环蛋白蛋白降解并抑制生长。同样，敲低 Axin 也可减少 NAMPT 抑制诱导的细胞死亡。此外，我们发现结直肠癌组织中的 NAMPT 水平明显高于配对正常组织中的水平，尤其是在结直肠癌 I 期和 II 期。并且 NAMPT 的过表达与不良的生存结果相关。
我们的研究结果表明，NAMPT 通过 Wnt/β-连环蛋白通路在结直肠癌增殖中发挥重要作用，这可能对结直肠癌的诊断、预后和治疗具有重要意义。
