烟酰胺-N-甲基转移酶在胃癌中高表达并与预后负相关:基于生物信息学方法

目的 探讨烟酰胺-N-甲基转移酶（NNMT）在胃癌中的表达、生物学功能和临床病理学意义。方法 运用公共数据库GEO、Oncomine及TCGA分析筛选与胃癌分型和临床预后相关的基因；利用STRING、GSEA、DAVID、Cytoscape等软件分析预测与候选基因相关的分子通路，构建蛋白质相互作用关系网络；通过qRT-PCR分析候选基因在28例胃癌和配对癌旁组织中mRNA的差异表达；CCK8增殖实验、平板克隆形成实验、划痕愈合实验、Transwell小室细胞运动实验等分析NNMT表达对胃癌细胞增殖、侵袭和迁移能力的影响。结果 NNMT在多个数据库分析中呈高表达且与胃癌预后负相关；通路分析显示，NNMT高表达与细胞外基质受体和细胞黏附分子等细胞粘附相关通路以及细胞因子受体等分子通路相关；而NNMT低表达可能与碱基错配修复和核黄素代谢等生物过程相关。蛋白相互作用分析显示，NNMT可能与AURKA等16个差异表达的蛋白存在相互作用关系，且与TAGLN、PTRF、AKAP12、IGF2BP2蛋白存在较高的共表达趋势。在临床组织标本中，qRT-PCR结果显示，胃癌组织中NNMTmRNA的表达明显高于癌旁组织（P<0.05）。在胃癌细胞系中，NNMT的过表达可显著促进细胞增殖、侵袭和迁移，而NNMT敲除可对细胞增殖、侵袭和迁移产生明显的抑制作用。结论 NNMT在胃癌中异常高表达并促进胃癌细胞的增殖、侵袭和转移；NNMT高水平表达与胃癌患者预后呈负相关，提示NNMT可能为胃癌预后相关分子。

Expression of nicotinamide-N-methyltransferase in gastric cancer and its biological and clinicopathological significance

Objective To investigate the expression of nicotinamide-N-methyltransferase (NNMT) in gastric cancer (GC) and explore its biological and clinicopathological significance. Methods We screened the candidate genes associated with the classification and prognosis of gastric cancer by analyzing GEO, Oncomine and TCGA datasets. The molecular pathways and protein interaction network involving these candidate genes were analyzed using STRING, GSEA, David and Cytoscape software. The expressions of the candidate genes in 28 pairs of gastric cancer and adjacent tissues were detected with qRT-PCR, and CCK-8 assay, clone formation assay, wound healing assay and Transwell assay were carried out to analyze the effects of modulation of NNMT expression on proliferation, invasion and migration of different gastric cancer cell lines. Results NNMT was highly expressed in gastric cancer tissues and was negatively correlated with the prognosis of patients with gastric cancer. Pathway analysis showed that the high expression of NNMT was associated with adhesion-related pathway molecules such as extracellular matrix receptors, cell adhesion molecules, and cytokine receptors, while its low expression was associated with base mismatch repair and riboflavin metabolism. Protein interaction analysis showed that NNMT interacted with 16 differentially expressed proteins such as AURKA and was co-expressed with TAGLN, PTRF, AKAP12 and IGF2BP2. In clinical tissue specimens, qRT-PCR results showed that the expression of NNMT mRNA was significantly higher in gastric cancer tissues than in the adjacent tissues (P<0.05). In gastric cancer cell lines, overexpression of NNMT was found to significantly promote cell proliferation, invasion and migration, while NNMT knockdown produced obvious inhibitory effects on cell proliferation, invasion and migration. Conclusion NNMT is highly expressed in gastric cancer and negatively correlated with the prognosis of gastric cancer patients. The high expression of NNMT promotes the proliferation, invasion and metastasis of gastric cancer cells, suggesting the potential of NNMT as prognostic marker of gastric cancer.