Research Institute for Clinical Oncology, Saitama Cancer Center, Kitaadachi-gun, Saitama, Japan.
Int J Cancer. 2014 May 15;134(10):2373-82. doi: 10.1002/ijc.28582. Epub 2013 Nov 19.
Helicobacter pylori strains produce tumor necrosis factor-α (TNF-α)-inducing protein, Tipα as a carcinogenic factor in the gastric epithelium. Tipα acts as a homodimer with 38-kDa protein, whereas del-Tipα is an inactive monomer. H. pylori isolated from gastric cancer patients secreted large amounts of Tipα, which are incorporated into gastric cancer cells by directly binding to nucleolin on the cell surface, which is a receptor of Tipα. The binding complex induces expression of TNF-α and chemokine genes, and activates NF-κB (nuclear factor kappa-light-chain-enhancer of activated B cells). To understand the mechanisms of Tipα in tumor progression, we looked at numerous effects of Tipα on human gastric cancer cell lines. Induction of cell migration and elongation was found to be mediated through the binding to surface nucleolin, which was inhibited by the nucleolin-targeted siRNAs. Tipα induced formation of filopodia in MKN-1 cells, suggesting invasive morphological changes. Tipα enhanced the phosphorylation of 11 cancer-related proteins in serine, threonine and tyrosine, indicating activation of MEK-ERK signal cascade. Although the downregulation of E-cadherin was not shown in MKN-1 cells, Tipα induced the expression of vimentin, a significant marker of the epithelial-mesenchymal transition (EMT). It is of great importance to note that Tipα reduced the Young's modulus of MKN-1 cells determined by atomic force microscopy: This shows lower cell stiffness and increased cell motility. The morphological changes induced in human gastric cancer cells by Tipα are significant phenotypes of EMT. This is the first report that Tipα is a new inducer of EMT, probably associated with tumor progression in human gastric carcinogenesis.
幽门螺杆菌菌株产生肿瘤坏死因子-α（TNF-α）诱导蛋白 Tipα，作为胃上皮的致癌因子。Tipα 作为一种 38kDa 蛋白质的同源二聚体发挥作用，而 del-Tipα 则是无活性的单体。从胃癌患者中分离出的幽门螺杆菌大量分泌 Tipα，通过直接与细胞表面核仁蛋白结合进入胃癌细胞，核仁蛋白是 Tipα 的受体。结合复合物诱导 TNF-α 和趋化因子基因的表达，并激活 NF-κB（核因子 kappa-轻链增强子的激活 B 细胞）。为了了解 Tipα 在肿瘤进展中的机制，我们研究了 Tipα 对多种人胃癌细胞系的作用。发现细胞迁移和伸长的诱导是通过与表面核仁蛋白结合介导的，而核仁蛋白靶向 siRNA 可抑制这种结合。Tipα 诱导 MKN-1 细胞形成丝状伪足，提示侵袭性形态变化。Tipα 增强了丝氨酸、苏氨酸和酪氨酸 11 种与癌症相关蛋白的磷酸化，表明 MEK-ERK 信号级联的激活。尽管在 MKN-1 细胞中未显示 E-钙粘蛋白的下调，但 Tipα诱导了上皮-间充质转化（EMT）的重要标志物波形蛋白的表达。需要注意的是，Tipα 通过原子力显微镜降低了 MKN-1 细胞的杨氏模量：这表明细胞硬度降低，迁移能力增强。Tipα 诱导人胃癌细胞发生的形态变化是 EMT 的显著表型。这是首次报道 Tipα 是 EMT 的新诱导因子，可能与人类胃癌发生中的肿瘤进展有关。
