Elevated Gab2 induces tumor growth and angiogenesis in colorectal cancer through upregulating VEGF levels.
Elevated Gab2 induces tumor growth and angiogenesis in colorectal cancer through upregulating VEGF levels.
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Gab2 升高通过上调 VEGF 水平诱导结直肠癌肿瘤生长和血管生成
DOI：
10.1186/s13046-017-0524-2
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发表时间：
2017-04-18
期刊：
影响因子：
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通讯作者：
Wu G
中科院分区：
文献类型：
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作者：
Ding C;Luo J;Fan X;Li L;Li S;Wen K;Feng J;Wu G
背景Grb2相关结合蛋白2(Gab2)是一种支架蛋白，在酪氨酸激酶受体下游发挥重要的信号放大作用。我们先前的研究表明，在结直肠癌(CRC)中，Gab2诱导上皮向间充质转化(EMT)并促进转移。方法采用免疫组织化学和定量逆转录聚合酶链式反应(qRT-PCR)方法检测不同类型结直肠癌组织中血管内皮生长因子(VEGF)的表达，探讨其与结直肠癌血管生成的相关性。构建了携带Gab2基因及其小干扰RNA的慢病毒载体，并将其导入大肠癌细胞系。分别用CCK-8比色法、集落形成实验和致瘤性实验检测Gab2对细胞体外增殖和体内致瘤性的影响。采用免疫组织化学方法检测Ki67、CD34和血管内皮生长因子受体2(VEGFR2)在结直肠癌组织中的表达，以探讨其在肿瘤生长和血管生成中的作用。最后，我们评估了Gab2对c-Myc和VEGF表达的影响，以及机械性靶向细胞外信号调节激酶(ERK)通路在抑制肿瘤生长和血管生成中的可能作用。外源性Gab2表达明显促进体外培养的人结直肠癌细胞的增殖和克隆形成，而沉默Gab2则抑制其增殖和克隆形成。值得注意的是，在Ki67高表达的小鼠移植瘤中，Gab2促进了肿瘤的形成和肿瘤的生长，并导致了具有强大CD34和VEGFR2活性的血管密度增加。此外，在大肠癌细胞中，高表达的Gab2明显上调了血管内皮生长因子的表达，并刺激了其下游基因ERK1/2和c-Myc的激活。相反，下调Gab2的表达显著降低了VEGF的水平，并抑制了ERK/c-Myc通路的转导。最后，我们揭示了丝裂原活化蛋白激酶(MEK)的机制靶点可以通过改变VEGF和c-Myc的水平来抑制Gab2诱导的肿瘤生长和血管生成。结论本研究结果提示Gab2通过上调MEK/ERK/c-Myc通路中的VEGF表达来促进肠道肿瘤的生长和血管生成。
BackgroundGrb2-associated binder 2 (Gab2) is a scaffolding protein that serves as a critical signaling amplifier downstream of tyrosine kinase receptors. Our previous study has shown that Gab2 induces epithelial-to-mesenchymal transition (EMT) and promotes metastasis in colorectal cancer (CRC). However, the role of Gab2 in CRC growth and angiogenesis remains unclear.MethodsThe expression of vascular endothelial growth factor (VEGF) in different colorectal tissues was detected by immunohistochemistry and qRT-PCR to evaluate its correlation with Gab2. Lentiviral vectors bearing Gab2 gene and its small interfering RNAs were constructed and transfected into CRC cell lines. The effects of Gab2 on the cell proliferation in vitro and tumorigenesis in vivo, were examined via CCK‑8 assay, colony formation assay as well as tumorigenicity assay respectively. Moreover, to assess its potential role in tumor growth and angiogenesis, the expression of Ki67, CD34 and vascular endothelial growth factor receptor-2 (VEGFR2) were detected by immunohistochemistry in CRC cells tumors. Finally, we evaluated the impact of Gab2 on the expression of c-Myc and VEGF, and the probable effect of mechanistic targeted extracellular signal-regulated kinase (ERK) pathway in suppressing tumor growth and angiogenesis.ResultsUp-regulation of Gab2 expression was found to be positively correlated with VEGF in CRC tissues. Exogenous expression of Gab2 obviously promoted, whereas silencing of Gab2 inhibited, proliferation and clone formation of human CRC cells in vitro. Of note, Gab2 enhanced tumorigenesis and tumor growth in mouse xenografts with high Ki67 expression, and led to an increased vessel density with strong CD34 and VEGFR2 activity. In addition, elevated Gab2 expression obviously up-regulated the expression of VEGF, and stimulated the activation of its downstream genes, ERK1/2 and c-Myc in CRC cells. Instead, down-regulated Gab2 expression significantly reduced the levels of VEGF, and inhibited the transduction of ERK/c-Myc pathway. Finally, we revealed that mechanistic target of mitogen-activated protein kinase (MEK) could attenuate Gab2-induced tumor growth and angiogenesis via altering VEGF and c-Myc levels.ConclusionsThe results from our study suggest that Gab2 promotes intestinal tumor growth and angiogenesis through upregulation of VEGF expression mediated by the MEK/ERK/c-Myc pathway.