miR-18a对结肠癌血管生成的影响

Overexpression of miR-18a suppresses tumor angiogenesis in colon cancer

目的探讨miR-18a对结肠癌血管生成的影响及其机制。方法以用合成的miR-18a模拟物转染人结肠癌细胞系SW620细胞。应用MTT法检测过表达miR-18a对细胞增殖活性的影响。分别用稳转miR-18a的SW620细胞接种建立裸鼠人结肠癌移植瘤模型。每周测量瘤体积。5周后麻醉处死裸鼠。免疫组化法检测增殖细胞核标志物Ki 67和血管内皮细胞标志物CD31的表达。应用Western blotting法检测血管生成相关的mTOR通路中mTOR下游靶蛋白S6K1和4E BP1的磷酸化情况,并检测肿瘤组织血管生成相关因子缺氧诱导因子1α(HIF-1α)和血管内皮生长凶子(VEGF)的表达。结果 miR-18a过表达显著降低SW620细胞的增殖能力(P<0.01)。并且,该基因对裸鼠人结肠癌移植瘤有明显的生长抑制作用,SW620组瘤体显著减小,抑瘤率达71.8%(P<0.01)。免疫组化检测显示,miR-18a显著抑制细胞增殖核抗原蛋白Ki-67(P<0.01)和血管内皮细胞标记物CD31(P<0.05)的表达。Western blot法检测显示,miR-18a显著抑制S6K(IP<0.01)和4E-BP(IP<0.05)的磷酸化,而且抑制肿瘤组织中HIF-1α(P<0.05)和VEGF蛋白(P<0.01)的表达。结论过表达miR-18a抑制结肠癌生长和血管生成,这可能与其抑制mTOR/VEGF通路有关,提示过表达miR-18a可能成为结肠癌治疗的新方法。

【Objective】 To investigate the effect of miR-18a on angiogenesis in colon cancer.【Methods】 SW620 cells were transfected with synthesized miR-18a mimics.Cell proliferation was assessed by the MTT assay.The effects of overexpressed miR-18a on tumor growth and angiogenesis were assessed.Because of the key role of mammalian target of rapamycin（mTOR） signaling in HCC progression,the effect of miR-18a overexpression on the mTOR path way was also tested.【Results】 Ectopic expression of miR-18a significantly diminished cell proliferation in SW620 cells（P ＆lt;0.01）.MiR-18a overexpression significantly retarded SW620 xenograit growth by 71.8% in vivo,and caused a marked reduction in tumor angiogenesis assessed by CD31-stained microvessel count.Western blot analysis of the xenografts showed that miR-18a overexprerrsion substantially reduced the phosphorylation of two mTOR substrates,S6K1 and 4E-BPl,indicative of art inactivation of the mTOR pathway.Because of mTOR inactivation,the angiogenie factors,hypoxia-inducible factor 1 alpha and vascular endothelial growth factor,were significantly downregulated.【Conclusion】 These data highlighted an important role for miR-18a in controlling colon cancer growth and angiogenesis,which offers a possible therapeutic strategy against this malignancy.