MiR-29a下调共刺激分子B7-H3的表达及其对脑胶质瘤细胞侵袭的影响

目的： 探讨miR-29a调控共刺激分子B7-H3在脑胶质瘤中的表达及其对脑胶质瘤细胞侵袭能力的影响。 方法： 通过Real-time PCR检测miR-29a和B7-H3在正常脑组织、脑胶质瘤组织及人胶质瘤细胞株U87中的表达，并利用脂质体将miR-29a的模拟物（mimics）和抑制剂（inhibitors）转入U87细胞，流式术验证miR-29a对B7-H3表达的调节效果；采用CCK-8和Transwell实验观察miR-29a对U87细胞的增殖和侵袭能力的影响，并通过流式术分析miR-29a干预前后U87细胞上与细胞侵袭相关的化学趋化因子的表达变化，以miRtarbase等软件预测miR-29a与 CXCR4 的结合能力。 结果： 胶质瘤组织及细胞株中miR-29a低表达而 B7-H3 mRNA高表达，且均与瘤组织病理分级相关。转染miR-29a mimics可以有效下调U87细胞中 B7-H3 mRNA的表达。转染miR-29a mimics可以显著抑制U87细胞的侵袭能力（P<0.05），但对细胞增殖并无显著影响。miR-29a过表达可同时下调U87细胞中CXCR4的表达，但软件分析 CXCR4 基因上并不存在miR-29a的结合位点。 结论： miR-29a可有效下调B7-H3分子的表达，进而抑制脑胶质瘤细胞的侵袭能力，其作用机制可能与CXCR4途径相关。

MiR-29a inhibited costimulatory molecule B7-H3 expression and the invasion of glioma growth

Objective : To determine the expression and possible roles of miR-29a and B7-H3 in glioma growth and invasion. Methods: Glioma tissue specimens were collected from 19 patients who underwent surgical glioma resection in the Department of Neurosurgery, Soochow University-Affiliated First Hospital between September, 2006 and December, 2010. Levels of miR-29a and B7-H3 mRNAs in the tissue specimens and human glioma U87 cells were determined by Real-time PCR. U87 cells were transfected with miR-29a mimics, and B7-H3 expression and invasive capacity in the transfectants were assessed by flow cytometry and transwell migration assay, respectively. The expression of invasion-related chemical chemokines was analyzed by flow cytometry, and the ability of miR-29a to bind to CXCR4 was predicted by the miRtarbase software. Results: In glioma tissue specimens, miR-29a and B7-H3 mRNA levels were inversely correlated. In vitro, miR-29a down-regulated B7-H3 mRNAs expression in U87 cells and miR-29a-mediated down-regulation of B7-H3 resulted in a significant decrease in the invasive ability but not proliferative activity in U87 cells. Parallel to down-regulation of B7-H3 expression, CXCR4 expression was also down-regulated in U87 cells transfected with miR-29a mimics. No miR-29a binding sites were detected in the CXCR4 gene. Conclusions: In human glioma, miR-29a can effectively down-regulate B7-H3 expression and inhibit invasive activity. It is likely that these effects of miR-29a were at least attributable dwon-regulated expression of CXCR4.