胶质瘤c-myc/miR-27a靶向SFRP1调控Wnt/β-catenin通路新机制

Abberant activation or inactivition of transcriptional factors, microRNAs and signaling pathways can always been found to be involved in malignant glioma progression as networks. However, the precise regulationship is still not yet clear. We have previously found that miR-27a was overexpressed in gliomas, and may be transcriptionally regulated by c-myc as was shown to be closely related to its expression. It has reportedly been shown that SFRP1，one member of SFRP family, as a negative regulator of Wnt signaling has important implications in gliomagenesis. Furthermore, We also found that SFRP1, which inhibited β-catenin/TCF4 transcriptional activity in glioma cell lines, was a potential target of miR-27a. Therefore, we aim to explore the regulational relationship of c-myc, miR-27a and SFRP1 in the Wnt/β-catenin/TCF4 signaling, and the roles in the progression of glioma malignancy. This research will clarify the regulational roles of transcriptional factor, miRNA and Wnt/β-catenin/TCF4 signaling invovled in the gliomagenesis. Furthermore, this work will make basestone for the target drugs.

异常激活或失活的转录因子、miRNAs及信号通路可形成调控网络，参与恶性胶质瘤发生发展，但三者之间具体调控机制仍不清楚。我们前期研究发现，miR-27a在胶质瘤中高表达，且与转录因子c-myc的表达相关，结合生物信息学预测结果提示，二者极可能存在转录调控关系。分泌型卷曲相关蛋白1(SFRP1)是胶质瘤中Wnt/β-catenin通路重要的负性调节因子。我们发现，SFRP1在胶质瘤细胞系中除可抑制β-catenin/TCF4转录活性，尚为miR-27a的潜在靶点。因此，本项目提出c-myc/miR-27a通过靶向SFRP1介导Wnt/β-catenin/TCF4通路调控胶质瘤恶性表型的假设。本研究可阐明胶质瘤中转录因子、miRNA与Wnt/β-catenin/TCF4信号通路相互作用新机制，研究结果将为胶质瘤的靶向基因治疗提供新靶点。

脑胶质瘤是最常见的原发性颅内肿瘤，各种治疗方法均无法明显改善其预后。多项研究发现Wnt/β-catenin与胶质瘤的发生发展密切相关。SFRP1可与Wnt配体结合从而抑制Wnt/β-catenin信号通路的活性。c-myc在半数以上肿瘤中异常活化，多项研究发现其可通过转录调控多个蛋白及包括miRNA在内的非编码RNA发挥相应作用。本研究拟探讨c-my与miR-27a调控关系，及miR-27a下游相关机制。首先，我们发现miR-27a在胶质瘤组织及细胞系中表达明显上调。此外，本研究还显示miR-27a抑制剂可抑制胶质瘤细胞增殖，阻滞细胞周期进展，诱导凋亡，并抑制细胞侵袭及迁移能力。荧光素酶实验和Western Blot表明，SFRP1是miR-27a的直接作用靶点。而miR-27a表达受抑制后，β-catenin可从胞核转移至胞浆。此外，miR-27a还可通过调控FASL及FADD表达，从而诱导胶质瘤细胞凋亡。体内实验结果表明，miR-27a inhibitor可抑制胶质瘤生长。进一步的研究还发现血清miR-27a在高级别胶质瘤中的表达明显高于低级别胶质瘤，垂体腺瘤，脑膜瘤及正常颅压脑积水患者。且血清miR-27a的高表达与胶质瘤患者预后密切相关，血清miR-27a高表达及胶质瘤的高分级是独立危险因素。综上，miR-27a是一个癌基因，且miR-27a在胶质瘤患者的诊疗中有潜在应用价值。