Abstract 5343: MicroRNAs regulate epithelial-mesenchymal transition in human glioma cells through modulation of the miRNA-VHL- β-catenin axis.

Abstract

Abstract Background. Glioblastoma (GBM) is the most common malignant primary brain tumor in adults and is a leading cause of cancer-related death due to its invasive nature. Despite advances in radiation and chemotherapy following surgical resection of the tumor, the prognosis of GBM remains poor with an average survival time of less than one year. Complex biological processes are involved in the establishment of invasion and metastasis of GBM and epithelial- mesenchymal transition (EMT) has been reported to play crucial role. The EMT converts epithelial cells into mesenchymal cells, a normal embryological process that frequently get activated during cancer invasion and metastasis. While increasing evidence indicates that the deregulation of miRNAs and beta-catenin signal pathway may play a critical role in EMT in a wide range of human cancers, there is no direct evidence showing that this pathway actually determines the EMT regulated by miRNAs in GBM. Methods. The expression of miRNAs (miR-21, miR-23b, and miR-566) in 48 clinical samples and five glioma cell lines with different grades was examined by FISH and qRT-PCR. TOP/FOP flash luciferase assays and transwell test were employed to identify the effect of the above miRNAs on the Wnt/β-catenin pathway activity and invasive activity of the glioma cells. Luciferase assay and western blot analysis were used to examine that VHL is a direct target of the above miRNAs. We further investigated the role of miRNAs on EMT by Western blot analysis. Results. We identified that expression of all of the above miRNAs are elevated in both glioma tissue samples and glioma cells by qRT-PCR and FISH analyses. Knock-down each of the above miRNAs could suppress invasion of glioma cells in vitro. Luciferase assay and western blot analysis revealed that VHL is a direct target of miR-23b. As such, restored expression of VHL inhibited glioma cell invasion. Mechanistic investigation revealed that miRNAs deletion suppressed β-catenin/Tcf-4 transcription activity in a VHL-dependent manner. Furthermore, expression of VHL was inversely correlated with miRNAs in glioblastoma samples. Conclusion. Our results indicate that down-regulation each of miRNAs (miR-21, miR-23b, and miR-566) inhibits EMT and invasion of glioma by expression of VHL. Genetic restoration of VHL bypassed the effects of miRNA overexpression, suppressing the transcriptional activities of β-catenin/Tcf-4 pathways. Based upon these observations, we conclude a role for the these miRNAs, upstream regulators of beta-catenin signal pathways, represent therapeutic targets to inhibit tumor metastasis in glioma cells. Citation Format: Lei Han, Luyue Chen, Kailiang Zhang, Zhendong Shi, Lingchao Chen, Peiyu Pu, Chunsheng Kang. MicroRNAs regulate epithelial-mesenchymal transition in human glioma cells through modulation of the miRNA-VHL- β-catenin axis. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 5343. doi:10.1158/1538-7445.AM2013-5343