Abstract 1909: Identification and characterization of microRNA-134 as a novel receptor tyrosine kinase-regulated tumor suppressive hub in glioblastoma

Abstract

Abstract Receptor tyrosine kinases (RTKs) are co-deregulated in a majority of glioblastoma (GBM), the most common and most deadly brain tumor. In this study, we uncovered microRNA-134 (miR-134) as a novel tumor suppressive hub that is co-regulated by multiple RTKs via MAPK and KLF4 and that acts via regulation of KRAS and STAT5B expressions. Using microRNA microarrays and qRT-PCR, we screened for microRNAs that are co-regulated by multiple RTKs in GBM. We found that miR-134 was one such microRNA that is downregulated by the activation of MET, EGFR, and PDGFR, the three most commonly deregulated RTKs in GBM. Using a combination of pharmacology, promoter analysis, transcription factor functional and rescue approaches and ChIP/qPCR, we uncovered the MAPK pathway and the transcriptional repressor KLF4 as mediators of the effects of RTKs on miR-134 repression. We then measured the expression of miR-134 and found that it was downregulated in human GBM tumors and GBM stem cells (GSCs) and that it inversely correlated with the activation levels of MET, EGFR, and PDGFR in the tumors. We demonstrated that miR-134 inhibits GBM cell and GSC proliferation, survival, and in vivo xenograft growth, as well as GSC self-renewal and stemness. We uncovered the oncogenes KRAS and STAT5B as direct targets of miR-134 with immunoblots and 3′UTR reporter assays, and showed with rescue experiments that they mediate miR-134 tumor suppressive effects. Thereafter, using a series of molecular and functional assays we established direct links and dependencies between RTKs, KLF4, miR-134, KRAS/STAT5B and malignancy in vitro and in vivo. Importantly, we also found that miR-134 induction is required for the anti-tumor effects of small molecule RTK inhibitors. Altogether, our extensive study identified miR-134 as a novel RTK-regulated tumor-suppressive hub that mediates RTK and RTK-inhibitor effects on GBM malignancy by controlling KRAS and STAT5B. These findings shed new light onto the molecular and functional interactions between RTKs and microRNAs and uncover opportunities for exploiting these interactions for therapeutic purposes. Citation Format: Ying Zhang, Jungeun Kim, Adam C. Mueller, Bijan Dey, Yanzhi Yang, Daehee Lee, Jan Hachmann, Sanjo Finderle, Deric M. Park, James Christensen, David Schiff, Benjamin Purow, Anindya Dutta, Roger Abounader. Identification and characterization of microRNA-134 as a novel receptor tyrosine kinase-regulated tumor suppressive hub in glioblastoma. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1909. doi:10.1158/1538-7445.AM2014-1909