Epigenetic Regulation of miRNA-211 by MMP-9 Governs Glioma Cell Apoptosis, Chemosensitivity and Radiosensitivity

Swapna Asuthkar,Bharathi Gorantla,Chandramu Chetty,Jasti S Rao,Kiran Kumar Velpula

doi:10.18632/oncotarget.683

Swapna Asuthkar, Bharathi Gorantla + Show 3 more

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https://doi.org/10.18632/oncotarget.683

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Abstract

Glioblastoma multiforme (GBM) is the most aggressive brain cancer, and to date, no curative treatment has been developed. In this study, we report that miR-211, a microRNA predicted to target MMP-9, is suppressed in grade IV GBM specimens. Furthermore, we found that miR-211 suppression in GBM involves aberrant methylation-mediated epigenetic silencing of the miR-211 promoter. Indeed, we observed a highly significant inverse correlation between miR-211 expression and MMP-9 protein levels, which is indicative of post-transcriptional control of gene expression. Additionally, shRNA specific for MMP-9 (pM) promoted miR-211 expression via demethylation of miR-211 promoter-associated CpG islands (-140 to +56). In independent experiments, we confirmed that miR-211 overexpression and pM treatments led to the activation of the intrinsic mitochondrial/Caspase-9/3-mediated apoptotic pathway in both glioma cells and cancer stem cells (CSC). We also investigated whether miR-211 is involved in the regulation of MMP-9 and thus plays a functional role in GBM. We found an acute inhibitory effect of miR-211 on glioma cell invasion and migration via suppression of MMP-9. Given the insensitivity of some GBMs to radiation and chemotherapy (temozolomide) along with the hypothesis that glioma CSC cause resistance to therapy, our study indicates that miR-211 or pM in combination with ionizing radiation (IR) and temozolomide significantly induces apoptosis and DNA fragmentation. Of note, miR-211- and pM-treated CSC demonstrated increased drug retention capacity, as observed by MDR1/P-gp mediated-Rhodamine 123 drug efflux activity assay. These results suggest that either rescuing miR-211 expression or downregulation of MMP-9 may have a new therapeutic application for GBM patients in the future.

Highlights

Transcriptional and post-transcriptional regulators of gene expression, including microRNAs, are being investigated as a relatively new and important class of oncogenes and tumor suppressors [1,2,3,4,5]
The Glioblastoma multiforme (GBM) tissues with low miR-211 levels showed significantly higher expression of Matrix metalloproteinase-9 (MMP-9) protein; the normal cerebrum (NC) tissues with high levels of miR211 showed lower expression of matrix metalloproteases (MMPs)-9 protein (Fig. 1A)
The analysis showed that the miR-211 level was inversely correlated with MMP-9 level in a total of 25 GBM specimens (p

Summary

Introduction

Transcriptional and post-transcriptional regulators of gene expression, including microRNAs (miRNAs), are being investigated as a relatively new and important class of oncogenes and tumor suppressors [1,2,3,4,5]. The miRNAs comprise a class of evolutionarily conserved small RNAs (22 nts long) that affect gene expression at the posttranscriptional level by blocking translation or degrading target messenger RNAs (mRNAs) [6, 7]. Several studies have reported that miRNA genes are often found in genomic regions linked to cancer [9, 10], and miRNA expression profiles are correlated with the developmental lineage and the differentiation state of tumors [11]. We focused on miRNA-211 (miR-211), which plays a functional role in the regulation of apoptosis and tumor progression.

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