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Oncogene. 2014 Apr 10;33(15):1922-33. doi: 10.1038/onc.2013.151. Epub 2013 Jun 3.

Irradiation-induced angiogenesis is associated with an MMP-9-miR-494-syndecan-1 regulatory loop in medulloblastoma cells.

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  • 1Department of Cancer Biology and Pharmacology, University of Illinois College of Medicine at Peoria, Peoria, IL, USA.
  • 21] Department of Cancer Biology and Pharmacology, University of Illinois College of Medicine at Peoria, Peoria, IL, USA [2] Department of Neurosurgery, University of Illinois College of Medicine at Peoria, Peoria, IL, USA.

Abstract

Matrix metalloproteinase-9 (MMP-9) represents one of the most prominent proteins associated with tumorigenesis and is a modulator of the tumor microenvironment during angiogenesis. Recently, syndecan-1 (SDC1), a transmembrane heparan sulfate-bearing proteoglycan, was also speculated to have a critical role in contributing to angiogenesis when associated with MMP-9. However, the mechanism behind their synergistic regulation is not fully understood. In the current study, we report for the first time that ionizing radiation (IR)-induced MMP-9 enhances SDC1 shedding, corroborating to tube-inducing ability of medulloblastoma (MB) cells. Furthermore, we observed that the tumor angiogenesis is associated with higher MMP-9-SDC1 interactions on both the cell surface and extracellular medium. Our results also revealed the existence of a novel regulatory mechanism where MMP-9 drives the suppression of miR-494, resulting in enhanced SDC1 shedding and angiogenesis. From the in situ hybridization analysis, we found that MMP-9-specific shRNA (shMMP-9) treatment of mouse intracranial tumors resulted in elevated expression of miR-494. This negative correlation between MMP-9 and miR-494 levels was observed to be dependent on the methylation status of a miR-494 promoter-associated CpG island region (-186 to -20), which was confirmed by bisulfite-sequencing and methylation-specific PCR (MSP) analysis. Further, validation of MMP-9 and SDC1 3'-untranslated region (3'-UTR) targets with luciferase reporter assay provided a more favorable result for miR-494-mediated regulation of SDC1 but not of MMP-9, suggesting that the 3'-UTR of SDC1 mRNA is a direct target of miR-494. Overall, our results indicate that angiogenesis induced by radiotherapy is associated with an MMP-9-miR-494-SDC1 regulatory loop and that MMP-9-SDC1 activity creates a negative feedback loop by regulating the expression of miR-494.

PMID:
23728345
[PubMed - indexed for MEDLINE]
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