International journal of oncology

MMP-2 suppression abrogates irradiation-induced microtubule formation in endothelial cells by inhibiting αvβ3-mediated SDF-1/CXCR4 signaling.

PMID 23381805


The majority of glioblastoma multiforme (GBM) tumors recur after radiation (IR) treatment due to increased angiogenesis and IR-induced signaling events in endothelial cells (ECs) that are involved in tumor neovascularization; however, these signaling events have yet to be well characterized. In the present study, we observed that IR (8 Gy) significantly elevated MMP-2 expression and gelatinolytic activity in 4910 and 5310 human GBM xenograft cells. In addition, ECs treated with tumor-conditioned media (CM) obtained from IR-treated 4910 and 5310 cells showed increased microtubule formation. In view of this finding, we investigated the possible anti-angiogenic effects of MMP-2 downregulation using siRNA ( in IR-treated cells. We also determined the effect of CM obtained from mock, pSV (scrambled vector) and on endothelial cell growth and vessel formation. ECs showed inhibited IR-CM-induced SDF-1, CXCR4, phospho-PI3K and phospho-AKT and αvβ3 expression levels. In vitro angiogenesis assays also showed that the decreased IR-induced vessel formation in ECs. Immunofluorescence and immunoprecipitation experiments indicated the abrogation of αvβ3-SDF-1 interaction in ECs when compared to mock or pSV treatments. External supplementation of either rhMMP-2 or rhSDF-1 counteracted and noticeably reversed SDF-1, CXCR4, phospho-PI3K and phospho-AKT expression levels and angiogenesis, thereby confirming the role of MMP-2 in the regulation of αvβ3-mediated SDF-1/CXCR4 signaling. In addition to the in vitro results, the in vivo mouse dorsal air sac model also showed reduced angiogenesis after injection of alone or in combination with IR-treated xenograft cells. In contrast, injection of mock or pSV-treated cells resulted in robust formation of characteristic neovascularization. Collectively, our data demonstrate the role of MMP-2 in the regulation of SDF-1/CXCR4 signaling-mediated angiogenesis in ECs and show the anti-angiogenic efficacy of combining MMP-2 downregulation and IR when treating patients with GBM in the future.