Invasive tumors, including gliomas, utilize proteinases to break down extracellular matrix components and diffuse into adjacent tissues or migrate towards distant ones. In addition, proteinase activity is critical for tumor angiogenesis. Because levels of the proteinase Matrix Metalloproteinase-2 (MMP-2) are highly increased in gliomas, we studied the effect of downregulation of MMP-2 via adenovirus-mediated transfer of small interfering RNAs (siRNAs) in gliomas. Delivery of double-stranded small RNA molecules results in efficient, sequence-specific silencing of the targeted gene, which occurs at the post-transcriptional level. siRNAs against MMP-2 mRNA (Ad-SM2) significantly decreased MMP-2 activity and protein levels in the glioblastoma cell lines, U87 and U251, as shown by gelatin zymography and western blotting of conditioned media from cultured cells. MTT proliferation assay revealed impaired cell growth of the Ad-SM2-treated glioma cells. Moreover, infection of cells with the adenoviral construct inhibited cell invasion through matrigel and decreased migration from tumor spheroids. We also observed decreased VEGF protein levels as well as decreased tumor-induced angiogenesis in vitro. In addition, the results of a dorsal skin-fold chamber assay in mice indicated the efficient inhibition of angiogenesis in vivo. Finally, Ad-SM2 treatment triggered the cleavage of caspase 3 and DNA fragmentation in U87 and U251--both events are characteristic of apoptotic cell death. Thus, specific targeting of MMP-2 may provide an efficient approach in the development of new strategies to treat gliomas and improve the poor prognosis of these brain tumors.

98th AACR Annual Meeting-- Apr 14-18, 2007; Los Angeles, CA