Expression and localization of 72 kDa type IV collagenase (MMP-2) in human malignant gliomas in vivo

Abstract

The 72 kDa type IV collagenase (gelatinase), a matrix metalloproteinase (MMP-2), has been proposed to potentiate the invasion and metastasis of malignant tumors. To determine the potential role of the MMP-2 in human gliomas and normal brain tissue, we examined the relative amounts of protein, mRNA, and distribution. Using gelatin zymography, densitometry, and an enzyme-linked immunosorbent assay for the quantitative determination of the MMP-2, we found that the enzyme's activity was significantly elevated in malignant astrocytomas, especially in glioblastoma multiforme, compared to low-grade glioma and normal brain tissues. As determined by Northern blot analysis, the amount of MMP-2 mRNA transcript was higher in anaplastic astrocytomas and glioblastoma multiforme tumors than in normal brain tissues or low-grade gliomas, a finding that was consistent with the amounts of MMP-2 protein detected in these tissues. Immunohistochemical studies demonstrated that MMP-2 was localized in tumor cells and vasculature cells of malignant astrocytomas. Staining intensity was clearly lower in low-grade astrocytomas, and immunoreactivity was very low or undetectable in normal brain astrocytes. The results suggest that expression of the MMP-2 is dramatically upregulated in malignant gliomas, correlating with the malignant progression of human gliomas in vivo.