Expression and Cellular Localization of Messenger RNA for Plasminogen Activator Inhibitor Type 1 in Human Astrocytomas in Vivo

We investigated the expression and cellular localization of plasminogen activator inhibitor type 1 (PAI-1) in human astrocytoma in vivo. Northern blot and densitometric quantitation of PAI-1 mRNA indicated that PAI-1 transcripts were significantly higher in human malignant astrocytomas and especially in glioblastomas than in low-grade gliomas and normal brain tissues in vivo. Using in situ hybridization with paraffin-embedded surgical specimens of human gliomas and normal brain tissues, PAI-1 mRNA was abundantly expressed in glioblastomas. PAI-1 mRNA was localized mainly in tumor cells and endothelial cells. The distribution of PAI-1 mRNA expression was particularly abundant around areas of vascular proliferation and in remnant tumor cells surrounding necrotic foci. PAI-1 mRNA was also expressed in both the tumor and endothelial cells of anaplastic astrocytomas, whereas it was not expressed or only weakly expressed in low-grade astrocytomas or normal brain tissues. These results suggest that high expression of PAI-1 is associated with the malignant progression of astrocytic tumors and that excessive PAI-1 expression might be associated with intratumoral necrosis in glioblastomas.