Urokinase-type plasminogen activator (uPA) activity is related to the malignant biological behaviour of tumours. In the present study, we examined the presence and distribution of uPA in human gliomas. The amounts of uPA were measured by Northern blotting hybridisation and immunohistochemistry in 43 gliomas and five normal brain specimens. Their relation to the clinical history was comprehensively analysed. All tissues expressed 2.5 kb transcripts of uPA mRNA. The uPA mRNA levels were significantly higher in high grade gliomas than they were in low grade gliomas and normal brain tissue (P < 0.01). Levels of uPA mRNA expression in tumour tissues with recurrence within 18 months postoperatively and survival less than 3 years were significantly higher than counterparts (P < 0.01). The uPA mRNA was also expressed in tumour cells near necrotic areas. The uPA protein expression was consistent with the uPA mRNA expression. The distribution of uPA protein immunoreactivity was mainly in tumour cells and microvascular endothelial cells of glioblastomas and anaplastic astrocytomas, localising in the cytoplasm, especially at sites of vascular proliferation and at the leading edges of tumours. These results suggest that expression of the uPA gene is associated with the malignant progression of gliomas and may play an important role in the recurrence and invasive behaviors of higher grade gliomas.
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