Neovascularisation and migration of tumour cells are two features of h
ighly malignant glioma. Vascular endothelial growth factor (VEGF) and
tissue plasminogen activator (tPA) seem to be of importance in the pro
cess of malignancy. In the present study a topographical co-expression
of tPA mRNA and VEGF mRNA (VEGF(121) and VEGF(165) isoforms) was demo
nstrated in the tumour edge of a rat malignant glioma, using in situ h
ybridisation. No signs of co-expression was seen in the normal brain t
issue. In the normal brain the forms of VEGF mainly expressed were VEG
F(121), VEGF(165), and VEGF(189). Further studies are required to show
whether VEGF and tPA are produced by the same tumour cells and to elu
cidate the role of this co-expression.