Angiogenically active vascular endothelial growth factor is over-expressedin malignant human and rat prostate carcinoma cells

Vascular endothelial growth factor (VEGF) is one of the most potent factors for stimulating angiogenesis, an essential process required for expansion of primary tumour and dissemination of malignant cells. To investigate the possible role of VEGF in facilitating metastasis of prostate cancer via sti mulating angiogenesis, we have used Northern and slot blotting, reverse tra nscription polymerase chain reaction, nucleotide sequence analysis and enzy me-linked immunosorbent assay to compare the VEGF expression in series of h uman and rat cell lines with either benign or malignant characteristics. We have also employed the chick chorioallantoic membrane (CAM) assay to measu re the angiogenic activity of the VEGF derived from both benign and maligna nt cells. The level of VEGF mRNA expressed in the seven malignant human and rat cell lines is 3.5- to 10-fold higher than that expressed in the benign cell lines. The three metastatic variants, generated by transfection of a benign cell line with DNA extracted from prostate carcinoma cells, expresse d 2.5 to 5 times more VEGF mRNA than their parental benign cells. While VEG F 121 and 165 were predominantly expressed by both the benign and malignant cells, the transcript representing VEGF 189 isoform was only detected in t he malignant cells. At protein level, three human malignant cell lines prod uced more VEGF (2.7-7.9 ng ml(-1)) than the benign cell line (1.3 ng ml(-1) ). CAM assay detected a VEGF-dependent angiogenic activity in the medium fr om malignant cells, but only a relatively weak VEGF-independent activity in the medium from benign cells. These results demonstrated that malignant ce lls did over-express VEGF and only the VEGF derived from malignant cells wa s angiogenically active. Thus, we suggest that the VEGF produced by maligna nt cells might play an important role in facilitating metastasis of prostat ic cancer. (C) 2000 Cancer Research Campaign.