ANGIOGENESIS IN TWO HUMAN PROSTATE CANCER CELL LINES WITH DIFFERING METASTATIC POTENTIAL WHEN GROWING AS SOLID TUMORS IN NUDE MICE

Abstract

Angiogenesis, typically a feature of aggressive tumors, is frequently associated with increased vascular endothelial growth factor (VEGF) production. Here, angiogenesis and angiogenic growth factor expression were assessed in two human prostate cancer cell models with differing metastatic potential. Prostatic tumors were obtained by injecting either highly metastatic PC-3M cells or poorly metastatic DU145 cells into the surgically exposed prostate glands of nude mice. Angiogenesis was evaluated by immunohistochemical staining, and tumor VEGF, transforming growth factors-beta (TGF-beta1 and TGF-beta2), and basic fibroblast growth factor (bFGF) levels were determined by immunoassays (ELISAs). VEGF isoforms were detected by Western blotting in both solid tumor extracts, and in culture medium conditioned by the same cell lines (CM). Angiogenesis was much more evident in PC-3M tumors (vessel counts: PC-3M tumors 360 +/- 42, DU145 tumors 156 +/- 25; p = 0.003), but ELISA-determined VEGF levels were approximately 3-fold higher in both DU145 cell tumors, and in DU145 cell CM. However, Western blotting showed that PC-3M tumors, but not CM, contained VEGF isoforms with molecular weights of 43 and 57 kDa. TGF-beta2, but not TGF-beta1 concentrations were higher in DU145 cell tumors (p < 0.001); bFGF levels were higher in the PC-3M cell tumors (p < 0.05). When growing in nude mouse prostate glands, the PC-3M cell line provides a model for the angiogenic activity associated with aggressive prostate cancer. This is accompanied by the expression of immunoreactive VEGF which is not detected by an ELISA antibody raised against the conventional VEGF165, but appears on Western blots as what may prove to be novel high molecular weight species. Observed differences in TGF-beta1 and -beta2, and bFGF expression, may also be associated with an angiogenic phenotype.