Expression of multiple angiogenic cytokines in cultured normal human prostate epithelial cells: Predominance of vascular endothelial growth factor

The cytokines that regulate angiogenesis in normal and malignant prostate tissue are not well studied. Using an RT‐PCR‐based screen, we observed that cultured, low‐passage normal human prostate epithelial cells (PrECs) express a variety of cytokines which have been shown to have angiogenic and/or endothelial cell–activating properties in various systems. These include vascular endothelial growth factor (VEGF), basic fibroblastic growth factor (bFGF), transforming growth factor‐α (TGF‐α), transforming growth factor‐β (TGF‐β), interleukin‐8 (IL‐8), tumor necrosis factor‐α (TNF‐α), granulocyte‐macrophage colony‐stimulating factor (GM‐CSF) and granulocyte colony‐stimulating factor (G‐CSF). Expression of VEGF, bFGF, GM‐CSF, G‐CSF, TGF‐α and TNF‐α in these cells was confirmed by immuno‐histochemistry. Culture medium conditioned by normal human PrECs for periods of up to 96 hr were found to contain VEGF, GM‐CSF, G‐CSF, IL‐8, TGF‐β1 and TGF‐β2 but not TNF‐α or bFGF, as determined by ELISA. Of these, VEGF was by far the most prominently expressed angiogenic cytokine (approx. 2,500 pg/ml conditioned medium at 96 hr vs. 30 to 100 pg/ml conditioned medium for the other cytokines). PrEC‐conditioned medium induced an approximately 2‐fold stimulation of [3H]‐thymidine incorporation in cultured human umbilical cord endothelial cells (HUVECs) deprived of the endothelial growth factors VEGF and bFGF; this stimulation was abolished by neutralizing antibodies directed against VEGF but not bFGF, IL‐8, GM‐CSF or TNF‐α. VEGF expression by PrECs was not markedly altered by administration or deprivation of other angiogenic cytokines for which these cells have receptors, suggesting that there is not a hierarchy of cytokines controlling its expression; however, retinoic acid, a component of PrEC growth medium, was found to modestly suppress VEGF at physiological concentrations (0.1 ng/ml). These data suggest that normal PrECs express a variety of angiogenic cytokines, most prominently VEGF, to recruit a supporting vasculature, even in culture. Our data also suggest that the ability of malignant PrECs to stimulate angiogenesis may be intrinsic and does not need to be acquired during oncogenesis. Int. J. Cancer80:868–874, 1999. © 1999 Wiley‐Liss, Inc.