Μελέτη του ρόλου του αυξητικού παράγοντα HARP στην παθοφυσιολογία του ανθρώπινου προστάτη

Abstract

The development and growth of human prostate cancer is mediated by many tumor cell-derived growth factors. Heparin affin regulatory peptide (HARP) seems to be involved in the progression of several tumors of diverse origin. In the present work, we sought to determine if HARP is implicated in human prostate cancer. An antisense strategy for inhibition of HARP expression in the human prostate cancer cell line LNCaP was used to study the role of HARP on cancer cell growth, migration and angiogenic potential in vitro and in vivo. Exogenous human recombinant HARP was mitogenic for LNCaP cells. By decreasing the expression of endogenous HARP, we found that HARP was essential for LNCaP cell migration, as well as anchorage-dependent and independent growth. Endothelial cell functions in vitro and blood vessel formation in vivo induced by LNCaP cells were also inhibited when HARP expression was diminished. Fibroblast growth factor 2 (FGF-2) is a pleiotropic growth factor that has been implicated in prostate carcinoma formation and progression. In the present study we found that exogenous FGF-2 significantly increased human prostate cancer LNCaP cell proliferation and migration. HARP seems to be an important mediator of FGF-2 stimulatory effects, since the latter had no effect on stably transfected LNCaP cells that did not express HARP. Moreover, FGF-2 significantly induced HARP expression and secretion by LNCaP cells and increased luciferase activity of a reporter gene vector carrying the full length promoter of HARP gene. The FGFR1-specific inhibitor SU-5402 blocked the FGF-2-increased HARP gene activation and the consequent protein release, leading to impairment of LNCaP cell proliferation. Treatment of LNCaP cells with the hydrogen peroxide scavenger pyruvate, pointed to the dependence of FGF-2-induced HARP expression and LNCaP cell proliferation on hydrogen peroxide generation, and blockade of FGFR1 activity abrogated the FGF-2-induced production of reactive oxygen species. Activator protein-1 (AP-1) seems to be involved in FGF-2-stimulated HARP expression and secretion by LNCaP cells, as revealed using AP-1 decoy oligonucleotides and point mutation analyses in the HARP gene promoter. Binding of AP-1 complexes consisting of Fra-1, JunD and phospho-c-Jun, to the HARP promoter seems to be amenable for FGF-2 effect. These results point to an important regulator role of HARP in diverse biological activities in human prostate cancer cells. Furthermore, the present work establishes the role and the mode of activity of FGF-2 in LNCaP cells and reflects the many-sidedness of growth factor pathways within prostate cancer.