BACKGROUND - Intracellular signaling responsible for gastrin-releasing peptide (GRP) receptor-mediated neovascularization is not clearly understood. We sought to determine the cellular mechanisms involved in the GRP receptor regulation of vascular endothelial growth factor (VEGF) release in neuroblastoma cells.
MATERIALS AND METHODS - BE(2)-C cells were treated with bombesin (BBS), the amphibian equivalent of GRP, Phorbol myristate acetate (PMA) a PKC agonist, or GF109293X (GFX), and analyses were performed for VEGF secretion, phosphorylated protein kinase B (AKT), extracellular signal-regulated kinases (ERK) and protein kinase D (PKD) expression.
RESULTS - BBS rapidly increased VEGF secretion at 30 min. Pre-treatment with PMA alone produced similar results; this effect was synergistic with the addition of GRP. Conversely, GFX blocked PMA-stimulated increase in VEGF secretion. Immunofluorescent staining for VEGF correlated to BBS, PMA and GFX.
CONCLUSION - PKC is critically responsible for rapid VEGF secretion by GRP receptor signaling in neuroblastoma cells. Inhibition of VEGF significantly reduced GRP-mediated cell proliferation, suggesting its crucial role in neuroblastoma tumorigenesis.