Expression of growth factors and growth factor receptors in capillary hemangioblastoma

To elucidate the mechanisms underlying the regulation of growth and differentiation of capillary hemangioblastoma we studied the expression of selected growth factors and growth factor receptors by immunocytochemistry. As stromal cells of capillary hemangioblastoma express high levels of vascular endothelial growth factor (VEGF) and placental growth factor (P1GF) mRNA, we studied the distribution of the corresponding VEGF and P1GF proteins. We also studied the expression of epidermal growth factor receptor (EGFR) and platelet-derived growth factor receptors (PDGFR) because their ligands have been reported to promote angiogenesis. The stromal cells expressed abundant EGFR and, in addition, some stromal cells expressed PDGFR-alpha but not PDGFR-beta. In contrast, the endothelial cells co-expressed PDGFR-alpha and PDGFR-beta. VEGF and P1GF were expressed by scattered stromal cells; however, more intense staining was observed in the endothelial cells of the intratumoral blood vessels, possibly indicating the secreted growth factors bound to their target receptors. We conclude that capillary hemangioblastomas express a variety of growth factor receptors and ligands, potentially involved in both autocrine and paracrine loops. The uniformly high EGFR expression is unique among brain tumors and may be associated with the typical morphology of capillary hemangioblastoma. The expression of highly angiogenic growth factors and their receptors may contribute to the rich vascularity of this enigmatic tumor.