that cause oncogenic osteomalacia

Objective: Oncogenic hypophosphatemic osteomalacia (OOM) is a rare disease characterized by hypo-phosphatemia, inappropriately low levels of circulating 1,25-dihydroxyvitamin D3 and osteomalacia. The disease is most commonly caused by benign mesenchymal tumors that produce, among several other factors, fibroblast growth factor-23 (FGF-23). Current evidence thus suggests that this protein has an important role in the regulation of phosphate homeostasis. By producing polyclonal antibodies against human FGF-23 protein we wanted to determine the localization of FGF-23 protein in OOM tumors that express FGF-23 mRNA. Design and methods: Three polyclonal antibodies were raised in rabbits against three different peptides with sequences derived from human FGF-23: [Cys-70]FGF-23(51 –69)amide, [Tyr-223]FGF-23(206 –222)amide and [Tyr-224]FGF-23(225 –244)amide. One of the resulting antisera was sub-sequently used for immunohistochemistry on sections from five different tumors causing OOM. FGF-23 mRNA expression was confirmed with in situ hybridization. Results: After affinity purification, two of three antisera detected recombinant human FGF-23 by Western blot analysis. Through immunohistochemical analysis using the anti-[Tyr-224]FGF