Immunohistochemical detection of FGF-23 protein in tumors that cause oncogenic osteomalacia.
OBJECTIVE
Oncogenic hypophosphatemic osteomalacia (OOM) is a rare disease characterized by hypophosphatemia, inappropriately low levels of circulating 1,25-dihydroxyvitamin D(3) 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.


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 subsequently 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-23(225-244)amide antibody and through in situ hybridization using full-length antisense FGF-23 cRNA as a probe, we showed that abundant amounts of FGF-23 protein and mRNA are present in certain tumor cells of five different OOM tumors.


CONCLUSIONS
We conclude that OOM tumors express FGF-23 protein and that the immunohistochemical detection of FGF-23 in OOM tumors is feasible and may help in establishing the diagnosis of tumor-induced hypophosphatemia through analysis of biopsies or surgical specimens.
Larsson
Tobias
T
Department of Medical Sciences, University Hospital, Uppsala, Sweden.
Zahradnik
Richard
R
Lavigne
Jeffrey
J
Ljunggren
Osten
O
Jüppner
Harald
H
Jonsson
Kenneth B
KB
D000328:Adult; D005260:Female; D000089703:Fibroblast Growth Factor-23; D005346:Fibroblast Growth Factors / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008637:Mesenchymoma / Q000150:complications* / Q000378:metabolism*; D008875:Middle Aged; D010018:Osteomalacia / Q000209:etiology*; D012333:RNA, Messenger / Q000378:metabolism
C000717427:FGF23 protein, human; D012333:RNA, Messenger; D005346:Fibroblast Growth Factors; D000089703:Fibroblast Growth Factor-23