title: An abnormally glycosylated isoform of erythropoietin in hemangioblastoma is associated with polycythemia.
abstract: BACKGROUND
  Hemangioblastomas express erythropoietin and the patients often present with polycythemia.
  
  
  METHODS
  Serum erythropoietin was measured using a commercial immunoassay, a functional erythropoietin assay and iso-electric focusing.
  
  
  RESULTS
  Despite the polycythemia, serum erythropoietin remained low, while a functional erythropoietin-assay showed a 4-5 higher activity in serum compared to the immunoassay. Iso-electric focusing of serum erythropoietin indicated overrepresentation of highly sialylated erythropoietin isoforms produced by the tumor. As a result, altered affinity of the monoclonal antibody used in the immunoassay for the hypersialylated isoforms was suggested.
  
  
  CONCLUSIONS
  Analysis of erythropoietin isoforms may be helpful in distinguishing the ectopic erythropoietin isoforms from normally glycosylated erythropoietin.
authors.affiliation: Department of Internal Medicine, AZ Maria Middelares, Ghent, Belgium.
authors.forename: Sigurd E
authors.initials: SE
authors.lastname: Delanghe
authors.affiliation: Department of Laboratory Medicine, AZ Maria Middelares, Ghent, Belgium.
authors.forename: Jan
authors.initials: J
authors.lastname: Dierick
authors.affiliation: Department of Clinical Chemistry, Ghent University Hospital, Ghent, Belgium.
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Maenhout
authors.affiliation: VIB, Department of Medical Protein Research, Ghent University, Ghent, Belgium.
authors.forename: Lennart
authors.initials: L
authors.lastname: Zabeau
authors.affiliation: VIB, Department of Medical Protein Research, Ghent University, Ghent, Belgium.
authors.forename: Jan
authors.initials: J
authors.lastname: Tavernier
authors.affiliation: Department of Genetics, Ghent University Hospital, Ghent, Belgium.
authors.forename: Kathleen
authors.initials: K
authors.lastname: Claes
authors.affiliation: Department of Internal Medicine, AZ Maria Middelares, Ghent, Belgium.
authors.forename: Joris
authors.initials: J
authors.lastname: Bleyen
authors.affiliation: Department of Clinical Chemistry, Ghent University Hospital, Ghent, Belgium. Electronic address: joris.delanghe@ugent.be.
authors.forename: Joris R
authors.initials: JR
authors.lastname: Delanghe
mesh_terms: D000911:Antibodies, Monoclonal / Q000737:chemistry / Q000276:immunology; D016477:Artifacts; D016543:Central Nervous System Neoplasms / Q000097:blood* / Q000150:complications / Q000175:diagnosis / Q000601:surgery; D004921:Erythropoietin / Q000032:analysis / Q000378:metabolism*; D006031:Glycosylation; D018325:Hemangioblastoma / Q000097:blood* / Q000150:complications / Q000175:diagnosis / Q000601:surgery; D006801:Humans; D007118:Immunoassay; D007525:Isoelectric Focusing; D008297:Male; D008875:Middle Aged; D011086:Polycythemia / Q000097:blood* / Q000150:complications / Q000175:diagnosis / Q000601:surgery; D020033:Protein Isoforms / Q000032:analysis / Q000378:metabolism
chemical_list: D000911:Antibodies, Monoclonal; D020033:Protein Isoforms; D004921:Erythropoietin
keywords: Erythropoietin isoforms; Glycosylation; Hemangioblastoma; von Hippel–Lindau