title: Proteases present in some pancreatic cyst fluids may affect mucin immunoassay by degrading antibodies and antigens.
abstract: OBJECTIVE
  Biomarker detection in pancreatic cyst fluids is of importance to improve the diagnosis of mucinous cystadenoma, a precancerous lesion. However, assay protocols are generally established for serum testing.
  
  
  METHODS
  Immunoradiometric assay of gastric M1/MUC5AC mucin was performed on pancreatic cyst fluids with well-characterized monoclonal antibodies.
  
  
  RESULTS
  Among 1466 pancreatic cyst fluids tested, about 10% to 15% of samples presented abnormal behaviors: (i) radioactivity measured after immunoradiometric assay much lower than the blank of the assay and (ii) increasing dilution of the fluids leading to apparent increase of M1/MUC5AC concentration. In contrast, none of the 109 hepatic cyst fluids tested presented interference.We demonstrate that some (n = 54) interfering fluids cause mucin degradation as well as antibody degradation. Western blot analysis showed that the C-terminal part of the M1/MUC5AC apomucin is most sensitive to degradation.
  
  
  CONCLUSIONS
  The presence of proteases that degrade antibodies as well as mucin may explain the pitfalls observed in 3.6% of the samples. To detect this interference, each fluid has to be systematically tested at 1:100 dilution in the presence of a saturating concentration of M1/MUC5AC mucin standard and in the absence of antiprotease reagents. Detection of interference could prevent false results caused by mucin degradation in situ.
authors.affiliation: INSERM UMR S-938 and UPMC Paris 6, Team Biology and Therapeutics of Cancer, Centre de Recherche Paris-St-Antoine, Paris, France. marie-elisabeth.forgue-lafitte@inserm.fr
authors.forename: Marie-Elisabeth
authors.initials: ME
authors.lastname: Forgue-Lafitte
authors.forename: Ritu
authors.initials: R
authors.lastname: Arambam
authors.forename: Jacques
authors.initials: J
authors.lastname: Bara
mesh_terms: D000911:Antibodies, Monoclonal / Q000378:metabolism; D020420:Cyst Fluid / Q000201:enzymology*; D006801:Humans; D015592:Immunoradiometric Assay / Q000379:methods*; D055271:Mucin 5AC / Q000032:analysis* / Q000276:immunology / Q000378:metabolism; D010181:Pancreatic Cyst / Q000201:enzymology*; D010447:Peptide Hydrolases / Q000378:metabolism*
chemical_list: D000911:Antibodies, Monoclonal; C524678:MUC5AC protein, human; D055271:Mucin 5AC; D010447:Peptide Hydrolases