title: Candidate biomarker verification: Critical examination of a serum protein pattern for human colorectal cancer.
abstract: OBJECTIVE
  We critically examine a candidate serum protein pattern for human colorectal cancer (CRC) with respect to reproducibility, sample handling, and disease specificity.
  
  
  METHODS
  Serum samples from CRC patients, patients with benign colon tumors and healthy individuals, were obtained at two collection sites and analyzed by SELDI-TOF MS on 8 days, over a period of 5 weeks. The spectra were subjected to multivariate analysis. Tissues from normal colon and CRC were analyzed by SELDI-TOF MS. Selected mass peaks were identified.
  
  
  RESULTS
  Using an elaborate experimental design we developed a multivariate classifier that correctly classified CRC and control serum measured on an independent day. The classifier did not discriminate between samples from CRC patients and patients with benign colon tumors, and, secondly, did not correctly classify serum from an independent collection site. All discriminatory mass peaks were identified as high abundant plasma proteins. Tissue profiling provided support of increased proteolytic activity in CRC tissue.
  
  
  CONCLUSIONS
  Critical verification did not justify advancing the identified CRC serum protein pattern into clinical validation without improvement. We believe that proteomics biomarker research could benefit if the presented, or a similar, verification scheme was more commonly employed in explorative biomarker studies.
authors.affiliation: Clinical Biochemistry Unit, Department of Diagnostics, Glostrup Hospital, Glostrup, Denmark. j_albrethsen@hotmail.com
authors.forename: Jakob
authors.initials: J
authors.lastname: Albrethsen
authors.forename: Rikke
authors.initials: R
authors.lastname: Bøgebo
authors.forename: Christian H
authors.initials: CH
authors.lastname: Møller
authors.forename: Jesper A
authors.initials: JA
authors.lastname: Olsen
authors.forename: Hans H
authors.initials: HH
authors.lastname: Raskov
authors.forename: Steen
authors.initials: S
authors.lastname: Gammeltoft
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D014408:Biomarkers, Tumor / Q000097:blood; D001798:Blood Proteins / Q000032:analysis; D016022:Case-Control Studies; D015179:Colorectal Neoplasms / Q000097:blood* / Q000175:diagnosis / Q000473:pathology; D005260:Female; D006801:Humans; D008297:Male; D013058:Mass Spectrometry / Q000379:methods; D008875:Middle Aged; D015999:Multivariate Analysis; D025341:Principal Component Analysis; D059748:Proteolysis; D020543:Proteome / Q000032:analysis*; D040901:Proteomics / Q000379:methods*; D015203:Reproducibility of Results; D012107:Research Design; D012680:Sensitivity and Specificity; D013048:Specimen Handling
chemical_list: D014408:Biomarkers, Tumor; D001798:Blood Proteins; D020543:Proteome