title: Limitations of cytokeratin 20 RT-PCR to detect disseminated tumour cells in blood and bone marrow of patients with colorectal cancer: expression in controls and downregulation in tumour tissue.
abstract: OBJECTIVE
  Despite informative staging of patients with colorectal cancer, some patients with localised disease at diagnosis will develop recurrence or metastasis. Attempts to improve staging include sensitive detection of disseminated tumour cells in blood and bone marrow by reverse transcriptase polymerase chain reaction (RT-PCR). The results of this study have been considered in relation to the controversial results in the literature to elucidate the usefulness of cytokeratin 20 (CK20) RT-PCR to detect disseminated tumour cells further.
  
  
  METHODS
  Blood and bone marrow samples from 30 patients with colorectal cancer were studied by CK20 RT-PCR. Specificity was evaluated in 47 blood and 15 bone marrow samples from non-cancer controls. In addition, the expression of CK20 mRNA and protein was studied in normal and tumour colon tissue samples.
  
  
  RESULTS
  CK20 expression was detected in nine of 30 and nine of 19 of the blood and bone marrow samples from patients with colorectal cancer, respectively. In non-cancer control blood and bone marrow samples, CK20 expression was detected in 10 of 47 and four of 15, respectively. A difference between patient and control samples may be observed in terms of frequency of positive PCR tests. In tissue samples, CK20 mRNA expression was downregulated in tumour compared with normal colon tissue.
  
  
  CONCLUSIONS
  CK20 expression was downregulated in tumour tissue compared with normal colon and a background expression of CK20 was seen in some control blood and bone marrow samples. Despite a lack of standardisation (which hampers comparison of studies), these results, together with other reports in the literature, suggest that CK20 may still be a suitable marker, but that background expression and threshold setting should be studied further.
authors.affiliation: Department of Surgery, University Medical Centre Nijmegen, PO Box 9101, 6500 HB Nijmegen, The Netherlands. f.vlems@pathol.azn.nl
authors.forename: F A
authors.initials: FA
authors.lastname: Vlems
authors.forename: J H S
authors.initials: JH
authors.lastname: Diepstra
authors.forename: I M H A
authors.initials: IM
authors.lastname: Cornelissen
authors.forename: T J M
authors.initials: TJ
authors.lastname: Ruers
authors.forename: M J L
authors.initials: MJ
authors.lastname: Ligtenberg
authors.forename: C J A
authors.initials: CJ
authors.lastname: Punt
authors.forename: J H J M
authors.initials: JH
authors.lastname: van Krieken
authors.forename: Th
authors.initials: T
authors.lastname: Wobbes
authors.forename: G N P
authors.initials: GN
authors.lastname: van Muijen
mesh_terms: D014408:Biomarkers, Tumor / Q000032:analysis* / Q000235:genetics; D019046:Bone Marrow Neoplasms / Q000175:diagnosis / Q000556:secondary*; D015179:Colorectal Neoplasms / Q000473:pathology*; D015536:Down-Regulation; D006801:Humans; D007381:Intermediate Filament Proteins / Q000032:analysis* / Q000235:genetics; D053554:Keratin-20; D009362:Neoplasm Metastasis; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism; D009367:Neoplasm Staging; D009360:Neoplastic Cells, Circulating / Q000737:chemistry*; D016133:Polymerase Chain Reaction / Q000379:methods; D011786:Quality Control; D012333:RNA, Messenger / Q000235:genetics; D012334:RNA, Neoplasm / Q000235:genetics
chemical_list: D014408:Biomarkers, Tumor; D007381:Intermediate Filament Proteins; C507499:KRT20 protein, human; D053554:Keratin-20; D009363:Neoplasm Proteins; D012333:RNA, Messenger; D012334:RNA, Neoplasm