title: Cytokeratin 20 is not a tissue-specific marker for the detection of malignant epithelial cells in the blood of colorectal cancer patients.
abstract: BACKGROUND
  The clinical benefit of using reverse transcription polymerase chain reaction (RT-PCR)-based assays to detect circulating tumour cells during post-operative surveillance of cancer patients remains unclear. Cytokeratin 20 has been proposed as a tissue-specific marker for the detection of micrometastases in the blood of colorectal cancer patients. However, recent reports have challenged its specificity, and hence the validity of its use.
  
  
  OBJECTIVE
  The aim of this study was to evaluate the tissue-specificity of ck20 mRNA transcription and its use for detecting circulating colon epithelial cells.
  
  
  METHODS
  RNA was isolated from the peripheral blood of 51 colorectal cancer patients, four patients with benign gastrointestinal disease and 42 healthy controls. In addition, it was prepared from 32 colorectal cancers, from a pituitary cancer, from normal kidney, liver, fibroblasts, keratinocytes and from 24 lymph nodes obtained from eight patients with benign gastrointestinal disease. Real-time RT-PCR assays were used to quantitative and compare ck20 transcription.
  
  
  RESULTS
  Significant levels of ck20 mRNA were detected in all 42 blood samples from healthy volunteers and in all pre- and post-operative blood samples from colorectal cancer patients regardless of the presence of metastatic disease. It was also detected in all other mRNA samples analysed.
  
  
  CONCLUSIONS
  The lack of colon tissue-specificity renders ck20 useless as a marker for the post-operative surveillance of colorectal cancer patients.
authors.affiliation: Academic Department of Surgery, St. Bartholomew's, Royal London School of Medicine and Dentistry, London, England. s.a.bustin@mds.qmw.ac.uk
authors.forename: S A
authors.initials: SA
authors.lastname: Bustin
authors.forename: V G
authors.initials: VG
authors.lastname: Gyselman
authors.forename: S
authors.initials: S
authors.lastname: Siddiqi
authors.forename: S
authors.initials: S
authors.lastname: Dorudi
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D014408:Biomarkers, Tumor / Q000032:analysis*; D015179:Colorectal Neoplasms / Q000175:diagnosis*; D004848:Epithelium / Q000737:chemistry; D005260:Female; D006801:Humans; D007381:Intermediate Filament Proteins / Q000032:analysis* / Q000235:genetics; D053554:Keratin-20; D008297:Male; D008875:Middle Aged; D009360:Neoplastic Cells, Circulating / Q000737:chemistry*; D012333:RNA, Messenger / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014158:Transcription, Genetic
chemical_list: D014408:Biomarkers, Tumor; D007381:Intermediate Filament Proteins; C507499:KRT20 protein, human; D053554:Keratin-20; D012333:RNA, Messenger