title: Ectopic expression of guanylyl cyclase C in CD34+ progenitor cells in peripheral blood.
abstract: OBJECTIVE
  To examine the utility of guanylyl cyclase C (GC-C)-specific nested reverse transcriptase polymerase chain reaction (RT-PCR) to detect circulating tumor cells in patients with colorectal cancer.
  
  
  METHODS
  Peripheral-blood mononuclear cells from 24 patients with Dukes' stage D colorectal cancer were analyzed by GC-C-specific nested RT-PCR using 1 microg of total RNA. Peripheral-blood mononuclear cells from 20 healthy volunteers served as controls. Additionally, peripheral-blood CD34+ progenitor cells were assayed for the expression of both GC-C and other epithelial cell-specific markers.
  
  
  RESULTS
  GC-C mRNA was detected in blood mononuclear cells from all 24 patients with colorectal cancer and all healthy volunteers. These unexpected positive results reflected low-level ectopic transcription of GC-C in CD34+ progenitor cells. Moreover, CD34+ progenitor cells expressed other epithelial cell-specific markers, including prostate-specific antigen, prostate-specific membrane antigen, carcinoembryonic antigen, CK-19, CK-20, mucin 1, and GA733.2. Limiting the quantity of mononuclear cell total RNA analyzed to < or = 0.8 microg eliminated detection of GC-C and other tissue-specific transcripts in blood of healthy volunteers. However, under the same conditions, GC-C mRNA was detected in mononuclear cells from all 24 patients with metastatic colorectal cancer. Using 0.5 microg of total RNA and GC-C-specific primers, nested RT-PCR detected a single human colon carcinoma cell (approximately 20 to 200 GC-C transcripts/cell) in 10(6) to 10(7) mononuclear blood cells.
  
  
  CONCLUSIONS
  These data suggest that GC-C may be useful for detecting circulating colorectal cancer cells. They also demonstrate that CD34+ cells are a source of ectopically expressed epithelial cell-specific markers and that CD34+ cells may contribute to the high false-positive rate generally observed when those markers are used to detect rare circulating metastatic cancer cells by RT-PCR.
authors.affiliation: Division of Clinical Pharmacology, and Department of Medicine, Thomas Jefferson University, Philadelphia, PA, USA.
authors.forename: T A
authors.initials: TA
authors.lastname: Fava
authors.forename: R
authors.initials: R
authors.lastname: Desnoyers
authors.forename: S
authors.initials: S
authors.lastname: Schulz
authors.forename: J
authors.initials: J
authors.lastname: Park
authors.forename: D
authors.initials: D
authors.lastname: Weinberg
authors.forename: E
authors.initials: E
authors.lastname: Mitchell
authors.forename: S A
authors.initials: SA
authors.lastname: Waldman
mesh_terms: D000328:Adult; D000368:Aged; D018952:Antigens, CD34 / Q000097:blood*; D014408:Biomarkers, Tumor / Q000097:blood* / Q000235:genetics; D002272:Carcinoembryonic Antigen / Q000097:blood; D015179:Colorectal Neoplasms / Q000097:blood / Q000201:enzymology* / Q000473:pathology; D004847:Epithelial Cells / Q000201:enzymology; D005260:Female; D016179:Granulocyte Colony-Stimulating Factor / Q000627:therapeutic use; D006162:Guanylate Cyclase / Q000096:biosynthesis / Q000097:blood* / Q000235:genetics; D006412:Hematopoietic Stem Cells / Q000201:enzymology*; D006801:Humans; D007963:Leukocytes, Mononuclear / Q000201:enzymology; D008297:Male; D008875:Middle Aged; D009362:Neoplasm Metastasis; D009367:Neoplasm Staging; D009360:Neoplastic Cells, Circulating / Q000378:metabolism; D012333:RNA, Messenger / Q000097:blood; D000074261:Receptors, Enterotoxin; D050705:Receptors, Guanylate Cyclase-Coupled; D018000:Receptors, Peptide / Q000096:biosynthesis / Q000097:blood* / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D018952:Antigens, CD34; D014408:Biomarkers, Tumor; D002272:Carcinoembryonic Antigen; D012333:RNA, Messenger; D018000:Receptors, Peptide; D016179:Granulocyte Colony-Stimulating Factor; D006162:Guanylate Cyclase; D000074261:Receptors, Enterotoxin; D050705:Receptors, Guanylate Cyclase-Coupled