title: Loss of heterozygosity at tumor suppressor genes detectable on fractionated circulating cell-free tumor DNA as indicator of breast cancer progression.
abstract: OBJECTIVE
  LOH on circulating DNA may provide tumor-specific information on breast cancer. As identification of LOH on cell-free DNA is impeded by the prevalence of wild type DNA in blood of cancer patients, we fractionated plasma DNA, and determined the diagnostic and prognostic value of both fractions.
  
  
  METHODS
  Our cohort of 388 patients with primary breast cancer before chemotherapy was selected from a multicenter study (SUCCESS). Postoperative plasma was fractionated in low- and high-molecular weight DNA by two different column systems. In both fractions, LOH was determined by a PCR-based microsatellite analysis using a panel of 8 polymorphic markers. Circulating tumor DNA in plasma from 30 patients after chemotherapy was additionally analyzed. The significance levels were adjusted for multiple comparisons.
  
  
  RESULTS
  More patients (38%) had LOH at all markers in the fraction containing short DNA fragments than in the fraction containing the long DNA molecules (28%, P = 0.0001). In both fractions 32.85% of LOH were concordant. LOH at the markers D3S1605, D10S1765, D12S1725, D13S218, and D17S855 significantly correlated with tumor stage, tumor size, and lymph node metastasis, positive progesterone, and HER2 receptor status. Most importantly, LOH at D12S1725 mapping to cyclin D2 correlated with shorter overall survival (P = 0.004).
  
  
  CONCLUSIONS
  The improved detection of LOH on cell-free DNA provides important information on DNA losses of tumor suppressor genes TIG1, PTEN, cyclin D2, RB1, and BRCA1 in breast cancer. In particular, loss of the cyclin D2 gene might become an important prognostic marker easily detectable in the peripheral blood.
authors.affiliation: Department of Tumor Biology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany. hschwarz@uke.uni-hamburg.de
authors.forename: Heidi
authors.initials: H
authors.lastname: Schwarzenbach
authors.forename: Corinna
authors.initials: C
authors.lastname: Eichelser
authors.forename: Jolanthe
authors.initials: J
authors.lastname: Kropidlowski
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Janni
authors.forename: Brigitte
authors.initials: B
authors.lastname: Rack
authors.forename: Klaus
authors.initials: K
authors.lastname: Pantel
mesh_terms: D000328:Adult; D000368:Aged; D001943:Breast Neoplasms / Q000097:blood / Q000235:genetics / Q000473:pathology; D002986:Clinical Trials as Topic; D004273:DNA, Neoplasm / Q000097:blood / Q000235:genetics; D018450:Disease Progression; D005260:Female; D006801:Humans; D053208:Kaplan-Meier Estimate; D019656:Loss of Heterozygosity / Q000235:genetics*; D008207:Lymphatic Metastasis / Q000235:genetics / Q000473:pathology; D018895:Microsatellite Repeats / Q000235:genetics; D008875:Middle Aged; D009367:Neoplasm Staging; D009360:Neoplastic Cells, Circulating; D011379:Prognosis; D016019:Survival Analysis
chemical_list: D004273:DNA, Neoplasm