title: SOX17 promoter methylation in circulating tumor cells and matched cell-free DNA isolated from plasma of patients with breast cancer.
abstract: BACKGROUND
  Detection of circulating tumor cells (CTCs) and cell-free DNA (cfDNA) in the peripheral blood of patients with solid tumors has been widely studied for the early detection of metastatic spread. We evaluated whether there was an association between the origin of cfDNA and CTCs. We investigated whether SRY (sex determining region Y)-box 17 (SOX17) promoter methylation in CTCs was associated with the methylation pattern of this gene in matched cfDNA isolated from plasma of patients with breast cancer.
  
  
  METHODS
  We examined SOX17 methylation in 79 primary breast tumors, in 114 paired samples of DNA isolated from CTCs and cfDNA, and in 60 healthy individuals. Isolated DNA was modified by sodium bisulfite and subjected to methylation specific PCR.
  
  
  RESULTS
  The SOX17 promoter was methylated in 68 (86.0%) of 79 of primary breast tumors. In CTCs, SOX17 was methylated in 19 (34.5%) of 55 patients with early breast cancer, 27 (45.8%) of 59 patients with metastatic cancer, and 1 (4.3%) of 23 healthy individuals, whereas in matched cfDNA SOX17 was methylated in 19 (34.5%) of 55, 24 (40.7%) of 59, and 1 (2.0%) of 49 of these same groups, respectively. There was a significant correlation between SOX17 methylation in cfDNA and CTCs in patients with early breast cancer (P = 0.008), but not in patients with verified metastasis (P = 0.283).
  
  
  CONCLUSIONS
  The SOX17 promoter is highly methylated in primary breast tumors, in CTCs isolated from patients with breast cancer, and in corresponding cfDNA samples. Our findings indicate a direct connection between the presence of CTCs and cfDNA in patients with operable breast cancer, after surgical removal of the primary tumor.
authors.affiliation: Analysis of Circulating Tumor Cells Laboratory, Laboratory of Analytical Chemistry, Department of Chemistry, University of Athens, Athens, Greece.
authors.forename: Maria
authors.initials: M
authors.lastname: Chimonidou
authors.forename: Areti
authors.initials: A
authors.lastname: Strati
authors.forename: Nikos
authors.initials: N
authors.lastname: Malamos
authors.forename: Vasilis
authors.initials: V
authors.lastname: Georgoulias
authors.forename: Evi S
authors.initials: ES
authors.lastname: Lianidou
mesh_terms: D001943:Breast Neoplasms / Q000235:genetics*; D002474:Cell-Free System; D019175:DNA Methylation; D004273:DNA, Neoplasm / Q000097:blood*; D005260:Female; D006801:Humans; D018189:Immunomagnetic Separation; D009360:Neoplastic Cells, Circulating / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D055760:SOXF Transcription Factors / Q000235:genetics*
chemical_list: D004273:DNA, Neoplasm; C109188:SOX17 protein, human; D055760:SOXF Transcription Factors