title: LOH at 6q and 10q in fractionated circulating DNA of ovarian cancer patients is predictive for tumor cell spread and overall survival.
abstract: BACKGROUND
  We recently showed that LOH proximal to M6P/IGF2R locus (D6S1581) in primary ovarian tumors is predictive for the presence of disseminated tumor cells (DTC) in the bone marrow (BM). For therapy-monitoring, it would be highly desirable to establish a blood-based biomarker. Therefore, we quantified circulating DNA (cirDNA) in sera of 63 ovarian cancer patients before surgery and after chemotherapy, measured incidence of LOH at four cancer-relevant chromosomal loci, correlated LOH with tumor cell spread to the BM and evaluated prognostic significance of LOH.
  
  
  METHODS
  cirDNA was fractionated into high- and low molecular-weight fraction (HMWF, LMWF) for LOH-profiling, utilizing PCR-based fluorescence microsatellite analysis. BM aspirates were analyzed for DTC by immunocytochemistry using the pan-cytokeratin antibody A45-B/B3.
  
  
  RESULTS
  cirDNA levels in the HMWF before surgery were predictive for residual tumor load (p = 0.017). After chemotherapy, we observed a significant decline of cirDNA in the LMWF (p = 0.0001) but not in the HMWF. LOH was prevalently detected in the LMWF with an overall frequency of 67%, only moderately ablating after chemotherapy (45%). Before surgery, LOH in the LMWF at marker D10S1765 and D13S218 significantly correlated with tumor grading and FIGO stage (p = 0.033, p = 0.004, respectively). In both combined fractions, LOH at D6S1581 additionally associated with overall survival (OS) (p = 0.030). Moreover, solely LOH at D10S1765 in LMWF after therapy correlated with DTC in BM after therapy (p = 0.017).
  
  
  CONCLUSIONS
  We demonstrate the applicability and necessity of DNA-fractionation prior to analyzing circulating LOH and identify LOH at D10S1765 and D6S1581 as novel blood-based biomarkers for ovarian cancer, being relevant for therapy-monitoring.
authors: Department of Gynecology and Obstetrics, University Hospital of Essen, Hufelandstrasse 55, Essen, D-45122, Germany. jandominik.kuhlmann@uk-essen.de
authors: Jan Dominik
authors: JD
authors: Kuhlmann
authors: Heidi
authors: H
authors: Schwarzenbach
authors: Pauline
authors: P
authors: Wimberger
authors: Micaela
authors: M
authors: Poetsch
authors: Rainer
authors: R
authors: Kimmig
authors: Sabine
authors: S
authors: Kasimir-Bauer
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D014408:Biomarkers, Tumor / Q000097:blood / Q000235:genetics; D001853:Bone Marrow / Q000473:pathology; D002879:Chromosomes, Human, Pair 10; D002896:Chromosomes, Human, Pair 6; D004273:DNA, Neoplasm / Q000097:blood*; D005260:Female; D006801:Humans; D019656:Loss of Heterozygosity; D008875:Middle Aged; D060787:Neoplasm Grading; D009367:Neoplasm Staging; D009360:Neoplastic Cells, Circulating; D010051:Ovarian Neoplasms / Q000235:genetics* / Q000401:mortality / Q000473:pathology; D011379:Prognosis; D055815:Young Adult
chemical_list: D014408:Biomarkers, Tumor; D004273:DNA, Neoplasm