title: Epigenetic silencing of the candidate tumor suppressor gene PROX1 in sporadic breast cancer.
abstract: Extensive hypermethylation and consecutive transcriptional silencing of tumorsuppressor genes have been documented in multiple tumor entities including breast cancer. In a microarray based genome-wide methylation analysis of five sporadic breast carcinomas we identified a hypermethylated CpG island within the first intron of the prospero related homeobox gene 1 (PROX1). We, therefore, investigated CpG island methylation of PROX1 in a series of 33 pairs of primary breast cancer and corresponding normal tissue samples by bisulfite sequencing and COBRA analyses. Seventeen of these (52%) breast cancer samples revealed a significant accumulation of methylated CpG sites along with a significant reduction of PROX1 transcription compared to normal breast tissues of the same patients. Frequent methylation was also observed in brain metastases from primary breast cancer (21/37 = 57% of cases). Secondary, we analysed 38 brain metastases of primary breast carcinomas and detected a significantly reduced expression of PROX1 compared to normal breast tissue (p < 0.001) and primary breast carcinomas (p < 0.05), respectively. Additionally, treatment of breast cancer cell lines with demethylating agents could reactivate PROX1 transcription. In summary, we have identified PROX1 as a novel target gene that is hypermethylated and transcriptionally silenced in primary and metastatic breast cancer.
authors.affiliation: Division of Molecular Gyneco-Oncology, Department of Gynecology and Obstetrics, University of Cologne, Germany.
authors.forename: Beatrix
authors.initials: B
authors.lastname: Versmold
authors.forename: Jörg
authors.initials: J
authors.lastname: Felsberg
authors.forename: Thomas
authors.initials: T
authors.lastname: Mikeska
authors.forename: Denise
authors.initials: D
authors.lastname: Ehrentraut
authors.forename: Juliane
authors.initials: J
authors.lastname: Köhler
authors.forename: Juergen A
authors.initials: JA
authors.lastname: Hampl
authors.forename: Gabriele
authors.initials: G
authors.lastname: Röhn
authors.forename: Dieter
authors.initials: D
authors.lastname: Niederacher
authors.forename: Beate
authors.initials: B
authors.lastname: Betz
authors.forename: Martin
authors.initials: M
authors.lastname: Hellmich
authors.forename: Torsten
authors.initials: T
authors.lastname: Pietsch
authors.forename: Rita K
authors.initials: RK
authors.lastname: Schmutzler
authors.forename: Andreas
authors.initials: A
authors.lastname: Waha
mesh_terms: D000328:Adult; D000368:Aged; D001374:Azacitidine / Q000494:pharmacology; D001932:Brain Neoplasms / Q000556:secondary; D001943:Breast Neoplasms / Q000235:genetics* / Q000473:pathology; D018899:CpG Islands; D019175:DNA Methylation; D004273:DNA, Neoplasm / Q000378:metabolism; D044127:Epigenesis, Genetic; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D020868:Gene Silencing; D016147:Genes, Tumor Suppressor; D018398:Homeodomain Proteins / Q000235:genetics*; D006801:Humans; D008875:Middle Aged; D020411:Oligonucleotide Array Sequence Analysis; D014158:Transcription, Genetic; D014407:Tumor Cells, Cultured; D025521:Tumor Suppressor Proteins / Q000235:genetics*; D000098551:Prospero-Related Homeobox 1 Protein
chemical_list: D004273:DNA, Neoplasm; D018398:Homeodomain Proteins; D025521:Tumor Suppressor Proteins; D000098551:Prospero-Related Homeobox 1 Protein; D001374:Azacitidine