title: Transgelin gene is frequently downregulated by promoter DNA hypermethylation in breast cancer.
abstract: BACKGROUND
  CpG hypermethylation in gene promoters is a frequent mechanism of tumor suppressor gene silencing in various types of cancers. It usually occurs at early steps of cancer progression and can be detected easily, giving rise to development of promising biomarkers for both detection and progression of cancer, including breast cancer. 5-aza-2'-deoxycytidine (AZA) is a DNA demethylating and anti-cancer agent resulting in induction of genes suppressed via DNA hypermethylation.
  
  
  RESULTS
  Using microarray expression profiling of AZA- or DMSO-treated breast cancer and non-tumorigenic breast (NTB) cells, we identified for the first time TAGLN gene as a target of DNA hypermethylation in breast cancer. TAGLN expression was significantly and frequently downregulated via promoter DNA hypermethylation in breast cancer cells compared to NTB cells, and also in 13/21 (61.9 %) of breast tumors compared to matched normal tissues. Analyses of public microarray methylation data showed that TAGLN was also hypermethylated in 63.02 % of tumors compared to normal tissues; relapse-free survival of patients was worse with higher TAGLN methylation; and methylation levels could discriminate between tumors and healthy tissues with 83.14 % sensitivity and 100 % specificity. Additionally, qRT-PCR and immunohistochemistry experiments showed that TAGLN expression was significantly downregulated in two more independent sets of breast tumors compared to normal tissues and was lower in tumors with poor prognosis. Colony formation was increased in TAGLN silenced NTB cells, while decreased in overexpressing BC cells.
  
  
  CONCLUSIONS
  TAGLN gene is frequently downregulated by DNA hypermethylation, and TAGLN promoter methylation profiles could serve as a future diagnostic biomarker, with possible clinical impact regarding the prognosis in breast cancer.
authors.affiliation: Department of Molecular Biology and Genetics, Bilkent University, Faculty of Science, TR-06800 Ankara, Turkey.
authors.forename: Nilufer
authors.initials: N
authors.lastname: Sayar
authors.affiliation: Department of Molecular Biology and Genetics, Bilkent University, Faculty of Science, TR-06800 Ankara, Turkey.
authors.forename: Gurbet
authors.initials: G
authors.lastname: Karahan
authors.affiliation: Department of Molecular Biology and Genetics, Bilkent University, Faculty of Science, TR-06800 Ankara, Turkey.
authors.forename: Ozlen
authors.initials: O
authors.lastname: Konu
authors.affiliation: Department of General Surgery, Ankara Numune Training and Research Hospital, 06100 Ankara, Turkey.
authors.forename: Betul
authors.initials: B
authors.lastname: Bozkurt
authors.affiliation: Department of Pathology, Ankara Numune Training and Research Hospital, 06100 Ankara, Turkey.
authors.forename: Onder
authors.initials: O
authors.lastname: Bozdogan
authors.affiliation: Department of Molecular Biology and Genetics, Bilkent University, Faculty of Science, TR-06800 Ankara, Turkey.
authors.forename: Isik G
authors.initials: IG
authors.lastname: Yulug
keywords: Breast cancer; DNA methylation; Diagnosis; Hypermethylation; Prognosis; SM22 alpha; TAGLN