title: 5-Carboxylcytosine levels are elevated in human breast cancers and gliomas.
abstract: BACKGROUND
  DNA methylation (5-methylcytosine (5mC)) patterns are often altered in cancers. Ten-eleven translocation (Tet) proteins oxidise 5mC to 5-hydroxymethylcytosine (5hmC), 5-formylcytosine (5fC) and 5-carboxylcytosine (5caC). In addition to their presumptive specific biological roles, these oxidised forms of 5mC may serve as intermediates in demethylation process. According to several reports, 5hmC levels are strongly decreased in cancers; however, the distribution of 5fC and 5caC in malignant tissue has not been studied.
  
  
  RESULTS
  Here, we examine the levels of 5hmC and 5caC in 28 samples of normal breast tissue, 59 samples of invasive human breast cancer and 74 samples of gliomas using immunochemistry. In agreement with previous reports, we show that 71 % of normal breast samples exhibit strong 5hmC signal, compared with only 18 % of breast cancer samples with equivalent levels of 5hmC staining. Unexpectedly, although 5caC is not detectable in normal breast tissue, 27 % of breast cancer samples exhibit significant staining for this modification (p < 0.001). Surprisingly, the presence of immunochemically detectable 5caC is not associated with the intensity of 5hmC signal in breast cancer tissue. In gliomas, we show that 5caC is detectable in 45 % of tumours.
  
  
  CONCLUSIONS
  We demonstrate that, unlike 5hmC, the levels of 5caC are elevated in a proportion of breast cancers and gliomas. Our results reveal another level of complexity to the cancer epigenome, suggesting that active demethylation and/or 5caC-dependent transcriptional regulation are pre-activated in some tumours and may contribute to their pathogenesis. Larger studies to evaluate the clinicopathological significance of 5caC in cancers are warranted.
authors: Division of Cancer and Stem Cells, School of Medicine, Centre for Biomolecular Sciences, University of Nottingham, University Park, Nottingham, NG7 2RD UK.
authors: Maria
authors: M
authors: Eleftheriou
authors: Division of Cancer and Stem Cells, School of Medicine, Centre for Biomolecular Sciences, University of Nottingham, University Park, Nottingham, NG7 2RD UK.
authors: Ana Jimenez
authors: AJ
authors: Pascual
authors: Medical Molecular Sciences, Centre for Biomolecular Sciences, University of Nottingham, University Park, Nottingham, NG7 2RD UK.
authors: Lee M
authors: LM
authors: Wheldon
authors: Academic Unit of Oncology, Division of Cancer and Stem Cells, School of Medicine, University of Nottingham, Nottingham, NG51PB UK.
authors: Christina
authors: C
authors: Perry
authors: Division of Cancer and Stem Cells, School of Medicine, Centre for Biomolecular Sciences, University of Nottingham, University Park, Nottingham, NG7 2RD UK ; Present address: Lab de Neurophysiologie, Université libre de Bruxelles, Campus Erasme CP 601, Bldg. C Room C3-143, 808, Route de Lennik, B-1070 Brussels, Belgium.
authors: Abdulkadir
authors: A
authors: Abakir
authors: Department of Oncology, Nottingham University Hospitals, Nottingham, NG5 1PB UK.
authors: Arvind
authors: A
authors: Arora
authors: School of Life Sciences, University of Nottingham, University Park, Nottingham, NG7 2RD UK.
authors: Andrew D
authors: AD
authors: Johnson
authors: Department of Academic Radiology, Queen's Medical Centre, Nottingham University Hospitals, University of Nottingham, Nottingham, NG7 2UH UK.
authors: Dorothee T
authors: DT
authors: Auer
authors: Department of Pathology, Division of Cancer and Stem Cells, School of Medicine, University of Nottingham, Nottingham, NG51PB UK.
authors: Ian O
authors: IO
authors: Ellis
authors: Academic Unit of Oncology, Division of Cancer and Stem Cells, School of Medicine, University of Nottingham, Nottingham, NG51PB UK.
authors: Srinivasan
authors: S
authors: Madhusudan
authors: Division of Cancer and Stem Cells, School of Medicine, Centre for Biomolecular Sciences, University of Nottingham, University Park, Nottingham, NG7 2RD UK.
authors: Alexey
authors: A
authors: Ruzov
keywords: 5-carboxylcytosine; 5-hydroxymethylcytosine; Breast cancer; Carcinogenesis; DNA methylation; Immunohistochemistry