title: Quantification of the sixth DNA base 5-hydroxymethylcytosine in colorectal cancer tissue and C-26 cell line.
abstract: BACKGROUND
  DNA methylation at the five position of cytosine is well recognized as an important epigenetic modification in human health and disease. Recent evidences demonstrated that 5-methylcytosine (5-mC) by the TET family of enzymes can be converted to 5-hydroxymethylcytosine (5-hmC). Here, we use an ultrasensitive and accurate isotope-based LC-MS/MS method to precisely determine the levels of 5-hmC and 5-mC in colorectal cancer and the C-26 colon adenocarcinoma cell line.
  
  
  RESULTS
  Our data showed that 5-hmC content is significantly reduced (approximately sixfold) in colorectal cancer as compared with adjacent normal tissue. Similarly, the ratio of 5-hmC to 5-mC dropped from 0.054 ± 0.005 in normal tissues, to 0.011 ± 0.002 in cancer.
  
  
  CONCLUSIONS
  The analysis of 5-hmC levels and the ratio of 5-hmC:5-mC during tumor progression might provide insight into the role of this modification in cellular immortalization and transformation.
authors.affiliation: Guangdong Medical College, Zhanjiang, Guangdong 524023, People's Republic of China.
authors.forename: Liang-Tao
authors.initials: LT
authors.lastname: Zhang
authors.forename: Li-Jian
authors.initials: LJ
authors.lastname: Zhang
authors.forename: Jun-Jie
authors.initials: JJ
authors.lastname: Zhang
authors.forename: Xiao-Xia
authors.initials: XX
authors.lastname: Ye
authors.forename: Ai-Mei
authors.initials: AM
authors.lastname: Xie
authors.forename: Li-Yu
authors.initials: LY
authors.lastname: Chen
authors.forename: Jing X
authors.initials: JX
authors.lastname: Kang
authors.forename: Chun
authors.initials: C
authors.lastname: Cai
mesh_terms: D044503:5-Methylcytosine / Q000031:analogs & derivatives; D045744:Cell Line, Tumor; D002471:Cell Transformation, Neoplastic / Q000235:genetics; D002853:Chromatography, Liquid / Q000379:methods; D015179:Colorectal Neoplasms / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D003596:Cytosine / Q000031:analogs & derivatives* / Q000032:analysis / Q000378:metabolism; D019175:DNA Methylation; D004273:DNA, Neoplasm / Q000032:analysis* / Q000235:genetics; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D053719:Tandem Mass Spectrometry / Q000379:methods
chemical_list: D004273:DNA, Neoplasm; C011865:5-hydroxymethylcytosine; D044503:5-Methylcytosine; D003596:Cytosine