Chowdhury Basudev, McGovern Andrew, Cui Yi, Choudhury Samrat Roy, Cho Il-Hoon, Cooper Bruce, Chevassut Timothy, Lossie Amy C, Irudayaraj Joseph
1] Department of Biological Sciences, Purdue University, West Lafayette 47907, IN [2] Bindley Biosciences Center, Discovery Park, Purdue University, West Lafayette 47907, IN.
1] Department of Healthcare Management and Policy, University of Surrey, Guildford, GY2 7XH, UK [2] Brighton and Sussex Medical School, Falmer, Brighton, East Sussex, BN1 9PS, UK.
Sci Rep. 2015 Apr 22;5:9281. doi: 10.1038/srep09281.
The USFDA approved "epigenetic drug", Decitabine, exerts its effect by hypomethylating DNA, demonstrating the pivotal role aberrant genome-wide DNA methylation patterns play in cancer ontology. Using sensitive technologies in a cellular model of Acute Myeloid Leukemia, we demonstrate that while Decitabine reduces the global levels of 5-methylcytosine (5mC), it results in paradoxical increase of 5-hydroxymethylcytosine (5hmC), 5-formylcytosine (5fC) and 5-carboxylcytosine (5caC) levels. Hitherto, the only biological mechanism known to generate 5hmC, 5fC and 5caC, involving oxidation of 5mC by members of Ten-Eleven-Translocation (TET) dioxygenase family, was not observed to undergo any alteration during DAC treatment. Using a multi-compartmental model of DNA methylation, we show that partial selectivity of TET enzymes for hemi-methylated CpG dinucleotides could lead to such alterations in 5hmC content. Furthermore, we investigated the binding of TET1-catalytic domain (CD)-GFP to DNA by Fluorescent Correlation Spectroscopy in live cells and detected the gradual increase of the DNA bound fraction of TET1-CD-GFP after treatment with Decitabine. Our study provides novel insights on the therapeutic activity of DAC in the backdrop of the newly discovered derivatives of 5mC and suggests that 5hmC has the potential to serve as a biomarker for monitoring the clinical success of patients receiving DAC.
美国食品药品监督管理局（USFDA）批准的“表观遗传药物”地西他滨通过使DNA低甲基化发挥作用，这表明全基因组异常的DNA甲基化模式在癌症发生过程中起关键作用。在急性髓系白血病的细胞模型中使用灵敏技术，我们证明，虽然地西他滨降低了5-甲基胞嘧啶（5mC）的整体水平，但它却导致5-羟甲基胞嘧啶（5hmC）、5-甲酰基胞嘧啶（5fC）和5-羧基胞嘧啶（5caC）水平出现反常增加。迄今为止，已知产生5hmC、5fC和5caC的唯一生物学机制是由十一-易位（TET）双加氧酶家族成员氧化5mC，但在DAC治疗期间未观察到该机制发生任何改变。使用DNA甲基化的多隔室模型，我们表明TET酶对半甲基化的CpG二核苷酸的部分选择性可能导致5hmC含量发生此类改变。此外，我们通过荧光相关光谱法在活细胞中研究了TET1催化结构域（CD）-绿色荧光蛋白（GFP）与DNA的结合，并检测到用地西他滨处理后TET1-CD-GFP与DNA结合部分逐渐增加。我们的研究在新发现的5mC衍生物的背景下为DAC的治疗活性提供了新见解，并表明5hmC有潜力作为监测接受DAC治疗患者临床疗效的生物标志物。
