Leegwater P A, De Abreu R A, Albertioni F
Laboratory for Paediatrics and Neurology, University Hospital of Nijmegen, The Netherlands.
Cancer Lett. 1998 Aug 14;130(1-2):169-73. doi: 10.1016/s0304-3835(98)00131-1.
DNA methylation of the CpG-rich 5' region of the deoxycytidine kinase (dCK) gene is potentially involved in the suppression of the gene and the resistance of tumour cells to arabinosylcytosine (ara-C). 2-Chlorodeoxyadenosine (cladribine, CdA) and 2-chloro-2'-arabino-fluoro-2'-deoxyadenosine (CAFdA) are purine nucleoside analogues which are also phosphorylated by dCK. We observed a reduction in dCK activity in a number of CCRF-CEM-derived cell lines that are resistant to these drugs and hypothesized that this reduction is due to DNA methylation of the 5' region of the dCK gene. The DNA methylation state was analyzed at the DNA sequence level after bisulfite modification of genomic DNA. The investigated region included 0.3 kb of DNA upstream to the start site of transcription, exon 1 and part of intron 1. Sensitive cells (CCRF-CEM/0) and three resistant cell lines (CCRF-CEM/CdA4000, CCRF-CEM/CAFdA100 and CCRF-CEM/CAFdA4000) were investigated. The region that was analyzed contained no methylated cytosine residues in the parental cell line CCRF-CEM/0 or in the resistant cell lines. Therefore, it is highly unlikely that DNA methylation plays a role in the suppression of dCK gene expression in these cell lines.
脱氧胞苷激酶（dCK）基因富含CpG的5'区域的DNA甲基化可能参与该基因的抑制以及肿瘤细胞对阿糖胞苷（ara-C）的耐药性。2-氯脱氧腺苷（克拉屈滨，CdA）和2-氯-2'-阿拉伯氟-2'-脱氧腺苷（CAFdA）是嘌呤核苷类似物，它们也由dCK磷酸化。我们观察到一些对这些药物耐药的源自CCRF-CEM的细胞系中dCK活性降低，并推测这种降低是由于dCK基因5'区域的DNA甲基化所致。在对基因组DNA进行亚硫酸氢盐修饰后，在DNA序列水平分析DNA甲基化状态。研究区域包括转录起始位点上游0.3 kb的DNA、外显子1和内含子1的一部分。研究了敏感细胞（CCRF-CEM/0）和三种耐药细胞系（CCRF-CEM/CdA4000、CCRF-CEM/CAFdA100和CCRF-CEM/CAFdA4000）。分析的区域在亲本细胞系CCRF-CEM/0或耐药细胞系中均未包含甲基化的胞嘧啶残基。因此，DNA甲基化极不可能在这些细胞系中dCK基因表达的抑制中起作用。
