中国急性白血病儿童与正常儿童CDA基因多态性研究

Single-nucleotide polymorphisms of the cytidine deaminase gene in childhood with acute leukemia and normal Chinese children

目的研究胞苷脱氨酶（cytidine deaminase,CDA）基因编码区单核苷酸多态性（coding single nucleotide polymorphisms,cSNPs）在急性白血病（acute leukemia,AL）患儿和正常中国儿童中的频率分布特征,为探讨CDA变异与AL患者阿糖胞苷化疗效应之间可能的相关性及肿瘤化疗个体化提供理论依据。方法采用变性梯度凝胶电泳、限制性片段长度多态性分析及DNA序列测定等方法对87例AL患儿和199名正常儿童的DNA进行了CDAcSNPs的筛查与鉴定,分析各基因型在两组之间的分布差异。结果在中国儿童CDA中鉴定了3种已知的cSNPs,即79A〉C（K27Q）、208G〉A（A70T）和435T〉C,其等位基因频率分别是12.1%、0.52%和76.2%。这些多态性与白血病的易感性无相关性。结论确定了中国儿童CDA中存在3种cSNPs以及各自的基因型分布和等位基因频率。提供了为预测不同个体间对脱氧胞苷同系物潜在敏感性差异的遗传学标志。

Objective Cytidine deaminase （CDA） is a key enzyme for metabolizing chemotherapeutic agent cytosine arabinoside （Ara-C）, a deoxycytidine analog used for treatment of acute leukemia and lymphomas. Significant variability in the antitumor efficacy and systemic toxicity of Ara-C has been observed in cancer patients. Two missense mutations changing Ara-C sensitivity and toxicity had been found in the human CDA. Coding single-nucleotide polymor- phisms （cSNPs） of CDA had been investigated in Japanese, Europeans Africans and Americans, but not in Chinese. The purpose of this study was to survey the allelic frequencies of CDA cSNPs in Chinese children. Mefthods The bone marrow samples from 87 childhood patients with acute leukemia and peripheral blood samples from 199 non-malignancy-bearing children were obtained to prepare complementary DNAs （cDNAs）. The cDNAs were analyzed for the polymorphisms in CDA by polymerase chain reaction （PCR）-denaturing gradient gel electrophoresis （DGGE）, PCR-restriction fragment length polymorphism （RFLP） and direct-sequencing. The distributive difference of each genotype was evaluated between children with acute leukemia and control children. Results Three known different polymorphisms, namely, 79A 〉 C （K27Q）, 208G〉 A （A70T） and 435T〉 C （silent） were identified in the coding region of CDA from the investigated Chinese population and displayed allelic frequencies of 12.1%, 0.52% and 76.2%, respectively. No association with susceptibihty to disease was observed. Conclusion This study demonstrates 3 cSNPs and their allelic frequencies of CDA in Chinese children, and provides the first step to identify genetic markers for predicting variability in Ara-C response and toxicity.