化学物暴露与白血病发病相关基因DNA甲基化对儿童急性白血病发病的影响

Chemical exposure, leukemia related DNA methylation changes and childhood acute leukemia

目的：探讨化学物暴露、白血病发病相关DNA甲基化改变以及二者交互作用与儿童急性白血病发病的关系。方法2009年1月1日至2010年12月31日，采用1∶1匹配的病例-对照研究方法，选取131例就诊于3家上海市三甲级儿童医院的0～15岁新发急性白血病患儿为病例组，选取病例所在医院的发育行为儿科或骨科门诊就诊或入院治疗与病例组同性别、同年龄的儿童为对照组，排除患血液系统疾病、肿瘤疾病等的儿童。对两组儿童进行相关环境因素的问卷调查，采用甲基化特异性聚合酶链反应（MSP）分析病例组与对照组儿童8个与白血病发病相关的基因（P16、P73、E-cadherin、DAPK、C-ABL、HSPA4L、PTEN、APAF-1）的甲基化状态，并分析环境暴露因素与基因甲基化水平改变之间的交互作用，以相对超额危险度（RERI）、归因比（API）与交互作用指数（S）描述其交互作用。结果病例组和对照组分别为131和140例，年龄分别为（6.9±3.8）和（6.9±3.9）岁（t=0.01，P=0.911）。将混杂因素校正后，儿童期（OR=3.90，95%CI：1.69～9.02）、母亲孕前及孕期（OR=2.71，95%CI：1.12～6.52）、父亲在母亲怀孕前（OR=1.91，95%CI：1.05～3.47）接触化学物与儿童急性白血病发生相关。病例组儿童DAPK、PTEN、P73基因甲基化程度高于对照组儿童[病例组分别为：3.1%（4例），16.0%（21例），7.6%（10例）；对照组分别为：0.7%（1例），2.9%（4例），0.7%（1例），χ2值分别为7.11、16.90、11.38，P值分别为0.029、0.000、0.003]，但病例组P16基因的甲基化程度低于对照组儿童[病例组比对照组：3.8%（5例）比8.6%（12例），χ2=10.33, P=0.007]。环境-基因交互作用结果显示，儿童化学物质接触史与PTEN、P16、P73等3种基因存在交互作用（PTEN：RERI=-7.01，API=-2.14，S=0.24；P16：RERI=4.08，API=0.53，S=2.59；P73：RERI=4.32，API=0.48，S=2.19）；母亲孕前或孕期化学物质接触史与PTEN、P16基因亦存在交互作用（PTEN：RERI=-1.30，API=-0.38，S=0.65；P16：RERI=1.70，API=0.38，S=1.97）。结论儿童不同发育阶段接触化学物质、多种基因DNA甲基化水平改变均是儿童急性白血病发病的危险因素，且两者呈现出不同程度的交互作用，可能在儿童急性白血病的发病过程中发挥着重要作用。

Objective To evaluate the association between chemical exposure, DNA methylation status and gene-environment interactions in the development of childhood acute leukemia （AL）. Methods From January 1st 2009 to December 31st 2010,an exploratory case-control study was conducted on childhood AL among children who were less than 15 years of age in Shanghai, China. A total of 131 patients with newly diagnosed AL were recruited from 3 Shanghai children hospitals. The controls selected from the same hospital were healthy children who attended the physical check-up held by the department of Children＇s Healthcare, or who visited the clinic of developmental pediatrics or orthopedics （excluding blood 〈br〉 diseases and malignant tumors）. 140 controls matched with cases in gender and age were included in this study. Chemical exposure were investigated by questionnaires, methylation specific polymerase chain reaction （MSP） was adopted to analyze the methylation or deletion status of 8 genes, and gene-environment interactions were analyzed by relative excess risk of interaction （RERI）, attributable proportion of interaction （API） and synergy index （S）. Results There were 131 and 140 subjects in case and control group,who were aged（6.9 ± 3.8）and（6.9 ± 3.9）years old（t=0.01,P=0.911）,respectively. After adjusting age and other potential confounding factors, chemical substances＇ exposure of children/mother/father were all significantly higher in cases than that in controls （Children： OR=3.90, 95%CI：1.69-9.02; Mother： OR=2.71, 95%CI：1.12-6.52;Father：OR=1.91, 95%CI：1.05-3.47）. For the 8 genes analyzed, the methylation status of DAPK and PTEN and P73 in case group were significantly higher than that in control group （cases：3.1%（4 cases）, 16.0%（21 cases）,7.6%（10 cases）;controls：0.7%（1 case）,2.9%（4 cases）,0.7%（1 case）;χ2：7.11,16.90,11.38;P value：0.029, 0.000, 0.003）. The methylation status of P16 in case group was significantly lower than that in control group （cases： 3.8%（5 cases）;controls： 8.6%（12 cases）, χ2=10.33, P=0.007）. The interactions of children chemical substances＇ exposure and 3 genes＇ （PTEN, P16 and P73） methylation status were probably existed after adjusted for confounding factors （PTEN：RERI=-7.01,API=-2.14,S=0.24;P16：RERI=4.08,API=0.53,S=2.59;P73：RERI=4.32,API=0.48,S=2.19）, we also found the potential interaction between maternal chemical substances＇ exposure and PTEN,P16 gene methylation status（PTEN：RERI=-1.30,API=-0.38,S=0.65;P16：RERI=1.70,API=0.38,S=1.97）. Conclusion The study suggested the strong combined effects of chemical substances exposure of children and abnormal methylation status were risk factors of childhood AL, and there existed different interaction between them, which may indicate the important role in the pathogenesis process of childhood AL.