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目的:研究半胱氨酸-天冬氨酸蛋白酶8相关蛋白2(Caspase 8 associated protein 2,CASP8AP2)基因在儿童急性淋巴细胞白血病(acute lymphoblastic leukemia,ALL)初诊和缓解时的启动子区Cp G位点的甲基化水平,及其与儿童ALL临床特征、预后的关系。方法:收集2007年8月到2010年3月于我院就诊的109例ALL患儿的初诊DNA样本,及其中94例患儿的缓解期DNA标本。DNA样本经硫化处理后,用本研究组建立的甲基化荧光法,测定CASP8AP2基因转录起始点上游的两个关键Cp G位点(-1189和-1176)的甲基化水平。结果:初诊患儿CASP8AP2基因启动子区上述2个位点的平均甲基化水平为(71.1±1.7)%,高于缓解患儿的样本(64.2±21.2%)(P=0.008)。受试者工作特征曲线下面积为0.687(P=0.024),说明这2个位点的甲基化水平具有一定的预测复发的能力。以76.9%为分界点,将初诊患儿分为高甲基化组(49例)和低甲基化组(60例)。高甲基化患儿更容易出现复发(20.4%vs 6.7%)(P=0.044),5年无复发生存率明显低于低甲基化组(Log rank,P=0.033)。初诊高甲基化与巩固治疗前微小残留病(minimal residual disease,MRD)高水平相关(P=0.011)。诱导缓解治疗后MRD≥10-4的34例患儿中,高甲基化患儿的复发率明显高于低甲基化患儿(8/16例vs 3/18例,P=0.038)。结论:CASP8AP2基因启动子区-1189和-1176两个Cp G位点的异常高甲基化可能与儿童ALL的发病相关,且高甲基化患儿的预后较差;将上述位点的甲基化水平与诱导缓解治疗结束时MRD水平相结合,能够更好地预测复发。
Objective: To investigate the expression of CpG-Caspase 8 associated protein 2 (CASP8AP2) gene in promoter region of newly diagnosed childhood acute lymphoblastic leukemia (ALL) Methylation level, and its relationship with the clinical features of children with ALL, prognosis. Methods: A total of 109 newly diagnosed ALL children were enrolled in our hospital from August 2007 to March 2010, and 94 cases of remission DNA samples were collected. After the DNA sample was sulfided, the methylation levels of two key CpG sites (-1189 and -1176) upstream of the transcription initiation site of CASP8AP2 gene were determined by methylation fluorescence method established by the research group. Results: The average methylation level of CASP8AP2 promoter in the two newly diagnosed children was (71.1 ± 1.7)%, higher than that in the children with remission (64.2 ± 21.2%) (P = 0.008). The area under the receiver operating characteristic curve was 0.687 (P = 0.024), indicating that the methylation levels of these two sites had some ability to predict recurrence. With 76.9% as the cut-off point, newly diagnosed children were divided into hypermethylation group (49 cases) and hypomethylation group (60 cases). Children with hypermethylation were more likely to relapse (20.4% vs 6.7%) (P = 0.044). The 5-year recurrence-free survival rate was significantly lower than that in the hypothymethyroidism group (Log rank, P = 0.033). The initial diagnosis of hypermethylation was associated with a high level of minimal residual disease (MRD) before consolidation (P = 0.011). Among 34 children with MRD ≥10-4 after induction of remission therapy, the recurrence rate was significantly higher in children with hypermethylation than in those with hypomethylation (8/16 vs 3/18, P = 0.038). CONCLUSIONS: The aberrant hypermethylation of two CpG loci of -1189 and -1176 in CASP8AP2 gene promoter may be related to the pathogenesis of childhood ALL, and the prognosis of hypermethylated children is poor. The methylation level of these loci and The combination of MRD levels at the end of induction remission therapy can better predict recurrence.