IKZF1基因拷贝数异常在儿童BCR/ABL阴性B系急性淋巴细胞白血病中的意义

Significance of IKZF1 gene copy number abnormalities in BCR/ABL-negative B-lineage acute lymphoblastic leukemia in children

摘要:

目的 了解BCR/ABL阴性B系急性淋巴细胞白血病(B-ALL)患儿IKZF1基因拷贝数异常情况,并分析IKZF1基因拷贝数异常与该部分患儿预后的相关性。方法 应用多重连接探针扩增(MLPA)技术检测180例初诊BCR/ABL阴性B-ALL患儿IKZF1基因拷贝数异常情况。根据有无IKZF1基因缺失将其分成两组:IKZF1缺失组和IKZF1正常组。回顾性分析IKZF1拷贝数缺失与BCR/ABL阴性B-ALL患儿预后的关系。结果 180例患儿中共有27例(15.0%)患儿发生了IKZF1缺失,其中IKZF1基因8个外显子全部缺失者4例,单纯1号外显子缺失者17例,4~7号外显子缺失者3例,2~7号外显子缺失者3例。IKZF1缺失组患儿初诊时白细胞水平及流式MRD-高危组患儿的比例明显高于IKZF1正常组;IKZF1缺失组患儿多发生在无特殊融合基因异常的BCR/ABL阴性患儿,且IKZF1基因缺失患儿易伴随出现11、8、5、7、21号等染色体的异常。Kaplan-Meier法分析显示,IKZF1缺失组无病生存率(DFS)明显低于IKZF1正常组(0.740±0.096 vs 0.905±0.034,P=0.002)。Cox法分析显示在排除了年龄、性别、初始WBC、初诊时脑脊液状态、泼尼松松试验反应情况、染色体核型后,IKZF1缺失仍不利于患儿的DFS(P<0.05)。结论 部分BCR/ABL阴性B-ALL患儿存在IKZF1缺失,IKZF1缺失为BCR/ABL阴性B-ALL患儿DFS的独立危险因素。

Abstract:

Objective To identify IKZF1 gene copy number abnormalities in BCR/ABL-negative B-lineage acute lymphoblastic leukemia (B-ALL) in children, and to investigate the association between such abnormalities and prognosis. Methods Multiplex ligation-dependent probe amplification (MLPA) was applied to detect IKZF1 gene copy number abnormalities in 180 children diagnosed with BCR/ABL-negative B-ALL. These children were classified into IKZF1 deletion group and IKZF1 normal group according to the presence or absence of IKZF1 gene deletion. The association between IKZF1 copy number abnormalities and prognosis of children with BCR/ABL-negative B-ALL was analyzed retrospectively. Results Among 180 children, 27 (15.0%) had IKZF1 deletion; among the 27 children, 4 had complete deletions of 8 exons of IKZF1 gene, 17 had deletion of exon 1, 3 had deletions of exons 4-7, and 3 children had deletions of exons 2-7. Compared with those in the IKZF1 normal group, children in the IKZF1 deletion group had higher white blood cell (WBC) count and percentage of individuals with high risk of minimal residual disease at the first visit. IKZF1 deletions often occurred in BCR/ABL-negative children with no special fusion gene abnormalities. They were frequently accompanied by abnormalities in chromosomes 11, 8, 5, 7, and 21. The analysis with Kaplan-Meier method showed that disease-free survival (DFS) in the IKZF1 deletion group was significantly lower than that in the IKZF1 normal group (0.740±0.096 vs 0.905±0.034; P=0.002). Cox analysis showed that after exclusion of sex, age, initial WBC count, cerebrospinal fluid state at the first visit, prednisone response, and chromosome karyotype, IKZF1 deletion still affected the children's DFS (P<0.05). Conclusions Some children with BCR/ABL-negative B-ALL have IKZF1 deletion, and IKZF1 deletion is an independent risk factor for DFS in children with BCR/ABL-negative B-ALL.