Equal frequency of TEL/AML1+ acute lymphoblastic leukemia in children with and without Down syndrome

Constitutional trisomy 21 is the most prominent predisposing factor to childhood leukemia, whereas the t(12;21)(p13;q22) with its molecular genetic counterpart, the TEL/AML1 fusion gene, is the most common acquired chromosomal rearrangement in childhood B-cell precursor (BCP) acute lymphoblastic leukemia (ALL). Thus, it was somewhat surprising that according to the currently available literature the incidence of TEL/AML1+ BCP ALL is extremely low in patients with Down syndrome (DS). To further investigate this issue in a population-based fashion, the authors retrospectively assessed the number of DS patients with a TEL/AML1+ ALL in two consecutive Austrian ALL multicenter trials. Accordingly, they were able to analyze 8 of 10 individuals with DS and a BCP ALL, including 2 who suffered from a TEL/AML1+ leukemia. Based on this observation we concluded that individuals with a constitutional trisomy 21 may have the similar likelihood to develop a TEL/AML1+ leukemia as BCP ALL patients without this specific predisposingfactor.     

Equal frequency of TEL/AML1 rearrangements in children with acute lymphoblastic leukemia with and without Down syndrome

Constitutional trisomy 21 is the most prominent predisposing factor to childhood leukemia, whereas the t(12;21)(p13;q22) with its molecular genetic counterpart, the TEL/AML1 fusion gene, is the most common acquired chromosomal rearrangement in childhood B-cell precursor (BCP) acute lymphoblastic leukemia (ALL). Thus, it was somewhat surprising that according to the currently available literature the incidence of TEL/AML1⁺ BCP ALL is extremely low in patients with Down syndrome (DS). To further investigate this issue in a population-based fashion, the authors retrospectively assessed the number of DS patients with a TEL/AML1⁺ ALL in two consecutive Austrian ALL multicenter trials. Accordingly, they were able to analyze 8 of 10 individuals with DS and a BCP ALL, two of whom who suffered from a TEL/AML1⁺ leukemia. Based on this observation they concluded that individuals with BCP leukemia and a constitutional trisomy 21 may have similar likelihood to have a TEL/AML1 rearrangement as BCP ALL patients without this specific predisposing factor.     

儿童急性淋巴细胞白血病常见融合基因的检测及意义

目的建立逆转录-巢式PCR检测融合基因的方法,检测4种常见融合基因在儿童急性淋巴细胞白血病中阳性率,并对阳性患儿进行初步临床资料分析。方法对收治的92例初发的急性淋巴细胞白血病(ALL)患儿,于化疗开始前抽取骨髓标本1.5～2.0 ml,采用巢式RT-PCR方法检测最常见的4种融合基因:TEL/AML1、E2A/PBX1、m-BCR/ABL和AF4/MLL。结果92例ALL患儿中TEL/AML1阳性21例,阳性率22.8%,占B细胞性ALL的24.7%(20/81例);6例E2A/PBX1阳性(6.5%),在前B细胞性ALL中占20.0%(3/15例);2例AF4/MLL阳性(2.2%),在婴儿ALL中占33.3%(2/6例);仅检测到1例m-BCR/ABL阳性(1.1%)。结论巢式RT-PCR方法是检测融合基因有效、敏感的方法。TEL/AML1在儿童ALL中阳性率最高,尤其是在B细胞性ALL中,该融合基因阳性的患儿病情较轻。     

Acute lymphoblastic leukemia in patients with Down syndrome with a previous history of acute myeloid leukemia

Patients with Down syndrome (DS) are predisposed to acute myeloid leukemia (AML) and acute lymphoblastic leukemia (ALL) in early and later childhood, respectively, but rarely experience both. We herein discuss four patients with DS with ALL and a history of AML who were treated with various chemotherapies, one of whom later received a bone marrow transplantation. Three patients survived and remain in remission. One patient died of fulminant hepatitis during therapy. No common cytogenetic abnormalities in AML and ALL besides constitutional +21 were identified, indicating that the two leukemia types were independent events. However, the underlying pathomechanism of these conditions awaits clarification.     

DOWN SYNDROME AND LEUKEMIA: WHAT HAVE WE LEARNED?

The increased risk of transient myeloproliferative disorder (TMD) and acute myeloid leukemia (AML) during early childhood in Down syndrome (DS) has stimulated research related to the role of trisomy 21 in the development of hematological neoplasm. The unique biological features of TMD including spontaneous resolution in the majority of cases, the increased risk of developing AML (25%) following resolution of TMD and the superior outcome of DS AML patients with cytarabine-based regimens highlight further areas of research interest. Alteration of intracellular redox reaction kinetics secondary to increased expression of chromosome 21-localized genes (e.g. superoxide dismutase) and the associated changes in apoptotic responses in DS tissues, may account for the increased sensitivity of DS myeloblasts to chemotherapy agents. The identification of the pharmacological and molecular basis for the increased sensitivity of DS myeloblasts to cytarabine and daunorubicin based on altered expression of chromosome 21-localized genes may ultimately lead to improvements in the therapy of AML in non-DS individuals.     

Molecular cytogenetic findings of acute leukemia included in the Brazilian Collaborative Study Group of Infant acute leukemia

BACKGROUND: Chromosome abnormalities often occur prenatally in childhood leukemia, characterizing an early event in leukemogenesis. The majority of the abnormalities occurring in infants involve the MLL gene on chromosome band 11q23. We describe the molecular cytogenetic findings of 207 infant acute leukemia (IAL) cases included in the Brazilian Collaborative Study Group of Infant acute leukemia. PROCEDURE: The diagnosis of Acute Lymphoblastic leukemia (ALL) or acute myeloblastic leukemia (AML) was made according to morphology and immunophenotyping classification, followed by conventional karyotyping. Samples were then screened using RT-PCR for the presence of specific chromosome translocations. FISH assay for MLL rearrangements was performed only in cases with negative or inconclusive cytogenetic or PCR results. RESULTS: The characteristics of children with IAL were as follows: 115 boys and 92 girls, age range 0-23 months, mean age 12 months, 145 ALL, and 62 AML. A statistically significant association was observed between pro-B ALL cases and MLL+ve (P=0.0001) cases and the age group 0-3 months with MLL+ve (P=0.008) cases. Two rare cases of pro-T ALL with MLL+ve were found. Other than MLL rearrangements, various other molecular aberrations were detected including TEL/AML1+ve (n=9), E2A/PBX1+ve (n=4), PML/RARA+ve (n=4), and AML1/ETO+ve (n=2). Cytogenetic analysis revealed hyperdiploidy (n=6), del(7) in two cases and del(11)(q23) in seven cases. CONCLUSIONS: Our results show that not only MLL rearrangements, but also other molecular abnormalities occur before birth and may contribute to leukemogenesis.     

寡核苷酸芯片方法检测儿童急性淋巴细胞性白血病融合基因

目的 探讨寡核苷酸芯片在儿童急性淋巴细胞性白血病(ALL)融合基因检测中的应用.方法 针对儿童ALL常见的5种融合基因:TEL/AML1、E2A/PBX1、BCR/ABLp190、BCR/ABLp210、MLL/AF4,设计特异的融合基因片段为芯片探针,合成后用点样仪点片制成寡核苷酸芯片.提取疾病初期白血病患儿的骨髓/外周血标本的总RNA,进行多重巢式逆转录聚合酶链反应(RT-PCR)、荧光标记并与芯片杂交,以检测白血病细胞中特异融合基因.结果 该芯片可以从患儿骨髓样本RNA中准确检测到阳性内参序列、特异的融合基因以及融合位点.结论 采用寡核苷酸芯片方法,可快速、同时筛选出5种染色体结构畸变产生的融合基因及融合位点,为ALL患儿危险分层、治疗选择、预后判断提供重要依据.此种方法应用于筛查初治白血病患儿融合基因表达时优缺点并存,具有一定临床实用价值.     

CD45+和CD45-儿童急性B淋巴细胞白血病的临床特征分析

目的探讨CD45抗原表达与儿童急性B淋巴细胞白血病(B-ALL)的临床相关性。方法利用多参数流式细胞术(FCM)以CD45/SSC设门对61例B-ALL患儿进行免疫分型检测;采用染色体核型分析和多重巢式RT-PCR技术进行染色体、融合基因分析。结果免疫表型分析显示CD45+组CD13、HLA-DR抗原表达明显高于CD45-组(P<0.05);CD45-组的融合基因主要为HOX11和E2A/PBX1,而CD45+组主要为TEL/AML1、MLL/AF9、HOX11;相关临床参数、染色体核型及疗效比较两组间差异均无显著性(P>0.05)。结论 CD45抗原的表达与否和B-ALL患儿的临床特征、染色体畸变、治疗效果无统计学相关性;CD45+组较CD45-组高表达CD13和HLA-DR。     

Near-triploid acute lymphoblastic leukemia with TEL/AML1 translocation

An 11-year-old girl was diagnosed as B-precursor acute lymphoblastic leukemia (ALL) with co-expression of myeloid antigens. Cytogenetic analysis revealed a near-triploid (75-82 chromosomes/cell) abnormal chromosomal complement.Fluroscent in situ hybridization studies indicated presence of TEL/AMLI fusion genes. We discuss the prognostic relevance of TEL/AML1 in this rare near-triploid subtype of ALL.     

p16 inactivation associated with aggressive clinical course and fatal outcome in TEL/AML1-positive acute lymphoblastic leukemia

The authors describe a 7-year-old boy with TEL/AML1-positive pre-B acute lymphoblastic leukemia, with hemizygous 9p21 deletion at presentation and no p16(INK4A) protein expression. Despite an initial response to a standard chemotherapy regimen, the patient suffered two hematologic relapses and died 34 months after diagnosis. The authors discuss the possibility that complete p16(INK4A) gene inactivation may adversely modify the prognostic significance of TEL/AML1 fusion in childhood acute lymphoblastic leukemia, and present evidence from clinical and in vitro observations in favor of this assumption.     

Hematological disorders and leukemia in children with Down syndrome

Constitutional trisomy 21 inherent to Down syndrome (DS) is associated with several hematological disorders occurring at different ages. Neonates with DS may present with transient asymptomatic blood count abnormalities such as neutrophilia, thrombocytopenia and polycythemia. Within 1-2 months of life, 3-10% of DS infants develop transient myeloproliferative disease. Despite a spontaneous regression in most of the cases, TMD can be fatal or lead to the subsequent development of myeloid leukemia in 20% of DS children (DS ML). DS ML has clinical and biological features that define a unique entity with a high sensitivity to chemotherapy and a favorable outcome. Children with DS also have an increased risk of developing acute lymphoblastic leukemia (ALL) characterized by a more heterogeneous pattern of genetic findings and by a higher rate of treatment-related toxicities. These features highlight the role of trisomy 21 in leukemogenesis and confirm the need of specific and adapted therapeutic approach for DS children with leukemia.     

Cytosine arabinoside and mitoxantrone treatment of relapsed or refractory childhood leukemia: Initial response and relationship to multidrug resistance gene 1

The objective of this study was to determine the response rate and toxicity of high-dose cytosine arabinoside (AC) and mitoxantrone (M) in relapsed or refractory childhood acute myeloid leukemia (AML) and acute lymphocytic leukemia (ALL) and to correlate response with the expression of the multidrug resistance gene 1 (mdr1). Twenty-nine patients were treated with AC 1.0 g/m² infused over 2 h every 12 h for eight doses (days 1-4) and M 12 mg/m² infused over 1 h (days 3-6). Mdr1 expression was determined by a polymerase chain reaction (per) assay. Ten of 15 patients (67%) with AML obtained a complete remission (CR) of 3 to 30+ months duration. Eight of 14 (57%) ALL patients obtained a CR of 1 to 23+ months duration. The major toxicities were hematopoietic and infectious. Seventy-nine per cent of patients developed a documented infection during induction. Mdr1 did not correlate with a lower induction rate. This AC/M regimen is active in childhood AML and ALL. © 1994 Wiley-Liss, Inc.     

伴髓系抗原表达的高危儿童急淋白血病临床生物学特征及长期预后分析

目的分析髓系抗原阳性(My+)的儿童高危急性淋巴细胞白血病(ALL)的临床生物学特征及长期预后关系。方法采用流式细胞仪直接免疫荧光法及RT-PCR法分别检测2001年8月至2003年3月在我院收治的初诊高危112例ALL患儿的髓系抗原及融合基因的表达,对其预后进行了中位时间达76个月的长期观察。结果髓系抗原的表达率为30.4%,B系ALL表达髓系抗原多于T系ALL,差异有显著性意义(P=0.019)。My+ALL患儿携带TEL-AML1融合基因者多于My-ALL患儿(P=0.049),My+ALL与My-ALL患儿在临床特点以及疗效等方面两组之间差异无显著性意义。结论高危ALL无论有无髓系抗原的表达其疗效无显著性差异,髓系抗原阳性表达在高危儿童ALL时不能作为预后不良的因素。     

Preponderant mitotic activity of nonleukemic cells plays an important role in failures to detect abnormal clone in childhood acute lymphoblastic leukemia

At diagnosis, clonal chromosomal abnormalities are found in the bone marrow blasts in more than two thirds of children with acute lymphoblastic leukemia (ALL). Practically, however, failure to detect these abnormalities is frequent and usually attributed to poor marrow sampling, inadequate metaphases, and/or a preponderant mitotic activity among nonleukemic cells. The authors applied fluorescence in situ hybridization (FISH) techniques to re-examine 30 cases of karyotypically "normal" childhood ALL to explore the role of preponderant mitotic activities of nonleukemic cells in failures to detect clonal abnormalities. The FISH test were performed using TEL/AML1 fusion gene probe and the centromere probes for chromosome 8 and 10 to detect the t(12;21) translocation and/or hyperdiploidy. Half of the karyotypically "normal" ALL cases examined have been found to have abnormal clones with t(12;21) rearrangement and/or hyperdiploidy by this specially designed FISH assay. Contrary to expectation, the authors found a higher incidence (52%) of clonal abnormalities in cases where over 20 metaphases had been examined than in cases (44%) where fewer than 20 metaphases had been analyzed. These findings suggest that a preponderant mitotic activity of nonleukemic cells plays an important role in failures to detect an abnormal clone by conventional cytogenetic studies. Therefore, karyotypically "normal" childhood ALL patients should undergo FISH studies to rule out the presence of t(12;21) and/or hyperdiploid clone.     

儿童Pre-B急性淋巴细胞白血病和急性髓系白血病特异遗传亚型

目的总结儿童急性白血病(AL)特异遗传亚型的发生率和特征,为评估预后提供依据。方法对365例AL患儿进行骨髓染色体核型检测分析白血病细胞的遗传学特点,荧光原位杂交(FISH)检测特异基因及相应位点拷贝数变异。结果 175例前体B急性淋巴细胞白血病(Pre-B ALL)和54例急性髓系白血病(AML)存在特异亚型。在Pre-B ALL中,高超二倍体最常见(33%),t(12;21)/ETV6-RUNX1、t(4;11)/MLL重排、t(9;22)、t(1;19)和iAMP21占比分别为22%、5%、3%、7%和1%。在AML中,MLL重排最常见(18%),其中t(9;11)型占56%;BCR/ABL阳性1例,FISH证实是隐匿核型ins(22;9);t(8;21)、t(15;17)和inv(16)分别占12%、15%和8%。倍体水平显示ALL高超二倍体和AML超二倍体获得染色体方式为非随机性。值得注意的是特异亚型中的变异型和不同附加异常,如额外融合,del(9p),del(12p),dup(1q)和非整倍体等畸变。结论儿童Pre-B ALL和AML中特异遗传亚型的发生率与西方儿童相似,揭示遗传异质性可能有助于预后研究。     

Biology and clinical significance of the TEL/AML1 rearrangement

The accurate identification of chromosomal abnormalities in patients with leukemia is essential for diagnosis and treatment assignment. Recent technical improvements in the detection of such aberrations have demonstrated that the previously unrecognized chromosomal translocation t(12;21) is the most prevalent structural aberration in childhood acute lymphoblastic leukemia. Both genes involved, translocation ets like gene (or ETV6) on chromosome 12 and acute myeloid leukemia 1 gene (or CBF alpha) on chromosome 21 had been identified for several years previously, which facilitated the rapid development of molecular diagnostic assays and their implementation in therapy trials. Although first described less than four years ago, the TEL/AML1 story is an excellent example of how close collaboration between physicians and molecular biologists is mandatory for achieving general insights into the molecular pathogenesis of leukemia and for further improvements in diagnosis and in monitoring response to chemotherapy.