白血病MLL基因重排及其融合基因检测的临床意义

目的:研究白血病MLL(mixed lineage leukemia)基因重排及其融合基因的检测及其临床意义。方法:采用荧光原位杂交(FISH)检测70例白血病患者MLL基因重排,对于MLL基因重排的患者,用巢式RT-PCR方法检测常见6种MLL融合基因类型。结果:9例白血病有MLL基因重排,发生率为12.86,5例B细胞系急性淋巴细胞白血病(B-ALL),其中融合基因2例为MLL/ENL,1例MLL/AF4,2例未扩出融合基因产物;3例为急性髓细胞白血病M5(AML-M5),其中2例融合基因均为MLL/AF9,1例未扩出融合基因产物;1例为幼年型粒单核细胞白血病(JMML),其融合基因为MLL/ENL。结论:巢式RT-PCR是检测MLL基因重排及其融合基因类型简便有效的方法,MLL基因重排见于B-ALL、AML-M5、JMML,预后差。     

急性白血病11q23/MLL基因易位重排及其临床意义

目的：研究11q23/MLL基因易位重排在急性白血病（AL）中的发生率、产生融合基因的常见类型及其临床意义.方法：用荧光原位杂交技术，MLL双色断裂分离重排探针检测50例AL患者（49例初治，1例难治）的11q23/MLL基因，用流式细胞仪检测免疫表型，对于11q23/MLL基因易位重排阳性的患者，用巢式RTPCR方法检测11q23/MLL基因易位重排形成的6种常见融合基因类型.结果：6例AL有11q23/MLL基因易位重排，发生率为12%，2例为AML-M5，4例为ALL且均为B-ALL.2例11q23/MLL基因易位重排阳性的AML M5患者融合基因均为MLL/AF9，其中1例为初治，发病时左侧小腿有白血病细胞浸润，本例患者化疗1疗程获CR;1例为难治性AL患者，于第3个疗程化疗后才达CR.4例11q23/MLL基因易位重排阳性的B-ALL患者中有2例于诊断后3周内死于全身衰竭和感染，化疗未获CR，其中1例患者的融合基因为MLL/ENL，1例未扩出融合基因产物;1例于诊断后第2天因DIC脑出血死亡，未进行化疗，其融合基因为MLL/AF9;1例发病时胸椎有白血病细胞浸润，1疗程化疗后获CR，其融合基因产物未扩出.结论：荧光原位杂交技术是检测AL11q23/MLL基因易位重排快速、灵敏的方法，巢式RT-PCR是检测11q23/MLL基因易位重排所产生的融合基因类型简便可行的方法;有11q23/MLL基因易位重排的AL患者临床症状凶险，预后差。     

Evidence favoring lineage fidelity in acute nonlymphocytic leukemia: absence of immunoglobulin gene rearrangements in FAB types M4 and M5

The concept of lineage fidelity in acute leukemia has recently been challenged by the finding of rearrangements of the immunoglobulin heavy chain genes in a leukemic cell line and in a small number of sporadic cases of acute nonlymphocytic leukemia with a monocytic phenotype. We therefore screened leukemic blood or bone marrow samples of 33 adult patients with acute nonlymphocytic leukemia of FAB types M4 (23 patients) and M5 (10 patients); 28 were obtained at diagnosis and 5 at relapse. All cases were well characterized pathologically and histochemically. Cytogenetic analysis performed in each case demonstrated karyotypes that were representative of those generally seen in these types of leukemia, with a clonal abnormality present in all except 9 of 32 patients who were successfully studied. DNA prepared from each sample was digested with the restriction enzyme BamH1 and analyzed by Southern blot hybridization to probes for the JH region of the immunoglobulin heavy chain. All 33 cases had DNA retained in the germline configuration with no evidence of rearrangement. This finding supports the concept of lineage fidelity, and suggests that true interlineage infidelity, myeloid to lymphoid, is a rare occurrence in adult acute nonlymphocytic leukemia.     

Characteristics and prognosis in adult acute myeloid leukemia patients with MLL gene rearrangements

正Objective To analyze the clinical and laboratory characteristics,and prognosis of adult acute myeloid leukemia(AML)patients with MLL gene rearrangements.Methods The medical records of 92 adult AML patients with MLL gene rearrangements from January 2010 to December 2016 were retrospectively analyzed.     

Validation of an interphase fluorescence in situ hybridization approach for the detection of MLL gene rearrangements and of the MLL/AF9 fusion in acute myeloid leukemia

To validate a 2-step FISH assay for the identification of the t(9;11)(p22;q23), 96 acute myeloid leukemias were studied by cytogenetic analysis, FISH and molecular biology. After a first FISH step using an MLL probe, 24/27 cases with 11q23 break showed MLL rearrangement. Southern blotting confirmed FISH data. In the second step, 24 cases with MLL rearrangement were studied using MLL and AF9 probes: 17/18 cases with t(9;11) showed MLL/AF9 fusion. In 6 patients with 11q23/MLL rearrangements other than t(9;11), FISH confirmed MLL involvement and excluded AF9 involvement. This is a reliable method for the identification of MLL/AF9 fusion in interphase cells, allowing for a reclassification of cases with suboptimal chromosome morphology. The frequency of deletion surrounding MLL and AF9 breakpoint is low.     

Prevalence and geographical distribution of major LDL receptor gene rearrangements in Finland.

In order to determine the prevalence of major rearrangements of the low density lipoprotein (LDL) receptor gene in Finland, DNA samples of 199 unrelated Finnish patients with the heterozygous form of familial hypercholesterolaemia (FH) were examined by Southern blot analysis. The FH-Helsinki mutation, characterized by a 9.5-kb deletion in the 3'-end of the LDL receptor gene, was found in 75 (38%) of the patients. The prevalence of this mutation ranged from 26-58% in different areas of Finland. A striking exception was the North Karelia region, where only one out of 26 (4%) FH patients was found to carry the FH-Helsinki allele. Two patients were found to carry other types of large nucleotide rearrangements of the LDL receptor gene. One mutation was a 7.5-kb deletion eliminating exons 7 to 10, and the other was a 13-kb deletion covering exons 11 to 16 of the LDL receptor gene. Serum lipoprotein levels were very similar in each category of mutation, i.e. in patients with the FH-Helsinki gene, those with the two other types of deletion, and the remaining patients with as yet unknown types of LDL receptor gene defects. These results show that, even in genetically uniform populations, FH may be heterogeneous at the DNA level. DNA techniques enable an unequivocal diagnosis for almost 40% of the Finnish patients with the heterozygous form of FH.     

Infant acute lymphoblastic leukemia with MLL gene rearrangements: outcome following intensive chemotherapy and hematopoietic stem cell transplantation

Forty-four infants with acute lymphoblastic leukemia (ALL) characterized by MLL gene rearrangements were treated on a protocol of intensive chemotherapy followed by hematopoietic stem cell transplantation (HSCT) between November 1998 and June 2002. The remission induction rate was 91.0%, and the 3-year overall survival and event-free survival (EFS) rates, with 95% confidence intervals, were 58.2% (43.5%-72.9%) and 43.6% (28.5%-58.7%), respectively. Univariate analysis of EFS by presenting features indicated a poorer outcome in patients younger than 6 months of age with high white blood cell counts (>/= 100 x 10(9)/L; EFS rate, 9.4% versus 55.1% for all others, P = .0036) and in those with central nervous system invasion (EFS rate, 10.0% versus 56.9% for all others, P = .0073). The 3-year posttransplantation EFS rate for the 29 patients who underwent HSCT in first remission was 64.4% (46.4%-82.4%). In this subgroup, only the timing of HSCT (first remission versus others) was a significant risk factor by multivariate analysis (P < .0001). These results suggest that early introduction of HSCT, possibly with a less toxic conditioning regimen, may improve the prognosis for infants with MLL(+) ALL. Identification of subgroups or patients who respond well to intensified chemotherapy alone should have a high priority in future investigations.     

Absence of point mutations within the AML-1 gene in patients with MDS/AML and loss of chromosome 5q or 7

 There is increasing evidence that the acute myeloid leukemia 1 (AML-1) gene plays a versatile role in hematopoiesis, and its inactivation has been described in various hematopoetic disorders, e.g., leukemia or familial thrombocytopenia. AML-1 can be affected by various mechanisms, such as chromosomal translocations or point mutations. On the other hand, the specific underlying molecular lesions in myelodysplastic syndromes (MDS) or leukemias with aberrations of chromosomes 5q or 7, respectively, are largely unknown. Despite extraordinary scientific effort no specific genes on chromosome 5q or 7, which act as tumor suppressors, have definitely been identified. Therefore, it has recently been speculated that the AML-1 gene, even if distantly located on chromosome 21q22, may be involved in leukemogenesis in patients with aberrations at chromosome 5q or monosomy 7 [2]. Therefore, we sequenced all exons of the AML-1 gene in 15 patients with MDS/AML and deleted chromosome 5q or 7q, respectively. None of the patients analyzed had any AML-1 mutation. Received: 8 April 2000 / Accepted: 21 July 2000     

Complex and cryptic chromosomal rearrangements involving the MLL gene in acute leukemia: A study of 7 patients and review of the literature

Chromosomal rearrangements involving the MLL gene have been associated with many different types of hematological malignancies. Most of them are easily recognized by conventional cytogenetics. However, in some cases, complex, unusual or cryptic rearrangements make the MLL involvement difficult or impossible to be detected by conventional cytogenetics. Fluorescent in situ hybridization with a panel of probes coupled with long distance inverse-PCR was used to identify chromosomal rearrangements involving the MLL gene. Seven unusual chromosomal rearrangements were identified, including two complex translocations, three insertions of material of chromosome 11 in another chromosome and one insertion of chromosome material into the MLL gene. Conventional cytogenetics showed three patients to have a deletion of 11q; one had an unexpected t(6;11)(q27;q23) whereas the other two patients had also an insertion of MLL material in another chromosome. Concurrent 3′ deletion in the MLL rearrangement was observed in two patients. We recommend a systematic approach to be used in all cases of acute leukemia starting with FISH analyses using a commercially available MLL split signal probe. Should an abnormality be discovered, the analysis has to be completed by further molecular cytogenetic and genomic PCR methods in order to unravel the recombination mechanism.     

Insights from clinical studies into the role of the MLL gene in infant and childhood leukemia

Translocations involving the Mixed Lineage Leukemia (MLL) gene at 11q23 are found in both acute lymphoblastic leukemia (ALL) and acute myeloblastic leukemia (AML), but have different prognostic implications depending on the phenotype of the leukemia in de novo pediatric cases. The majority of MLL gene rearrangements are associated with infant ALL, and their presence predicts a poor prognosis which worsens with earlier age of presentation. Rearrangements of the MLL gene are found in most cases of infant AML and regardless of age confer an intermediate risk. The treatment of MLL-rearranged ALL in children involves increased intensification of chemotherapy, and infants with ALL are treated with an intensive regimen of ALL- and AML-like chemotherapy, with the proportion of MLL-rearranged cases being responsible for the poor outcome in this age group. The use of DNA microarray analysis to distinguish a particular gene signature for MLL-rearranged leukemias is shedding light on the molecular mechanisms and potential therapeutic targets of these leukemias. It may also prove to have a useful role in both diagnosis and prognosis. This review considers recent advances in our understanding of the role of MLL gene rearrangements in pediatric clinical practice.     

急性髓系白血病M4/M5亚型的临床和遗传学研究

目的研究伴11q23异常的急性粒单细胞和单核细胞白血病患者的临床和细胞遗传学特征。方法用染色体G显带和间期荧光原位杂交技术对30例急性髓系白血病（AML）-M4、M5患者进行染色体检测,患者均接受柔红霉素、阿糖胞苷为主的化疗方案,并对其随访。结果伴11q23异常13例,其中M59例（M5a1例、b15b8例）、M4b5例;异常核型为t（11;19）、t（11;17）、t（9;11）、t（10;11）、t（6;11）、t（11：？）（q23：）、del（11）（q23）。混合细胞白血病（MLL）基因阳性13例,其中hi58例、hi45例,其完全缓解（CR）率15．4％,低于MLL阴性者的57．0％;MLL阳性者中位生存期85d,低于MLL阴性者的130d。结论11q23异常以MLL．hi5、hi4患者发生率高,MLL阳性者CR率低,平均生存期短。提示MLL基因异常是MLL患者预后不佳的标志。     

Acute lymphoblastic leukemias with deletion of 11q23 or a novel inversion (11)(p13q23) lack MLL gene rearrangements and have favorable clinical features

Balanced translocations affecting the 11q23 region are among the most frequent chromosomal abnormalities in childhood acute lymphoblastic leukemia (ALL), comprising 5% to 6%. These cases consistently have a rearranged MLL gene and are associated with high-risk presenting features, hyperleukocytosis and younger age, and a poor treatment outcome. To assess the clinical and biologic significance of 11q23- associated structural chromosomal abnormalities other than translocations, we studied 17 cases of childhood ALL [14 with del(11)(q23) and 3 with inv(11)(p12q23)] that were identified among 785 cases with successful chromosome analysis. In contrast to reported cases with 11q23 and MLL gene rearrangement, our series was characterized by relatively low leukocyte counts (median, 15.1 x 10(9)/L), expression of CD10 antigen but not myeloid-associated CD15 and CDw65 antigens, a relatively high frequency of T-cell immunophenotypes, and a generally favorable prognosis. All 13 cases with interpretable molecular analysis lacked MLL gene rearrangements. We suggest that most cases with deletions or inversions affecting the 11q23 region represent clinically and biologically different entities as compared with those defined by 11q23 translocation.     

Clonal, nonconstitutional rearrangements of the MLL gene in infant twins with acute lymphoblastic leukemia: in utero chromosome rearrangement of 11q23

Rearrangements of chromosome band 11q23 are common in infant leukemias, comprising more than 70% of the observed chromosome abnormalities in children less than 1 year of age. The MLL gene, which is located at the 11q23 breakpoint in infant, childhood, and adult acute leukemias, has been cloned and has homology to the Drosophila trithorax gene. The breakpoints in MLL are restricted to an 8.3-kilobase pair (kb) region of the gene that is involved in translocations with as many as 29 other chromosomal regions in a number of phenotypically distinct acute leukemias. We have detected an identical, clonal, nonconstitutional rearrangement of the MLL gene in peripheral blood cells from a pair of female infants twins with acute lymphoblastic leukemia (ALL) and a t(11;19)(q23;p13.3). The detection of nonidentical IGH rearrangements suggests that the MLL rearrangement took place in a B-cell precursor or hematopoietic stem cell in one twin which was transferred in utero to the other fetus resulting in ALL with an identical aneuploid karyotype in both infants. We speculate that the other MLL-related infant leukemias may also develop in utero, and that the rearrangements may occur consistently in stem cells or early precursor cells, accounting for the frequency of mixed-lineage leukemia in infants.     

急性粒单,单核细胞白血病的细胞遗传学研究

对27例急性粒单、单核细胞白血病进行了细胞遗传学分析。其中15例检出染色体畸变。4例M4中2例为inv（16）（p13q22）。M523例、12例有核型异常，其中涉及11q23结构异常者7例。显示11q23突变在急性单核细胞白血病中有着重要的生物学作用。