Genome-wide analysis of genetic alterations in acute lymphoblastic leukaemia

Chromosomal aberrations are a hallmark of acute lymphoblastic leukaemia (ALL) but alone fail to induce leukaemia. To identify cooperating oncogenic lesions, we performed a genome-wide analysis of leukaemic cells from 242 paediatric ALL patients using high-resolution, single-nucleotide polymorphism arrays and genomic DNA sequencing. Our analyses revealed deletion, amplification, point mutation and structural rearrangement in genes encoding principal regulators of B lymphocyte development and differentiation in 40% of B-progenitor ALL cases. The PAX5 gene was the most frequent target of somatic mutation, being altered in 31.7% of cases. The identified PAX5 mutations resulted in reduced levels of PAX5 protein or the generation of hypomorphic alleles. Deletions were also detected in TCF3 (also known as E2A), EBF1, LEF1, IKZF1 (IKAROS) and IKZF3 (AIOLOS). These findings suggest that direct disruption of pathways controlling B-cell development and differentiation contributes to B-progenitor ALL pathogenesis. Moreover, these data demonstrate the power of high-resolution, genome-wide approaches to identify new molecular lesions in cancer.     

Novel chimaeric protein expressed in Philadelphia positive acute lymphoblastic leukaemia

Cytogenic changes are becoming increasingly important in understanding the pathogenesis of human malignancies. The t(9;22) (q34;q11) translocation is one of the most consistent and generates the Philadelphia chromosome (Ph1) (ref. 1) in chronic myeloid leukaemia (CML); it has also been observed in some acute lymphoblastic leukaemias (ALL) (ref. 2). In CML the breakpoints occur on chromosome 22 in the region designated bcr (ref. 3) and result in the expression of a bcr-abl fusion product of relative molecular mass (MT) 210,000 (210K) with associated in vitro tyrosine kinase activity (P210bcr-abl). In some cases of Ph1-positive ALL, a novel abl-related protein (P190all-abl) of 190K has been shown to have tyrosine kinase activity. In this report we demonstrate that the P190all-abl protein has a bcr determinant from the amino-terminal region, but is lacking a bcr determinant normally found in the P210bcr-abl near the bcr-abl junction. The chimaeric nature of the P190all-abl was confirmed by sequential immunoprecipitation with antisera against abl and bcr peptides.     

Diversity of immunoglobulin expression in leukaemic cells resembling B-lymphocyte precursors

Approximately 20% of patients with acute lymphocytic leukaemia (ALL) have leukaemic blasts with features of pre-B cells which are the recently characterized precursors of B lymphocytes in normal development (for a review, see ref. 2). Pre-B cells isolated from normal bone marrow or fetal liver, and malignant cells from patients with pre-B cell leukaemia, are rapidly dividing lymphoid cells that contain cytoplasmic immunoglobulin mu heavy chains, but have no detectable surface immunoglobulin. The resemblance of immunoglobulin-containing ALL cells to normal precursors of B lymphocytes and their availability in relatively pure preparations allowed us to explore them as models of early stages in the differentiation of the B-lymphocyte line. We report here observations on the occurrence of intermediate pre-B/B-cell phenotypes, immunoglobulin isotype switching and the asynchrony of immunoglobulin heavy and light chain expression in 30 cases of ALL and 3 cases of chronic myelogenous leukaemia in lymphoblastic crisis (CML-BC).     

BCL6 enables Ph+ acute lymphoblastic leukaemia cells to survive BCR-ABL1 kinase inhibition

Tyrosine kinase inhibitors (TKIs) are widely used to treat patients with leukaemia driven by BCR-ABL1 (ref. 1) and other oncogenic tyrosine kinases. Recent efforts have focused on developing more potent TKIs that also inhibit mutant tyrosine kinases. However, even effective TKIs typically fail to eradicate leukaemia-initiating cells (LICs), which often cause recurrence of leukaemia after initially successful treatment. Here we report the discovery of a novel mechanism of drug resistance, which is based on protective feedback signalling of leukaemia cells in response to treatment with TKI. We identify BCL6 as a central component of this drug-resistance pathway and demonstrate that targeted inhibition of BCL6 leads to eradication of drug-resistant and leukaemia-initiating subclones.     

Localization of the c-ab1 oncogene adjacent to a translocation break point in chronic myelocytic leukaemia

The human c-ab1 oncogene maps within the region (q34-qter) of chromosome 9 which is translocated to chromosome 22, the Philadelphia (Ph') chromosome, in chronic myelocytic leukaemia (CML). The position of the Ph' chromosomal break point is shown to be variable and, in one CML patient, has been localized immediately 5' of, or within, the c-ab1 oncogene. A DNA restriction fragment corresponding to this site has been molecularly cloned and shown to represent a chimaeric fragment of DNA from chromosomes 9 and 22.     

The t(8; 14) chromosomal translocation occurring in B-cell malignancies results from mistakes in V-D-J joining

The reciprocal chromosome translocation, t(8;14), involving the heavy chain locus on chromosome 14 and the c-myc oncogene on chromosome 8 is a characteristic of the B-cell malignancies Burkitt's lymphoma and acute lymphoblastic leukaemia (ALL). We have cloned and sequenced the t(8; 14) breakpoints of an African Burkitt's lymphoma cell line, P3HR-1, and a pre-B cell ALL cell line, 380. In each case the region of chromosome 8 involved has recombined with a JH region on chromosome 14. The two sites of breakage on chromosome 8 lie within 70 base pairs (bp) of one another. At each joining site, sequences homologous to the signal sequences thought to be recognized by the V-D-J recombinase were identified, as were N regions. In B-cell chronic lymphocytic leukaemias (B-CLL) carrying the t(11; 14) chromosome translocation and in follicular lymphomas carrying the t(14; 18) translocation, the V-D-J recombinase is implicated in the mechanism of chromosomal translocations. We speculate that the same enzymatic mechanism is responsible for the t(8; 14) translocations in African Burkitt's lymphoma and pre-B cell ALL.     

金属裸支架植入治疗冠状动脉不同病变的远期疗效比较

目的探讨冠心病(CHD)患者植入金属裸支架(BMS)的远期疗效.方法随访植入BMS的CHD患者224例.随访指标:1)全因死亡;2)主要心脏不良事件(MACE);3)靶病变血管重建(TLR)、靶血管重建(TVR);4)支架内再狭窄和/或支架节段内再狭窄等.结果 224例中累积MACE发生率为35.7%,平均每年MACE发生率为4.58%.CAG复查的148例中,冠状动脉A型病变再狭窄率16.4%,B1型病变24.1%,B2型病变62.2%,C型病变66.7%.晚期管腔丢失率平均为(29.32±10.17)%.结论植入BMS治疗冠状动脉病变A型和B1型,远期MACE发生率和再狭窄率均较低,远期效果与安全性好.     

双特异性酪氨酸磷酸化调节激酶在宫颈病变组织和癌细胞中的表达

目的探讨双特异性酪氨酸磷酸化调节激酶1b(DYRK1b)在宫颈病变组织和癌细胞中的表达情况及其作用.方法选取宫颈癌患者127例为研究组,同期确诊为慢性宫颈炎患者32例为对照组,收集上述患者石蜡组织标本,免疫组化SP法检测DYRK1b蛋白表达情况.依据宫颈癌细胞系He La 229和Si Ha细胞将标本分为实验组(加DYRK1b抑制剂Az191)、对照组(不加Az191),Western blod法检测细胞中DYRK1蛋白表达情况,MTT法检测细胞增殖情况,流式细胞仪检测细胞凋亡情况.结果子宫颈鳞癌阳性表达率明显高于慢性宫颈炎、低级别鳞状上皮内病变、高级别鳞状上皮内病变,差异均具有统计学意义(P0.01);高级别鳞状上皮内病变明显高于慢性宫颈炎、低级别鳞状上皮内病变,差异具有统计学意义(P0.05).在He La 229和Si Ha细胞中,DYRK1b蛋白表达量随Az191剂量增加而减少,且均明显低于对照组,差异具有统计学意义(P0.01).研究组He La 229和Si Ha细胞抑制率随Az191浓度增加而提升,均明显高于对照组,差异具有统计学意义(P0.05).10μmol/L的Az191作用后,研究组He La 229和Si Ha细胞凋亡率明显高于对照组,差异具有统计学意义(P0.05).结论宫颈病变过程中DYRK1b蛋白表达水平逐渐提升,宫颈癌组织和细胞中均呈高表达;下调DYRK1b蛋白表达后可抑制宫颈癌细胞增殖,促进凋亡.     

PCR检测白血病患者外周血中EB病毒的DNA

目的：了解白血病患者ＥＢ病毒感染情况。方法：收集２１例急性淋巴细胞白血病、１例慢性淋巴细胞白血病、１５例急性粒细胞白血病、８例慢性粒细胞白血病患者及３２例正常对照组的外周血,分离单个核细胞,提取ＤＮＡ,应用ＰＣＲ方法检测ＥＢ病毒ＤＮＡ。结果：在１例初诊慢性粒细胞白血病病人样本中发现ＥＢ病毒阳性,余均为阴性。结论：白血病患者存在ＥＢ病毒感染情况,但并不普遍。     

A new human immunoglobulin VH family preferentially rearranged in immature B-cell tumours

The prevalent forms of adult and childhood B-cell neoplasia are chronic lymphocytic (CLL) and acute lymphocytic (ALL) leukaemia, and are typified by a nearly monoclonal accumulation of cells expressing a single heavy (H) and light (L) chain variable (V) region. V gene selection could be random, or quite biased if the disease or the developmental status of the transformed cell somehow influenced DNA rearrangement. We have cloned and sequenced three germ-line VH gene segments that constitute a new human VH family (subgroup V) linked within 160 kilobase pairs of the DH-JH complex. One VH(V) member is rearranged in about 30% of patients with CLL and ALL, but not in IgM-expressing B-cell lines from peripheral blood. In some tumours, we detect a truncated (VH(V) RNA devoid of constant regions that originates from unrearranged VH(V) genes. In other tumours and in resting splenocytes, we detect large amounts of normally sized VH(V)-associated mRNA, although stimulation by mitogen of splenic B cells results in loss of VH(V)-hybridizing RNA. These features suggest that biased rearrangement of subgroup V may be under developmental selection.     

子宫颈癌组织p16基因突变及其蛋白表达研究

目的研究子宫颈癌患者p16蛋白表达和p16基因缺失突变及点突变情况.方法利用免疫组织化学方法(SP法)、聚合酶链反应(PCR)和聚合酶链反应-单链构象多态性(PCR-SSCP)分析技术,分别检测正常子宫颈组织30例、子宫颈癌前病变组织10例及原发性子宫颈癌组织28例,观察其p16蛋白表达和p16基因缺失突变及点突变状况.结果 1)在原发性子宫颈癌组织中为67.85%(19/28),明显低于正常子宫颈组织和子宫颈癌前病变组织(P<0.05);2)28例原发性子宫颈癌组织中有11例发生p16基因缺失突变,2例发生p16基因点突变,突变率为46.42%,正常子宫颈组织和子宫颈癌前病变组织未发现p16基因缺失突变和点突变.结论 1)p16蛋白缺乏与子宫颈细胞增殖失控及分化不良紧密相关.2)原发性子宫颈癌存在p16基因点突变,以低分化癌多见,但不是较频繁的事件;原发性子宫颈癌存在p16基因缺失突变,以低分化癌多见,是较频繁的事件.3)未发现p16蛋白表达与p16基因突变有相关性.     

Abelson murine leukaemia virus transformation involves loss of epidermal growth factor-binding sites

Malignant transformation by mammalian RNA sarcoma viruses has previously been shown to involve a reduction in receptor sites for a well characterized 6,000-molecular weight (MW) growth-promoting substance, designated epidermal growth factor (EGF). Although Abelson murine leukaemia virus (AbLV) resembles sarcoma viruses in its ability to transform embryo fibroblasts in cell culture, AbLV induces a rapid B-cell lymphoid leukaemia rather than fibrosarcomas in vivo. The major translational product of AbLV is a highly phosphorylated polyprotein of MW 120,000 which exhibits an associated tyrosine-specific protein kinase activity and probable transforming function. We show here that AbLV transformation resembles transformation by RNA sarcoma viruses with respect to the abolition of EGF-binding sites. EGF binding is restored to control levels following loss of polyprotein expression in morphological revertants of AbLV-transformed clones and remains uninfluenced in cell lines infected with transformation-defective (td) AbLV mutants encoding polyproteins deficient in protein kinase activity. These findings indicate that AbLV transformation involves a polyprotein-associated, tyrosine-specific protein kinase activity which mediates its effect through a mechanism resulting directly or indirectly in the abolition of EGF-binding sites.     

Inhibition of retroviral protease activity by an aspartyl proteinase inhibitor

Retrovirus protease is an enzyme that cleaves gag and gag-pol precursor polyproteins into the functional proteins of mature virus particles. The correct processing of precursor polyproteins is necessary for the infectivity of virus particles: in vitro mutagenesis which introduces deletions into the murine leukaemia virus genome produces a protease-defective virus of immature core form and lacking infectivity. A therapeutic drug effective against disease caused by retrovirus proliferation could likewise interfere with virus maturation. The primary structure has so far been determined for the protease of avian myeloblastosis virus, and of murine, feline and bovine leukaemia viruses. Amino acid sequencing of the retrovirus proteases, either after their purification or from prediction from the nucleotide sequence, shows that they possess the Asp-Thr-Gly sequence characteristic of the aspartyl proteinases. In this report we show that retrovirus proteases belong to the aspartyl proteinase group and demonstrate an inhibition by the aspartyl proteinase-specific inhibitor, pepstatin A, on the activity of bovine leukaemia, Moloney murine leukaemia and human T-cell leukaemia virus proteases.     

Evolution of human BCR-ABL1 lymphoblastic leukaemia-initiating cells

Many tumours are composed of genetically diverse cells; however, little is known about how diversity evolves or the impact that diversity has on functional properties. Here, using xenografting and DNA copy number alteration (CNA) profiling of human BCR-ABL1 lymphoblastic leukaemia, we demonstrate that genetic diversity occurs in functionally defined leukaemia-initiating cells and that many diagnostic patient samples contain multiple genetically distinct leukaemia-initiating cell subclones. Reconstructing the subclonal genetic ancestry of several samples by CNA profiling demonstrated a branching multi-clonal evolution model of leukaemogenesis, rather than linear succession. For some patient samples, the predominant diagnostic clone repopulated xenografts, whereas in others it was outcompeted by minor subclones. Reconstitution with the predominant diagnosis clone was associated with more aggressive growth properties in xenografts, deletion of CDKN2A and CDKN2B, and a trend towards poorer patient outcome. Our findings link clonal diversity with leukaemia-initiating-cell function and underscore the importance of developing therapies that eradicate all intratumoral subclones.