FTY720, a new alternative for treating blast crisis chronic myelogenous leukemia and Philadelphia chromosome-positive acute lymphocytic leukemia

Blast crisis chronic myelogenous leukemia (CML-BC) and Philadelphia chromosome-positive (Ph1-positive) acute lymphocytic leukemia (ALL) are 2 fatal BCR/ABL-driven leukemias against which Abl kinase inhibitors fail to induce a long-term response. We recently reported that functional loss of protein phosphatase 2A (PP2A) activity is important for CML blastic transformation. We assessed the therapeutic potential of the PP2A activator FTY720 (2-amino-2-[2-(4-octylphenyl)ethyl]-1,3-propanediol hydrochloride), an immunomodulator in Phase III trials for patients with multiple sclerosis or undergoing organ transplantation, in CML-BC and Ph1 ALL patient cells and in in vitro and in vivo models of these BCR/ABL+ leukemias. Our data indicate that FTY720 induces apoptosis and impairs clonogenicity of imatinib/dasatinib-sensitive and -resistant p210/p190(BCR/ABL) myeloid and lymphoid cell lines and CML-BC(CD34+) and Ph1 ALL(CD34+/CD19+) progenitors but not of normal CD34+ and CD34+/CD19+ bone marrow cells. Furthermore, pharmacologic doses of FTY720 remarkably suppress in vivo p210/p190(BCR/ABL)-driven [including p210/p190(BCR/ABL)(T315I)] leukemogenesis without exerting any toxicity. Altogether, these results highlight the therapeutic relevance of rescuing PP2A tumor suppressor activity in Ph1 leukemias and strongly support the introduction of the PP2A activator FTY720 in the treatment of CML-BC and Ph1 ALL patients.     

Targeting autophagy potentiates tyrosine kinase inhibitor–induced cell death in Philadelphia chromosome–positive cells, including primary CML stem cells

Imatinib mesylate (IM), a potent inhibitor of the BCR/ABL tyrosine kinase, has become standard first-line therapy for patients with chronic myeloid leukemia (CML), but the frequency of resistance increases in advancing stages of disease. Elimination of BCR/ABL-dependent intracellular signals triggers apoptosis, but it is unclear whether this activates additional cell survival and/or death pathways. We have shown here that IM induces autophagy in CML blast crisis cell lines, CML primary cells, and p210^BCR/ABL-expressing myeloid precursor cells. IM-induced autophagy did not involve c-Abl or Bcl-2 activity but was associated with ER stress and was suppressed by depletion of intracellular Ca²⁺, suggesting it is mechanistically nonoverlapping with IM-induced apoptosis. We further demonstrated that suppression of autophagy using either pharmacological inhibitors or RNA interference of essential autophagy genes enhanced cell death induced by IM in cell lines and primary CML cells. Critically, the combination of a tyrosine kinase inhibitor (TKI), i.e., IM, nilotinib, or dasatinib, with inhibitors of autophagy resulted in near complete elimination of phenotypically and functionally defined CML stem cells. Together, these findings suggest that autophagy inhibitors may enhance the therapeutic effects of TKIs in the treatment of CML.     

慢性粒细胞白血病cyclin D2基因的表达研究

目的研究cyclin D2基因表达与慢性粒细胞白血病(CML)特征性的P210^BCR/ABL蛋白酪氨酸激酶活性之间的相关性。方法以RT-PCR、免疫印迹法及流式细胞术检测cyclin D2基因在BCR／ABL K562细胞系中的表达。通过表达抗ABL蛋白酪氨酸激酶区胞内抗体的模型即K562-ib-eGFP细胞，检测cyclin D2表达的变化。结果在P210^BCR/ABL蛋白酪氨酸激酶活性受抑制的K562-ib-eGFP细胞中，cyclin D2的表达(18．90％)明显低于K562细胞组(48．10％)，且K562-ib-eGFP组S期细胞比例(40．40％)也明显低于K562细胞组(64．34％)。结论cyclin D2可能是CML-P210^BCR/ABL蛋白酪氨酸激酶下游相关信号传递分子，其表达增高可能促进了CML细胞的过度增殖。     

BCR/ABL induces multiple abnormalities of cytoskeletal function.

The BCR/ABL oncogene causes human chronic myelogenous leukemia (CML), a myeloproliferative disease characterized by massive expansion of hematopoietic progenitor cells and cells of the granulocyte lineage. When transfected into murine hematopoietic cell lines, BCR/ABL causes cytokine-independence and enhances viability. There is also growing evidence that p210(BCR/ABL) affects cytoskeletal structure. p210(BCR/ABL) binds to actin, and several cytoskeletal proteins are tyrosine phosphorylated by this oncoprotein. Also, at least one aspect of cytoskeletal function is abnormal, in that the affinity of beta1 integrins for fibronectin is altered in CML cells. However, isolated changes in beta1 integrin function would be unlikely to explain the clinical phenotype of CML. We used time-lapse video microscopy to study cell motility and cell morphology on extracellular cell matrix protein-coated surfaces of a series of cell lines before and after transformation by BCR/ABL. BCR/ABL was associated with a striking increase in spontaneous motility, membrane ruffling, formation of long actin extensions (filopodia) and accelerated the rate of protrusion and retraction of pseudopodia on fibronectin-coated surfaces. Also, while untransformed cells were sessile for long periods, BCR/ABL-transformed cells exhibited persistent motility, except for brief periods during cell division. Using cell lines transformed by a temperature-sensitive mutant of BCR/ABL, these kinetic abnormalities of cytoskeletal function were shown to require BCR/ABL tyrosine kinase activity. Similar abnormalities of cytoskeletal function on fibronectin-coated surfaces were observed when hematopoietic progenitor cells purified by CD34 selection from patients with CML were compared with CD34 positive cells from normal individuals. Interestingly, alpha-interferon treatment was found to slowly revert the abnormal motility phenotype of BCR/ABL-transformed cells towards normal. The increase in spontaneous motility and other defects of cytoskeletal function described here will be useful biological markers of the functional effects of BCR/ABL in hematopoietic cells.     

Chronic myeloid leukemia: pathophysiology,diagnostic parameters,and current treatment concepts

Chronic myeloid leukemia (CML) is a stem cell disease characterized by excessive accumulation of clonal myeloid (precursor) cells in hematopoietic tissues. CML cells display the translocation t(9; 22) that creates the bcr/abl oncogene. The respective oncoprotein (= BCR/ABL) exhibits constitutive tyrosine kinase activity and promotes growth and survival in CML cells. Clinically, CML can be divided into three phases: the chronic phase (CP), the accelerated phase (AP), and the blast phase (BP) that resembles acute leukemia. Progression to AP and BP is associated with occurrence of additional genetic defects that cooperate with bcr/abl in leukemogenesis and lead to resistance against antileukemic drugs. The prognosis in CML is variable depending on the phase of disease, age, and response to therapy. The only curative approach available to date is stem cell transplantation. For those who cannot be transplanted, the BCR/ABL tyrosine kinase inhibitor STI571 (Glivec, Imatinib), interferon-alpha (with or without ARAC), or other cytoreductive drugs are prescribed. Currently available data show that STI571 is a superior compound compared to other drugs in producing complete cytogenetic and molecular responses. However, despite superior initial data and high expectations for an effect on survival, long term results are not available so far, and resistance against STI571 has been reported. Forthcoming strategies are therefore attempting to prevent or counteract STI571 resistance by co-administration of other antileukemic drugs. Whether these strategies will lead to curative drug therapy in CML in the future remains at present unknown.     

BCR/ABL-mediated increased expression of multiple known and novel genes that may contribute to the pathogenesis of chronic myelogenous leukemia

The BCR/ABL chimeric protein plays a central role in the pathogenesis of chronic myelogenous leukemia (CML). Intensive research has elucidated many signal transduction pathways activated by BCR/ABL. However, few studies addressed BCR/ABL-dependent alterations in gene expression that may contribute to the pathobiology of CML. To additionally define such downstream genes, we performed a subtractive hybridization between cord blood (CB) CD34(+) cells transduced with an MSCV-retrovirus vector containing either enhanced green fluorescent protein (eGFP) alone or p210(BCR/ABL)-internal ribosome entry site-eGFP. Thirty-four subtracted clones expressed in p210-eGFP but not eGFP-transduced CD34(+) cells have been confirmed by Northern blot and sequenced. Fifty-nine percent represent novel proteins, and 41% are homologous to known genes. Quantitative real-time PCR analysis confirmed that 14 of 14 genes tested were also overexpressed in additional populations of p210(BCR/ABL)-transduced CB CD34(+) cells, as well as in CD34(+) cells from primary newly diagnosed CML patients versus GFP-transduced CB or samples from normal donors. Western blot analysis showed that the known sequences were also overexpressed at the protein level. Treatment of BCR/ABL(+) cells with the Abl-specific tyrosine kinase inhibitor STI571 decreased expression at the mRNA as well as protein level of some but not all of the gene products. This suggests that increased gene expression is in some cases tyrosine kinase-independent. Some of the overexpressed genes are implicated in cellular processes known to be disturbed in CML, including the mitogen-activated protein kinase or the ubiquitin pathway, whereas overexpression of other genes, including RAN and NUP98, may implicate new cellular pathways involved in CML. Additional characterization of downstream genes activated by BCR/ABL may lead to important new insights in the molecular mechanisms underlying CML and identify potentially novel therapeutic targets for CML.     

Differential diagnosis of chronic myeloid leukemia and the related disorders]

Chronic myeloid leukemia(CML) is a generic term that includes five subtypes; i.e. chronic granulocytic leukemia(CGL) (95% of all CML, 90% are Ph+, 5% are Ph-, BCR/ABL+), atypical CML(survival is worse than that of CGL), chronic myelomonocytic leukemia(a subtype of myelodysplastic syndrome), chronic neutrophilic leukemia (Ph-, BCR/ABL-) and juvenile CML(Ph-, BCR/ABL-). It is not so easy to make a diagnosis of Ph-negative CML. Also, about 25% of adult acute lymphoid leukemia(ALL) patients and some essential thrombocythemia patients have Ph chromosome. In addition, about a half of cases with Ph-positive ALL have the same size of BCR/ABL fusion protein as that in Ph-positive CML. It is necessary to distinguish them by the distinctive morphological, cytogenetical and immunological characteristics of these diseases.     

RQ-PCR在慢性粒细胞白血病细胞BCR-ABL融合基因检测中的应用

目的探讨采用实时荧光定量逆转录聚合酶链反应(RQ-PCR)技术检测慢性粒细胞白血病(CML)细胞的BCRABLp210融合基因的临床价值。方法应用RQ-PCR技术对60例CML患者骨髓细胞BCR-ABLp210融合基因进行定量检测分析。结果 60例BCR-ABLp210融合基因阳性的CML患者中,慢性期33例,加速期13例,急变期14例,且CML急变期患者BCR-ABLp210转录本水平明显高于慢性期和加速期患者。经异基因造血干细胞移植治疗或经伊马替尼治疗6个月后,BCRABLp210转录本水平均较6个月前明显降低。但这两种方法治疗CML患者12个月后的效果比较差异无统计学意义(P0.05),而采用其他酪氨酸激酶抑制剂治疗CML 12个月后也可达到相似的治疗效果。结论 RQ-PCR技术监测CML患者细胞BCR-ABLp210融合基因表达有助于CML的诊断、治疗效果评价及微小残留的监测。     

RHBDD1基因在慢性髓系白血病患者骨髓细胞中的表达及临床意义

本研究旨在检测RHBDD1（Rhomboid domain containing 1）基因在慢性髓系白血病（CML）患者骨髓细胞中的表达水平并初步探讨其临床意义。采用实时定量PCR的方法检测RHBDD1在正常人和CML患者骨髓单个核细胞中的相对表达水平。结果表明,CML患者RHBDD1的表达水平明显高于正常人;BCR／ABL p210表达阴性的患者RHBDD1的表达水平显著高于BCR／ABLp210阳性的患者;≥50岁的患者RHBDD1表达水平低于〈50岁的患者;RHBDD1的表达水平与患者的性别无明显相关性。结论：RHBDD1基因可能参与了CML的发生与发展,尤其在BCR／ABL p210阴性患者的发病中可能发挥重要作用。     

骨髓形态学染色联合荧光原位杂交技术在急性白血病鉴别诊断中的应用

目的 探讨联合骨髓形态学染色和荧光原位杂交(MGG-FISH)技术在Ph染色体阳性急性淋巴细胞白血病(Ph+ALL)和慢性粒细胞白血病急性淋巴细胞白血病变(CML-LBC)鉴别诊断中的临床应用价值.方法 应用BCR(绿色)和ABL(橘红色)双色双融合探针,通过MGG-FISH技术对4例Ph+ALL患者、4例CML-LBC患者、1例CML急性白血病变合并淋巴瘤、1例CML急性混合细胞白血病变患者的骨髓涂片标本进行检测,依据形态学分别检测10份标本红细胞系、粒细胞系和淋巴细胞系的BCR/ABL融合信号阳性细胞百分率.结果 通过MGG-FISH方法分析,4份Ph+ALL骨髓标本红细胞系未累及,BCR/ABL融合信号阳性细胞百分率均为0%;粒细胞系阳性率分别为11%(1/9)、8%(1/12)、0%(0/8)、10%(1/10);淋巴细胞系阳性率分别为97%(76/78)、98%(87/89)、98%(97/99)、97%(75/77).4份CML-LBC骨髓标本红细胞系阳性率分别为100%(8/8)、91%(10/11)、82%(9/11)、88%(7/8);粒细胞系阳性率分别为89%(8/9)、96%(94/98)、100%(47/47)、98%(40/41);淋巴细胞系阳性率分别为96%(78/81)、93%(52/56)、96%(68/71)、95%(58/61).其余2份标本阳性率均超过80%,且通过MGG-FISH分析鉴定了恶性克隆的来源.结论 MGG-FISH技术可以准确、快速地对原发性Ph+ALL和CML-LBC进行鉴别,并可进行克隆源性分析.     

慢性髓细胞白血病BCR/ABL1突变克隆演化和治疗策略

伊马替尼的应用使很多慢性髓细胞白血病(chronic myeloid leukemia,CML)患者获得了长期生存,但是CML的BCR-ABL1融合基因激酶区突变(kinase domain mutation,KDM)会造成耐药.KDM有多种类型,不同类型是随机出现的.带有不同KDM特征的白血病克隆有一定的演变规律.在伊马替尼用药期间,耐药程度较高的突变细胞容易发展为优势克隆.建议在治疗伊马替尼耐药的CML时,除了努力发展下一代酪氨酸激酶抑制剂以外,还可考虑用传统药物来辅助治疗.     

慢性髓系白血病急变期分子遗传学研究进展

9号和22号染色体相互易位产生Ph染色体及BCR-ABL融合基因,几乎在所有慢性髓系白血病（CML）出现,BCR-ABL编码的蛋白具有持续增高的酪氨酸激酶活性,使白血病细胞异常增殖。急变期是CML的晚期,在此期间常常出现其它附加染色体和分子的改变。大量研究表明,BCR-ABL基因与其他失调的基因共同作用并异常激活下游的信号传导通路,促进了疾病的进展。酪氨酸激酶抑制剂伊马替尼对大多数慢性期CML患者治疗效果显著。IRIS5年的临床试验显示：用伊马替尼治疗的98%患者达血液学完全缓解,92%患者达主要细胞遗传学缓解,87%患者达完全细胞遗传学缓解。然而,仍有少数慢性期和大多数进展期患者用伊马替尼治疗疗效欠佳。在耐药机制的研究中发现ABL激酶区点突变与临床耐药关系密切。第二代酪氨酸激酶抑制剂可改善伊马替尼耐药,本文就急性变的分子机制、伊马替尼耐药等做一综述。     

A chimeric receptor/oncogene that can be regulated by a ligand in vitro and in vivo.

The BCR/ABL oncogene encodes an activated tyrosine kinase that causes human chronic myelogenous leukemia. The mechanism of transformation, however, is complex and not well understood. One of the important contributions of BCR to transformation is believed to be dimerization or oligomerization of ABL, thereby activating ABL tyrosine kinase activity. We reasoned that if ABL was dimerized through other mechanisms, activation of the tyrosine kinase activity should also result, and the activated kinase may also be transforming. Erythropoietin is known to activate its receptor by causing dimerization, and therefore a synthetic oncogene was created by linking the extracytoplasmic and transmembrane domains of the EPO receptor with c-ABL. This chimeric receptor was stably expressed in Ba/F3 cells and, in the absence of EPO, had no detectable biological effect on the cells. EPO, however, induced a rapid, dose-dependent activation of ABL tyrosine kinase activity and phosphorylation of several cellular proteins. The major target proteins have been identified, and are very similar to the known substrates of BCR/ABL, including Shc, CBL, CRKL, and several proteins in the cytoskeleton. EPO treatment also resulted in biological effects that were remarkably similar to those of BCR/ABL, including improved viability, altered integrin function, and a weak mitogenic signal. The biological effects were in part dose-dependent, in that low EPO concentrations enhanced viability but did not cause proliferation. At high EPO doses, kinase activation was maximal, and a mitogenic effect was also revealed. In nude mice, Ba/F3 cells expressing this chimeric receptor did not cause detectable disease without administration of pharmacologic doses of EPO. If EPO was given intraperitoneally 5 days a week, however, a dose-dependent lethal leukemia resulted. This ligand-regulatable oncogene mimics some of the biological effects of BCR/ABL, and analysis of ABL mutants in this system will be useful to dissect the signaling pathways that cause CML.     

慢性髓细胞白血病的酪氨酸激酶抑制剂耐药机制

近年,慢性髓细胞白血病(CML)的治疗方法不断取得进展,包括药物化疗、脾切除术、干扰素治疗、造血干细胞移植(HSCT)等方法.第一代酪氨酸激酶抑制剂(TKI)伊马替尼,可使CML患者的总体生存(OS)率与无事件生存(EFS)率均显著提高,已成为CML的一线治疗药物.然而,部分CML患者出现原发性或继发性TKI耐药,成为导致CML患者治疗失败的主要原因.探索TKI耐药机制、寻找应对TKI耐药的新策略成为CML相关研究热点.TKI耐药的机制复杂,与多种基因产物与细胞内信号分子相关,主要分为断裂点簇集区/Abelson白血病病毒(BCR/ABL)依赖途径与非BCR/ABL依赖途径,而这些耐药机制可以单独或同时存在于同一例CML患者.随着相关研究的深入,对CML患者TKI耐药机制的研究取得较大进展,笔者拟就相关研究进展进行综述.     

Liposomal cytarabine for treatment of myeloid central nervous system relapse in chronic myeloid leukaemia occurring during imatinib therapy

BACKGROUND: Central nervous system (CNS) relapse in chronic myeloid leukaemia (CML) is rare and if recorded is usually found to occur in patients with lymphoblastic transformation. The BCR/ABL tyrosine kinase inhibitor imatinib is highly effective in patients with CML, but hardly crosses the blood-brain barrier. PATIENTS AND METHODS: We report on two CML patients who developed a myeloid CNS relapse during treatment with imatinib. One patient was in major cytogenetic response at the time of CNS relapse. In both cases, the myeloid origin of neoplastic cells in the cerebrospinal fluid (CSF) was demonstrable by immunophenotyping, and their leukaemic origin by detection of the BCR/ABL oncoprotein. No BCR/ABL kinase domain mutations were found. Both patients received intrathecal liposomal cytarabine (50 mg each cycle; 6 cycles). In one patient, additional CNS radiation was performed, whereas in the other, consecutive treatment with dasatinib (70 mg per os twice daily) was started. RESULTS: In response to therapy, the clinical symptoms resolved, and the leukaemic cells in the CSF disappeared in both cases. After three months of observation, both patients are in complete cytogenetic and major molecular response, without evidence for a systemic or a CNS relapse. CONCLUSIONS: 'Anatomic' resistance against imatinib in the CNS can lead to a myeloid CNS relapse. Liposomal cytarabine with or without radiation is effective as local therapy in these patients. For systemic treatment and prophylaxis, BCR/ABL kinase inhibitors crossing the blood-brain barrier such as dasatinib should be considered in patients with CNS relapse.     

趋化因子MIP-1α和MCP-1及其受体CCR-1和CCR-2在慢性髓系白血病细胞中的表达

本文旨在研究MIP-1α和MCP-1及其受体CCR-1和CCR-2在慢性髓系白血病细胞中的表达,同时观察P210bcr/abl融合蛋白中酪氨酸激酶对MIP-1α和MCP-1及其受体CCR-1和CCR-2 mRNA表达的影响.在bcr/abl融合基因阴性和阳性慢性髓系白血病细胞中,采用半定量RT-PCR方法检测MIP-1α、MCP-1、CCR-1、CCR-2mRNA的表达水平.结果表明MIP-1αmRNA和CCR-1 mRNA在bcr/abl融合基因阳性细胞中不表达,但在bcr/abl融合基因阴性细胞中表达,而MCP-1 mRNA和CCR-2mRNA在bcr/abl融合基因阳性和阴性细胞中均不表达.当P210bcr/abl融合蛋白中酪氨酸激酶被抑制后,MIP-1α和CCR-1的mRNA表达水平恢复至正常水平.结论：P210bcr/abl融合蛋白抑制慢性髓系白血病细胞中MIP-1α和CCR-1 mRNA的表达,但对MCP-1和CCR-2mRNA的表达无影响.