An intron-derived insertion/truncation mutation in the BCR-ABL kinase domain in chronic myeloid leukemia patients undergoing kinase inhibitor therapy

Although targeted inhibition of BCR-ABL with imatinib is an effective therapy for patients with chronic myeloid leukemia (CML), a minority of patients acquire mutations in the BCR-ABL kinase domain, resulting in imatinib resistance. The spectrum of kinase domain mutations discovered to date is quite heterogeneous, consisting almost exclusively of single nucleotide substitutions affecting key amino acids that regulate drug binding or BCR-ABL function. Here, we describe an alternative kinase domain insertion/truncation mutation in three CML patients undergoing kinase inhibitor therapy. In each of these patients, direct DNA sequencing of BCR-ABL RT-PCR products revealed that the same 35 nucleotides from ABL intron 8 had been inserted at the normal exon 8 to 9 splice junction. This 35-bp intronic sequence was flanked by excellent consensus splice donor and acceptor sequences, suggesting alternative splicing as the likely mutational mechanism. The insertion created a premature translational stop codon after 10 intron-encoded amino acids (amino acid 484). This resulted in truncation of 653 C-terminal amino acids, which included part of the kinase domain and the entire "last exon" region. These findings demonstrate that kinase domain insertions are an alternative (and not entirely uncommon) mutational mechanism in CML patients undergoing kinase inhibitor therapy.     

酪氨酸激酶抑制剂STI571治疗慢性粒细胞白血病的研究

目的:研究特异性酪氨酸激酶抑制剂STI571对慢性粒细胞白血病(简称慢粒)细胞增殖、凋亡、周期调控及bcr-abl融合基因表达的影响,为慢粒的基因治疗提供理论依据。方法:细胞培养慢粒急变细胞系K562细胞株,通过MTT检测STI571作用下细胞存活率,流式细胞仪检测周期变化,电镜及DNA电泳检测细胞凋亡,半定量RT-PCR检测STI571对bcr-abl融合基因表达的影响。结果:STI571作用后K562细胞中G1期细胞明显增加,S期细胞明显减少。流式细胞图中的二倍体峰前可见一明显亚二倍体峰———凋亡峰(apoptosispeak),提示STI571能明显诱导K562细胞凋亡。电镜发现STI571作用于K562细胞12～72h后,诱导出各期凋亡细胞及凋亡小体。半定量PCR灰度扫描结果显示bcr-abl基因的mRNA表达下降,电泳检测扩增产物,荧光亮度减弱。结论:STI571能明显抑制白血病细胞增殖,细胞阻滞于G0/G1期,且具有明显的诱导凋亡作用,反馈抑制bcr-abl融合基因的表达。     

1193例慢性粒细胞白血病细胞及分子遗传学分析

目的了解国内慢性粒细胞白血病（CML）不同病期染色体核型及其演变和ber—abl融合基因特点。方法对1193例CML患者的染色体核型及524例CML患者的ber-abl融合基因资料进行回顾性分析。染色体的检测采用R显带技术，融合基因检测采用RT-PCR技术。结果在所有病例中，Ph染色体阳性（Ph^＋）患者占98．07％，Ph^-患者占1．93％。在Ph^＋患者中，95．64％为典型Ph染色体阳性，4．36％为变异型Ph染色体阳性。11．88％的典型Ph^＋患者发生染色体核型演变。急变期、加速期和慢性期染色体核型演变的发生率分别为49．04％、27．78％及7．94％。在所有典型Ph^＋患者中，发生染色体核型演变后最常见的附加染色体异常类型为＋Ph（14．62％），＋8（10．77％）和-21（7．69％）。急变期和加速期最常见的附加染色体异常类型为＋Ph（28．57％），＋8（16．67％）和＋19（7．14％）；慢性期最常见的附加染色体异常为-21（10．26％），＋Ph（8．97％）和＋8（8．97％）。附加染色体异常联合出现类型以＋Ph与＋8的联合最多（3．60％）。在所有524例检测过融合基因的标本中，h3a2（＋）为54．01％，b2a2（＋）为27．67％。结论国内CML患者染色体的核型及演变可能有着自己的特点。     

酪氨酸激酶抑制剂治疗慢性期老年人慢性粒细胞白血病的疗效及安全性分析

目的 回顾性分析酪氨酸激酶抑制剂(TKI)治疗慢性期慢性粒细胞白血病(CML)老年患者的疗效及安全性.方法 收集2005年1月至2016年1月于华西医院血液内科就诊的发病年龄≥60岁且接受TKI治疗的慢性期CML老年患者共计52例作为研究对象.其中,33例患者的一线治疗方案选择伊马替尼(IM)治疗,2例患者一线治疗方案选择二代TKI尼洛替尼(NIL)治疗,其余17例患者接受IM治疗前经过干扰素治疗.对其治疗反应、总体生存(OS)、无事件生存(EFS)、伴随疾病情况及药物不良反应进行回顾性分析,总结TKI治疗老年CML的疗效及安全性.结果 ①随访结束时,所有患者累积完全血液学缓解(CHR)、主要细胞遗传学缓解(MCyR)、完全细胞遗传学缓解(CCyR)和主要分子学缓解(MMR)率分别为100.0％(52/52)、82.7％(43/52)、80.8％(42/52)和71.2％(37/52).所有患者1、5和10年OS率分别为100.0％、95.1％和75.3％,EFS率分别为92.3％、73.3％和51.4％.②25例患者诊断为CML时存在伴随疾病,所有52例患者查尔森合并症指数(CCI)评分均≤2分.32例CCI评分=0分与20例CCI评分＞0分的患者相比,累积CCyR、MCyR、MMR率,以及Ⅲ～Ⅳ级血液学与非血液学不良反应发生率差异均无统计学意义(x2 =0.948、0.525、0.021、0.288、0.519,P＞0.05).③50例接受IM治疗患者中,Ⅲ～Ⅳ级中性粒细胞减少、血小板减少、贫血发生率分别为16.0％(8/50)、28.0％ (14/50)及18.0％(9/50),Ⅲ～Ⅳ级非血液学不良反应发生率为28.0％(14/50),5例(10.0％,5/50)患者因为IM不耐受而选择二代TKI治疗.结论 TKI对慢性期CML老年患者具有良好的疗效及安全性,轻微的伴随疾病不影响疾病治疗.     

慢性髓性白血病患者BCR-ABL融合基因的规范化检测及临床应用

BCR-ABL融合基因(mRNA)是慢性髓性白血病(CML)的分子标志,靶向BCR-ABL的酪氨酸激酶抑制剂(TKIs)是当前CML治疗的基本药物。BCR-ABL mRNA水平是TKI疗效评估的重要指标,ABL酪氨酸激酶区突变提示耐药机制、指导随后TKIs的选择等治疗策略。规范化的BCR-ABL检测是精准指导临床治疗的前提,是CML患者获得最佳疗效的保证。规范化体现在样本类型、检测内容、实验室检测方案、报告方式等方面,本文结合新近文献探讨了CML患者BCR-ABL定量和突变的规范化检测及临床应用。     

Identification of side effects associated with intolerance to BCR-ABL inhibitors in patients with chronic myeloid leukemia

Clinical intolerance occurs when the toxicity of a medication outweighs its clinical benefit. Early recognition of clinical intolerance to BCR-ABL inhibitors used for chronic myeloid leukemia (CML) is important for maximizing patient benefit. In CML, most side effects associated with BCR-ABL inhibitor therapy are mild and easily managed, so recognizing, monitoring, and addressing serious side effects may ensure optimal outcome. However, a subset of patients will be intolerant to first-line imatinib. Patients who experience unresponsive grade 3 or any grade 4 nonhematologic side effects to imatinib may require discontinuation and switching to second-line therapies, such as dasatinib or nilotinib, after identification of intolerance. The most common side effects associated with dasatinib and nilotinib are hematologic and generally are reversible with dose adjustment. Pleural effusions are more common with dasatinib use and may be managed by dose interruption and reduction. Both drugs possess warnings regarding QT prolongation, but nilotinib carries a black box warning for QT prolongation and sudden death.     

Treatment of chronic myelogenous leukemia with tyrosine kinase inhibitor]

STI571(imatinib) selectively inhibits the ABL-tyrosine kinase, the activity of which is activated by the formation of chimeric BCR/ABL. Phase I study in USA showed a remarkable effectiveness of STI571 in interferon-refractory chronic myelogenous leukemia with little adverse effects. STI571 will plausibly become the first choice drug prior to stem cell transplantation and interferon in the treatment of this leukemia.     

慢性髓系白血病Ph染色体分析与bcr/abl mRNA检测

目的 为进一步明确慢性髓系白血病（ＣＭＬ）患者中Ｐｈ染色体阳性细胞与ｂｃｒ／ａｂｌ融合基因表达之间的关系和比较细胞遗传学分的与聚合酶链反应（ＰＣＲ）方法在ＣＭＬ应用中的优缺点,方法 用热变性姬姆萨Ｒ显带（ＲＨＧ）技术和逆转录筑巢式聚合酶链反应（ＲＴ－ｎｅｓｔ－ＰＣＲ）对３３例ＣＭＬ患者的骨髓或外周血进行了分析,对其中１１例异基因骨髓移植（Ａｌｌｏ－ＢＭＴ）或α干扰素（ＩＦＮ－α）＋小剂量羟基脲（Ｈ     

Prediction of interferon therapy efficacy in chronic myeloid leukemia according to data of histomorphological study

AIM: To investigate factors determining prognosis and efficacy of induction therapy including interferon-alpha-2b (intron-A, Schering Plough) in patients at an early chronic stage of Ph-positive chronic myeloid leukemia (CML) as shown by histomorphological examination. MATERIAL AND METHODS: The analysis covered 52 CML patients treated at an early chronic phase with intron-A in a standard daily dose 5 IU/m2 in combination with low-dose cytosinearabinoside (10 mg/m2, s.c. , daily for 10 days of each month). The treatment efficacy was assessed by the international criteria of complete and partial hematological remission and cytogenetic response. The cytogenetic study employed the direct method, even and G-differential staining, fluorescent hybridization in situ (FISH). The sections were stained with hematoxilin-eosine by Gomori, van Gieson. Histological samples were examined with histomorphometry. Immunohistochemical examination was made on paraffin sections using a panel of monoclonal antibodies CD3, CD4, CD8, CD20, NK, PCNA, Ki-67 (Dako, Denmark). RESULTS: Repeated assessment of histomorphological parameters such as erythroid lineage, degree of myelofibrosis and reduction of leukemic population indicate the treatment efficacy. Estimation of the level of leukemic population proliferation in trephine biopsies from CML patients with monoclonal antibodies PCNA and Ki-67 before the treatment is prognostically significant as it further correlates with the cytogenetic response (r = 0.821, p = 0.000000). CONCLUSION: It is valid to study histomorphological picture of CML to prognosticate and assess treatment efficacy with standard doses of interferon-alpha with high probability.     

Recovery of polyclonial hemopoiesis in females with chronic myeloid leukemia with a complete cytogenetic response

AIM: To study feasibility of hemopoiesis clonality determination in assessment of remission completeness in patients with chronic myeloid leukemia (CML) using polymerase chain reaction (PCR HUMARA). MATERIAL AND METHODS: We have examined 28 patients with newly diagnosed CML, 10 CML patients with a complete cytogenetic response (CCR) to therapy with imatinib mesilate and/or alpha-interferon, 24 healthy control females. Twelve patients with untreated CML were homozygous by HUMARA gene (human androgenic receptor gene) and were withdrawn from the study. Leukocytes of peripheral blood from all the patients were investigated with PCR HUMARA for mono- or polyclonal hemopoiesis. Clonality was defined as allele proportion (a/p) of polymorphic loci of HUMARA gene. Remission completeness was confirmed cytogenetically and by molecular methods. RESULTS: The value a/p in 10 patients with CCR varies from 0.69 to 1.33 and is similar to those in the control group. CONCLUSION: The PCR HUMARA technique adequately assesses reduction of Ph-positive clone in CML patients with CCR and points to polyclonal hemopoiesis.     

Sequential ABL kinase inhibitor therapy selects for compound drug-resistant BCR-ABL mutations with altered oncogenic potency

Molecularly targeted kinase inhibitor cancer therapies are currently administered sequentially rather than simultaneously. We addressed the potential long-term impact of this strategy in patients with chronic myelogenous leukemia (CML), which is driven by the fusion oncogene BCR-ABL. Analysis of BCR-ABL genotypes in CML patients who relapsed after sequential treatment with the ABL inhibitors imatinib and dasatinib revealed evolving resistant BCR-ABL kinase domain mutations in all cases. Twelve patients relapsed with the pan-resistant T315I mutation, whereas 6 patients developed novel BCR-ABL mutations predicted to retain sensitivity to imatinib based on in vitro studies. Three of these patients were retreated with imatinib (or the chemically related compound nilotinib) and responded; however, selection for compound mutants (2 or 3 BCR-ABL mutations in the same molecule) can substantially limit the potential effectiveness of retreating patients with inhibitors that have previously failed. Furthermore, drug-resistant mutations, when compounded, can increase oncogenic potency relative to the component mutants in transformation assays. The Aurora kinase inhibitor VX-680, currently under clinical evaluation based on its activity against the T315I mutation, is also effective against the other commonly detected dasatinib-resistant mutation in our analysis, V299L. Our findings demonstrate the potential hazards of sequential kinase inhibitor therapy and suggest a role for a combination of ABL kinase inhibitors, perhaps including VX-680, to prevent the outgrowth of cells harboring drug-resistant BCR-ABL mutations.     

Investigating siRNA delivery to chronic myeloid leukemia K562 cells with lipophilic polymers for therapeutic BCR-ABL down-regulation

RNAi represents a new alternative for treatment of chronic myeloid leukemia (CML) to overcome the difficulties of current drug treatments such as the acquired resistance. However, potent carriers that can overcome delivery barriers to RNAi agents and have therapeutic efficacy especially in difficult-to-transfect CML cells are needed. Here, we explored the use of lipid-modified polyethylenimines (PEI) of low molecular weights (0.6, 1.2 and 2.0 kDa) in K562 cells and showed that the delivery efficiency was dependent on the type of lipid used for polymer modification, degree of lipid substitution and polymer molecular weight. Among the lipid-substituted polymers investigated, palmitic acid (PA)-substituted 1.2 kDa PEI (~ 2 lipids/PEI) has proven to be highly efficient in delivering siRNA and silencing of the reporter gene green fluorescent protein (GFP). The silencing efficacy achieved with this polymer was found to be higher than the 25 kDa PEI and is similar to commercial reagent Lipofectamine™ 2000. Moreover, when BCR-ABL protein was targeted in K562 cells, a reduction in the corresponding mRNA levels was observed, as well as an induction of early and late stage apoptosis. The results of this study demonstrated that PA-substitutions on low MW polymers could be useful for siRNA delivery in CML cells for therapeutic purposes.     

Human chronic myeloid leukemia stem cells are insensitive to imatinib despite inhibition of BCR-ABL activity

Imatinib therapy, which targets the oncogene product BCR-ABL, has transformed chronic myeloid leukemia (CML) from a life-threatening disease into a chronic condition. Most patients, however, harbor residual leukemia cells, and disease recurrence usually occurs when imatinib is discontinued. Although various mechanisms to explain leukemia cell persistence have been proposed, the critical question from a therapeutic standpoint--whether disease persistence is BCR-ABL dependent or independent--has not been answered. Here, we report that human CML stem cells do not depend on BCR-ABL activity for survival and are thus not eliminated by imatinib therapy. Imatinib inhibited BCR-ABL activity to the same degree in all stem (CD34+CD38-, CD133+) and progenitor (CD34+CD38+) cells and in quiescent and cycling progenitors from newly diagnosed CML patients. Although short-term in vitro imatinib treatment reduced the expansion of CML stem/progenitors, cytokine support permitted growth and survival in the absence of BCR-ABL activity that was comparable to that of normal stem/progenitor counterparts. Our findings suggest that primitive CML cells are not oncogene addicted and that therapies that biochemically target BCR-ABL will not eliminate CML stem cells.     

慢性粒细胞白血病患者酪氨酸激酶抑制剂的耐药管理

酪氨酸激酶抑制剂(TKI)的应用使慢性粒细胞白血病(CML)的治疗发生了革命性的变化,但是随着其在临床中的广泛应用,耐药成为临床治疗中面临的巨大挑战.二代、三代TKI.及某些新型药物的研发给一代TKI伊马替尼(IM)耐药的患者带来了新的治疗选择和希望.不断完善的疗效监测体系和ABL激酶区突变检测的应用为TKI的选择、疗效评价,以及药物转换提供了客观且敏感的指标.因此,只有将治疗药物与相应的监测体系相结合,才能使CML患者得到更为合理和规范的治疗.本文拟就CML患者使用TKI耐药后,治疗方案选择及疗效监测体系的研究进展进行阐述.     

伊马替尼治疗早期BCR-ABL转录本水平在251例慢性髓性白血病患者中的预后价值

目的 了解慢性髓性白血病(CML)患者伊马替尼治疗早期BCR-ABL转录本水平的预后价值,为CML患者早期预后评估和治疗选择提供依据.方法 回顾性分析251例接受伊马替尼—线治疗CML慢性期(CML-CP)患者的临床资料,分别比较治疗后3个月及6个月不同BCR-ABL转录本水平患者的无进展生存(PFS)率及总体生存(OS)率,并采用卡方检验及Logistic回归分析方法分析疾病进展的危险因素.结果 伊马替尼治疗3个月BCR-ABL转录本＞10％组(92例)、＞1％～10％组(94例)、≤1％组(65例)的PFS率分别为53.3％、71.3％、86.2％ (P＜0.05),OS率分别为92.4％、96.8％和93.8％ (P＞0.05).伊马替尼治疗后6个月时BCR-ABL转录本＞10％组(22例)、＞1％～10％(50例)组、≤1％(110例)组PFS率分别为27.3％、66.0％和82.7％(P＜0.05),OS率分别为86.4％、94.0％、100％(P＜0.05).Logistic回归分析结果显示3个月及6个月BCR-ABL转录本水平为影响疾病进展的独立危险因素.结论 伊马替尼治疗3个月及6个月BCR-ABL转录本水平对CML患者预后评估具有重要价值.