Growth Arrest of BCR-ABL Positive Cells with a Sequence-Specific Polyamide-Chlorambucil Conjugate

Chronic myeloid leukemia (CML) is characterized by the presence of a constitutively active Abl kinase, which is the product of a chimeric BCR-ABL gene, caused by the genetic translocation known as the Philadelphia chromosome. Imatinib, a selective inhibitor of the Bcr-Abl tyrosine kinase, has significantly improved the clinical outcome of patients with CML. However, subsets of patients lose their response to treatment through the emergence of imatinib-resistant cells, and imatinib treatment is less durable for patients with late stage CML. Although alternative Bcr-Abl tyrosine kinase inhibitors have been developed to overcome drug resistance, a cocktail therapy of different kinase inhibitors and additional chemotherapeutics may be needed for complete remission of CML in some cases. Chlorambucil has been used for treatment of B cell chronic lymphocytic leukemia, non-Hodgkin's and Hodgkin's disease. Here we report that a DNA sequence-specific pyrrole-imidazole polyamide-chlorambucil conjugate, 1R-Chl, causes growth arrest of cells harboring both unmutated BCR-ABL and three imatinib resistant strains. 1R-Chl also displays selective toxicities against activated lymphocytes and a high dose tolerance in a murine model.     

Proteasome inhibition leads to significant reduction of Bcr-Abl expression and subsequent induction of apoptosis in K562 human chronic myelogenous leukemia cells

The chimeric oncogene bcr-abl is detected in virtually every case of chronic myelogenous leukemia. It has been shown that cells (such as K562) expressing Bcr-Abl/p210, a protein tyrosine kinase, not only undergo cellular transformation but also demonstrate multiple drug resistance. Recent studies also demonstrate that the proteasome is involved in the survival signaling pathway(s). In the current study, we tested the hypothesis that the proteasome might play a role in regulating Bcr-Abl function. We have demonstrated by using a variety of inhibitors that inhibition of the proteasome, but not of the cysteine protease, activity is able to activate the apoptotic cell death program in K562 cells. Proteasome inhibition-induced apoptosis is demonstrated by condensation and fragmentation of nuclei, appearance of an apoptotic population with sub-G1 DNA content, the internucleosomal fragmentation of DNA, and cleavage of poly(ADP-ribose) polymerase, and can be blocked by a specific caspase-3-like tetrapeptide inhibitor. Western blot analysis with specific antibodies to c-Abl and Bcr proteins show that treatment of K562 cells with a proteasome inhibitor results in significant reduction of Bcr-Abl protein expression, which occurs several hours before the onset of apoptotic execution. Levels of c-Abl/p145 and Bcr/p160 proteins, however, remain essentially unaltered at that time. Furthermore, reduced Bcr-Abl expression is reflected in significantly attenuated Bcr-Abl-mediated protein tyrosine phosphorylation. Taken together, these results indicate that proteasome inhibition is sufficient to inactivate Bcr-Abl function and subsequently activate the apoptotic death program in cells that are resistant to apoptosis induced by chemotherapy.     

慢性粒细胞白血病病人Mcl一1基因和Bcr／Abl基因的表达及临床意义

目的探讨慢性粒细胞白血病（CML）病人Mcl—l基因和Bcr／Abl融合基因的表达水平及临床意义。方法应用实时荧光定量PCR技术检测了4l例cML病人（包括慢性期15倒、加速期6例、急变期6例、伊马替尼治疗后遗传学完全缓解8例及非伊马替尼治疗的未缓解的CML病人6例）骨髓标本Mel—l基因、Ber／Abl融合基因的表达水平,以10例正常人作为对照。结果CML各组Mcl—I和Bcr／AblmRNA的表达水平差异均有显著性（X2=19．12—36．08,P〈0．05）。伊马替尼治疗组与正常对照组Mel—lmRNA的表达明显低于其他各组（z=2．547—3．254,P〈0．05）;加速期、急变期及非伊马替尼治疗组之间Mcl—lmRNA的表达水平差异无显著性（z=0．481一1．922,P〉0．05）,但均明显高于慢性期（z=2．65—3．465,P〈0．05）。Ber／AblmRNA在慢性期、加速期、急变期及非伊马替尼治疗组之间表达差异无显著性（z=0．48—1．196,P〉0．05）。CML患者Mel—l与Bcr／AblmRNA的表达水平呈正相关（r=0．68,P〈0．05）。结论Mcl—l和Ber／Abl与CML的病情密切相关,参与cML的发生和发展,是判断病情进展及预后的分子标记物。     

Combination with an antisense oligonucleotide synergistically improves the antileukemic efficacy of erucylphospho-N,N,N-trimethylpropylammonium in chronic myeloid leukemia cell lines

The aim of this study was to enhance the antileukemic efficacy of the alkylphosphocholine erucylphospho-N,N,N-trimethylpropylammonium (ErPC3) in chronic myeloid leukemia (CML)-derived cell lines by a bcr-directed antisense oligonucleotide (ASO-bcr). The mechanism was substantiated by Western blotting of the BCR-ABL expression level of CML cells, and the efficacy was substantiated by inhibition of colony formation compared with normal hematopoietic cells. The clonogenicity of K-562 cells expressing high levels of p210(BCR-ABL) was inhibited significantly by the ASO-bcr (T/C%, 30; P < 0.05) but not by ErPC3 (T/C%, 70). Combined sequential exposure to ErPC3 and the ASO-bcr, however, inhibited synergistically colony growth (T/C%, 3; P < 0.01). The colony growth of BV-173 cells expressing lower levels of p210(BCR-ABL) than K562 cells was inhibited to a greater extent by the ASO-bcr (T/C%, 15; P < 0.01). AR-230 cells that express high levels of p230(BCR-ABL) showed an intermediate decrease in colony formation in response to the ASO-bcr (T/C%, 20; P < 0.05). BCR-ABL levels of BV-173, CML-T1, and LAMA-84 cells were reduced in response to the ASO-bcr, as evidenced by Western blot. However, K-562 and AR-230 cells showed reduced BCR-ABL expression only after repeated treatment. ErPC3 and the ASO-bcr did not reduce colony formation (CFU-GM) of normal mouse bone marrow cells from long-term bone marrow cell cultures; instead, ErPC3 stimulated colony formation (P < 0.05) and did not induce chromosomal aberrations in mouse bone marrow. In conclusion, the combination of ErPC3 with a suitable antisense oligonucleotide inhibited synergistically colony formation of CML cell lines without damaging normal cells and thus might have a bearing on the purging of autologous hematopoietic transplants in CML patients.     

Dihydroartemisinin inhibits the Bcr/Abl oncogene at the mRNA level in chronic myeloid leukemia sensitive or resistant to imatinib

Due to the mutations of the Bcr/Abl oncogene that obstacle the binding of the protein with imatinib, the resistance to imatinib has developed in a significant portion of chronic myeloid leukemia (CML) patients. It stimulated the search for novel molecules for treatment of imatinib-resistance CML. Inhibiting the amplification of Bcr/Abl oncogene is believed to be a new effective strategy to override the imatinib resistance on CML cells. In present research, we demonstrated that dihydroartemisinin (DHA), a safe and effective antimalarial analog of artemisinin, could significantly inhibit the Bcr/Abl fusion gene at the mRNA level in CML cells sensitive or resistant to imatinib (including the primary CML cells with T315I mutation) and induce cell death. Moreover, dihydroartemisinin could also lead to the inhibition of the Bcr/Abl protein expression and tyrosine kinase activity, and strongly suppress on the downstream signals of Bcr/Abl, which included inhibition of tyrosine kinase activity of AKT and ERK, promotion of cytochrome c release from the mitochondria and the consequential activation of caspase-9/3 in imatinib-resistant CML cells. These results suggest for the first time that Dihydroartemisinin might be a potential novel drug candidate for treatment of imatinib-resistant CML and worthy of further study.     

Role of Dok-1 and Dok-2 in myeloid homeostasis and suppression of leukemia

Dok-1 and Dok-2 are closely related rasGAP-associated docking proteins expressed preferentially in hematopoietic cells. Although they are phosphorylated upon activation of many protein tyrosine kinases (PTKs), including those coupled with cytokine receptors and oncogenic PTKs like Bcr-Abl, their physiological roles are largely unidentified. Here, we generated mice lacking Dok-1 and/or Dok-2, which included the double-deficient mice succumbed to myeloproliferative disease resembling human chronic myelogenous leukemia (CML) and chronic myelomonocytic leukemia. The double-deficient mice displayed medullary and extramedullary hyperplasia of granulocyte/macrophage progenitors with leukemic potential, and their myeloid cells showed hyperproliferation and hypo-apoptosis upon treatment and deprivation of cytokines, respectively. Consistently, the mutant myeloid cells showed enhanced Erk and Akt activation upon cytokine stimulation. Moreover, loss of Dok-1 and/or Dok-2 induced blastic transformation of chronic phase CML-like disease in mice carrying the bcr-abl gene, a cause of CML. These findings demonstrate that Dok-1 and Dok-2 are key negative regulators of cytokine responses and are essential for myeloid homeostasis and suppression of leukemia.     

慢性粒细胞白血病病人Mcl-1和Bcr/Abl基因表达

目的探讨慢性粒细胞白血病（CML）病人Mcl-1基因和Bcr/Abl融合基因的表达水平及临床意义。方法应用实时荧光定量PCR技术检测了41例CML病人（包括慢性期15例、加速期6例、急变期6例、伊马替尼治疗后遗传学完全缓解8例及非伊马替尼治疗的未缓解的CML病人6例）骨髓标本Mcl-1基因、Bcr/Abl融合基因的表达水平,以10例正常人作为对照。结果 CML各组Mcl-1和Bcr/Abl mRNA的表达水平差异均有显著性（χ2=19.12～36.08,P〈0.05）。伊马替尼治疗组与正常对照组Mcl-1 mRNA的表达明显低于其他各组（Z=2.547～3.254,P〈0.05）;加速期、急变期及非伊马替尼治疗组之间Mcl-1 mRNA的表达水平差异无显著性（Z=0.481～1.922,P〉0.05）,但均明显高于慢性期（Z=2.650～3.465,P〈0.05）。Bcr/Abl mRNA在慢性期、加速期、急变期及非伊马替尼治疗组之间表达差异无显著性（Z=0.480～1.196,P〉0.05）。CML病人Mcl-1与Bcr/AblmRNA的表达水平呈正相关（r=0.68,P〈0.05）。结论 Mcl-1和Bcr/Abl与CML的病情密切相关,参与CML的发生和发展,是判断病情进展及预后的分子标记物。     

Bcr/Abl融合基因阳性、Flk1+CD34-慢性粒细胞白血病细胞体内生物学特性的研究

目的体内研究慢性粒细胞白血病(CML)患者骨髓中BCR/ABL+、Flk1+CD34-细胞的白血病干细胞特性。方法取CML患者骨髓,淋巴细胞分离液分离单个核细胞,常规接种培养,免疫磁珠分选CD45-、GlyA-及CD34-的贴壁细胞,流式细胞术鉴定其免疫表型,将其输入经亚致死量照射的NOD/SCID小鼠体内,检测人源细胞的植入及分化情况。结果植入的CML患者骨髓源BCR/ABL+、Flk1+CD34-细胞在受体小鼠体内分化为白血病细胞,受体小鼠骨髓细胞中存在Bcr/Abl融合基因阳性细胞。结论Bcr/Abl融合基因阳性Flk1+CD34-细胞具有白血病干细胞特性。     

BCR-ABL kinase is dead; long live the CML stem cell

Chronic myeloid leukemia (CML) is a hematopoietic disease characterized by expansion of myeloid blood cells. It is caused by the t(9;22) chromosomal translocation that results in the expression of the fusion tyrosine kinase BCR-ABL. Tyrosine kinase inhibitor (TKI) therapy has led to long-term remissions, but patients remain BCR-ABL+. There is agreement that TKIs do not kill CML stem cells; however, it is controversial whether this is because of a lack of BCR-ABL kinase inhibition in CML stem cells or because CML stem cells do not require BCR-ABL for survival. In this issue of the JCI, Corbin and colleagues provide definitive evidence that BCR-ABL is kinase active in CML stem cells and that TKIs inhibit this kinase activity without affecting CML stem cell survival. Rather, CML stem cells revert to a normal dependence on cytokines for survival and proliferation. These results demonstrate that the CML stem cell is not BCR-ABL addicted and have important implications for developing curative therapeutic approaches to CML.     

Bcr/Abl融合基因阳性、Flk1+CD34-慢性粒细胞性白血病干细胞的分离纯化及其生物学特性的研究

目的分离慢性粒细胞白血病(ChronicMyelogenousLeukemia,CML)患者骨髓中表达BCR/ABL肿瘤基因的细胞亚群,并研究其生物学特性。方法淋巴细胞分离液分离CML患者骨髓单个核细胞,免疫磁珠分选CD45-、GlyA-及CD34-细胞,极限稀释法获得单克隆细胞,流式细胞术鉴定其免疫表型,体外定向诱导分化检测其干细胞特性,并检测其Bcr/Abl融合基因的表达情况。结果CML患者骨髓源单克隆扩增细胞不表达造血细胞和内皮细胞的特征性表型,但Bcr/Abl融合基因阳性;诱导后的细胞能同时向造血细胞及血管内皮细胞分化。结论Bcr/Abl融合基因的产生至少发生在比造血干细胞更为早期的血液血管干细胞水平上,即CML至少起源于血液血管干细胞。     

New insights into small‐molecule inhibitors of Bcr‐Abl

Chronic myelogenous leukemia (CML) is a myeloproliferative disease associated with a defined genetic abnormality, the Bcr‐Abl fusion gene on the Philadelphia chromosome that expresses the constitutively activated tyrosine kinase (TK) Bcr‐Abl. This enzyme leads to the malignant transformation of primitive hematopoietic cells and to the consequent disease. The central role of Bcr‐Abl in the pathogenesis of CML culminated in the discovery of imatinib (an ATP‐competitive inhibitor), which is currently the frontline therapy for CML. Unfortunately, the initial enthusiasm generated by its high response rate has been dampened by the development of resistance, especially in the advanced phases of CML. To overcome imatinib resistance, several second‐generation ATP‐competitive inhibitors endowed with increased potency against imatinib‐resistant mutants have been developed: the dual Src/Abl inhibitor dasatinib and the Abl inhibitor nilotinib have been recently approved by US‐FDA for the treatment of imatinib‐resistant CML, and many other compounds are currently in clinical trial. Although second‐generation TK inhibitors have shown to be clinically effective against most of the imatinib‐resistant mutants, to date poor results have been obtained in the treatment of the Bcr‐Abl T315I mutant. In this review we will report the most interesting second‐generation Abl and dual Src/Abl inhibitors recently entered in clinical trial, but also the new ATP‐competitive and uncompetitive inhibitors published in the last few years, focusing on their chemical structure, mechanism of action, and structure–activity relationship. © 2009 Wiley Periodicals, Inc. Med Res Rev, 31, No. 1, 1–41, 2010     

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.     

STI-571 (imatinib mesylate) enhances the apoptotic efficacy of pyrrolo-1,5-benzoxazepine-6, a novel microtubule-targeting agent, in both STI-571-sensitive and -resistant Bcr-Abl-positive human chronic myeloid leukemia cells

Interactions between the Bcr-Abl kinase inhibitor STI-571 (imatinib mesylate) and a novel microtubule-targeting agent (MTA), pyrrolo-1,5-benzoxazepine (PBOX)-6, were investigated in STI-571-sensitive and -resistant human chronic myeloid leukemia (CML) cells. Cotreatment of PBOX-6 with STI-571 induced significantly more apoptosis in Bcr-Abl-positive CML cell lines (K562 and LAMA-84) than either drug alone (P < 0.01). Cell cycle analysis of propidium iodide-stained cells showed that STI-571 significantly reduced PBOX-6-induced G2M arrest and polyploid formation with a concomitant increase in apoptosis. Similar results were obtained in K562 CML cells using lead MTAs (paclitaxel and nocodazole) in combination with STI-571. Potentiation of PBOX-6-induced apoptosis by STI-571 was specific to Bcr-Abl-positive leukemia cells with no cytoxic effects observed on normal peripheral blood cells. The combined treatment of STI-571 and PBOX-6 was associated with the down-regulation of Bcr-Abl and repression of proteins involved in Bcr-Abl transformation, namely the antiapoptotic proteins Bcl-x(L) and Mcl-1. Importantly, PBOX-6/STI-571 combinations were also effective in STI-571-resistant cells. Together, these findings highlight the potential clinical benefits in simultaneously targeting the microtubules and the Bcr-Abl oncoprotein in STI-571-sensitive and -resistant CML cells.     

Bcr/Abl expression stimulates integrin function in hematopoietic cell lines.

Cell adhesion to the extracellular matrix is largely mediated by adhesion molecules of the integrin family and is often diminished upon oncogenic transformation. However, we show here that the chronic myelogenous leukemia oncogene Bcr/Abl has positive effects on VLA-4 and VLA-5 integrin function. The presence of Bcr/Abl in the GM-CSF- or IL-3-dependent hematopoietic cell lines MO7e, 32D, and BaF/3 enhanced cell binding to both soluble and immobilized fibronectin. The effect was due to enhanced function of the VLA-5 integrin fibronectin receptor and not to increased surface expression. In parallel, Bcr/Abl stimulated cell adhesion to the VLA-4 integrin ligand VCAM-1. Stimulation of VLA-5 function directly correlated with induction of Bcr/Abl tyrosine kinase activity in a temperature-sensitive kinase mutant. Thus, Bcr/Abl stimulates integrin-dependent cell adhesion, by a mechanism involving increased ligand binding, with the tyrosine kinase activity of Bcr/Abl likely playing a key role. Consistent with these results, hematopoietic precursor cells from chronic myelogenous leukemia patients also showed increased adhesion to fibronectin.     

慢性粒细胞白血病的治疗进展

慢性粒细胞白血病(CML)是一种造血干细胞克隆性骨髓增殖性肿瘤.尽管酪氨酸激酶抑制剂(TKI)可抑制Bcr/Abl激酶活性,并在慢性期CML治疗中取得了很好的疗效,而且耐受性良好,但TKI有很多的不良反应.目前对于CML患者和社会而言,TKI的治疗已成为一个沉重的负担.因此,迫切需要探索清除来源于Ph+恶性干细胞克隆的CML微小残留病灶有望获得CML永久治愈和长期无病生存的方法,现就其治疗进展作一综述.