T315I-mutated Bcr-Abl in chronic myeloid leukemia and imatinib: insights from a computational study

The early stage of chronic myeloid leukemia is triggered by the tyrosine kinase Bcr-Abl. Imatinib mesylate, a selective inhibitor of Bcr-Abl, has been successful in chronic myeloid leukemia clinical trials, but short-lived remissions are usually observed in blast crisis patients. Sequencing of the BCR-ABL gene in relapsed patients revealed a set of mutants that mediate drug resistance. Previously reported work postulated that the missense T315I mutation both alters the three-dimensional structure of the protein binding site, thus decreasing the protein sensitivity for the drug, and does not feature a fundamental hydrogen bond that is critical for binding with imatinib. These speculations, however, were not supported by investigations at the molecular modeling level. Here, we present the results obtained from the application of molecular dynamics simulations to the study of the interactions between T315I Bcr-Abl and imatinib. For the first time, we show that, with respect to the wild-type system, the absence of the supposedly critical H-bond is not the only cause for the failure of receptor inhibition by imatinib, but also a plethora of other protein/drug interactions are drastically and unfavorably changed in the mutant protein.     

Sonic hedgehog signaling regulates Bcr-Abl expression in human chronic myeloid leukemia cells

Purpose

Bcr-Abl fusion protein activates tyrosine kinase, resulting in the proliferation of leukemia cells, especially chronic myeloid leukemia (CML) cells. Imatinib (IM) effectively targets Bcr-Abl tyrosine kinase, but development of resistance to IM occurs with varying frequency.

Methods

Elucidation of the common regulatory pathway upstream of Bcr-Abl in IM-sensitive and IM-resistant CML cells is important for developing novel therapeutics against CML.

Results

This study demonstrated that IM preferentially inhibited the viability and Bcr-Abl expression in IM-sensitive K562 (K562) cells, but not in Bcr-Abl overexpressing IM-resistant K562 (K562R) cells. Both K562 and K562R cells expressed Shh preproprotein, cleaved Shh C-terminal and N-terminal peptides, as well as mRNA level of major Shh signaling molecules, including sonic hedgehog (Shh), patched (PTCH), smoothened (Smo) and Gli-1. Moreover, Gli-1 translocation into nucleus was evident in these two cell lines, suggesting that both K562 and K562R cells possess activated and major components of the Shh signaling pathway. Silencing of Gli-1 by interference RNA was accompanied by inhibition of Bcr-Abl protein expression. Pharmacological suppression of Bcr-Abl expression was restored by the Smo agonist purmorpharmine. Treatment of Shh peptide in both K562 and K562R cells not only increased Shh and Gli-1 expression, but also up-regulated Bcr-Abl expression. Resveratrol, a known Bcr-Abl inhibitor, reduced Gli-1 activation and inhibited the viability of CML cells.

Conclusions

Shh signaling may regulate Bcr-Abl expression in human chronic myeloid leukemia cells. Novel compounds inhibiting both Shh signaling and Bcr-Abl expression, such as resveratrol, may have potential to be effective agents against CML independent of IM resistance.     

中国慢性髓系白血病诊断与治疗指南(2011年版)

慢性髓系白血病(CML)是骨髓造血干细胞克隆性增殖形成的恶性肿瘤,占成人白血病的15%[1],全球年发病率为1.6～2.0/10万.我国1986至1988年在22个省(市、自治区)46个调查点进行白血病发病情况调查显示CML的年发病率为0.36/10万[2].此后国内几个地区的流行病学调查显示CML的年发病率为0.39～0.55/10万[3-6].中国CML患者较西方更为年轻化,国内几个地区的流行病学调查显示CML中位发病年龄为45～50岁[3-6],而西方国家CML的中位发病年龄为67岁.     

Molecular monitoring of chronic myeloid leukemia: present and future

Introduction: Fusion of BCR-ABL1 genes causes chronic myeloid leukemia (CML). As a reliable marker of disease burden, it also serves as the target of tyrosine kinase inhibitors (TKIs). New more sensitive molecular diagnostic tools for BCR-ABL1 can contribute to therapeutic decision-making, especially in considering drug discontinuation for patients enjoying prolonged deep molecular response.

Areas covered: Several novel platforms are transforming CML molecular diagnostics to enable faster point-of-care devices, better understanding of clonal diversity and resistance mutations. Here, we review these molecular platforms, knowing implementation in other hematological malignancies will ensue.

Expert commentary: Treatment with TKI in CML is the first example of a highly effective targeted therapy. Monitoring of BCR-ABL1 mRNA is standard in assessing disease burden being highly predictive of outcomes recommended by both European LeukemiaNet (ELN) and National Comprehensive Cancer Network (NCCN); however, studies has demonstrated poor adherence to these recommendations. In both clinical practice and assay performance, further optimizing of BCR-ABL1 monitoring can be envisioned including point-of-care methods for increased availability of rapid, standardized testing and increasingly sensitive molecular assays that allow for quantification of MRD and detecting resistance mutations.     

慢性粒细胞白血病肿瘤干细胞的免疫功能

背景：研究认为间充质干细胞可能是骨髓造血微环境的免疫保护位点。由于慢性粒细胞白血病存在造血微环境异常和免疫异常,所以推测间充质干细胞可能在慢性粒细胞白血病的病理过程中扮演了一个重要角色。目的：观察慢性粒细胞白血病骨髓来源的肿瘤干细胞的免疫学特征,比较其与正常人来源的间充质干细胞是否存在免疫功能的异常。方法：分离正常人和慢性粒细胞白血病患者的骨髓间充质干细胞,分别检测它们对T细胞周期、活化、抑制和增殖的作用。结果与结论：慢性粒细胞白血病和正常志愿者骨髓来源的间充质干细胞形态和表型没有差异,慢性粒细胞白血病患者来源的间充质干细胞抑制T细胞增殖的作用减弱,抑制T细胞周期及活化的能力减弱,慢性粒细胞白血病患者抑制T细胞凋亡的作用增强。提示慢性粒细胞白血病患者骨髓来源的间充质干细胞存在明显的免疫调节功能缺陷,如果使用慢性粒细胞白血病患者自体的间充质干细胞移植治疗可能不是一种很好的选择,对于骨髓增生异常综合征患者最好是选用异基因的间充质干细胞移植。     

慢性粒细胞白血病肿瘤干细胞的免疫功能

背景:研究认为间充质干细胞可能是骨髓造血微环境的免疫保护位点。由于慢性粒细胞白血病存在造血微环境异常和免疫异常,所以推测间充质干细胞可能在慢性粒细胞白血病的病理过程中扮演了一个重要角色。目的:观察慢性粒细胞白血病骨髓来源的肿瘤干细胞的免疫学特征,比较其与正常人来源的间充质干细胞是否存在免疫功能的异常。方法:分离正常人和慢性粒细胞白血病患者的骨髓间充质干细胞,分别检测它们对T细胞周期、活化、抑制和增殖的作用。结果与结论:慢性粒细胞白血病和正常志愿者骨髓来源的间充质干细胞形态和表型没有差异,慢性粒细胞白血病患者来源的间充质干细胞抑制T细胞增殖的作用减弱,抑制T细胞周期及活化的能力减弱,慢性粒细胞白血病患者抑制T细胞凋亡的作用增强。提示慢性粒细胞白血病患者骨髓来源的间充质干细胞存在明显的免疫调节功能缺陷,如果使用慢性粒细胞白血病患者自体的间充质干细胞移植治疗可能不是一种很好的选择,对于骨髓增生异常综合征患者最好是选用异基因的间充质干细胞移植。     

Engraftment with chronic granulocytic leukemia cells in acute myeloid leukemia

A deliberate engraftment with nonirradiated chronic granulocytic leukemia (CGL) cells was performed in a patient with acute myeloid leukemia (AML) at a time when he was resistant to cytotoxic drug chemotherapy, pancytopenic and developed an infection. The CGL engraftment was confirmed by the presence of a Ph1-positive donor clone in the recipient's bone marrow and by the pattern of colony growth of the recipient's bone-marrow cells cultured in vitro. Bone marrow engraftment in the host helped in the resolution of infection and permitted the administration of further cytotoxic drugs, as a result of which a remission of AML occurred.     

miRNA与慢性髓系白血病研究进展

microRNA(miRNA)是一种内源性的、长度约为22 nt的小非编码RNA,在转录后水平参与调控基因表达,广泛参与细胞的凋亡、增殖、分化、代谢等过程,具有重要的生物功能,并且可行使癌基因或抑癌基因功能。研究表明,miRNA的异常表达与慢性髓系白血病密切相关,参与调控慢性髓系白血病的发生、进展及耐药等过程,可成为潜在的诊疗靶点。本文就miRNA的合成与作用方式、慢性髓系白血病发病、耐药、治疗相关miRNA的研究进展作一综述。     

CML患者骨髓间质干细胞的干细胞因子mRNA表达水平检测

目的 研究慢性粒细胞白血病(CML)患者骨髓间质干细胞(MSCs)生长活性及干细胞因子(SCF)表达水平,探讨MSCs在CML发病中的作用.方法 以慢性期CML患者为实验组,健康人为对照组,抽取骨髓液行MSCs体外培养,动态观察细胞形态并进行计数、绘制生长曲线;取第3、4代MSCs提取总RNA,逆转录,real-time PCR法检测SCF mRNA表达水平.结果 慢性期CML患者骨髓MSCs生长活性较健康人无明显差别;实验组MSCs表达SCF mRNA水平较对照组明显高(P＜0.05).结论 CML患者骨髓MSCs异常表达SCF参与CML发病,对其检测有指导诊断意义.     

A novel mutation of SETBP1 in atypical chronic myeloid leukemia transformed from acute myelomonocytic leukemia

To investigate an oncogenic mutation of SETBP1 in the evolution from acute myelomonocytic leukemia (M4) to secondary aCML. Clinical data and molecular studies were analyzed of paired aCML and 'normal'DNA from a case with M4. We identified a mutation in SETBP1 (encoding a p.Asp868Ala alteration). The analysis of paired sample indicated that SETBP1 mutation was acquired during leukemic evolution.