Novel Illumina-based next generation sequencing approach with one-round amplification provides early and reliable detection of BCR-ABL1 kinase domain mutations in chronic myeloid leukemia

The occurrence of mutations in the BCR-ABL1 kinase domain (KD) can lead to treatment resistance in chronic myeloid leukaemia patients. Nowadays, next-generation sequencing (NGS) is an alternative method for the detection of kinase domain mutations, compared to routinely used Sanger sequencing, providing a higher sensitivity of mutation detection. However, in the protocols established so far multiple rounds of amplification limit reliable mutation detection to approximately 5% variant allele frequency. Here, we present a simplified, one-round amplification NGS protocol for the Illumina platform, which offers a robust early detection of BCR-ABL1 KD mutations with a reliable detection limit of 3% variant allele frequency.     

CML - Not only BCR-ABL1 matters

BCR-ABL1 is in the center of chronic myeloid leukemia (CML) pathology, diagnosis and treatment, as confirmed by the success of tyrosine kinase inhibitor (TKI) therapy. However, additional mechanisms and events, many of which function independently of BCR-ABL1, play important roles, particularly in terms of leukemic stem cell (LSC) persistence, primary and secondary resistance, and disease progression. Promising therapeutic approaches aim to disrupt pathways which mediate LSC survival during successful TKI treatment, in the hope of improving long-term treatment-free-remission and perhaps provide a functional cure for some patients. Over the years through advances in sequencing technology frequent molecular aberrations in addition to BCR-ABL1 have been identified not only in advanced disease but also in chronic phase CML, often affecting epigenetic regulators such as ASXL1, DNMT3A and TET2. Analyses of serial samples have revealed various patterns of clonal evolution with some mutations preceding the BCR-ABL1 acquisition. Such mutations can be considered to be important co-factors in the pathogenesis of CML and could potentially influence therapeutic strategies in the future.     

BCR-ABL inhibitors: Updates in the management of patients with chronic-phase chronic myeloid leukemia

Objectives

This article reviews recent clinical experiences with first-line and second-line second-generation BCR-ABL inhibitors and discusses considerations for selection of therapy for patients with chronic-phase chronic myeloid leukemia.

Methods

We reviewed recent publications on PubMed and abstracts from major congresses relevant to the topic.

Results

Therapeutic options for front-line treatment have increased with the approval of two second-generation BCR-ABL inhibitors, dasatinib and nilotinib. Both agents are also treatment options for patients with resistance or intolerance to front-line imatinib. More recently, bosutinib, ponatinib, and omacetaxine have also been approved for patients with resistance or intolerance to prior therapy.

Discussion

Expanded treatment options coupled with rapidly changing treatment guidelines have led to numerous questions regarding the selection and monitoring of therapy. Common concerns include how to best select therapy based upon patient-specific comorbidities, monitoring and interpretation of treatment outcomes, and optimization of dosing when side effects occur.     

BCR-ABL基因阳性成人急性淋巴细胞白血病29例临床分析

目的总结BCR-ABL融合基因阳性的急性淋巴细胞白血病（acute lymphoblastic leukemia,ALL）患者的临床特点、疗效和预后。方法回顾分析29例确诊为BCR-ABL基因阳性的ALL患者,予传统化疗、伊马替尼和异基因造血干细胞移植治疗,随访期3～80月,评价治疗效果。结果178例ALL患者中,BCR-ABL基因阳性者29例（16.3%）,其中B细胞性28例,T细胞性者1例。14例患者在首1～2个疗程化疗后获得完全缓解（48.3%）,部分缓解者1例（3.4%）,2例在首2个疗程未获CR后加用伊马替尼获得骨髓细胞学完全缓解（10.3%）,无效12例（41.4%）。29例患者中位生存期14.5月。伊马替尼联合传统化疗化疗者完全缓解率80%,高于单用传统化疗者（50%（）χ2=5.894,P〈0.01）,生存期（18.6月）大于单用传统化疗未进行移植者（11.1月）（t=2.469,P〈0.05）。结论BCR/ABL融合基因阳性的ALL患者传统化疗疗效差,联合伊马替尼可提高完全缓解率和生存期,异基因造血干细胞移植可使部分患者长期无病生存。     

慢性粒细胞白血病患者血液肿瘤相关基因突变研究进展

慢性粒细胞白血病（CML）是以Ph染色体异位为特征的骨髓增殖性疾病,酪氨酸激酶抑制剂（TKI）的应用显著改善了CML患者的预后。细胞遗传学和分子学监测用于评估TKI疗效并指导疾病管理已成为CML治疗的重要组成部分。然而,在疾病诊断、转化和耐药性方面扩大基因组分析是CML研究中尚未完全探索的领域。文章旨在探讨CML最初诊断和治疗失败转化时的基因突变频率和类别,分析诊治中基因突变与CML患者预后的关系。     

RAG enhances BCR-ABL1-positive leukemic cell growth through its endonuclease activity in vitro and in vivo

BCR-ABL1 gene fusion associated with additional DNA lesions involves the pathogenesis of chronic myelogenous leukemia (CML) from a chronic phase (CP) to a blast crisis of B lymphoid (CML-LBC) lineage and BCR-ABL1⁺ acute lymphoblastic leukemia (BCR-ABL1⁺ ALL). The recombination-activating gene RAG1 and RAG2 (collectively, RAG) proteins that assemble a diverse set of antigen receptor genes during lymphocyte development are abnormally expressed in CML-LBC and BCR-ABL1⁺ ALL. However, the direct involvement of dysregulated RAG in disease progression remains unclear. Here, we generate human wild-type (WT) RAG and catalytically inactive RAG-expressing BCR-ABL1⁺ and BCR-ABL1⁻ cell lines, respectively, and demonstrate that BCR-ABL1 specifically collaborates with RAG recombinase to promote cell survival in vitro and in xenograft mice models. WT RAG-expressing BCR-ABL1⁺ cell lines and primary CD34⁺ bone marrow cells from CML-LBC samples maintain more double-strand breaks (DSB) compared to catalytically inactive RAG-expressing BCR-ABL1⁺ cell lines and RAG-deficient CML-CP samples, which are measured by γ-H2AX. WT RAG-expressing BCR-ABL1⁺ cells are biased to repair RAG-mediated DSB by the alternative non–homologous end joining pathway (a-NHEJ), which could contribute genomic instability through increasing the expression of a-NHEJ-related MRE11 and RAD50 proteins. As a result, RAG-expressing BCR-ABL1⁺ cells decrease sensitivity to tyrosine kinase inhibitors (TKI) by activating BCR-ABL1 signaling but independent of the levels of BCR-ABL1 expression and mutations in the BCR-ABL1 tyrosine kinase domain. These findings identify a surprising and novel role of RAG in the functional specialization of disease progression in BCR-ABL1⁺ leukemia through its endonuclease activity.