Bypassing Oncogene Addiction: Mechanisms of off-target resistance in CML

描述（由申请人提供）：慢性髓性白血病（CML）的特征是保留分化能力的髓性祖细胞过度增殖。自然 慢性粒细胞白血病的病史包括进展到更侵袭性的疾病急变期，其中终末分化受损，并且该疾病表现出急性白血病的特征。与许多其他已知的骨髓增生性疾病一样，CML与激活的酪氨酸激酶有关。在CML的情况下，在9号和22号染色体之间的相互染色体易位事件之后产生的融合蛋白BCR-ABL是该疾病的病因。目前CML的治疗包括使用酪氨酸激酶抑制剂（TKI），已显示其在大多数病例中导致深度临床缓解。然而，阻止ATP口袋中TKI结合的抗性赋予突变的出现通常是疾病复发的原因。已开发出第二代和第三代TKI，它们共同保留了对所有耐药突变的活性。随着对这种“靶向”耐药机制的控制得到改善，未来的临床耐药将越来越多地是脱靶耐药机制的结果，而脱靶耐药机制目前还知之甚少。这项工作的目的是确定和验证CML脱靶耐药的候选分子介质。在涉及从具有BCR-ABL非依赖性疾病的临床特征和持续MAPK和JAK/STAT信号传导（尽管BCR-ABL抑制）的CML患者获得的原始样本分析的初步数据中，我们已经确定了与EVI-1过表达相关的活化NRAS突变的存在。因此，我们假设活化的NRAS和EVI-1过表达可协同赋予对BCR-ABL TKI治疗的脱靶耐药。在目标1中，我们将使用BCR-ABL表达细胞系和小鼠模型来评估这些病变单独和组合赋予BCR-ABL TKI耐药性的能力。在目标2中，我们将评估这些突变的引入顺序对分化和进展为原始细胞危象表型的影响。最后在 目的3我们将评估这些病变对关键信号通路状态的影响。它 预计这项工作将提供有价值的见解的性质“癌基因成瘾”，现象的精致依赖于活动的一个特定的致癌病变。此外，我们希望能够确定可改善CML和其他与酪氨酸激酶病理激活相关的恶性肿瘤患者治疗结局的连续治疗靶点。 公共卫生相关性：慢性骨髓性白血病（CML）是一种潜在的致命性白色血细胞癌症。虽然已经开发出有效的靶向治疗方法，但耐药疾病的发生仍然是一部分患者的重大问题。我们的研究旨在确定和验证负责这种耐药性的分子机制，最终目标是确定新的治疗靶点。我们坚信，我们对CML靶向治疗耐药的分子机制的了解将适用于靶向治疗治疗的新兴癌症，并将为癌症生物学提供有价值的见解。

DESCRIPTION (provided by applicant): Chronic myeloid leukemia (CML) is characterized by hyperproliferation of myeloid progenitors that retain the capacity for differentiation. The natural history of CML involves progression to a more aggressive disease blast crisis phase, where terminal differentiation is impaired, and the disease exhibits features of acute leukemia. Much like many of the other known myeloproliferative disorders, CML is associated with an activated tyrosine kinase. In the case of CML, the fusion protein, BCR-ABL, which is produced following a reciprocal chromosomal translocation event between chromosomes 9 and 22 is causative of the disease. Current treatment for CML involves the use of tyrosine kinase inhibitors (TKI), which have been shown to result in a deep clinical remission in the majority of cases. However, the emergence of resistance-conferring mutations preventing TKI binding in the ATP pocket is frequently responsible for disease relapse. Second and third generation TKIs have been developed which collectively retain activity against all resistance-conferring mutations. With improved control of this "on-target" resistance mechanism, clinical resistance in the future will increasingly be a consequence of off-target resistance mechanisms, which are presently poorly understood. The objective of this work is to identify and validate candidate molecular mediators of off-target resistance in CML. In preliminary data involving analysis of primary samples obtained from CML patients with clinical features of BCR-ABL-independent disease and persistent MAPK and JAK/STAT signaling despite BCR-ABL inhibition, we have identified the presence of activating NRAS mutations in conjunction with EVI-1 overexpression. We therefore hypothesize that activated NRAS and EVI-1 overexpression can cooperatively confer off-target resistance to BCR-ABL TKI treatment. In Aim 1 we will use BCR-ABL-expressing cell line and murine models to assess the ability of these lesions alone and in combination to confer resistance to BCR-ABL TKIs. In Aim 2 we will assess the impact of the sequence of introduction of these mutations on differentiation and progression to a blast crisis like phenotype. Finally, in Aim 3 we will assess the impact of these lesions upon the status of critical signaling pathways. It is anticipated that this work will provide valuable insights into the nature of "oncogene addiction", the phenomenon of exquisite reliance upon the activity of a particular oncogenic lesion. Additionally, it is hoped that adjunctive therapeutic targets will be identified that may improve treatment outcomes for patients with CML and other malignancies associated with pathologic activation of tyrosine kinases. PUBLIC HEALTH RELEVANCE: Chronic Myeloid Leukemia, or CML, is a potentially fatal cancer of the white blood cells. Although effective targeted treatments have been developed, the occurrence of drug-resistant disease remains a significant problem for a proportion of patients. Our research aims to identify and validate molecular mechanisms responsible for this resistance to treatment, with the eventual goal of identifying new therapeutic targets. We strongly believe that what we learn about molecular mechanisms of resistance to targeted therapies in CML will be applicable to the burgeoning number of cancers treated with targeted therapies, and will provide valuable insights into cancer biology.