Biology of Imatinib-Resistant Mutants of BCR-ABL

描述(由申请人提供)： 大多数早期慢性粒细胞白血病(CML)患者在接受伊马替尼治疗后都取得了持久的疗效，伊马替尼是BCR-ABL的特异性抑制剂，BCR-ABL是导致CML的酪氨酸激酶。然而，复发在晚期疾病患者中很常见，通常是bcr-abl激酶域(KD)点突变的结果。出乎意料的是，在伊马替尼-初治患者中也检测到了KD突变克隆，这与突变株在没有伊马替尼的情况下比野生型bcr-abl具有生长优势一致。此外，无论bcr-abl对伊马替尼的敏感性如何，bcr-abl的ATP结合环的突变都会导致不良的预后。这些观察表明，KD突变除了在赋予伊马替尼耐药性方面的作用外，还可能改变CML的生物学特性。与此一致，我们有初步数据显示，一些突变体与野生型bcr-abl之间的转化效力存在差异。虽然在某些情况下，这些差异可能与激酶活性改变有关，但我们有数据表明，KD突变也会改变信号转导。我们建议综合分析从CML患者中分离出来的一组bcr-abl突变。我们将确定激酶活性、信号通路激活(使用一种新的极其敏感的磷酸蛋白质组学方法)和基因表达谱的动力学参数，并将这些数据与生物检测中的转化潜力相关联。我们将整合这些信息，以确定或多或少具有侵略性的表型的候选介体，然后在适当的生物系统中进行验证。这项研究有两个全球目标。首先，我们将阐明KD突变在CML疾病进展中的作用。鉴于慢性粒细胞白血病从慢性期进展到加速期和急变期的机制尚不清楚，这将增加对慢性粒细胞白血病生物学的了解。其次，我们将在一个严格控制的实验系统中确定显著影响转化效率的介体。通过这种方法，我们的目标是确定可用于治疗慢性粒细胞白血病的新的治疗靶点，并进一步用于目前尚无有效治疗方法的其他类型的癌症。 一些慢性粒细胞白血病患者在接受伊马替尼(Gleevec)治疗时复发，因为他们在一种关键蛋白上发生了突变。有证据表明，其中一些突变也可能导致白血病的进展，并给患者带来非常糟糕的预后。我们将准确地研究突变是如何使白血病更具侵袭性的，目的是识别在调节更具侵袭性的行为中至关重要的蛋白质。然后，这些关键蛋白质可能被用作治疗慢性粒细胞白血病以及其他类型癌症的药物靶点。

DESCRIPTION (provided by applicant): Most patients with early chronic myeloid leukemia (CML) achieve durable responses to treatment with imatinib, a specific inhibitor of BCR-ABL, the tyrosine kinase responsible for CML. However, relapse is frequent in patients with advanced disease and usually is the result of point mutations in the kinase domain (KD) of BCR-ABL. Unexpectedly, KD mutant clones were also detected in imatinib-nave patients, consistent with a growth advantage of mutants over wild type BCR-ABL in the absence of imatinib. Moreover, mutations in the ATP-binding loop of BCR-ABL confer a poor prognosis irrespective of their sensitivity to imatinib. These observations suggest that KD mutations may alter the biology of the CML in addition to and independent of their role in conferring imatinib resistance. Consistent with this, we have preliminary data that show differences in transformation potency between some mutants and wild type BCR-ABL. While these differences may be related to altered kinase activity in some cases, we have data showing that KD mutations also alter signal transduction. We propose to comprehensively analyze a panel of BCR-ABL mutants isolated from CML patients. We will determine kinetic parameters of kinase activity, activation of signaling pathways (using a novel extremely sensitive phosphoproteomics approach) and gene expression profiles, and correlate these data with transformation potency in biological assays. We will integrate this information to identify candidate mediators of a more or less aggressive phenotype that will then be validated in the appropriate biological systems. This study has two global objectives. Firstly, we will clarify role of KD mutations for disease progression of CML. Given that the mechanisms responsible for progression of CML form the chronic phase to accelerated and blastic phase are poorly understood, this will increase the knowledge of CML biology. Secondly, we will identify mediators that significantly affect transformation potency in a tightly controlled experimental system. Using this approach, we aim to identify novel therapeutic targets that could be exploited for the treatment of CML, and further, for other types of cancer for which there are currently no effective therapies available. Some patients with chronic myeloid leukemia relapse on therapy with imatinib (Gleevec), because they develop mutations in a critical protein. There is evidence that some of these mutations may also contribute to leukemia progression and confer a very bad prognosis to patients. We will study precisely how the mutations make the leukemia more aggressive, with the aim of identifying proteins that are critical in mediating the more aggressive behavior. Such crucial proteins may then be exploited as drug targets for the treatment of chronic myeloid leukemia, and further, for other types of cancer.