The Role of Oncogenic Ras in Leukemogenesis and Response to Targeted Therapies

描述（由申请人提供）：了解白血病生长的分子和生化基础对于开发靶向治疗至关重要。然而，除了甲磺酸伊马替尼之外，在实现开发有效和安全的白血病特异性分子抑制剂的目标方面取得了有限的进展。信号开关分子p21 ras（Ras）家族在骨髓恶性肿瘤中失调，包括急性骨髓性白血病（AML）、骨髓增生异常综合征（MDS）和骨髓增生性疾病（MPD）。对人类白血病样本的研究表明，NRAS和KRAS 2点突变、BCR-ABL融合、PTPN 11突变、FLT 3内部串联重复和NF 1失活都使Ras信号转导失调。我们的实验室已经产生了小鼠品系，这些小鼠由于内源性基因座的致癌KrasG 12 D的条件性表达或Nf 1肿瘤抑制基因的失活而发生MPD。这两种菌株都不会自发地发展AML，这表明合作突变对于从MPD进展到AML是必要的。我的长期职业目标是增加我们目前对恶性生长的分子和生化机制的理解，并利用这些见解开发更有效，毒性更小的治疗方法。骨髓性白血病为解决这些问题提供了一个易于处理的实验系统。此外，AML、MDS和大多数类型的MPD迫切需要新的治疗方法。我已经产生了从其在造血细胞中的内源性位点表达致癌NrasG 12 D的小鼠，并且已经表明这导致了独特的MPD。我还利用逆转录病毒插入诱变（RIM）作为一种通用策略，引入突变，与致癌Nras和Kras在白血病的发生。K 08申请的总体目标是利用这些人类骨髓恶性肿瘤的精确模型，通过三个特定目标解决生物学和临床前问题。这些目标是：1）鉴定和表征在髓系白血病发生中与过度活跃的Ras协同作用的基因：2）表征NrasG 12 D表达如何改变Ras调节的信号网络和干扰原代造血细胞的生长，并研究Nras和Kras的致癌异构体在白血病发生中的功能差异; 3）研究抑制MEK对白血病生长的影响，并鉴定体内调节对靶向抑制剂的敏感性和抗性的基因。 急性髓性白血病发生在各种临床环境中，治疗很大程度上不令人满意。该项目的目标是使用准确模拟人类疾病的小鼠品系来识别对白血病发展重要的基因，并测试更有效地靶向和根除肿瘤细胞的新疗法。

DESCRIPTION (provided by applicant): Understanding the molecular and biochemical basis of leukemic growth is essential for developing targeted therapeutics. However, with the notable exception of imatinib mesylate, limited progress has been made toward achieving the goal of developing effective and safe inhibitors of leukemia-specific molecules. The p21ras (Ras) family of signal switch molecules is deregulated in myeloid malignancies including acute myeloid leukemia (AML), myelodysplastic syndrome (MDS), and myeloproliferative disorders (MPD). Studies of human leukemia samples have shown that NRAS and KRAS2 point mutations, the BCR-ABL fusion, PTPN11 mutations, FLT3 internal tandem duplications, and NF1 inactivation all deregulate Ras signaling. Our laboratory has generated strains of mice that develop MPD due to conditional expression of an oncogenic KrasG12D from the endogenous locus or inactivation of the Nf1 tumor suppressor gene. Neither strain spontaneously develops AML, suggesting that cooperating mutations are necessary for the progression from MPD to AML. My long-term career goal is to increase our current understanding of the molecular and biochemical mechanisms that underlie malignant growth, and to use these insights to develop more effective and less toxic therapies. Myeloid leukemia offers a tractable experimental system for addressing these questions. Moreover, new treatments are urgently needed for AML, MDS, and most types of MPD. I have generated mice that express oncogenic NrasG12D from its endogenous locus in hematopoietic cells, and have shown that this results in a distinctive MPD. I have also utilized retroviral insertional mutagenesis (RIM) as a general strategy for introducing mutations that cooperate with oncogenic Nras and Kras in leukemogenesis. The overall goal of this K08 application is to exploit these accurate models of human myeloid malignancies to address biologic and preclinical questions through three specific aims. These aims are: 1) To identify and characterize genes that cooperate with hyperactive Ras in myeloid leukemogenesis; 2) To characterize how NrasG12D expression alters Ras-regulated signaling networks and perturbs the growth of primary hematopoietic cells, and to investigate functional difference between oncogenic isoforms of Nras and Kras in leukemogenesis; 3) To investigate the effect of inhibiting MEK on leukemic growth and to identify genes that modulate sensitivity and resistance to targeted inhibitors in vivo. Acute myeloid leukemia arises in a variety of clinical settings and the treatment is largely unsatisfactory. The goal of this project is to use mouse strains that accurately model human disease to identify genes important for leukemia development and to test novel therapies that target and eradicate tumor cells more effectively.