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，在开发有效且安全的白血病特异性分子抑制剂方面进展有限。p21ras （Ras）信号开关分子家族在髓系恶性肿瘤中失调，包括急性髓系白血病（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KRAS2点突变、BCR-ABL融合、PTPN11突变、FLT3内部串联复制和NF1失活都会解除Ras信号的调控。我们的实验室已经培育出了由于内源性致癌KrasG12D的条件表达或Nf1肿瘤抑制基因失活而发生MPD的小鼠品系。这两种菌株都不会自发发展为AML，这表明从MPD到AML的进展需要协同突变。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。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MPD类型迫切需要新的治疗方法。我已经培养了从造血细胞的内源性位点表达致癌NrasG12D的小鼠，并表明这会导致一种独特的MPD。我还利用逆转录病毒插入突变（RIM）作为引入突变的一般策略，这些突变在白血病发生中与致癌的Nras和Kras合作。K08应用的总体目标是利用这些精确的人类髓系恶性肿瘤模型，通过三个具体目标来解决生物学和临床前问题。这些目标是：1)鉴定和表征在髓性白血病发生中与过度活跃的Ras合作的基因；2)表征NrasG12D表达如何改变ras调控的信号网络并干扰原代造血细胞的生长，探讨Nras和Kras致癌亚型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，并在体内发现调节靶向抑制剂敏感性和耐药性的基因。

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.