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的进展有限。P21ras(RAS)家族信号开关分子在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)在内的髓系恶性肿瘤中被解除调控。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失活都使RAS信号失控。我们的实验室已经产生了由于内源性基因座致癌KrasG12D的有条件表达或NF1肿瘤抑制基因失活而患上MPD的小鼠品系。两种菌株都不会自发地发展为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背后的分子和生化机制的理解，并利用这些见解开发更有效和毒性更低的疗法。髓系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。我已经培育出了从造血细胞中的内源性位点表达致癌NrasG12D的小鼠，并证明了这会导致一种独特的MPD。我还利用逆转录病毒插入突变(RIM)作为一种一般策略，引入在白血病发生中与致癌NRAS和Kras协同的突变。这个K08应用程序的总体目标是利用这些人类髓系恶性肿瘤的准确模型，通过三个具体目标来解决生物学和临床前问题。这些目的是：1)鉴定和鉴定髓系白血病发生中与高活性RAS协同作用的基因；2)鉴定NrasG12D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，并在体内鉴定调节靶向抑制剂敏感性和耐药性的基因。 急性髓系白血病的临床表现多种多样，治疗效果很不理想。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至关重要的基因，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.