Transcription Factor Regulation by the BCR/ABL Oncogene

描述（申请人提供）：BCR/ABL癌蛋白，费城染色体（Ph 1）易位的白血病特异性基因产物，通过其失调的酪氨酸激酶活性诱导和维持白血病表型;这种活性对于募集和激活多个途径是必需的，所述多个途径阻断导致生长因子非依赖性增殖的信号，抑制凋亡，以及髓样前体细胞的分化改变。虽然对BCR/ABL细胞质下游效应物的激活机制有了一定的了解，但对导致转录因子调节的途径知之甚少。在本申请中，我们将研究导致转录因子c-Myb表达变化的BCR/ABL依赖性途径，并通过以下方式评估c-Myb和c-Myb靶标在表达BCR/ABL的造血祖细胞的增殖、存活和分化调节中的作用：1）研究F-box蛋白FBXL-3在p210 BCR/ABL表达细胞中调节c-Myb水平的作用，方法是评估：a）FBXL-3依赖性降解c-Myb的机制; B）FBXL-3在正常和表达p210 BCR/ABL的造血祖细胞中的作用。2)通过评估：a）c-Myb靶标c-Kit在表达p210 BCR/ABL的c-Myb和c-Myb原始造血祖细胞的转化和白血病发生中的作用和需求; B）c-Myb靶标c-Kit和Bcl-2在表达p210 BCR/ABL的c-Myb原始造血祖细胞的转化和白血病发生中的协同作用，研究p210 BCR/ABL依赖性白血病发生中c-Myb的需求。c）c-Myb靶标Jak 2单独和与c-Kit协同作用在表达p210 BCR/ABL的造血祖细胞的转化和白血病发生中的作用。3)通过评估：a）来自双转基因p190 BCR/ABL/c-Myb小鼠的B细胞祖细胞亚群的转化和白血病发生; b）在NOD-SCID小鼠中c-Myb沉默的p190 BCR/ABL表达Z-181人B细胞白血病细胞的白血病发生; c）通过微阵列杂交鉴定的c-Myb靶标在p190 BCR/ABL依赖性白血病发生中的作用。公共卫生相关性：白血病是血液祖细胞的恶性肿瘤，可能由特定的染色体异常引起。在慢性骨髓性白血病和与费城染色体相关的急性白血病中，BCR/ABL癌基因通过激活核蛋白如c-Myb促进造血细胞的转化。了解c-Myb在白血病发生中的作用对于开发基于抑制其表达/活性的疗法是重要的。

DESCRIPTION (provided by applicant): The BCR/ABL oncoproteins, the leukemia-specific gene products of the Philadelphia chromosome (Ph1) translocation, induce and maintain the leukemic phenotype through their deregulated tyrosine kinase activity; such activity is essential for recruitment and activation of multiple pathways that transduce signals leading to growth factor-independent proliferation, inhibition of apoptosis, and altered differentiation of myeloid precursor cells. While the mechanisms of activation of the cytoplasmic downstream effectors of BCR/ABL are understood in some detail, much less is known on the pathways leading to transcription factor regulation. In this application we will investigate the BCR/ABL-dependent pathways leading to changes in the expression of the transcription factor c-Myb and assess the role of c-Myb and c-Myb targets in the regulation of proliferation, survival, and differentiation of BCR/ABL-expressing hematopoietic progenitors by: 1) Investigating the role of the F-box protein FBXL-3 in regulating c-Myb levels in p210 BCR/ABL-expressing cells by assessing: a) the mechanisms of FBXL-3-dependent degradation of c-Myb; b) the effects of FBXL-3 in normal and p210BCR/ABL-expressing hematopoietic progenitors. 2) Investigating the requirement of c-Myb in p210BCR/ABL-dependent leukemogenesis by assessing: a) role and requirement of the c-Myb target c-Kit in transformation and leukemogenesis of p210BCR/ABL-expressing c-Myb and c-Myb primitive hematopoietic progenitors; b) cooperation of c-Myb targets c-Kit and Bcl-2 in transformation and leukemogenesis of p210BCR/ABL -expressing c-Myb primitive hematopoietic progenitors. c) effects of the c-Myb target Jak2 , individually and in cooperation with c-Kit, in transformation and leukemogenesis of p210BCR/ABL-expressing hematopoietic progenitors. 3) Investigate the requirement of c-Myb in p190BCR/ABL-dependent leukemogenesis by assessing: a) transformation and leukemogenesis of B-cell progenitor subsets from double transgenic p190BCR/ABL/c-Myb mice; b) leukemogenesis of c-Myb-silenced p190BCR/ABL-expressing Z-181 human B-cell leukemia cells in NOD-SCID mice; c) the role of c-Myb targets identified by microarray hybridization in p190BCR/ABL-dependent leukemogenesis. PUBLIC HEALTH RELEVANCE: Leukemias are malignancies of blood cell progenitors which may be caused by specific chromosomal abnormalities. In chronic myelogenous leukemia and in acute leukemias associated with the Philadelphia chromosome, the BCR/ABL oncogene promotes transformation of hematopoietic cells by activating nuclear proteins such as c-Myb. Understanding the role of c-Myb in leukemogenesis is important for developing therapies based on inhibition of its expression/activity.