Role of Vav and Rac in KIT oncogenesis

Vav 和 Rac 在 KIT 肿瘤发生中的作用

• 批准号: 8197832
• 负责人: Reuben Kapur
• 金额: $ 38.12万
• 依托单位: INDIANA UNIV-PURDUE UNIV AT INDIANAPOLIS
• 依托单位国家: 美国
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-01-19 至 2013-11-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8197832
• 关键词: AML1-ETO fusion protein; Acute Myelocytic Leukemia; Adult Acute Myeloblastic Leukemia; Binding; Cells; Childhood Acute Myeloid Leukemia; Chromosomal translocation; Chromosome abnormality; Chronic Myeloid Leukemia; Chronic Myelomonocytic Leukemia; Clinical; Core-Binding Factor; Dimerization; Disease; Etiology; FLT3 gene; Family; Gastrointestinal Stromal Tumors; Gene Mutation; Genetic; Germ Cells; Germ cell tumor; Gleevec; Goals; Growth; Guanine; Guanine Nucleotide Exchange Factors; Guanosine Triphosphate Phosphohydrolases; Hematological Disease; Hematopoietic; Hematopoietic stem cells; Imatinib; Imatinib mesylate; In Vitro; Interstitial Cell of Cajal; KIT gene; Ligand Binding; Ligands; Link; Lobe; Lymphoma; MYH11 gene; Mediating; Membrane; Molecular Conformation; Molecular Target; Mus; Mutate; Mutation; Myeloproliferative disease; Nature; PDGFRB gene; Pathway interactions; Pharmaceutical Preparations; Phosphorylation; Phosphotransferases; Physiological; Play; Protein Tyrosine Kinase; RUNX1 gene; Role; Signal Pathway; Signal Transduction; Signaling Molecule; Stem cells; Systemic Mastocytosis; Testing; Tissues; Transcription factor genes; Transgenes; Tyrosine; Tyrosine Kinase Domain; Tyrosine Kinase Inhibitor; Ursidae Family; base; bcr-abl Fusion Proteins; disease phenotype; effective therapy; fusion gene; in vivo; indexing; insight; leukemia; leukemogenesis; mast cell; melanocyte; mutant; new therapeutic target; outcome forecast; receptor; rho; rho GTP-Binding Proteins; stem; t(8; 21)(q22; q22); transcription factor; tumorigenesis

ABSTRACT KIT is a unique receptor with important functional roles in melanocytes, germ cells, interstitial cells of Cajal, mast cells, and hematopoietic stem cells. Consistent with the importance of KIT in these defined tissues, activating mutations of KIT have been described in germ cell tumors, gastrointestinal stromal tumors (GISTs), sinonasal lymphomas, acute myeloid leukemia (AML), and systemic mastocytosis (SM). A significant proportion of these diseases commonly bear the KIT activation loop mutation KITD816V. Activation loop mutations of KIT have also been observed in core binding factor-acute myeloid leukemia (CBF-AML), leukemias that bear either the t(8;21) or inv(16) cytogenetic abnormality, generating the fusion genes AML1- ETO or CBF¿-MYH11, respectively. Studies examining both adult and pediatric AML have indicated that the presence of the KITD816V mutation in CBF-AML carrying t(8;21) worsens the prognosis based on several clinical indices. Although KIT mutations within the juxtamembrane region that are commonly found in GISTs are sensitive to inhibition by the tyrosine kinase inhibitor, imatinib mesylate (Gleevec); KIT mutations within the carboxy-terminal lobe of the tyrosine kinase domain, such as KITD816V, stabilizes the KIT activation loop conformation in its active form, which precludes sufficient imatinib binding for tyrosine kinase inhibition. Therefore, in contrast to successful use of Gleevec to treat GISTs, Gleevec is ineffective for the treatment of the hematologic diseases harboring the KIT activation loop mutants (i.e. KITD816V), including SM and CBF- AML. Importantly, nature of the receptor proximal and/or downstream signals by which activation loop mutations in KIT (KITD816V) induce transformation in primary hematopoietic cells are poorly defined. We have evidence to demonstrate that KITD816V (KITD814V in mice) induced transformation in primary hematopoietic stem and progenitor cells results in constitutive activation of GEF Vav/Rho GTPase Rac pathway and that genetic disruption of hematopoietic specific Vav1 and/or Rac2 in mice abrogates ligand independent growth via KITD814V, leading us to hypothesize that signals involved in KITD814V induced transformation may in part be mediated via the hyperactivation of this pathway. Furthermore, we have evidence demonstrating that mutating the tyrosine residues within the intracellular domain of KITD814V results in complete loss of KITD814V induced ligand independent growth, leading us to hypothesize that the intracellular tyrosines within the juxtamembrane and the kinase insert region of KITD814V are likely to contribute to KITD814V induced transformation. Based on these findings, the central hypothesis of this application is that hyperactivation of the Vav/Rac pathway contributes to the etiology of diseases associated with systemic mastocytosis, AML as well as other diseases involving the KITD814V mutation. Our proposed studies will provide mechanistic insight into the physiologic significance of the Vav/Rac pathway as well as the involvement of the juxtamembrane and the kinase insert sequences in regulating KITD814V induced transformation for which currently no drugs exist.

抽象的 KIT 是一种独特的受体，在黑素细胞、生殖细胞、Cajal 间质细胞、 肥大细胞和造血干细胞。与 KIT 在这些特定组织中的重要性一致， KIT 的激活突变已在生殖细胞肿瘤、胃肠道间质瘤 (GIST)、 鼻窦淋巴瘤、急性髓系白血病 (AML) 和系统性肥大细胞增多症 (SM)。一个重要的 这些疾病中有一部分通常带有 KIT 激活环突变 KITD816V。激活循环 在核心结合因子-急性髓系白血病 (CBF-AML) 中也观察到了 KIT 突变， 具有 t(8;21) 或 inv(16) 细胞遗传学异常的白血病，产生融合基因 AML1- 分别为 ETO 或 CBF¿-MYH11。对成人和儿童 AML 的研究表明， 携带 t(8;21) 的 CBF-AML 中 KITD816V 突变的存在会使预后恶化 临床指标。尽管 GIST 中常见的近膜区域内的 KIT 突变 对酪氨酸激酶抑制剂甲磺酸伊马替尼（格列卫）的抑制敏感； KIT 突变 酪氨酸激酶结构域的羧基末端叶，例如 KITD816V，可稳定 KIT 激活环 其活性形式的构象，这妨碍了伊马替尼充分结合以抑制酪氨酸激酶。 因此，与成功使用格列卫治疗 GIST 相比，格列卫对于治疗 GIST 无效。 携带 KIT 激活环突变体（即 KITD816V）的血液疾病，包括 SM 和 CBF- 反洗钱。重要的是，激活环路所通过的受体近端和/或下游信号的性质 KIT (KITD816V) 突变诱导原代造血细胞转化尚不清楚。我们有 有证据表明 KITD816V（小鼠中的 KITD814V）诱导初级造血细胞转化 干细胞和祖细胞导致 GEF Vav/Rho GTPase Rac 通路的组成型激活 小鼠造血特异性 Vav1 和/或 Rac2 的基因破坏通过消除配体独立生长 KITD814V，使我们推测参与 KITD814V 诱导转化的信号可能部分是 通过该途径的过度激活介导。此外，我们有证据表明突变 KITD814V 胞内结构域内的酪氨酸残基导致 KITD814V 完全丢失 诱导配体独立生长，使我们假设细胞内酪氨酸 KITD814V 的近膜和激酶插入区域可能有助于 KITD814V 诱导 转变。基于这些发现，本申请的中心假设是过度激活 Vav/Rac 通路有助于与系统性肥大细胞增多症、AML 相关疾病的病因学 与涉及 KITD814V 突变的其他疾病一样。我们提出的研究将提供机制上的见解 Vav/Rac 通路的生理意义以及近膜和 调节 KITD814V 诱导转化的激酶插入序列目前尚无药物。