Role of Vav and Rac in KIT oncogenesis

Vav 和 Rac 在 KIT 肿瘤发生中的作用

• 批准号: 7759156
• 负责人: Reuben Kapur
• 金额: $ 38.5万
• 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/7759156
• 关键词: Acute Myelocytic Leukemia; Adult; 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; Genes; 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; Ligand Binding; Ligands; Link; Lobe; Lymphoma; 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; public health relevance; receptor; rho; rho GTP-Binding Proteins; stem; t(8; 21)(q22; q22); transcription factor; tumorigenesis

DESCRIPTION (provided by applicant): 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 CBF2-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. PUBLIC HEALTH RELEVANCE: It is now unequivocal that activating mutations of KIT contribute to germ cell tumors, gastrointestinal stromal tumors (GISTs), sinonasal lymphomas, acute myeloid leukemia (AML), and systemic mastocytosis (SM). Our proposed studies will provide mechanistic insight into the signaling pathways that regulate transformation via an activating KIT mutation for which currently no drugs exist. Our results are expected to provide new targets for molecular therapies for the treatment of diseases such as AML and SM.

描述(申请人提供)：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中具有重要的功能作用。与KIT在这些已确定的组织中的重要性一致，KIT的激活突变已在生殖细胞瘤、胃肠道间质瘤(GIST)、鼻腔鼻淋巴瘤、急性髓系白血病(AML)和系统性肥大细胞增多症(SM)中被描述。这些疾病中有相当大一部分通常携带KIT激活环突变KITD816V。在核心结合因子-急性髓系白血病(CBF-AML)中也发现了KIT激活环突变，这些白血病携带t(8；21)或inv(16)细胞遗传学异常，分别产生融合基因AML1-ETO或CBF2-MYH11。对成人和儿童AML的研究表明，根据一些临床指标，携带t(8；21)的CBF-AML中存在KITD816V突变会恶化预后。虽然在GIST中常见的KIT膜旁区域的KIT突变对酪氨酸激酶抑制剂甲磺酸伊马替尼(Gleevec)的抑制很敏感；但在酪氨酸激酶结构域的羧基末端叶内的KIT突变，如KITD816V，使KIT激活环构象稳定在其活性形式，从而排除了足够的伊马替尼结合用于酪氨酸激酶抑制。因此，与成功使用格列卫治疗GIST相比，格列卫对含有KIT激活环突变的血液病(即KITD816V)无效，包括SM和CBF-AML。重要的是，KIT(KITD816V)中激活环突变导致原代造血细胞转化的受体近端和/或下游信号的性质尚不清楚。我们有证据表明，KITD816V(KITD814V在小鼠体内)诱导的原代造血干/祖细胞转化导致了全球环境基金Vav/Rho GTPase Rac途径的结构性激活，而小鼠造血特异性Vav1和/或rac2的基因破坏导致了KITD814V诱导的配体非依赖性生长，从而使我们假设KITD814V诱导转化中的信号可能部分是通过该途径的过度激活来介导的。此外，我们有证据表明，突变KITD814V胞内区的酪氨酸残基会导致KITD814V诱导的非配体非依赖性生长完全丧失，这使我们假设KITD814V胞内的酪氨酸和KITD814V的激酶插入区域可能参与了KITD814V诱导的转化。基于这些发现，这一应用的中心假设是Vav/Rac途径的过度激活与系统性肥大细胞增多症、AML以及其他涉及KITD814V突变的疾病的病因学有关。我们提出的研究将从机制上深入了解Vav/Rac途径的生理意义，以及膜旁和激酶插入序列参与调节KITD814V诱导的转化，目前尚无药物。公共卫生相关性：现在明确的是，KIT的激活突变会导致生殖细胞肿瘤、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)。我们提议的研究将提供对通过激活试剂盒突变调节转化的信号通路的机械性洞察，目前还没有针对该突变的药物。我们的研究结果有望为AML和SM等疾病的分子治疗提供新的靶点。