Oncogenic Kit receptor signaling in vivo

描述（由申请方提供）：本提案的总体目标有两个，1）继续研究体内致癌Kit受体信号传导，重点是造血，2）开发伊马替尼耐药GIST的小鼠模型。在鼠W基因座编码的Kit受体在造血、配子发生、黑素生成和肠道运动中起作用。正常Kit受体介导的功能包括细胞增殖、细胞存活、细胞粘附、细胞迁移、分泌应答和分化。在人类肿瘤形成中，Kit的致癌激活在胃肠道间质瘤（GIST）、肥大细胞增多症/肥大细胞白血病、急性髓性白血病、黑色素瘤的一个子集和生殖细胞肿瘤的一个子集中起作用。Kit受体功能由激酶活化、受体自磷酸化和与各种信号分子和信号级联的缔合介导。受体酪氨酸激酶如Kit如何在胚胎发育和出生后动物中介导不同细胞类型的不同细胞反应？不同类型的细胞发生致癌转化产生癌症的条件是什么？我们已经在小鼠中产生了在Kit受体基因中含有敲入点突变的小鼠，其阻断Kit介导的PI 3-激酶活化和信号传导或Src家族激酶SFK活化和信号传导。这些小鼠在配子发生和造血方面具有明显不同的表型。我们还研究了PI 3-激酶和Src家族激酶信号在Kit介导的骨髓源性肥大细胞（BMMC）增殖、凋亡抑制、细胞粘附、趋化和分泌反应中的作用。尽管Kit介导的PI 3-激酶信号传导对于细胞增殖、细胞存活、细胞粘附、趋化性和分泌应答是关键的，但Kit介导的SFK信号传导主要具有负调节作用。此外，基因表达谱表明阻断SFK信号传导减少了KitL诱导的BMMC中TH2-细胞因子基因的表达。为了研究致癌Kit活化Kit在肿瘤发生中的作用，我们已经产生了携带胞膜结构域敲入Kit突变的小鼠并复制了人家族性GIST综合征（Sommer等人，2003年）。部分我们的研究将试图调查PI 3-激酶，SFK和Ras信号在Kit介导的肿瘤发生中的作用。此外，我们将产生和表征携带致癌伊马替尼耐药Kit等位基因的小鼠。

DESCRIPTION (provided by applicant): The overall objective of this proposal is twofold, 1) to continue our investigations of oncogenic Kit receptor signaling in vivo with emphasis on hematopoiesis and 2) to develop mouse models for imatinib resistant GIST. The Kit receptor encoded at the murine W locus functions in hematopoiesis, gametogenesis, melanogenesis and gut motility. Normal Kit receptor mediated functions include cell proliferation, cell survival, cell adhesion, cell migration, secretory responses and differentiation. In human neoplasia oncogenic activation of Kit has roles in gastrointestinal stromal tumors (GIST), mastocytosis/mast cell leukemia, acute myelogenous leukemia, a subset of melanomas and a subset of germ cell tumors. Kit receptor functions are mediated by kinase activation, receptor autophosphorylation and association with various signaling molecules and signaling cascades. How do receptor tyrosine kinases such as Kit mediate distinct cellular responses in different cell types during embryonic development and in the postnatal animal? And what are the requirements for oncogenic transformation in different cell types to produce cancer. We have produced mice containing knock-in point mutations in the Kit receptor gene in mice which block Kit mediated PI 3-kinase activation and signaling or Src family kinase, SFK, activation and signaling. These mice have distinctly different phenotypes in gametogenesis and hematopoiesis. We have also investigated the role of PI 3-kinase and Src family kinase signaling in Kit mediated cell proliferation, suppression of apoptosis, cell adhesion, chemotaxis and secretory responses in vitro in bone marrow derived mast cells (BMMC). Whereas Kit mediated PI 3-kinase signaling is critical for cell proliferation, cell survival, cell adhesion, chemotaxis and secretory responses, Kit mediated SFK signaling has mostly a negative regulatory role. Furthermore, gene expression profiling indicates that blocking SFK signaling reduces KitL induced expression of TH2-cytokine genes in BMMC. To investigate the role of oncogenic Kit activation Kit in tumorigenesis we have produced mice carrying a juxtamembrane domain knock-in Kit mutation and reproduced human familial GIST syndrome (Sommer et al., 2003). In part our proposed studies will attempt to investigate the role of PI 3-kinase, SFK and Ras signaling in Kit-mediated tumorigenesis. Furthermore we will produce and characterize mice carrying oncogenic imatinib resistant Kit alleles.