c-Kit Mutations and Their Role in Tumor Biology

描述（由申请方提供）：肥大细胞瘤（MCT）是最常诊断的犬恶性肿瘤。我们之前已经证明，至少30%的犬MCT在原癌基因c-kit中存在突变，包括编码负调节性质膜结构域的外显子11/12中的串联重复。这些突变导致在不存在配体结合的情况下Kit的组成性磷酸化。还发现Kit的失调发生在许多人类肿瘤中，包括异常表达（小细胞肺癌、泌尿生殖系统癌症）和导致组成性激活的胞质结构域中的突变（肥大细胞病症、胃肠道间质瘤）。最近对各种实验性激酶抑制剂的研究表明，抑制Kit信号传导可能对这些恶性肿瘤患者有显著益处。然而，要使其应用成功，关键是要更清楚地定义c-kit突变在肿瘤性疾病发生和发展中的作用。这一假设的基础是激活突变的c-kit与恶性肥大细胞疾病的发展和进展，通过促进细胞存活和诱导金属蛋白酶基因表达的侵袭和转移。本研究的具体目的是：1）对犬MCT中的c-kit突变进行细致的表征，包括其对MCT生物学行为的影响，并识别与其发展相关的潜在风险因素; 2）通过产生表达各种形式的突变型c-受体的转基因小鼠，研究Kit失调对体内正常细胞群体的影响。kit在高度调节的诱导型启动子下的表达;和3）评估吲哚啉酮激酶抑制剂在体外和Kit突变的小鼠模型中对失调的Kit的作用。集成的详细调查试剂盒失调的小鼠与综合研究的自发模型的c-kit突变的狗将有助于澄清这种突变的生物学和生化后果。此外，将激酶抑制剂纳入这些研究提供了一个独特的机会，以评估潜在的有用性和有效性，这些药物在治疗肿瘤性疾病，其中试剂盒功能障碍是明显的。

DESCRIPTION (provided by applicant): Mast cell tumors (MCTs) are the most frequently diagnosed malignant tumor of the dog. We have previously demonstrated that at least 30% of canine MCTs possess mutations in the proto-oncogene c-kit consisting of tandem duplications in exons 11/12 encoding the negative regulatory juxtamembrane domain. These mutations result in constitutive phosphorylation of Kit in the absence of ligand binding. Dysregulation of Kit has also been found to occur in many human tumors including aberrant expression (small cell lung carcinoma, genitourinary cancers) and mutation in the cytoplasmic domain leading to constitutive activation (mast cell disorders, gastrointestinal stromal tumors). Recent studies with various experimental kinase inhibitors suggest that inhibition of Kit signaling may be of significant benefit to patients with these malignancies. However, for their application to be successful, it is critical that the role of c-kit mutations in the initiation and progression of neoplastic disorders be more clearly defined. The hypothesis underlying this proposal is that activating mutations of c-kit are associated with the development and progression of malignant mast cell disease through the promotion of cell survival and induction of metalloproteinase gene expression linked to invasion and metastasis. The specific aims of this study are: 1) to undertake a meticulous characterization of c-kit mutations in dog MCTs including their impact on the biologic behavior of MCTs, and identification of potential risk factors associated with their development; 2) to study the effect of Kit dysregulation on normal cell populations in vivo through the generation of transgenic mice expressing various forms of mutant c-kit under a highly regulated inducible promoter; and 3) to evaluate the effects of indolinone kinase inhibitors on dysregulated Kit both in vitro and in mouse models of Kit mutation. The integration of detailed investigations of Kit dysregulation in the mouse with comprehensive studies of a spontaneous model of c-kit mutation in the dog will help to clarify the biological and biochemical consequences of such mutations. Moreover, the incorporation of kinase inhibitors into these studies offers a unique opportunity to evaluate the potential usefulness and efficacy of such agents in the treatment of neoplastic diseases in which Kit dysfunction is evident.