c-Kit Mutations and Their Role in Tumor Biology

描述（由申请人提供）：肥大细胞瘤（mct）是犬类最常见的恶性肿瘤。我们之前已经证明，至少30%的犬mct具有原癌基因c-kit突变，包括编码负调控近膜域的外显子11/12的串联重复。这些突变在没有配体结合的情况下导致Kit的组成性磷酸化。Kit的失调也被发现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）和细胞质域突变导致组成性激活（肥大细胞疾病、胃肠道间质肿瘤）。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的益处。然而，为了使其应用成功，c-kit突变在肿瘤疾病的发生和发展中的作用得到更明确的定义是至关重要的。这一提议的假设是，c-kit的激活突变通过促进细胞存活和诱导与侵袭和转移相关的金属蛋白酶基因表达，与恶性肥大细胞病的发生和进展相关。本研究的具体目的是：1)对犬mct中c-kit突变进行细致的表征，包括其对mct生物学行为的影响，以及识别与mct发展相关的潜在危险因素；2)通过在高度调控的诱导启动子下产生表达多种形式的c-kit突变体的转基因小鼠，研究Kit失调对体内正常细胞群的影响；3)在体外和Kit突变小鼠模型中评价吲哚啉酮激酶抑制剂对Kit失调的影响。将小鼠Kit失调的详细研究与犬c-kit自发突变模型的综合研究相结合，将有助于阐明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来评估这些药物在治疗Kit功能障碍明显的肿瘤疾病中的潜在有用性和疗效。

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.