Defining a Role for c-KIT in Melanoma

描述(申请人提供)：尽管在黑色素瘤研究方面取得了重大进展，从预防、检测、诊断到治疗，但黑色素瘤的发病率继续急剧上升，晚期疾病患者的5年存活率保持在不到15%的水平。随着我们进入靶向治疗时代，在基础上对肿瘤进行亚组是至关重要的 他们驱动致癌突变，以便可以开发适当的治疗剂。大多数黑色素瘤存在BRAF的激活突变，BRAF促进丝裂原活化蛋白激酶(MAPK)信号通路的激活。然而，有一些不同的黑色素瘤亚型，包括慢性日光损伤(CSD)、肢端和粘膜，很少含有BRAF突变。C-kit(如K642E和L576P)的扩增和/或功能获得改变已被认为是这些黑色素瘤亚型中最常见的致癌事件。这导致了对具有异常c-kit的分层黑色素瘤患者使用几种c-kit抑制剂的临床评估。尽管在接受c-kit抑制剂治疗的患者中，有四分之一的患者有初步的应答率，但即使随着剂量的增加，最终也会产生耐药性。考虑到在这些肿瘤中经常发现高水平的基因组改变，以及当前一代c-kit抑制剂缺乏特异性，目前尚不清楚c-kit是否是这些黑色素瘤亚群的可行治疗靶点。随着c-kit定向疗法的发展，需要开发出忠实地模拟人类疾病的临床前模型。为此，我们开发了一种新的黑色素瘤小鼠模型，使我们能够解决c-kit在促进黑色素瘤的启动、维持和体内进展中的作用。在Ink4a/Arf缺失的情况下，突变c-kit(L576P)在小鼠体内黑素细胞中的表达导致四分之一的小鼠发生黑色素瘤，平均潜伏期为120天。拟议研究的目的是利用这种灵活的黑色素瘤小鼠模型来评估c-kit在肿瘤的启动、维持和发展中的作用，并确定协同的遗传事件，以促进针对其肿瘤具有c-kit改变的患者的治疗干预策略的发展。我们假设激活的c-kit可以启动黑色素瘤，并且在体内，通过增加协同遗传事件(例如，HIF1a或MITF的共表达)，肿瘤的生长和外显性将被增强。我们将通过(目的1)评估在黑色素瘤中经常观察到的额外的c-kit突变体和潜在的协同基因在体内启动肿瘤的能力；(目的2)评估c-kit在通过药理学和遗传学手段维持肿瘤中的作用；以及(目的3)研究c-kit在促进黑色素瘤体内转移中的作用，以检验这一假说。。

DESCRIPTION (provided by applicant): Despite significant progress in melanoma research, from prevention, detection, and diagnosis to treatment, the incidence of melanoma continues to rise dramatically and 5-year survival for those with advanced disease remains static at less than 15 percent. As we enter the era of targeted therapy, it is critical to subgroup tumors on the basis of their driving oncogenic mutations so that appropriate therapeutic agents can be developed. The majority of melanomas possess activating mutations in BRAF, which promotes activation of the mitogen- activated protein kinase (MAPK) signaling pathway. However, there are distinct subtypes of melanoma including chronic sun damaged (CSD), acral, and mucosal that rarely harbor BRAF mutations. Amplification and/or gain-of-function alterations in c-KIT (e.g., K642E and L576P) have been identified as the most common oncogenic event in these melanoma subtypes. This has led to clinical evaluation with several c-KIT inhibitors in stratified melanoma patients possessing aberrant c-KIT. Despite an initial response rate in one-quarter of patients treated with c-KIT inhibitors, resistance eventually develops even with dose escalation. Given the high level of genomic alterations frequently identified in these tumors and the lack of specificity of current generation c-KIT inhibitors, it remains unclear if c-KIT is a viable therapeutic target in these melanoma subsets. Moving forward with c-KIT directed therapies requires the development of preclinical models that faithfully mimic the human disease. To this end we have developed a novel melanoma mouse model that enables us to address a role for c-KIT in promoting melanoma initiation, maintenance, and progression in vivo. Expression of mutant c- KIT (L576P) in mouse melanocytes in vivo in the context of Ink4a/Arf loss resulted in the development of melanoma in one-quarter of the mice with a mean latency of 120 days. The goal of the proposed studies is to utilize this flexible melanoma mouse model to evaluate the role of c-KIT in tumor initiation, maintenance and progression and to identify cooperating genetic events to facilitate the development of therapeutic intervention strategies for patients whose tumors possess alterations in c-KIT. We hypothesize that active c-KIT can initiate melanoma and that tumor growth and penetrance will be enhanced in vivo by the addition of cooperating genetic events (e.g., co-expression of HIF1A or MITF). We will test this hypothesis by (Aim 1) assessing the ability of additional c-KIT mutants and potential cooperating genes frequently observed in melanoma to initiate tumors in vivo; (Aim 2) evaluating a role for c-KIT in tumor maintenance through pharmacological and genetic means; and (Aim 3) investigating a role for c-KIT in promoting melanoma metastasis in vivo. .