Mechanism-based abrogation of BCC pathogenesis

描述(申请人提供)：基底细胞癌(BCC)是美国最常见的人类恶性肿瘤类型；每年有超过1,000,000美国人被诊断患有BCC。这些肿瘤的管理是医疗保健费用的主要贡献者。基底细胞癌的风险与暴露于环境太阳紫外线(UV)辐射直接相关 这些肿瘤表现出激活的Sonic Hedgehog(Shh)信号，Shh是胚胎发育中最基本的信号转导途径之一。激活的Shh信号继而失活该途径的抑制子Ptch中的胚系突变，这是人类和小鼠BCC的特征。这与一种罕见的、以遗传为主的疾病有关，这种疾病被称为戈林综合征。这些患者除了发展成髓母细胞瘤等各种皮外肿瘤外，还会发生大量的基底细胞癌。对Shh信号在推动基底细胞癌发病机制中的重要性的认识导致了针对该途径的不同成分的小分子的识别，包括Smo、Shh和Gli-1。然而，由于Shh信号通路对于发育和组织动态平衡是不可或缺的，Shh抑制剂的潜在毒性是人类使用的一个重要考虑因素。此外，临床前和我们最近完成的临床试验都表明，单纯靶向Shh途径并不能完全阻断BCC细胞的增殖，提示额外的途径(S)可能参与了BCC的发病。我们已经产生的初步数据显示，通过同时抑制Shh、Akt1和mTOR通路，有效地抑制了UVB诱导的基底细胞癌的生长，从而暗示Akt1-mTOR信号通路参与了基底细胞癌的发展。此外，我们还发现Shh途径直接调节mTOR的表达，并且mTOR是受Gli-1调控的转录因子SOX9的直接转录靶点。在这个提议中，我们将检验这样的假设，即Akt1和Shh通路之间存在协同作用，并且汇聚在mTOR上，并且阻断Shh和Akt1通路是成功阻断BCC发病所必需的。利用体外试验和本实验室建立的BCC小鼠模型来概括Gorlin综合征(ptch1+/-/SKH-1和Akt KO/ptch1+/-/SKH-1，以及Gli-荧光素酶/PTCH+/-/SKH-1)，我们将(1)确定Akt1在基底细胞癌发病机制中的重要性，(2)确定Akt1和Shh通路之间协同作用在调节mTOR中的机制，以及(3)测试能够同时针对这两条通路的治疗药物的组合使用。这里提出的研究有很大的潜力为推动基底细胞癌发病的信号事件的潜在机制提供重要的见解。通过在不同的组合中使用无毒的靶向药物，我们很可能开发出预防/治疗人类基底细胞癌的新的治疗方法。 公共卫生相关性：皮肤基底细胞癌是美国最常见的人类癌症类型。BCC在Sonic Hedgehog(Shh)信号通路中存在异常，Sonic Hedgehog(Shh)信号通路是动物和人类发育的关键调节因子之一。我们的数据显示，对细胞存活至关重要的Akt1-mTOR通路与Shh通路协同工作，这些通路共同驱动BCC的生长。这项拟议的研究将从两个方面探讨基底细胞癌的发病机制：1)Shh和Akt1-mTOR通路之间的交叉通讯，推动BCC的发展；2)使用长期用于治疗其他人类疾病的药物组合，同时抑制Shh和Akt1通路的有效性和安全性。这项建议将进行的研究旨在帮助寻找新的安全有效的药物来治疗基底细胞癌。

DESCRIPTION (provided by applicant): Basal cell carcinomas (BCCs) are the most common type of human malignancy in the United States; more than 1,000,000 Americans are diagnosed with BCCs each year. The management of these tumors is a major contributor to health care costs. BCC risk directly correlates with exposure to environmental solar ultraviolet (UV) radiation and these tumors manifest activated sonic hedgehog (Shh) signaling and Shh is among the most fundamental signal transduction pathways in embryonic development. Activated Shh signaling secondary to inactivating germline mutations in Ptch, the repressor of this pathway, characterizes both human and murine BCCs. This is associated with the rare, dominantly inherited disorder known as Gorlin syndrome. These patients develop large numbers of BCCs in addition to developing various extracutaneous tumors such as medulloblastomas. Knowledge of the importance of Shh signaling in driving BCC pathogenesis has led to the identification of small molecules that target different components of this pathway including Smo, Shh, and Gli-1. However, because the Shh signaling pathway is indispensable for development and tissue homeostasis, the potential toxicity of Shh inhibitors is an important consideration for human use. Moreover, both preclinical and our recently-completed clinical trials indicate that simply targetin the Shh pathway does not totally block the proliferation of BCC cells, suggesting that additional pathway(s) may contribute to BCC pathogenesis. We have generated preliminary data showing efficacious suppression of the growth of UVB-induced BCCs by simultaneously inhibiting the Shh and Akt1 and mTOR pathways thereby implicating Akt1-mTOR signaling in BCC development. Furthermore, we have shown that the Shh pathway directly regulates mTOR expression and that mTOR is a direct transcriptional target of SOX9, a transcription factor regulated by Gli-1. In this proposal we will test the hypothesis that there are cooperative interactions between Akt1 and Shh pathways that converge on mTOR, and that blocking both Shh and Akt1 pathways is necessary to successfully block BCC pathogenesis. Using both in vitro assays and BCC murine models generated in our laboratory to recapitulate Gorlin syndrome (Ptch1+/-/SKH-1 and Akt KO/Ptch1+/-/SKH-1, and Gli-luciferase/Ptch+/-/SKH-1), we will (1) define the importance of Akt1 in the pathogenesis of BCCs, (2) determine the mechanism of the cooperative interactions between Akt1 and Shh pathways in regulating mTOR, and (3) test the use of combinations of therapeutic agents capable of targeting both pathways simultaneously. The studies proposed here have substantial potential to provide important insights into the mechanisms underlying signaling events that drive the pathogenesis of BCCs. By utilizing non-toxic targeted agents in various combinations, it is likely that we can develop novel therapeutic approaches for preventing/treating human BCCs. PUBLIC HEALTH RELEVANCE: Basal cell carcinomas (BCCs) of the skin are the most common type of human cancer in the United States. BCCs are known to have abnormalities in the sonic hedgehog (Shh) signaling pathway, one of the key regulators of animal and human development. Our data show that a pathway crucial for survival of cells, the Akt1-mTOR pathway, cooperates with the Shh pathway, and these pathways together drive the growth of BCCs. The proposed study will investigate two aspects of BCC pathogenesis: 1) the cross-communication between the Shh and Akt1-mTOR pathways in driving BCC development, and 2) the efficacy and safety of simultaneously inhibiting the Shh and Akt1 pathways using a combination of drugs that long have been used to treat other human diseases. The studies to be conducted in this proposal are designed to help identify novel safe and effective drugs to treat BCCs.