Cooperation of Hippo/Yap and Hedgehog Pathways in BCC Development

 描述(由申请人提供)：重要证据支持器官发生控制失败和肿瘤形成过程的重叠。事实上，HIPPO/YAP信号通路是祖细胞增殖和器官大小检查点的中心调节因子，在各种人类肿瘤中经常过度表达。在小鼠表皮中，YAP的过表达诱导毛囊间表皮(IFE)中祖细胞的扩张。人基底细胞癌(BCC)是一种皮肤肿瘤，起源于IFE前体细胞，是Hedgehog信号激活的结果。Hedgehog和Hippo途径诱导IFE前体细胞增殖的能力表明，这两条途径在肿瘤形成过程中可能是协同作用的。事实上，河马/YAP通路被发现是Hedgehog驱动的髓母细胞瘤进展的重要中介。然而，河马和刺猬信号在基底细胞癌中的相互作用还完全不清楚。我们的初步实验表明，YAP是由活跃的Hedgehog信号上调的，并且是BCC发病所必需的。我们假设，在基底细胞癌的启动和进展过程中，河马和刺猬通路在皮肤基础干细胞中相互作用。以下特定目的将验证我们的假设：(1)确定HIPPO/YAP通路在Hedgehog驱动的肿瘤中的需求；(2)研究YAP促进SmoM2驱动的肿瘤发生的机制。为了询问我们的第一个特定目标，我们将在体内研究SmoM2和Ptch诱导的BCC在肿瘤起始或维持过程中对YAP表达的依赖性。将进行详细的宏观和微观分析，以确定河马的功能。我们将在多个时间点对YAP熟练和YAP缺失的表皮进行比较，以了解BCC的克隆进化、增殖和凋亡。在具体目标2中，我们将研究YAP与TEAD转录因子的共激活功能，并鉴定SmoM2驱动的BCC中YAP调控的基因特征。使用每条通路都有报告的细胞系，我们将确定刺猬-河马串扰的确切点。总体而言，我们的实验方法将研究BCC肿瘤对YAP表达的依赖性，并确定YAP在Hedgehog诱导的肿瘤发生中的机制作用。基底细胞癌是最常见的肿瘤类型，发病率持续上升。晚期BCC肿瘤通常对Hedgehog途径拮抗剂具有耐药性，部分原因是其他途径的合作支持进展。因此，识别相互作用的信号分子，增强Hedgehog驱动的基底细胞癌的发病机制，对于未来的治疗干预具有巨大的潜力。更全面地了解河马和刺猬途径的相互作用将发现新的和生物学相关的治疗靶点。

 DESCRIPTION (provided by applicant): Significant evidence supports overlap of failed organogenesis control and tumorigenic process. Indeed, a central regulator of progenitor cell proliferation and organ size checkpoint, the Hippo/YAP signaling pathway, is frequently overexpressed in variety of human tumors. In the mouse epidermis, overexpression of Yap induces expansion of progenitor cells in the interfollicular epidermis (IFE). Human basal cell carcinoma (BCC) is a skin tumor originating from the IFE progenitor cells as a result of activated Hedgehog signaling. The capacity of the Hedgehog and Hippo pathways to induce proliferation of the IFE progenitor cells suggests that these two pathways could cooperate during a tumorigenic process. Indeed, The Hippo/Yap pathway was found to be an essential mediator of the Hedgehog-driven medulloblastoma progression. Nevertheless, interaction between the Hippo and Hedgehog signaling in BCC is completely unclear. Our preliminary experiments show that Yap is upregulated by active Hedgehog signaling and required for BCC pathogenesis. We hypothesize that the Hippo and Hedgehog pathways interact in the skin basal stem cell during BCC initiation and progression. Following specific aims will test our hypothesis: (1) To determine requirement of Hippo/YAP pathway in the Hedgehog-driven tumor; (2) to investigate a mechanism by which YAP promotes SmoM2-driven tumorigenesis. To interrogate our first specific aim, we will study in vivo dependence of SmoM2 and Ptch-induced BCC on Yap expression during tumor initiation or maintenance. Detailed macroscopic and microscopic analyses will be performed in resulting BCC tumors to delineate Hippo functions. The Yap proficient and Yap-null epidermis will be compared at multiple time points for BCC clonal evolution, proliferation, and apoptosis. In the specific aim 2, we will investigate Yap co-activato function with TEAD transcription factors and identify Yap-regulated gene signature in the SmoM2-driven BCC. Using cell lines with a reporter for each pathway, we will determine exact point of Hedgehog-Hippo crosstalk. Overall, our experimental approach will investigate dependence of BCC tumors on Yap expression and define a mechanistic role of Yap during the Hedgehog-induced tumorigenesis. Human BCC is the most common tumor type with continued increase in the incidence. The advanced BCC tumors are commonly resistant to the Hedgehog pathway antagonists in part due to cooperation of other pathways to support progression. Thus identification of interacting signaling molecules that potentiate Hedgehog-driven BCC pathogenesis has an enormous potential for the future of therapeutic intervention. A more comprehensive understanding of the Hippo and Hedgehog pathway interaction will uncover novel and biologically relevant therapeutic targets.