Signaling and targeting of CRTC1-MAML2 fusion oncoprotein in salivary gland tumor

描述(申请人提供)：粘液表皮样癌(MEC)是最常见的涎腺恶性肿瘤，也可发生在多个其他器官部位。目前，晚期、不能切除的MEC患者的治疗选择有限，治疗结果也很差。我们首次从恶性MEC细胞的复发t(11；19)(q14-21；p12-13)中克隆了一个新的融合癌基因CRTC1-MAML2。Crtc1是CREB介导的转录共激活因子，新发现在新陈代谢、衰老和癌症中发挥作用，而MAML2是Notch途径的转录辅助激活因子，在发育和癌症中具有关键功能。CRTC1-MAML2融合癌基因与超过50%的人类MEC病例相关，代表着MEC潜在的主要致病分子缺陷。尽管NCI和NIDCR已经将发展小鼠模型以研究CRTC1-MAML2生物学作为优先目标，但自2006年第一次涎腺癌研讨会以来，一直没有取得任何进展。该项目的目标是通过表征CRTC1-MAML2致瘤性的第一个动物模型来弥合这一重大差距。这个激动人心的项目将阐明CRTC1-MAML2的作用和机制，并探索阻断下游致癌信号的方法。我们先前已经证明，CRTC1-MAML2具有很强的转录共激活活性，并能够通过共激活转录因子CREB在体外转化ART上皮细胞。我们最近的初步研究表明，在体外检测或作为异种移植瘤在体内繁殖时，CRTC1-MAML2融合表达缺失会降低人恶性MEC细胞的生长和存活。这些发现表明CRTC1-MAML2在维持MEC恶性表型方面是必不可少的，因此是一个有希望的治疗靶点。更好地了解这种融合癌基因的生物学特性将为阻断MEC提供新的靶向机会。然而，该融合癌基因在MEC发生发展过程中的关键调节因子及其在体内的作用尚不清楚。我们已经产生了令人兴奋的、有意义的初步数据来支持我们的中心假设：CRTC1-MAML2融合癌基因通过靶基因和通路的异常激活在MEC的发病中发挥关键作用；因此，靶向融合诱导的异常信号在阻断融合阳性MEC方面是有效的。这一假设将通过三个具体目标来解决。目的1利用我们新建立的CRTC1-MAML2小鼠条件性模型，评价CRTC1-MAML2融合癌基因在MEC肿瘤发生中的作用。目的验证CRTC1-MAML2调控的靶基因，探讨CRTC1-MAML2依赖的细胞信号在MEC维持中的作用。目标3将从功能上表征新型CRTC1-MAML2/ERR？相互作用侧重于其在调节肿瘤血管生成中的作用。这些目标的成功完成将大大增加我们对唾液腺肿瘤生物学的了解，重要的是，可能发现新的CRTC1-MAML2特异性治疗靶点。

DESCRIPTION (provided by applicant): Mucoepidermoid carcinoma (MEC) is the most common salivary gland malignancy and also arises in multiple other organ sites. Currently, patients with advanced, unresectable MEC have limited therapeutic options and poor treatment outcomes. We were the first to clone a novel fusion oncogene, CRTC1-MAML2 from a recurrent t(11;19)(q14-21;p12-13) in malignant MEC cells. CRTC1 is a transcriptional co-activator for CREB-mediated transcription with newly discovered roles in metabolism, aging, and cancer, whereas MAML2 is a transcriptional co-activator for the Notch pathway with critical functions in development and cancer. The CRTC1-MAML2 fusion oncogene is associated with more than 50% of human MEC cases and represents a potential major etiologic molecular defect for MEC. Although NCI and NIDCR had identified the development of a mouse model to study CRTC1-MAML2 biology as a high-priority goal, there had been no progress since the First Salivary Gland Cancer Workshop in 2006. The goal of this project is to bridge this significant gap by characterizing the first animal model for CRTC1-MAML2 tumorigenicity. This exciting project will elucidate the role and mechanisms of CRTC1-MAML2 and explore approaches to block downstream oncogenic signals. We previously showed that the CRTC1-MAML2 has strong transcriptional co-activator activity and is capable of transforming epithelial cells in vitro, in art through co-activating the transcription factor CREB. Our recent preliminary studies indicate that depletion of CRTC1-MAML2 fusion expression reduced the growth and survival of human malignant MEC cells when assayed in vitro or when propagated as xenograft tumors in vivo. These findings indicate that CRTC1-MAML2 is essential in maintaining MEC malignant phenotype and thus serves as a promising therapeutic target. A better understanding of the biology of this fusion oncogene will provide new targeting opportunities to block MEC. However, the critical mediators and the in vivo roles of this fusion oncogene in the development and progression of MEC remain poorly elucidated. We have generated exciting, significant preliminary data to support our central hypothesis of this proposal: the CRTC1-MAML2 fusion oncogene has critical roles in MEC pathogenesis through the aberrant activation of target genes and pathways; consequently, the targeting of fusion-induced abnormal signaling is effective in blocking fusion-positive MEC. This hypothesis will be addressed by three specific aims. Aim 1 will assess the in vivo roles of CRTC1-MAML2 fusion oncogene in MEC tumorigenesis using our newly developed conditional CRTC1-MAML2 mouse model. Aim 2 will validate the CRTC1-MAML2-regulated target genes and investigate the importance of aberrantly activated CRTC1-MAML2-dependent cell signaling in the maintenance of MEC. Aim 3 will functionally characterize the novel CRTC1-MAML2/ERR? interaction focusing on its role in regulating tumor angiogenesis. The successful completion of these aims will significantly increase our understanding of the biology of salivary gland tumors, and importantly, may identify novel CRTC1-MAML2-specific therapeutic targets.