Drosophila models of Ret fusions in Papillary Thyroid Carcinoma

描述（由申请人提供）：在过去的几十年里，甲状腺癌的发病率增加了两倍，使其成为增长最快的癌症。80%的甲状腺癌是乳头状甲状腺癌（PTC），它是由甲状腺滤泡细胞的转化引起的。转移性PTC没有有效的治疗方法，5年生存率为50%，在美国每年导致约1500名患者死亡。5-30%的PTC病例涉及融合蛋白，其中Ret受体酪氨酸激酶融合到各种细胞质蛋白的卷曲结构域。最近，Ret融合也在肺腺癌的一个亚群中被发现。因此，Ret融合驱动肿瘤的治疗方法仍然是一个未满足的需求。CCDC6-RET （PTC1）和NcoA4-RET （PTC3）两种Ret融合占PTC融合的90%以上。虽然这两种融合蛋白都会导致Ret的激活，但这两种融合蛋白与不同的PTC亚型相关。CCDC6-RET与经典型密切相关，是一种更良性的亚型，而NcoA4-RET与实型密切相关，是一种更具侵袭性和恶性的亚型。Cagan实验室的工作已经验证了与甲状腺髓样癌（MTC）相关的致癌Ret亚型的果蝇模型。这些模型用于探索功能以及确定先导治疗命中。本提案的目的是表征由Ret融合激活的信号通路CCDC6-RET和NcoA4-RET，确定具有临床意义的差异，并制定优化的治疗方案。首先，通过Western blot分析和免疫荧光技术对果蝇CCDC6-RET和NcoA4-RET表达引起的信号变化进行表征和比较。其次，将临床相关的激酶抑制剂喂给表达的果蝇

DESCRIPTION (provided by applicant): Rates of thyroid cancer have tripled in the last few decades, making it the fastest growing form of cancer. 80% of thyroid cancer cases are Papillary Thyroid Carcinoma (PTC), which arises from transformation of follicular cells in the thyroid. Metastatic PTC has no effective treatment, a five-year survival rate of 50%, and results in the death of approximately 1500 patients in the US each year. 5-30% of PTC cases involve fusion proteins in which the Ret receptor tyrosine kinase is fused to the coiled-coiled domain of various cytoplasmic proteins. Recently, Ret fusions have also been identified in a subset of lung adenocarcinomas. Thus, therapeutics for Ret fusion-driven tumors remains an unmet need. Two Ret fusions, CCDC6-RET (PTC1) and NcoA4-RET (PTC3) account for greater than 90% of fusions found in PTC. Although both fusion proteins lead to activation of Ret, the two fusions are associated with different PTC subtypes. CCDC6-RET is closely associated with the classic variant, a more benign subtype, and NcoA4-RET is closely associated with the solid subtype, which is more aggressive and malignant. Work by the Cagan lab has validated Drosophila models of oncogenic Ret isoforms that are associated with Medullary Thyroid Carcinoma (MTC). These models were used to explore function as well as identify lead therapeutic hits. The aim of this proposal is to characterize the signaling pathways activated by Ret fusions CCDC6-RET and NcoA4-RET, identify differences that are clinically significant, and develop an optimized therapy. First, signaling changes caused by expression of CCDC6-RET and NcoA4-RET in Drosophila will be characterized and compared by Western blot analysis and immunoflourescence. Secondly, clinically relevant kinase inhibitors will be fed to flies expressing either Ret fusion to identify potential therapies based on rescue of transgene-induced phenotypes. Lastly, the relevance of genetic complexity of PTC tumors on treatment will be evaluated using a functional driver vs. passenger screen using a pre-existing Drosophila kinome RNAi library. All identified therapies will be evaluated in mammalian models, such as cancer cell lines, to ensure the findings are relevant to patients. The innovative studies proposed here will provide critical insight into how Ret fusions drive PTC, how different Ret fusions may differ in their effects, and how Ret fusion driven tumors may respond to targeted therapies.