Identification of DCLK2-TBK1 signaling axis as a potential therapeutic target in kidney cancer

项目摘要 透明细胞肾细胞癌（ccRCC）约占所有肾癌的85%，具有耐药性。 对多种癌症疗法都有很大的杀伤力von Hippel-Lindau（VHL）是最重要的肿瘤 在肾癌中的抑制因子，其缺失导致缺氧诱导因子α（HIFα，包括HIF 1 α和HIF 2 α） 积累尽管HIF 2 α抑制剂已被开发为肾癌的潜在治疗靶点， 只有一小部分患者对HIF 2 α受体拮抗剂治疗有反应，这表明 鉴定VHL缺陷型肾癌的其他治疗弱点。我们最近发表的作品 证明VHL缺失激活TANK结合激酶1（TBK 1），其在肿瘤细胞中起关键作用。 增殖、肿瘤生长和自发转移。靶向TBK 1抑制VHL缺陷型癌细胞 生长，同时使VHL恢复细胞不受影响。虽然TBK 1参与先天免疫信号传导， 磷酸化转录因子IRF 3，我们没有观察到在VHL-1中p-IRF 3（或I型干扰素的产生）。 提示ccRCC中TBK 1的替代功能的缺陷型癌症。因此，TBK 1是一种有前途的治疗药物 目标然而，目前可用的抑制剂缺乏特异性，并可能损害先天免疫。鉴定 ccRCC中的TBK 1调节剂可能导致开发更特异性的抑制剂，以保护TBK 1在肾细胞癌中的功能。 其他区室（即免疫细胞）。通过全激酶组siRNA筛选，我们鉴定了Doublecortin Like 激酶2（DCLK 2）作为潜在的TBK 1激活剂。通过多种siRNA消耗DCLK 2降低TBK 1 磷酸化和蛋白质水平。相反，DCLK 2的过度表达诱导TBK 1磷酸化， 在体外和体内。虽然DCLK 2被报道在视神经损伤后促进生长锥的重建， DCLK 2在癌症中的作用尚未探索。我们的初步数据表明，DCLK 2缺失减少了ccRCC细胞的增殖。 增殖、集落形成和异种移植肿瘤生长。我们假设DCLK 2-TBK 1调节基因 节点作为一种新的信号传导轴在ccRCC与VHL损失，可以利用治疗。 这是第一个描述DCLK 2在癌症中作用的研究。此外，TBK 1是第一个已知的DCLK 2 激酶底物。在具体目标1中，我们将描述DCLK 2在肾脏中的功能意义。 癌在具体目标2中，我们将描述DCLK 2有助于肾脏的分子机制。 肿瘤发生在具体目标3中，我们将研究靶向DCLK 2-TBK 1在肾脏中的治疗潜力。 通过UT Southwestern Kidney获得的癌症原位异种移植物和患者来源的异种移植物（PDX） 癌症卓越研究专业计划（SPORE）。成功实现这些目标将为 对一种新的信号通路的机制性洞察，并为靶向治疗干预奠定基础 ccRCC中的DCLK 2-TBK 1轴。

Project Summary Clear cell renal cell carcinoma (ccRCC), which accounts for approximately 85% of all renal cancers, is resistant to a variety of cancer therapies and is highly lethal. von Hippel-Lindau (VHL) is the most important tumor suppressor in renal cancer, its loss leads to hypoxia inducible factor α (HIFα, including HIF1α and HIF2α) accumulation. Although HIF2α inhibitor has been developed as a potential therapeutic target in renal cancer, only a small propotion of patients will respond to HIF2α inhibitore treatment, suggesting the importance of identifying additional therapeutic vulnerabilities in VHL-deficient kidney cancer. Our recently published work demonstrated that VHL loss activates TANK Binding Kinase 1 (TBK1), which plays a critical role in tumor cell proliferation, tumor growth and spontaneous metastasis. Targeting TBK1 inhibits VHL-deficient cancer cell growth while leaving VHL restored cells unaffected. While TBK1 is involved in innate immune signaling and phosphorylates the transcription factor IRF3, we did not observe p-IRF3 (or type I interferon production) in VHL- deficient cancers suggesting alternate functions for TBK1 in ccRCC. Thus, TBK1 is a promising therapeutic target. However, currently available inhibitors lack specificity and may impair innate immunity. Identification of TBK1 regulators in ccRCC may lead to development of more specific inhibitors that preserve TBK1 function in other compartments (i.e. immune cells). Through a kinome-wide siRNA screen, we identified Doublecortin Like Kinase 2 (DCLK2) as a potential TBK1 activator. DCLK2 depletion by multiple siRNAs decreased TBK1 phosphorylation and protein levels. Conversely, overexpression of DCLK2 induced TBK1 phosphorylation both in vitro and in vivo. While DCLK2 was reported to promote growth cone reformation after optic nerve injury, a role for DCLK2 in cancer is unexplored. Our preliminary data show that DCLK2 depletion reduced ccRCC cell proliferation, colony formation and xenograft tumor growth. We hypothesize that the DCLK2-TBK1 regulatory node serves as a novel signaling axis in ccRCCs with VHL loss that could be exploited therapeutically. This is the first study to characterize the role of DCLK2 in cancer. In addition, TBK1 is the first known DCLK2 kinase substrate in cancer. In Specific Aim 1, we will characterize the functional significance of DCLK2 in kidney cancer. In Specific Aim 2, we will delineate the molecular mechanism by which DCLK2 contributes to kidney tumorigenesis. In Specific Aim 3, we will investigate the therapeutic potential of targeting DCLK2-TBK1 in kidney cancer ortothopic xenografts and patient derived xenografts (PDXs) available through UT Southwestern Kidney Cancer Specialized Program of Research Excellence (SPORE). Successful completion of these aims will provide mechanistic insight into a novel signaling pathway and set the foundation for therapeutic interventions targeting the DCLK2-TBK1 axis in ccRCC.