A chemical biology approach towards understanding the anti-cancer innate immunity

简介（由申请人提供）：李凌银博士接受过化学生物学和生物化学方面的培训。她的研究生是在威斯康星大学麦迪逊分校的劳拉·基斯林教授的指导下进行的，在那里她使用化学/工程策略来控制干细胞的命运，并获得了有机化学博士学位。为了了解生物医学研究中最重要的问题是什么，她正在哈佛医学院寻求Timothy Mitchison教授的博士后培训。凭借她在癌症药理学方面的经验，李博士的长期目标是带领她的学术团队对癌症治疗产生影响，并显著改善患者的生活质量。利用反向药理学，李博士最近发现了一种名为DMXAA的药物的分子靶点，这种药物通过激活先天免疫来治愈小鼠的实体肿瘤，但在人体临床试验中失败了。她发现DMXAA是小鼠的激动剂配体，而不是人类的干扰素基因刺激剂（STING），这就解释了DMXAA在小鼠身上有活性，而在人类身上没有效果。STING是新发现的第二信使2'3'- cgamp的受体，它是由cGAS在细胞质中响应DNA合成的。2’3’-cGAMP与STING结合，激活TBK-1（一种激酶）和IRF-3（一种转录因子），诱导包括干扰素α/ß在内的一系列宿主应答基因。这一途径为治疗干预开辟了多种可能的途径。在这个拟议的项目中，李博士将寻求揭示cGAMP- STING通路的生化机制，并同时发展治疗假设和先导化合物。她建议使用她合成的2'3'-cGAMP类似物来靶向人类STING，她的初步结果显示这些类似物具有细胞外活性。她还发现了2'3'-cGAMP的主要水解酶，这是一种细胞外酶。这些结果提示了2'3'-cGAMP的细胞外生物学，这是免疫学领域尚未研究的，并可能使药物的快速开发成为可能。在她的目标1中，李博士计划进一步表征她的类似物并在小鼠肿瘤模型中进行测试，这是她对癌症治疗产生影响的第一个大胆举动。在aim 2中，李博士将研究2'3'-cGAMP的降解机制及其内化动力学。该结果将提示是否存在2’3’-cGAMP的细胞表面信号受体或最终导致细胞内2’3’-cGAMP信号传导的膜转运体。在Aim 3中，李博士将使用遗传学筛选来识别细胞外2'3'-cGAMP的信号成分（例如膜受体或转运体），这将导致新的生物学和新的药物靶点。激活先天免疫系统，停止培育癌细胞，转而攻击它们，作为一种治疗理念，已经显示出很高的潜力。李博士的化学遗传学方法将提供更多的工具来唤醒我们的抗癌免疫。

DESCRIPTION (provided by applicant): Dr. Lingyin Li was trained in chemical biology and biochemistry. Her graduate training was with Professor Laura Kiessling at University of Wisconsin-Madison, where she used chemistry/engineering strategies to control stem cell fate and she received a Ph. D in organic chemistry. Hoping to learn what the most important problems are in biomedical research, she is seeking her postdoc training with Professor Timothy Mitchison at Harvard Medical School. With her experience there in cancer pharmacology, Dr. Li's long-term goal is to lead her academic team to make an impact on cancer treatment and significantly improve patients' quality of life. Using reverse pharmacology, Dr. Li recently identified the molecular target of a drug called DMXAA that cured solid tumors in mice via activating innate immunity, but failed in phase III human clinical trials. She discovered that DMXAA functions as an agonist ligand for mouse, but not human STING (Stimulator of the Interferon Genes), explaining its activity in mouse and lack of efficacy in man. STING is the receptor for the newly- discovered 2nd messenger 2'3'-cGAMP, which is synthesized by cGAS in response to DNA in the cytoplasm. 2'3'-cGAMP binds to STING, activates TBK-1 (a kinase) and IRF-3 (a transcription factor), and induces a panel of host response genes including interferon α/ß. This pathway opens multiple possible routes to therapeutic intervention. In this proposed project, Dr. Li will seek to uncover biochemical mechanisms in the cGAMP- STING pathway and in parallel develop therapeutic hypotheses and lead compounds. She proposes to use 2'3'-cGAMP analogs that she has synthesized to target human STING and her preliminary results showed extracellular activity of these analogs. She has also discovered the dominant hydrolase for 2'3'-cGAMP, which turned out to be an extracellular enzyme. These results hint extracellular biology of 2'3'-cGAMP, which is not being pursued by the immunology field, and might allow rapid drug development. In her aim 1, Dr. Li plans to further characterize her analogs and test them in mouse tumor models, which is her first bold move towards making an impact on cancer therapy. In aim 2, Dr. Li will study the degradation mechanisms of 2'3'-cGAMP and its internalization kinetics. The results will suggest whether there exists a cell surface signaling receptor for 2'3'-cGAMP or a membrane transporter that eventually leads to intracellular 2'3'-cGAMP signaling. In Aim 3, Dr. Li will use a genetics screen to identify signalig components for extracellular 2'3'-cGAMP (e.g. a membrane receptor or transporter) and this will lead to new biology and novel drug targets. Activating the innate immune system to stop nurturing cancer cells and instead attack them has already shown high potential as a therapeutic philosophy. Dr. Li's chemical genetics approach will provide more tools to awaken our anti- cancer immunity.