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

简介(申请人提供)：李凌银博士曾接受过化学生物学和生物化学方面的培训。她在威斯康星大学麦迪逊分校接受了劳拉·基斯林教授的研究生培训，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与蒂莫西·米奇森教授一起进行博士后培训。凭借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，并显著提高患者的生活质量。利用反向药理学，李博士最近确定了一种名为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实体肿瘤，但在人类临床试验的第三阶段失败了。她发现，DMXAA对小鼠来说是一种激动剂配体，但不是人类刺痛(干扰素基因的刺激物)，这解释了它在小鼠身上的活性和在人类身上的无效。SING是新近发现的第二信使2‘3’-cGAMP的受体，它是cGAS对细胞质中DNA的反应而合成的。2‘3’-cGAMP与STING结合，激活Tbk-1(一种激酶)和Irf-3(一种转录因子)，并诱导一系列宿主反应基因，包括干扰素α/？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途径中的生化机制，并同时开发治疗假说和先导化合物。她建议使用她合成的2‘3’-cGAMP类似物来靶向人类刺痛，她的初步结果显示了这些类似物的细胞外活性。她还发现了2‘3’-cGAMP的主要水解酶，结果证明是一种胞外酶。这些结果提示了2‘3’-cGAMP的细胞外生物学，这并没有被免疫学领域所追求，并可能允许快速的药物开发。在她的目标1中，李博士计划进一步描述她的类似物，并在小鼠肿瘤模型中测试它们，这是她在癌症治疗方面采取的第一个大胆举措。在目标2中，李博士将研究2‘3’-cGAMP的降解机制及其内化动力学。这些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信号的膜转运体。在目标3中，李博士将使用遗传学筛选来识别细胞外2‘3’-cGAMP的重要成分(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滋养癌细胞，转而攻击它们，已经显示出作为一种治疗哲学的高潜力。李博士的化学遗传学方法将提供更多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.