Targeting Tankyrases to Mitigate Immunosuppression and Enhance Cancer Immunotherapy

项目摘要 肝激酶B1（LKB 1）是细胞能量稳态的关键调节剂和众所周知的肿瘤抑制因子， 在许多癌症中，特别是肺癌，它在约30%的肿瘤中缺失。LKB 1抑制 或消耗导致增强的肿瘤发生，增加的免疫抑制，和降低的反应， 免疫检查点抑制剂。尽管LKB 1负调控对肿瘤生长和肿瘤生长的重要性， 由于LKB 1具有攻击性，因此没有已知的LKB 1上游调节因子。通过合理设计的药物筛选， 我们鉴定了端锚聚合酶（TNKS; TNKS 1或PARP 5A，和TNKS 2或PARP 5 B），为上游阴性， LKB 1的调节器。TNKS属于聚（ADP-核糖）聚合酶（PARP）的密切相关成员 使用β-NAD+作为底物将ADP-核糖部分添加到靶蛋白的家族，称为PAR基化。 TNKS对靶蛋白的PAR基化通常导致泛素化和蛋白酶体降解，例如 AXIN（其在Wnt信号传导中螯合APC/β-连环蛋白）、PTEN和端粒酶。然而， LKB 1不导致LKB 1降解，但抑制LKB 1活性。TNKS过表达刺激肿瘤 细胞增殖并增强体内肿瘤发生，其是LKB 1依赖性的。肺肿瘤（两者 腺癌和鳞状细胞癌）在表达LKB 1的肿瘤中过表达TNKS 1 预示着预后较差。鉴于LKB 1突变型肺肿瘤是免疫抑制的， 对免疫检查点抑制剂反应不佳，我们假设TNKS可能是阴性的。 在LKB 1野生型肿瘤中诱导免疫抑制的LKB 1调节剂。我们将通过以下方式检验我们的假设： (1)确定TNKS在肿瘤微环境中赋予免疫抑制的作用， 使用同基因原位模型和遗传工程小鼠模型（GEMM），以更好地了解 如果TNKS水平在肿瘤中赋予免疫抑制状态;和（2）利用同源原位肿瘤模型 评估TNKS表达产生对免疫疗法的抗性的能力，并确定TNKS表达的免疫耐受性。 TNKS抑制对增强免疫治疗应答的有效性。在这个项目完成后，我们 将有一个更清楚的了解免疫抑制状态，是由TNKS赋予通过 LKB 1的负调控。本研究将暗示TNKS作为临床翻译的目标，以提高 目前肺癌的治疗方法

PROJECT SUMMARY Liver kinase B1 (LKB1) is a key regulator of cellular energy homeostasis and well known tumor suppressor gene in many cancers, particularly lung cancer, where it is deleted in ~30 percent of tumors. LKB1 suppression or depletion leads to enhanced tumorigenesis, increased immunosuppression, and reduced response to immune checkpoint inhibitors. Despite the importance of LKB1 negative regulation on tumor growth and aggressiveness, there is no known upstream regulator of LKB1. Through a rationally designed drug screen, we identified tankyrases (TNKS; TNKS1, or PARP5A, and TNKS2, or PARP5B), as upstream negative regulators of LKB1. TNKS belong to the closely related members of the poly (ADP-ribose) polymerase (PARP) family that adds ADP-ribose moieties to target proteins using β-NAD+ as substrate, termed PARsylation. PARsylation of target proteins by TNKS typically leads to ubiquination and proteasome degradation, such as AXIN (which sequesters APC/β-catenin in Wnt signaling), PTEN, and telomerase. However, PARsylation of LKB1 does not lead to LKB1 degradation, but inhibit LKB1 activity. Overexpression of TNKS stimulates tumor cellular proliferation in vitro and enhances tumorigenesis in vivo that is LKB1-dependent. Lung tumors (both adenocarcinoma and squamous cell carcinoma) that overexpress TNKS1 in LKB1 expressing tumors portended to poorer prognosis. Given the fact that LKB1 mutant lung tumors are immune suppressed and respond poorly to immune checkpoint inhibitors, we hypothesize that TNKS potentially could be the negative regulator of LKB1 that induce immune suppression in LKB1 wild type tumors. We will test our hypothesis by: (1) determining the role of TNKS on conferring immunosuppression in the tumor microenvironment through the use of syngeneic orthotopic models and Genetically-Engineered Mouse Models (GEMMs) to better understand if TNKS levels confers immunosuppressive state in tumors; and (2) utilizing syngeneic orthotopic tumor models to evaluate the ability of TNKS expression to generate resistance to immunotherapy and determine the effectiveness of TNKS inhibition on enhancing immunotherapy response. Upon completion of this project, we will have a clearer understanding of the immunosuppressive state that is conferred by TNKS through the negative regulation of LKB1. This research will implicate TNKS as a target for clinical translation to improve current therapies in lung cancer.