Therapeutic Induction and Image Guided Exploitation of Cellular senescence for Cancer Therapy

在上一个资助期获得的数据导致发现了一种新型的细胞衰老，称为核糖体检查点诱导衰老（RCIS）。功能性遗传筛选鉴定了RNA聚合酶I依赖性转录的多蛋白复合物的组分作为诱导RCIS的可药用靶点。体外和体内概念验证研究表明，CX-5461（一种破坏RNA聚合酶I依赖性转录的小分子）可稳健诱导治疗诱导衰老（TIS）。同时开发了一种新型的PET示踪剂，用于检测生物体中的衰老，使我们现在处于独特的位置，探索CX-5461和其他促衰老疗法的图像引导使用的概念。在癌基因诱导衰老（OIS）背景下的研究表明，衰老细胞的持续存在可能促进癌症进展，然而，目前还不清楚TIS是否也对邻近的非衰老癌细胞发挥促肿瘤发生作用。因此，我们将着手解决这一基本问题，在衰老生物学使用小鼠模型，允许遗传诱导TIS的一个亚部分的癌细胞。由于这些癌细胞将被基因工程改造以表达鼠HB-EGF，白喉毒素的全身应用将允许有效和定点消除这些细胞。这些研究将模拟目前正在开发的药物衰老清除疗法的使用。概述的系统将使我们能够探测治疗诱导衰老（TIS）和衰老清除策略对肝癌维持和进展的影响。此外，我们将寻求双重核糖体靶向治疗结直肠癌和其他实体瘤的策略。这一目标可以被视为床边到实验室的方法，因为我们最近在携带Shwachman-Bodian-Diamond综合征（SBDS）蛋白杂合突变的晚期耐药结直肠癌（CRC）患者中观察到对CX-5461的明显治疗反应。我们假设患者表现出明显的反应，因为即使是SBDS功能的杂合缺失也可能与核糖体成熟缺陷和核糖体应激相关，因此可能是CX-5461介导的RNA聚合酶-I抑制的合成致死性。在本研究项目中，我们将使用体外和体内模型对这种可能性进行机械表征。最后，与Antti波索（Z 02）密切合作，我们的目标是开发直接或间接抑制SBDS功能的药理学工具和探针。

Data acquired in the previous funding period led to the discovery of a novel type of cellular senescence, designated ribosomal checkpoint induced senescence (RCIS). Functional genetic screens identified components of the multiprotein complex of RNA Polymerase I dependent transcription as druggable targets to induce RCIS. Proof-of-concept studies in vitro and in vivo showed that CX-5461, a small molecule disrupting RNA Polymerase I dependent transcription, robustly induced therapy induced senescence (TIS). The parallel development of a novel first in class PET tracer, to detect senescence in living organisms, brings us now in the unique position to explore the concept of an image guided use of CX-5461 and other pro-senescence therapies.Studies in the context of Oncogene Induced Senescence (OIS) have shown that a sustained presence of senescent cells might promote cancer progression, however it is currently unclear whether TIS also exerts protumorigenic effects on adjacent non-senescent cancer cells. We will therefore set out to address this fundamental question in senescence biology using mouse models allowing to genetically induce TIS in a subfraction of cancer cells. As these cancer cells will be genetically engineered to express murine HB-EGF, a systemic application of Diptheria Toxin will allow for an efficient and site directed elimination of these cells. These studies will mimick the use of pharmacological senolytic therapies which are currently under development. The outlined system will allow us to probe the impact of therapy induced senescence (TIS) and senolytic strategies on liver cancer maintenance and progression. We furthermore will pursue strategies for a dual ribosome targeting for the treatment of colorectal cancer and other solid tumors. This aim can be seen as a bedside to bench approach, as we recently observed a pronounced therapy response towards CX-5461 in a patient with advanced therapy resistant colorectal cancer (CRC) carrying a heterozygous mutation of the Shwachman-Bodian-Diamond syndrome (SBDS) protein. We hypothesize that the patient showed a pronounced response because even a heterozygous loss of SBDS function might be associated with a defect in ribosome maturation and ribosomal stress and might thus be synthetic lethal with CX-5461 mediated inhibition of RNA Polymerase-I. Within this research project we will mechanistically characterize this possibility using in vitro and in vivo models. Finally, in close collaboration with Antti Poso (Z02), we aim to develop pharmacological tools and probes for direct or indirect inhibition of SBDS function.