Project 4: Therapeutic Targeting of Replication Stress Vulnerabilities in Small Cell Lung Cancer

项目4项目概要/摘要 本项目的目标是开发新的、合成致死的、复制应激相关的小细胞肺癌治疗方法 根据肿瘤的分子特征对患者进行诊断。SCLC治疗有两个主要的未满足的需求：第一， 大多数患者将经历对临床可用的化疗的原发性或获得性抗性， 免疫疗法;第二，尽管新的数据支持SCLC的分子和生物学上不同的子集， 对于生物标志物驱动的个性化治疗还没有建立的方法（例如对于 NSCLC中的靶向致癌驱动因子）。目前许多“不可治愈的”致癌变化， 在SCLC中常见，通过复制应激（RS）和基因组不稳定性促进肿瘤发生。这些 “癌症的标志”导致高肿瘤突变负荷和染色体畸变。SCLC有一个 由于p53和RB 1功能的普遍丧失以及 癌基因如MYC。在RS存在的情况下，癌细胞依赖于RS反应（RSR），这是一种免疫反应。 DNA损伤修复反应（DDR）的分支，以解决DNA损伤和停滞的复制叉。几 RSR抑制剂正在临床开发中，我们在临床前模型中的初步发现表明， SCLC细胞系、异种移植物和基因工程小鼠模型（GEMM）对靶向SCLC的药物敏感。 RSR或增加RS或基因组不稳定性超过可容忍的水平。后一类包括极光激酶 抑制剂（在高RS水平下诱导有丝分裂灾难，以及直接抑制DNA 修复和降低复制叉稳定性）和6-硫代-dG（不同于众所周知的药物6硫代鸟嘌呤） 其被端粒酶阳性细胞掺入，导致端粒破坏和RS增加。 此外，我们最近发现RS的治疗靶向（例如，通过Chk 1或PARP抑制剂） 增加细胞质DNA，导致先天性免疫应答的激活（通过干扰素刺激因子 基因[STING]途径）、免疫介导的细胞毒性和增强的免疫检查点应答 封锁我们假设：1. RS靶向（通过极光激酶抑制或端粒破坏）将 导致SCLC分子定义子集的合成致死性（目的1）;和2. RS瞄准将增强 免疫治疗难治性SCLC亚群对免疫检查点阻断的反应，通过激活 先天免疫系统（目标2和3）。具体来说，我们预计RS靶向治疗将导致复制 癌基因驱动的肺癌中的灾难和细胞死亡，并增强对免疫检查点的反应 封锁（例如，抗PD-L1）。我们将测试我们的假设在一个广泛的小组的分子特征 孢子肺癌细胞系，患者来源的异种移植物（PDX，肿瘤和循环肿瘤细胞（CTC）来源）， GEM衍生的动物模型（目的1和2），以及来自体外循环启动的II期临床标本 Aurora激酶抑制联合检查点抑制剂免疫治疗的临床试验（目标3）， SCLC分期。

Project 4 Project Summary/Abstract The goal of this project is to develop novel, synthetic lethal, replication stress related, approaches for SCLC patients based on their tumor’s molecular profiles. There are two major unmet needs for SCLC therapy: first, the majority of patients will experience primary or acquired resistance to clinically available chemotherapy and immunotherapy; and second, despite new data supporting molecularly and biologically distinct subsets of SCLC, there are no established approaches for biomarker-driven personalized treatments (such as is standard for targetable oncogenic drivers in NSCLC). Many of the currently “undruggable” oncogenic changes that are common in SCLC promote tumorigenesis through replication stress (RS) and genomic instability. These “hallmarks of cancer” lead to high tumor mutational burden and chromosomal aberrations. SCLCs have a continuous high degree of RS due to the universal loss of p53 and RB1 function, and frequent activation of oncogenes such as MYC. In the presence of RS, cancer cells depend on RS responses (RSR), which are a branch of DNA damage repair responses (DDR), to resolve DNA damage and stalled replication forks. Several RSR inhibitors are in clinical development, and we have preliminary findings in preclinical models indicating that SCLC lines, xenografts, and genetically engineered mouse models (GEMMs) are sensitive to agents that target RSR or that increase RS or genomic instability beyond tolerable levels. The latter group includes aurora kinase inhibitors (which induce mitotic catastrophe in the setting of high RS levels, as well as directly inhibiting DNA repair and decreasing replication fork stability) and 6-thio-dG (distinct from the well-known drug 6 thioguanine) which is incorporated by telomerase positive cells, leading to telomere disruption, and increased RS. Furthermore, we have recently found that therapeutic targeting of RS (e.g., by inhibitors of Chk1 or PARP) increases cytoplasmic DNA, resulting in activation of the innate immune response (via the Stimulator of Interferon Genes [STING] pathway), immune-mediated cytotoxicity, and enhanced response to immune checkpoint blockade. We hypothesize that: 1. RS targeting (through Aurora Kinase inhibition or telomere disruption) will lead to synthetic lethality in molecularly-defined subsets of SCLC (Aim 1); and 2. that RS targeting will enhance response to immune checkpoint blockade in immunotherapy-refractory subsets of SCLC via activation of the innate immune system (Aims 2 and 3). Specifically, we expect that RS-targeted therapies will lead to replication catastrophe and cell death in oncogene-driven lung cancers and enhance responses to immune checkpoint blockade (e.g., anti-PD-L1). We will test our hypotheses in an extensive panel of molecularly characterized SPORE lung cancer cell lines, patient derived xenografts (PDXs, tumor and circulating tumor cell (CTC)-derived), GEM-derived animal models (Aims 1 and 2), and in clinical specimens from an investigator-initiated Phase 2 clinical trial (Aim 3) of Aurora Kinase inhibition combined with checkpoint inhibitor immunotherapy in extensive- stage SCLC.