Escape from CAR T surveillance through lineage plasticity

项目总结 癌细胞基因组的可塑性可以使实体瘤和 恶性血液病。通过一种细胞毒性或分子靶向治疗逃脱 对分化状态或谱系重新编程的固有能力现已描述如下 成人上皮性肿瘤的过继细胞治疗或免疫检查点阻断。T的转让 转基因细胞表达针对B细胞的嵌合抗原受体(CAR T细胞) 细胞表面抗原CD19诱导70%-90%的复发/难治性B细胞患者缓解 细胞性急性淋巴细胞白血病(B-ALL)导致FDA批准这一适应症。然而， 这些患者中有很大一部分在治疗后一年内复发。这主要发生在两个方面 模式，1)早期抗原阳性(CD19pos)复发，归因于Car T细胞扩增不良或缺乏 2)抗原阴性的复发。逃避CD19靶向免疫治疗 可能是由于失去所有B系表型标记而获得了稳定的、可供选择的 MLL重排(MLL-r)、BCR-ABL驱动、TCF3-ZNF384等亚型的表型 全。值得注意的是，CD19靶向的表型转换可以在数年后出现 免疫疗法。了解免疫治疗耐药的机制和机制 确定克服这些问题的策略将是提高缓解深度和 反应的耐久性。 我们的建议将解决癌症模型中的两个主要缺陷，以确定因素 导致免疫治疗复发的原因：缺乏免疫完整的模型系统 概述使用CD19靶向免疫治疗观察到的谱系转换现象 缺乏忠实的小鼠模型来概括婴儿/童年时期的MLL-r B-ALL。这 协作性提案汇集了安永集团在生物学领域的广泛专业知识 利用Fry/Kohler小组的CAR T细胞专业知识，进行MLL-r白血病和造血的研究 开发创新的新模型系统，通过以下方式研究CAR T细胞治疗的逃避 世系重编。我们的初步CAR T细胞数据使用了免疫完好的小鼠模型 为了说明CD19neg复发包括表现出髓系抗原增加和 髓系转录图谱。在儿科B-ALL方面，我们开发了一种逆转录病毒系统来 产生B-ALL，捕捉MLL-r白血病的固有可塑性并切换到AML 活着。我们的建议评估了白血病的内在和外在宿主的能力- 环境因素通过血统影响汽车T细胞死亡逃逸 重新编程。我们的研究结果，包括发现新的拦截策略 世系重新编程有可能为发展类似的方法提供信息 其他形式的癌症接受细胞治疗，可能还有免疫检查点 抑制剂。此外，这些研究可能有助于更好地理解谱系可塑性和 表观遗传异质性导致复发的程度，这可以直接告知 治疗性疗法的设计。

PROJECT SUMMARY Cancer cell genomic plasticity can enable resistance to cancer therapy for both solid tumors and hematologic malignancy. Escape from cytotoxic or molecularly targeted therapy through an inherent capacity to reprogram differentiation state or lineage has now been described following adoptive cell therapy or immune checkpoint blockade in adult epithelial tumors. Transfer of T cells genetically modified to express chimeric antigen receptors (CAR T cells) targeting the B cell surface antigen CD19 induces remission in 70-90% of patients with relapsed/refractory B cell acute lymphocytic leukemia (B-ALL) resulting in FDA-approval for this indication. However, a large fraction of those patients relapse within one year of treatment. This occurs with two main patterns, 1) early antigen-positive (CD19pos) relapse, attributed to poor CAR T expansion or lack of persistence, and 2) later antigen-negative relapse. Evasion of CD19-targeted immunotherapy can result from loss of all B lineage phenotypic markers with acquisition of stable, alternative phenotypes in MLL-rearranged (MLL-r), BCR-ABL driven, TCF3-ZNF384 and other subtypes of ALL. Remarkably, emergence of phenotypic switch can occur years after CD19-targeted immunotherapy. Understanding the mechanisms of immunotherapeutic resistance and identifying strategies to overcome these will be critical in improving remission depth and durability of response. Our proposal will address two major deficits in cancer models to identify factors contributing to relapse from immunotherapy: the lack of immune-intact model systems that recapitulate the lineage switching phenomenon observed using CD19-targeted immunotherapy and the lack of faithful mouse models recapitulating infant/childhood MLL-r B-ALL. This collaborative proposal brings together the extensive expertise of the Ernst group in the biology of MLL-r leukemia and hematopoiesis with the CAR T cell expertise of the Fry/Kohler groups to develop innovative new models systems to study evasion from CAR T cell therapy through lineage reprogramming. Our preliminary CAR T cell data employs immune-intact mouse models to illustrate that CD19neg relapse includes cells that exhibit gain of myeloid antigens and a myeloid transcriptional profile. On the pediatric B-ALL front, we develop a retroviral system to produce B-ALL that captures the inherent plasticity of MLL-r leukemias and switches to AML in vivo. Our proposal assesses the ability for both leukemia-intrinsic as well as extrinsic host- environmental components to influence escape from CAR T killing through lineage reprogramming. The findings of our studies, including the discovery of novel strategies to block lineage reprogramming have the potential to inform the development of similar approaches in other forms of cancer treated with cellular therapy and, potentially, immune checkpoint inhibitors. In addition, these studies may lead to a better understanding of lineage plasticity and the extent to which epigenetic heterogeneity contributes to relapse, which can directly inform the design of curative therapies.