Escape from CAR T surveillance through lineage plasticity

项目摘要 癌细胞基因组可塑性可以使实体瘤和肿瘤细胞对癌症疗法具有抗性。 恶性血液病通过一种免疫抑制剂逃避细胞毒性或分子靶向治疗， 下面描述了重编程分化状态或谱系固有能力 过继细胞疗法或免疫检查点阻断。转让T 经遗传修饰以表达靶向B的嵌合抗原受体的细胞（CAR T细胞 细胞表面抗原CD 19诱导70-90%复发/难治性B患者缓解 细胞急性淋巴细胞白血病（B-ALL）导致FDA批准该适应症。然而，在这方面， 这些患者中有很大一部分在治疗后一年内复发。这种情况发生在两个主要 模式，1）早期抗原阳性（CD 19阳性）复发，归因于CAR T扩增不良或缺乏 2）晚期抗原阴性复发。逃避CD 19靶向免疫治疗 可能是由于所有B谱系表型标记的丢失， MLL-r、BCR-ABL驱动、TCF 3-ZNF 384和其他亚型的表型 所有.值得注意的是，表型转换的出现可以发生在CD 19靶向治疗后数年。 免疫疗法了解免疫抵抗的机制， 确定克服这些问题的策略对于改善缓解深度至关重要， 反应的持久性。 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：缺乏免疫完整的模型系统， 概括了使用CD 19靶向免疫疗法观察到的谱系转换现象 以及缺乏重现婴儿/儿童MLL-r B-ALL的可靠小鼠模型。这 合作提案汇集了恩斯特集团在生物学领域的广泛专业知识， 利用Fry/科勒团队的CAR T细胞专业知识， 开发创新的新模型系统，研究CAR T细胞治疗的逃避， 谱系重编程我们初步的CAR T细胞数据采用免疫完整的小鼠模型 为了说明CD 19阴性复发包括表现出髓系抗原获得的细胞和 骨髓转录谱。在儿科B-ALL方面，我们开发了一种逆转录病毒系统， 产生B-ALL，捕获MLL-r白血病的固有可塑性，并在 vivo.我们的建议评估白血病的能力-内在的以及外在的主机- 环境成分通过谱系影响CAR T杀伤逃逸 重新编程我们的研究结果，包括发现新的策略，以阻止 谱系重编程有可能为类似方法的发展提供信息， 用细胞疗法和潜在的免疫检查点治疗的其他形式的癌症 抑制剂的此外，这些研究可能有助于更好地理解谱系可塑性， 表观遗传异质性在多大程度上有助于复发，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.