Approximately 50% of patients with hematologic malignancies relapse after chimeric antigen receptor (CAR) T cell treatment; mechanisms of failure include loss of CAR T persistence and tumor resistance to apoptosis. We hypothesized that both of these challenges could potentially be overcome by overexpressing one or more of the Bcl-2 family proteins in CAR T cells to reduce their susceptibility to apoptosis, both alone and in the presence of BH3 mimetics, which can be used to activate apoptotic machinery in malignant cells. We comprehensively investigated overexpression of different Bcl-2 family proteins in CAR T cells with different signaling domains as well as in different tumor types. We found that Bcl-xL and Bcl-2 overexpression in CAR T cells bearing a 4-1BB costimulatory domain resulted in increased expansion and antitumor activity, reduced exhaustion, and decreased apoptotic priming. In addition, CAR T cells expressing either Bcl-xL or a venetoclax-resistant Bcl-2 variant led to enhanced antitumor efficacy and survival in murine xenograft models of lymphoma and leukemia in the presence or absence of the BH3 mimetic venetoclax, a clinically approved BH3 mimetic. In this setting, Bcl-xL overexpression had stronger effects than overexpression of Bcl-2 or the Bcl-2(G101V) variant. These findings suggest that CAR T cells could be optimally engineered by overexpressing Bcl-xL to enhance their persistence while opening a therapeutic window for combination with BH3 mimetics to prime tumors for apoptosis.

中文翻译：

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单独的 CAR T 细胞和与 BH3 模拟物联合使用的 Bcl-2 家族蛋白过表达的比较分析


大约50%的血液系统恶性肿瘤患者在嵌合抗原受体（CAR）T细胞治疗后复发；失败的机制包括 CAR T 持久性丧失和肿瘤对细胞凋亡的抵抗。我们假设，通过在 CAR T 细胞中过度表达一种或多种 Bcl-2 家族蛋白，降低其对细胞凋亡的敏感性，可以克服这两个挑战，无论是单独使用还是在 BH3 模拟物存在的情况下，BH3 模拟物可用于激活恶性细胞中的凋亡机制。我们全面研究了不同 Bcl-2 家族蛋白在具有不同信号传导域的 CAR T 细胞以及不同肿瘤类型中的过表达。我们发现，在带有 4-1BB 共刺激结构域的 CAR T 细胞中，Bcl-xL 和 Bcl-2 过表达会导致扩增和抗肿瘤活性增加、耗竭减少和凋亡启动减少。此外，在存在或不存在 BH3 模拟 Venetoclax（一种临床批准的 BH3）的情况下，表达 Bcl-xL 或 Venetoclax 耐药 Bcl-2 变体的 CAR T 细胞可增强淋巴瘤和白血病小鼠异种移植模型的抗肿瘤功效和存活率。模仿的。在这种情况下，Bcl-xL 过表达比 Bcl-2 或 Bcl-2(G101V) 变体的过表达具有更强的效果。这些发现表明，可以通过过表达 Bcl-xL 来优化 CAR T 细胞的设计，以增强其持久性，同时打开与 BH3 模拟物组合的治疗窗口，以启动肿瘤细胞凋亡。