Abstract：
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.
摘要：
大约50％的恶性血液病患者在嵌合抗原受体（CAR）T细胞治疗后复发；失败的机制包括丧失CART持久性和肿瘤对细胞凋亡的抵抗力。我们假设这两个挑战都可以通过在CAR-T细胞中过表达一种或多种Bcl-2家族蛋白来降低它们对细胞凋亡的敏感性来克服。无论是单独还是在BH3模拟物的存在下，可用于激活恶性细胞的凋亡机制。我们全面研究了不同Bcl-2家族蛋白在具有不同信号结构域的CART细胞以及不同肿瘤类型中的过表达。我们发现Bcl-xL和Bcl-2在带有4-1BB共刺激结构域的CAR-T细胞中过表达导致扩增和抗肿瘤活性增加。减少疲惫，和减少凋亡引发。此外,表达Bcl-xL或venetoclax抗性Bcl-2变体的CART细胞导致在存在或不存在BH3模拟venetoclax的小鼠淋巴瘤和白血病异种移植模型中增强的抗肿瘤功效和存活率。临床批准的BH3模拟物。在此设置中，Bcl-xL过表达比Bcl-2或Bcl-2(G101V)变体的过表达具有更强的作用。这些发现表明，可以通过过表达Bcl-xL来优化CART细胞，以增强其持久性，同时为与BH3模拟物组合打开治疗窗口，以引发肿瘤凋亡。
