T-cell immunoglobulin mucin 3 (Tim3) is an immune checkpoint receptor that plays a central role in chimeric antigen receptor (CAR) T cell exhaustion within the tumor microenvironment. This study was aimed to evaluate the effects of targeted-knockdown of Tim3 on the antitumor function of anti-mesothelin (MSLN)-CAR T cells. To knockdown Tim3 expression, three different shRNA sequences specific to different segments of the human Tim3 gene were designed and co-inserted with an anti-MSLN-CAR transgene into lentiviral vectors. To investigate the efficacy of Tim3 targeting in T cells, expression of Tim3 was assessed before and after antigen stimulation. Afterwards, cytotoxic effects, proliferative response and cytokine production of MSLN-CAR T cells and Tim3-targeted MSLN-CAR T cells were analyzed. Our results showed that activation of T cells and MSLN-CAR T cells led to up-regulation of Tim3. Tim3 knockdown significantly decreased its expression in different groups of MSLN-CAR T cells. Tim3 knockdown significantly improved cytotoxic function, cytokine production and proliferation capacity of MSLN-CAR T cells. Our findings indicate that targeted knockdown of Tim3 allows tumor-infiltrating CAR T cells that would otherwise be inactivated to continue to expand and carry out effector functions, thereby altering the tumor microenvironment from immunosuppressive to immunosupportive via mitigated Tim3 signaling.

T 细胞免疫球蛋白粘蛋白 3 (Tim3) 是一种免疫检查点受体，在肿瘤微环境中的嵌合抗原受体 (CAR) T 细胞耗竭中起核心作用。本研究旨在评估靶向敲除 Tim3 对抗间皮素 (MSLN)-CAR T 细胞抗肿瘤功能的影响。为了抑制 Tim3 表达，设计了三种不同的 shRNA 序列，这些序列特异于人类 Tim3 基因的不同片段，并与抗 MSLN-CAR 转基因共同插入慢病毒载体中。为了研究 Tim3 在 T 细胞中靶向的功效，在抗原刺激之前和之后评估了 Tim3 的表达。然后，分析了 MSLN-CAR T 细胞和 Tim3 靶向 MSLN-CAR T 细胞的细胞毒作用、增殖反应和细胞因子产生。我们的结果表明 T 细胞和 MSLN-CAR T 细胞的激活导致 Tim3 的上调。Tim3 敲低显着降低其在不同组 MSLN-CAR T 细胞中的表达。Tim3 敲低显着改善了 MSLN-CAR T 细胞的细胞毒功能、细胞因子产生和增殖能力。我们的研究结果表明，Tim3 的靶向敲低允许肿瘤浸润的 CAR T 细胞（否则会被灭活）继续扩增并发挥效应器功能，从而通过减轻 Tim3 信号转导将肿瘤微环境从免疫抑制变为免疫支持。MSLN-CAR T细胞的细胞因子产生和增殖能力。我们的研究结果表明，Tim3 的靶向敲低允许肿瘤浸润的 CAR T 细胞（否则会被灭活）继续扩增并发挥效应器功能，从而通过减轻 Tim3 信号转导将肿瘤微环境从免疫抑制变为免疫支持。MSLN-CAR T细胞的细胞因子产生和增殖能力。我们的研究结果表明，Tim3 的靶向敲低允许肿瘤浸润的 CAR T 细胞（否则会被灭活）继续扩增并发挥效应功能，从而通过减轻 Tim3 信号转导将肿瘤微环境从免疫抑制变为免疫支持。