Blocking the programmed death-ligand 1 (PD-L1) on tumor cells with monoclonal antibody therapy has emerged as powerful weapon in cancer immunotherapy. However, only a minority of patients presented immune responses in clinical trials. To develop an alternative treatment method based on immune checkpoint blockade, we designed a novel and efficient CRISPR-Cas9 genome editing system delivered by cationic copolymer aPBAE to downregulate PD-L1 expression on tumor cells via specifically knocking out Cyclin-dependent kinase 5 (Cdk5) gene in vivo. The expression of PD-L1 on tumor cells was significantly attenuated by knocking out Cdk5, leading to effective tumor growth inhibition in murine melanoma and lung metastasis suppression in triple-negative breast cancer. Importantly, we demonstrated that aPBAE/Cas9-Cdk5 treatment elicited strong T cell-mediated immune responses in tumor microenvironment that the population of CD8+ T cells was significantly increased while regulatory T cells (Tregs) was decreased. It may be the first case to exhibit direct in vivo PD-L1 downregulation via CRISPR-Cas9 genome editing technology for cancer therapy. It will provide promising strategy for preclinical antitumor treatment through the combination of nanotechnology and genome engineering.

中文翻译：

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由CRISPR-Cas9基因组介导的Cdk5敲除可编辑PD-L1衰减并增强抗肿瘤免疫力。

用单克隆抗体疗法阻断肿瘤细胞上的程序性死亡配体1（PD-L1）已成为癌症免疫疗法的有力武器。但是，只有少数患者在临床试验中表现出免疫反应。为了开发基于免疫检查点封锁的替代治疗方法，我们设计了一种新型且有效的CRISPR-Cas9基因组编辑系统，该系统由阳离子共聚物aPBAE提供，以通过特异性敲除细胞周期蛋白依赖性激酶5（Cdk5）下调肿瘤细胞上PD-L1的表达。体内基因。通过敲除Cdk5，PD-L1在肿瘤细胞上的表达显着减弱，从而导致鼠黑色素瘤中有效的肿瘤生长抑制和三阴性乳腺癌中的肺转移抑制。重要的，我们证明，aPBAE / Cas9-Cdk5处理在肿瘤微环境中引起强烈的T细胞介导的免疫反应，即CD8 + T细胞的数量显着增加，而调节性T细胞（Tregs）减少。这可能是第一个通过CRISPR-Cas9基因组编辑技术直接在体内PD-L1下调的癌症治疗方法。通过纳米技术和基因组工程的结合，它将为临床前抗肿瘤治疗提供有希望的策略。