Taizhou Jiangyan Traditional Chinese Medicine Hospital, Jiangyan Affiliated Hospital of Nanjing University of Chinese Medicine, Taizhou, Jiangsu, China.
Department of Pharmacy, The Affiliated Taizhou People's Hospital of Nanjing Medical University, Taizhou, Jiangsu, China.
Front Immunol. 2024 Aug 23;15:1434078. doi: 10.3389/fimmu.2024.1434078. eCollection 2024.
Reactivate the T cell immunity by PD-1/PD-L1 checkpoint blockade is widely used in non-small cell lung cancer (NSCLC) patients, while the post-translational modification of Programmed death ligand-1 (PD-L1) is commonly existed in various cancer cells, thus increases the complexity and difficulty in therapy development. Ginsenoside Rg3 is an active component of traditional Chinese herb Ginseng with multiple pharmacological effects including immune regulation. However, the effect on the glycosylation of PD-L1 is unknown.
NSCLC cell lines were tested for glycosylation of PD-L1, and the potential mechanisms were investigated. Tumor cell-T cell coculture experiment was conducted and the activation of T cells and cytotoxicity were measured by flow cytometry. In vivo xenograft mouse tumor model was used to investigate the effects of Rg3 on PD-L1-mediated immunosuppression and tumor growth.
Here, we identified PD-L1 is widely N-linked glycosylated in NSCLC cell lines, while Rg3 could inhibit the glycosylation of PD-L1 by downregulating the EGFR signaling and further activate GSK3b-mediated degradation, thus resulted in reduced PD-L1 expression. Moreover, the inhibition of PD-L1 glycosylation promoted the activation and cytotoxicity of T cells under coculture condition. In addition, Rg3 could decrease the tumor volume and enhance anti-tumor T cell immunity as evidence by the upregulated expression of Granzyme B and perforin in CD8+T cells, along with elevated serum IL-2, IFN-g and TNF-a level in Rg3-treated mice.
These results suggest that Rg3 inhibits PD-L1 glycosylation and thus enhance anti-tumor immunity, which provide new therapeutic insight into drug discovery.
通过 PD-1/PD-L1 检查点阻断来重新激活 T 细胞免疫在非小细胞肺癌（NSCLC）患者中得到广泛应用，而程序性死亡配体-1（PD-L1）的翻译后修饰在各种癌细胞中普遍存在，从而增加了治疗开发的复杂性和难度。人参皂苷 Rg3 是传统中药人参的一种活性成分，具有多种药理作用，包括免疫调节。然而，其对 PD-L1 糖基化的影响尚不清楚。
检测 NSCLC 细胞系中 PD-L1 的糖基化，并研究其潜在机制。进行肿瘤细胞-T 细胞共培养实验，通过流式细胞术测量 T 细胞的激活和细胞毒性。使用体内异种移植小鼠肿瘤模型研究 Rg3 对 PD-L1 介导的免疫抑制和肿瘤生长的影响。
在这里，我们发现 PD-L1 在 NSCLC 细胞系中广泛发生 N 连接糖基化，而 Rg3 通过下调 EGFR 信号通路抑制 PD-L1 的糖基化，进而激活 GSK3b 介导的降解，从而导致 PD-L1 表达降低。此外，PD-L1 糖基化的抑制在共培养条件下促进了 T 细胞的激活和细胞毒性。此外，Rg3 可降低肿瘤体积并增强抗肿瘤 T 细胞免疫，这可通过 CD8+T 细胞中 Granzyme B 和穿孔素表达上调以及 Rg3 治疗小鼠血清中 IL-2、IFN-g 和 TNF-a 水平升高得到证实。
这些结果表明，Rg3 抑制 PD-L1 糖基化，从而增强抗肿瘤免疫，为药物发现提供了新的治疗思路。
