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Abstract：
Lung cancer ranks the top of malignancies that cause cancer-related deaths worldwide. The leaves of Morus alba L are traditional Chinese medicine widely applied in respiratory diseases. Our previous work has demonstrated the anti-lung cancer effect of secondary metabolites of mulberry leaf, but their mechanism of action has still not fully elucidated. We synthesized Moracin N (MAN)-Probe conjugated with alkyne to label lung cancer cells and identified protein targets by chemical proteomic analysis. MAN and its probe exerted similar growth-inhibitory effect on human lung cancer cells. Chemical proteomic results showed that MAN targeted the programmed death ligand 1 (PD-L1) checkpoint pathway and T cell receptor (TCR) signaling pathway, indicating its immune-regulatory function. Cell-free surface plasmon resonance (SPR) results showed the direct interaction of MAN with PD-L1 protein. Molecular docking analysis demonstrated that MAN bound to E158 residue of PD-L1 protein. MAN downregulated the expression levels of PD-L1 in a time- and dose-dependent manner and disrupted the PD-L1/programmed death 1 (PD-1) binding, including other secondary metabolites of mulberry leaves Guangsangon E (GSE) and Chalcomoracin (CMR). Human peripheral blood mononuclear cells (PBMCs) co-cultured with MAN-treated A549 cells, resulting in the increase of CD8+ GZMB+ T cells and the decrease of CD8+ PD-1+ T cells. It suggested that MAN exerts anti-cancer effect through blocking the PD-L1/PD-1 signaling. In vivo, MAN combined with anti-PD-1 antibody significantly inhibited lung cancer development and metastasis, indicating their synergistic effect. Taken together, secondary metabolites of mulberry leaves target the PD-L1/PD-1 signaling, enhance T cell-mediated immunity and inhibit the tumorigenesis of lung cancer. Their modulatory effect on tumor microenvironment makes them able to enhance the therapeutic efficacy of immune checkpoint inhibitors in lung cancer.
摘要：
肺癌在全球导致癌症相关死亡的恶性肿瘤中名列前茅。桑叶是广泛应用于呼吸系统疾病的中药。我们以前的工作已经证明了桑叶次级代谢产物的抗肺癌作用，但是它们的作用机制仍然没有完全阐明。我们合成了与炔烃缀合的MoracingN(MAN)-探针以标记肺癌细胞并通过化学蛋白质组学分析鉴定蛋白质靶标。MAN及其探针对人肺癌细胞具有相似的生长抑制作用。化学蛋白质组学结果显示,MAN靶向程序性死亡配体1(PD-L1)检查点通路和T细胞受体(TCR)信号通路,表明其免疫调节功能。无细胞表面等离子体共振(SPR)结果显示MAN与PD-L1蛋白直接相互作用。分子对接分析表明MAN与PD-L1蛋白的E158残基结合。MAN以时间和剂量依赖性方式下调PD-L1的表达水平，并破坏PD-L1/程序性死亡1（PD-1）结合，包括桑叶的其他次生代谢产物广桑果E（GSE）和查尔科霉素（CMR）。人外周血单核细胞（PBMC）与MAN处理的A549细胞共培养，导致CD8+GZMB+T细胞的增加和CD8+PD-1+T细胞的减少。这表明MAN通过阻断PD-L1/PD-1信号传导发挥抗癌作用。在体内,MAN联合抗PD-1抗体显著抑制肺癌的发展和转移,表明它们的协同作用。一起来看,桑叶的次生代谢产物靶向PD-L1/PD-1信号，增强T细胞介导的免疫力，抑制肺癌的发生。它们对肿瘤微环境的调节作用使它们能够增强免疫检查点抑制剂在肺癌中的治疗效果。
