Chen Cheng, Mu Chuanyong, Qu Qiuxia, Zhu Yibei, Sun Jing, Zhang Xueguang, Huang Jian'an
Department of Respiratory Medicine, Key Laboratory of Medicine and Clinical Immunology of Province of Jiangsu, the First Affiliated Hospital of Soochow University, Suzhou 215006, China.
Zhongguo Fei Ai Za Zhi. 2009 Aug 20;12(8):859-63. doi: 10.3779/j.issn.1009-3419.2009.08.05.
Tumor-associated PD-L1 expression was recently shown to promote T-cell apoptosis and proposed as a potential mechanism of immune evasion by tumors. On the basis of the ability of tumor-associated PD-L1 to mediate activated T-cell death, it is likely that manipulation of the PD-L1 pathway at defined time points during the development of the T-cell antitumor immune response can enhance the efficacy of T-cell-based immunotherapy. Here, the levels of expression of PD-L1 on lung cancer cell lines and its role in interaction of CTL and target cells was investigated.
Human PBMC derived DCs were loaded with apoptotic tumor cells and stimulated by CD40 mAb (5C11). Tumor specific CTL was generated in vitro by autologous T cells co-cultured with mature DCs. Expression of PD-L1 on lung cancer cell lines H1299 and A549 were analyzed by FCM. JAM assay was used to detect the cytolytic activity of CTL with or without blocking PD-L1 by PD-L1 mAb respectively. The concentrations of IFN-gamma in supernatants from distinct groups were analyzed by ELISA.
Tumor cells-loaded mature DCs could induce the generation of the tumor specific CTL. Expression of PD-L1 was low on A549 cell, but high on H1299 cell. Blockade of PD-L1 on A549 could not improve cytolytic effect of CTL on target cells and IFN-gamma production, but fragmentation of H1299 cells and IFN-gamma production were significantly enhanced by the combination of PD-L1 mAb and CTL.
Expression of PD-L1 on lung cancer cell line can decrease the cytolytic effect of CTL on target cells.
肿瘤相关的程序性死亡配体-1（PD-L1）表达最近被证明可促进T细胞凋亡，并被认为是肿瘤免疫逃逸的一种潜在机制。基于肿瘤相关PD-L1介导活化T细胞死亡的能力，在T细胞抗肿瘤免疫反应发展的特定时间点操纵PD-L1途径可能会增强基于T细胞的免疫治疗效果。在此，研究了肺癌细胞系上PD-L1的表达水平及其在细胞毒性T淋巴细胞（CTL）与靶细胞相互作用中的作用。
用人外周血单个核细胞（PBMC）来源的树突状细胞（DC）负载凋亡肿瘤细胞，并通过CD40单克隆抗体（5C11）刺激。通过与成熟DC共培养的自体T细胞在体外产生肿瘤特异性CTL。通过流式细胞术分析肺癌细胞系H1299和A549上PD-L1的表达。分别用PD-L1单克隆抗体阻断或不阻断PD-L1，采用JAM试验检测CTL的细胞溶解活性。通过酶联免疫吸附测定（ELISA）分析不同组上清液中γ-干扰素（IFN-γ）的浓度。
负载肿瘤细胞的成熟DC可诱导产生肿瘤特异性CTL。A549细胞上PD-L1表达低，而H1299细胞上表达高。阻断A549上的PD-L1不能提高CTL对靶细胞的细胞溶解作用和IFN-γ产生，但PD-L1单克隆抗体与CTL联合使用可显著增强H1299细胞的裂解和IFN-γ产生。
肺癌细胞系上PD-L1的表达可降低CTL对靶细胞的细胞溶解作用。
