Department of Medical Oncology and Cancer Center, Shiga University of Medical Science, Seta-Tsukinowa, Otsu, Shiga 520-2192, Japan; Center for Advanced Medicine against Cancer, Shiga University of Medical Science, Seta-Tsukinowa, Otsu, Shiga 520-2192, Japan; Center for Antibody and Vaccine Therapy, Research Hospital, Institute of Medical Science, The University of Tokyo, 4-6-1, Shirokanedai, Minato-ku, Tokyo 108-8639, Japan.
Department of Surgery, Shiga University of Medical Science, Seta-Tsukinowa, Otsu, Shiga 520-2192, Japan.
Lung Cancer. 2019 Nov;137:56-63. doi: 10.1016/j.lungcan.2019.09.013. Epub 2019 Sep 16.
Cancer-associated fibroblasts (CAFs) are a dominant cell type in tumor stroma and support the generation of pro-tumorigenic microenvironment. CAFs have frequent opportunities to interact with immune cells infiltrating the tumor stroma, but the process remains to be determined. In this study, we focused on immune checkpoint mechanism. We also examined the induction of programmed cell death-ligand 1 (PD-L1) on CAFs by immune cell, and the clinical significance of PD-L1-expressed CAFs in non-small cell lung cancer (NSCLC).
CAFs were isolated from human NSCLC tissues, and PD-L1 expression levels in CAFs were analyzed by real-time polymerase chain reaction and flow-cytometry. Following immunohistochemical analysis of PD-L1 in surgically resected pN0M0 NSCLC (n = 125, including 88 invasive adenocarcinomas and 37 squamous cell carcinomas), the correlation of PD-L1-positive CAFs with clinicopathological features was investigated.
PD-L1 mRNA and protein expression on CAFs was upregulated by exogenously supplemented interferon-gamma (IFN-γ) and downregulated through the depletion of IFN-γ. PD-L1 expression on CAFs was upregulated by co-culture with activated lymphocytes releasing IFN-γ. Immunohistochemistry revealed that PD-L1-positive CAFs were observed in 31 cases (24.8%). Postoperative relapse-free survival was significantly prolonged in patients with PD-L1-positive CAFs as compared with those with PD-L1-negative CAFs, with 5-year relapse-free probabilities of 84.5% and 66.3%, respectively (P = 0.031). Multivariate analysis revealed that PD-L1 expression on CAFs was an independent prognostic factor of longer relapse-free survival after surgery (hazard ratio: 3.225, P = 0.027).
PD-L1 expression on CAFs is reversibly regulated by environmental stimuli including IFN-γ from activated lymphocytes. In the non-metastatic NSCLC, PD-L1 expression on CAFs suggests the induction of anti-tumor immune responses, contributing to better prognosis after surgery.
癌症相关成纤维细胞（CAFs）是肿瘤基质中主要的细胞类型，支持生成促肿瘤微环境。CAFs 有频繁的机会与浸润肿瘤基质的免疫细胞相互作用，但这一过程仍有待确定。在这项研究中，我们重点研究了免疫检查点机制。我们还研究了免疫细胞对 CAFs 程序性细胞死亡配体 1（PD-L1）的诱导作用，以及 PD-L1 表达的 CAFs 在非小细胞肺癌（NSCLC）中的临床意义。
从人非小细胞肺癌组织中分离 CAFs，通过实时聚合酶链反应和流式细胞术分析 CAFs 中 PD-L1 的表达水平。对 125 例手术切除的 pN0M0 NSCLC（包括 88 例浸润性腺癌和 37 例鳞状细胞癌）进行 PD-L1 的免疫组织化学分析，研究 PD-L1 阳性 CAFs 与临床病理特征的相关性。
外源性补充干扰素-γ（IFN-γ）可上调 CAFs 中 PD-L1 mRNA 和蛋白的表达，而 IFN-γ 耗竭则可下调其表达。CAFs 与释放 IFN-γ 的活化淋巴细胞共培养可上调 PD-L1 的表达。免疫组化显示 31 例（24.8%）患者的 CAFs 呈 PD-L1 阳性。与 PD-L1 阴性 CAFs 相比，PD-L1 阳性 CAFs 患者的术后无复发生存期显著延长，5 年无复发生存率分别为 84.5%和 66.3%（P=0.031）。多因素分析显示，CAFs 中 PD-L1 的表达是手术切除后无复发生存期延长的独立预后因素（风险比：3.225，P=0.027）。
CAFs 中 PD-L1 的表达可被包括活化淋巴细胞产生的 IFN-γ在内的环境刺激物可逆调节。在非转移性 NSCLC 中，CAFs 中 PD-L1 的表达提示诱导了抗肿瘤免疫反应，有助于手术后更好的预后。
