Department of Chemical Engineering, University of Michigan, Ann Arbor, MI, USA.
Biointerfaces Institute, University of Michigan, Ann Arbor, MI, USA.
Sci Rep. 2019 Jan 24;9(1):566. doi: 10.1038/s41598-018-36096-7.
Preclinical studies demonstrated that radiation up-regulates PD-L1 expression in tumor cells, providing a rationale for combining PD-1/PD-L1 inhibitors with radiation. However this has not been validated in patients with non-small cell lung cancer due to the difficulty to obtain serial biopsies. Measuring PD-L1 expression in circulating tumor cells (CTCs), may allow real-time monitoring of immune activation in tumor. In this study, whole blood from non-metastatic NSCLC patients was collected before, during, and after radiation or chemoradiation using a microfluidic chip. PD-L1 expression in CTCs was assessed by immunofluorescence and qPCR and monitored through the course of treatment. Overall, PD-L1(+) CTCs were detected in 25 out of 38 samples (69.4%) with an average of 4.5 cells/ml. After initiation of radiation therapy, the proportion of PD-L1(+) CTCs increased significantly (median 0.7% vs. 24.7%, P < 0.01), indicating up-regulation of PD-L1 in tumor cells in response to radiation. In addition, patients positive for PD-L1 (≥5% of CTCs positive for PD-L1) at baseline had shorter PFS. Gene expression analysis revealed that higher levels of PD-L1 were associated with poor prognosis. Therefore, CTCs can be used to monitor dynamic changes of PD-L1 during radiation therapy which is potentially prognostic of response to treatment.
临床前研究表明，辐射会上调肿瘤细胞中 PD-L1 的表达，为 PD-1/PD-L1 抑制剂与辐射联合提供了理论依据。然而，由于难以获得连续的活检，这在非小细胞肺癌患者中尚未得到验证。测量循环肿瘤细胞（CTC）中的 PD-L1 表达，可能允许实时监测肿瘤中的免疫激活。在这项研究中，使用微流控芯片从非转移性 NSCLC 患者的全血中在放疗或放化疗之前、期间和之后采集。通过免疫荧光和 qPCR 评估 CTC 中的 PD-L1 表达，并在治疗过程中进行监测。总的来说，在 38 个样本中的 25 个（69.4%）中检测到 PD-L1(+)CTC，平均每毫升 4.5 个细胞。在开始放疗后，PD-L1(+)CTC 的比例显著增加（中位数 0.7%比 24.7%，P<0.01），表明肿瘤细胞对辐射的 PD-L1 上调。此外，基线时 PD-L1（≥5%的 CTC 阳性）的患者 PFS 更短。基因表达分析显示，PD-L1 水平较高与预后不良相关。因此，CTC 可用于监测放疗期间 PD-L1 的动态变化，这可能与对治疗的反应预后相关。
