Abstract 4599: PD-1/PD-L1 axis in cancer cells contributes to cellular EMT in lung adenocarcinoma

Abstract

Abstract Background: Since intrinsic PD-1 receptor functions promote tumor growth was reported, we will investigate the role of PD-L1 in lung adenocarcinoma cells, and their impact on clinical outcome. Materials and methods: Lung adenocarcinoma CL1-5 cells, derived from CL1-0 cells have more invasive ability. We prepared PDL1-overexpression human lung adenocarcinoma cell line, derived from CL1-0 cells (CL1-0-PD1) and from PC14PE6 cells (PC14PE6-PD-L1). We observed the cellular morphology, and invasiveness; epithelial-mesenchymal transition (EMT) markers and regulators were also evaluated. To explore interaction between PD-1 and PD-L1, we treated the CL1-0, CL1-5, CL1-0-PDL1 cells, PC14PE6 cells, and PC14PE6-PD-L1 cells with anti-PD-1 antibody, and then evaluated cellular invasion. We also suppressed PD-1 to test whether PD-1/PDL-1 interaction contributed to the EMT change. Further, we evaluated cellular proliferation and chemosensitivity by MTT assay and colony formation assay. Finally, we correlated PD-L1 expression with clinical outcome in patients’ tumor specimen. Results: CL1-5 cells possessed higher PD-L1 expression than parental CL1-0 cells. CL1-0 cells with PD-L1 overexpression had more expression of EMT regulators and mesenchymal markers. Overexpression of PD-L1 in another lung adenocarcinoma PC14PE cells (PC14PE6-PD-L1 cells) become more aggressive. On the contrary, down-regulation of PD-L1 in CL1-5 cells and PC14-PE6-PD-L1 cells became indolent. Besides through the observation from confocal microscopy, PD-L1 expression was more co-localized with vimentin and slug, individually in CL1-5, CL1-0-PD-L1 and PC14PE6-PD-L1 cells. Therefore, PD-L1 promoted EMT in human lung adenocarcinoma cells. After adding anti-PD-1 antibody in CL1-5, CL1-0, and CL1-0-PDL1 cells, migration and invasion ability were decreased. Similar phenomenon was found when PD-1 antibody treatment in PC14PE6 cells, and PC14PE6-PD-L1 cells. Silencing PD-1 by siRNA also disrupt the cellular aggressivenss in CL1-0-PD-L1 and PC14PE6-PD-L1 cells. These results indicated PD-1/PD-L1 axis regulated cancer cells migration and invasiveness. PD-L1 expression also decreased cellular proliferation and had little influence on chemsensitivity. Finally, we found that higher PD-L1 expression was correlated with lymph node metastasis in clinical specimen. Conclusion: Lung adenocarcinoma cells with higher PD-L1 expression promote EMT via PD-1 receptor. PD-L1 expression lowers proliferation rate, but has little impact on chemosensitivity. Lung cancer patients with high PD-L1 expression in tumor have higher lymph node metastasis. Citation Format: Wen-Pin Su, Li-Chan Chang, Jing-Jou Yan, Wu-Chou Su. PD-1/PD-L1 axis in cancer cells contributes to cellular EMT in lung adenocarcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4599.