Abstract 4980: Upregulation of PD-L1 expression by cisplatin in esophageal squamous cell carcinoma cells is independent of interferon/JAK/STAT pathway
Authors: Huang Ta-Chen , Lin Kuan-Ling , Cheng Ann-Lii , Hsu Chih-Hung 
Published: July 2016

Abstract
Introduction
Blockade of immune check points, especially the program cell death 1 (PD-1) and its major ligand PD-L1 signaling, has become an important mode of therapy against cancers. The upregulation of PD-L1 expression in cancer cells is an important mechanism contributing to immune evasion of cancers. The PD-L1 upregulation in cancer cells could be mediated by intrinsic genetic or signaling alterations, or could be induced in response to specific cytokines, in particular interferon (IFN)-gamma, produced by tumor-infiltrating immune cells. Whether chemotherapy per se has direct impact on PD-L1 expression in cancer cells is currently unclear.
Materials and Methods
Four esophageal squamous cell carcinoma (ESCC) cell lines, TE5, KYSE70, KYSE270, KYSE510, were included. The expression of PD-L1 in ESCC cells, treated with various concentrations of cisplatin, were evaluated by flow cytometry, Western blotting, and qRT-PCR. To study the potential signaling pathways involved in the PD-L1 upregulation induced by cisplatin, we evaluated the nuclear expression of p-STAT1 and IRF1 (for IFN/JAK/STAT pathway), and p65 and p50 (for NF-kB pathway). Finally, we used BAY-11-7082, an irreversible inhibitor of IKKα, to validate the significance of NF- kB pathway in mediating the PD-L1 upregulation induced by cisplatin.
Results
Cisplatin at the doses of 5∼ 10 μM increased the proportions of PD-L1-expressing cells detected by flow cytometry in all tested ESCC cells. The folds of increase were 19.29±2.27, 10.13±8.42, 23.19±10.12, 6.20±0.81 for TE5, KYSE70, KYSE270, and KYSE510 treated with 10 μM of cisplatin, respectively. The kinetics of this cisplatin- induced PD-L1 expression, evaluated in TE5 cells, was: after exposure to cisplatin for 24 hours, the PD-L1 expression peaked at 48 hours, and remained elevated at 144 hours after drug exposure. In multiple ESCC cells, exposure to cisplatin did not increase the expression of p-STAT1 and IRF1, suggesting that IFN/JAK/STAT pathway did not involve in the PD-L1 upregulation induced by cisplatin. In co-culture experiments with cisplatin-treated TE5 cells or with condition medium from cisplatin-treated TE5 cells, we confirmed that the PD-L1 upregulation in ESCC cells was not through paracrine manners. In TE5 cells, cisplatin treatment induced nuclear translocation of p65, suggesting that NF-kB pathway was activated. The cotreatment of BAY11-7082 could partially abrogate the PD-L1 upregulation induced by cisplatin in TE5 cells.
Conclusion
PD-L1 expression in ESCC cancer cells can be up-regulated by cisplatin. Our data indicated that this activation is not mediated through the IFN/JAK/STAT pathway, but may involve in activation of NF-κB signaling. (The study was supported by the grant NTUH 104-M2891 and the grant MOST 104-2314-B-002-111)
Citation Format: Ta-Chen Huang, Kuan-Ling Lin, Ann-Lii Cheng, Chih-Hung Hsu. Upregulation of PD-L1 expression by cisplatin in esophageal squamous cell carcinoma cells is independent of interferon/JAK/STAT pathway. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4980.