Abstract 4254: Changes in PD-L1 expression during cisplatin containing treatment in patients with head and neck squamous cell carcinoma, and their association with epithelial-mesenchymal transformation

Abstract

Abstract Background: Programmed death-ligand 1 (PD-L1) expression is regarded as a predictive marker to anti-PD-1/ PD-L1 therapy. However, the underlying mechanism of PD-L1 up-regulation has been poorly defined. The purposes of study are to explore 1) the changes of PD-L1 expression in head and neck squamous cell carcinoma (HNSCC) during cisplatin containing treatment, and 2) PD-L1 up-regulation related genetic alteration. Methods: We compared PD-L1 expressions by immunohistochemisty (IHC, score 0-3) with rabbit anti-PD-L1 antibody (E1L3N) XP (Cell Signaling Technology, Danvers, MA, USA) of 33 baseline tissue samples of HNSCC and 17 paired follow-up tissue samples after ciaplain containing treatment. Baseline PD-L1 expression as well as a change of PD-L1 expression were analyzed with overall survival (OS) of the patients. Changes of PD-L1 expressions in HPV-negative PD-L1 positive HNSCC cell lines (SNU-1066, SNU-1076, Detroit-562) were also analyzed by flow cytometry after various dose of cisplatin treatment. RNA sequencing (RNAseq) of eight HNSCC cell lines was analyzed to find genes of significant correlation with PD-L1 expression by regression method. RNA expression of PD-L1 was assayed by comparing ranks of fragments per kilobase of transcript per million. Results: Among the 17 patients who had paired samples after cisplatin containing treatment, PD-L1 expressions of HNSCC tumor were changed in 10 patients (58.8%). PD-L1 expressions were decreased in 5 patients, and increased in 5 patients. We analyzed changes of PD-L1 expression in 3 HPV negative PD-L1 positive HNSCC cell lines, In vitro, PD-L1 expression was up-regulated after cisplatin treatment in dose-dependent manner (1-10 micromole/L for 24 hours). RNA expression profile by RNAseq of 8 HNSCC cell lines showed that PD-L1 expression was significantly correlated with expression level of epithelial-mesenchymal transformation (EMT) related genes. Expression of epithelial markers such as EPCAM, E-cadherin, SYK, and MUC1 were decreased as PD-L1 expression increased, in contrast, the positive correlations between PD-L1 and mesenchymal markers such as Vimentin, ADAM12, FGF2, and FGFR1 were observed. Conclusion: PD-L1 expression in HNSCC can be changed during cisplatin containing treatment in more than half of patients. When considering anti PD-1/ PD-L1 therapy, PD-L1 expression should be evaluated using most recent biopsy. In vitro, PD-L1 expression was induced in response to cisplatin, and it was correlated with EMT related gene expression. Citation Format: Chan-Young Ock, Bhumsuk Keam, Sehui Kim, Jong-Yeon Shin, Yong-Oon Ahn, Tae Min Kim, Yoon Kyung Jeon, Se-Hoon Lee, Dong-Wan Kim, Dae Seog Heo. Changes in PD-L1 expression during cisplatin containing treatment in patients with head and neck squamous cell carcinoma, and their association with epithelial-mesenchymal transformation. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4254. doi:10.1158/1538-7445.AM2015-4254