Abstract 3625: MET signaling upregulates PD-L1 expression in human lung and gastric cancer

Abstract

Abstract Background: Tyrosine kinase receptor, MET, plays an important role for the progression of tumor through diverse mechanisms. Cancer immunotherapy targeting PD-1/PD-L1 pathway shows clinical benefit in patient with PD-L1 expressing solid tumor. In our previous study on non-small cell lung cancer (NSCLC) using immunohistochemistry, MET overexpression was significantly associated with programmed cell death-ligand 1 (PD-L1) overexpression. Thus, we investigated if MET signaling pathway is involved in PD-L1 expression in tumor cells. Method and Result: Lung adenocarcinoma cell lines including H596 (harboring MET exon 14 skipping mutation), H1993 (harboring MET gene amplification), H23 and H522 (MET wild-type), and a gastric carcinoma cell line, Hs746T (harboring MET exon 14 skipping mutation and gene amplification) were used. Hs746T cells were treated with MET inhibitor or transfected with MET siRNA and subject to microarray analysis. MET inhibition or knockdown led to changes in expression level of variable immune-related molecules, of which PD-L1 was one of the most down-regulated molecules. Stimulation of H596, H23 and H522 cells with HGF, a MET ligand, increased PD-L1 expression at the mRNA and protein level. Treatment of H1993 and Hs746T cells with MET inhibitor or MET knockdown using siRNA resulted in down-regulation of PD-L1 at the mRNA, total protein, and surface expression levels. PI3K/Akt and MAPK/Erk signaling pathways were involved in MET-mediated PD-L1 up-regulation in H1993 and Hs746T cells. Finally, the Cancer Genome Atlas (TCGA) analysis showed that MET and PD-L1 expression are significantly positively correlates with each other in patients with lung cancer (in NSCLC, rho=0.219 [p<0.001]; in adenocarcinoma, r=0.401 [p<0.001]; in squamous cell carcinoma, r=0.144 [p=0.001]) and in patients with gastric cancer (r=0.137 [p=0.005]). Conclusion: This study demonstrates that MET signaling increases PD-L1 transcription and protein overexpression in lung and gastric cancer cells, which might contribute to immune escape of tumor via PD-1/PD-L1 pathway. MET-targeted therapy may be considered as combination therapy with PD-1/PD-L1 blockades. Citation Format: Hyunkyung Ahn, Sehui Kim, Ji Young Jang, Dohee Kwon, Jaemoon Koh, Young A Kim, Doo Hyung Chung, Yoon Kyung Jeon. MET signaling upregulates PD-L1 expression in human lung and gastric cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3625.