159 METFORMIN DOWNREGULATES PD-L1 EXPRESSION IN ESOPHAGEAL SQUAMOUS CELL CARCINOMA BY INHIBITING IL-6 SIGNALING PATHWAY,Diseases of the Esophagus

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159 METFORMIN DOWNREGULATES PD-L1 EXPRESSION IN ESOPHAGEAL SQUAMOUS CELL CARCINOMA BY INHIBITING IL-6 SIGNALING PATHWAY
Diseases of the Esophagus ( IF 2.3 ) Pub Date : 2021-09-17 , DOI: 10.1093/dote/doab052.159
Feng Wang ₁ , Dao Xin ₁ , Xiangrui Meng ₁ , Qingxia Fan ₁

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ESCC is an aggressive cancer with poor prognosis in China. Metformin with low cost and toxicity have proved to have anti-cancer effects in many kinds of cancers, while its role in combination of immune checkpoint blockade and mechanism in ESCC has seldom been studied. This study was designed to evaluate the potential role of combinatorial anti-tumor effect with metformin and immunomodulatory monoclonal antibodies (mAbs) targeting programmed cell death protein-1 (PD-1) in vitro and in vivo. Methods Reverse transcription-quantitative polymerase chain reaction, western blot and immunohistochemistry (IHC) assays were used to study the effects of metformin on the expression levels of PD-L1. In addition, T cell activation and killing assay were performed in the co-culture system of ESCC cell and peripheral blood mononuclear cells (PBMCs) treated with metformin or IL-6 to evaluate the function of inhibiting PD-L1 expression. In vivo assay, we used NPIdKOTM mice model, which was re-constructed replaced immune system by transplanting PBMCs through intravenously injecting. Mice were treated with metformin alone as well as in combination with anti-PD-1 mAbs. Results PD-L1 expression were downregulated by metformin via JAK2 and STAT3 signaling pathway. The results showed that metformin promoted CD3/CD28 induced ERK phosphorylation at a dose dependent measure. And IL-2 was increased in the supernatant of KYSE-450/PBMC coculture system after metformin treatment. Both of which are indicators of T cell activation. T cell mediated tumor killing assay showed that metformin inducing PD-L1 downregulation could protect T cell function, and it could be reversed by IL-6. It showed that metformin enhanced its efficacy in TE-7 cells-harboring mice in the combination treatment group, reflected by tumor sizes assay, and in vivo imaging system. Conclusion Various approaches are under way to expand the benefits and improve the efficacy of these immune checkpoint inhibitors. Another approach is combining immunotherapy with existing anticancer therapies. In this regard, we have evaluated the mechanism of metformin inhibiting PD-L1 expression in ESCC. This finding indicated that metformin significantly improved the antitumor effects by anti-PD-1 blockade without detectable toxicity and suggested that metformin has strong potential to be used in combination with immunotherapy.

更新日期：2021-09-17

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