TRAIL Promotes Epithelial-to-mesenchymal Transition by Inducing PD-L1 Expression in Esophageal Squamous Cell Carcinomas

Abstract Background: Tumor necrosis factor-associated apoptosis-inducing ligand (TRAIL) was initially considered an immunity guard; however, its function remains controversial. Besides immune cells, lung and colon cancer cells have also been reported to express TRAIL, which can promote tumor invasion and metastasis. However, the biological function and underlying mechanism of action of TRAIL in esophageal squamous cell carcinoma (ESCC) remain poorly elucidated.Methods: The ESCC cells stemness, migration, and proliferation ability was assessed by sphere formation, Transwell, and CCK8 assay. The stemness- and EMT- related genes expression levels were analyzed by Western blot and RT-qPCR. The signal activation was conducted by Western blot. The PDX Model were performed to confirm our findings in vitro.Results: Herein, we found that TRAIL is a negative predictor in patients with ESCC. To further investigate the biological function of TRAIL, we established TRAIL knockdown and overexpression ESCC cell lines and found that TRAIL induced epithelial-mesenchymal transition (EMT) and promoted tumor aggressiveness. Furthermore, we demonstrated that TRAIL- overexpressing cells upregulated PD-L1 expression, which was dependent on the p-ERK/STAT3 signaling pathway. We obtained similar results when using recombinant human TRAIL. Finally, we validated the biological role and mechanism of action of TRAIL in vivo.Conclusions: These findings demonstrate that TRAIL promotes ESCC progression by enhancing PD-L1 expression, which induces EMT. This may explain the failure of TRAIL preclinical trials.Financial support: This work was supported by the National Key Research and Development (2018YFC1313400), the National Nature Science Foundation of China (U1804281, 91942314) and the National Science Fund for Distinguished Young Scholars (82001659).