Upregulation of syncytin-1 promotes invasion and metastasis by activating epithelial-mesenchymal transition-related pathway in endometrial carcinoma

Background: Endometrial carcinoma (EC) is the most common and lethal malignancy worldwide. Syncytin-1 is expressed in multiple types of cancer. However, the expression A-pattern and potential mechanism of syncytin-1 and its clinical significance in EC remain unclear. Materials and methods: We analyzed 130 primary EC specimens from Binzhou Medical University to investigate the clinical role of syncytin-1 in EC by using different advanced pathological stages of EC tissues. Kaplan-Meier analysis was used to measure the overall survival of EC patients. Syncytin-1 expression was analyzed by Western blot assays in HECCL-1 and RL-95-2 cells. Cell proliferation, cycle, migration, and invasion abilities were detected by cell counting kit-8, flow cytometry, and transwell assays. AKT and epithelial-mesenchymal transition (EMT)-related genes were assessed by Western blot assays in HECCL-1 and RL-95-2 cells. Results: Syncytin-1 was upregulated in EC tissues and cells and was related to clinical stages, expression of ER, Ki-67, and overall survival of EC. Functional research revealed that overexpression of syncytin-1 can promote cell proliferation, cell cycle progression, and the migration and invasion of EC cells. Suppression of syncytin-1 expression also inhibited cell proliferation and apoptosis in vitro. The expression of syncytin-1 substantially improved the expression levels of EMT-related genes (vimentin, E-cadherin, slug, and ZEB1) but significantly decreased those of epithelial markers (N-cadherin and snail). In addition, we found that syncytin-1 was not correlated with AKT-related genes (total-AKT, p-AKT, and vinculin). Conclusion: Our results suggested that syncytin-1 may promote aggressive behavior and can serve as a novel prognostic biomarker for EC. Our study provides new insights into the regulatory mechanism of EMT signaling.