Cancer-associated fibroblasts derived-exosomal circ_0076535 promotes esophageal squamous cell carcinoma progression

BackgroundEsophageal cancer (EC) is a common malignant tumor of the digestive tract and an important health-related problem in many developing countries. Esophageal squamous cell carcinoma (ESCC) is the most common subtype of EC. The cancer-associated fibroblasts (CAFs) are the major stromal cells in ESCC microenvironment. They play important role in ESCC proliferation, metastasis, angiogenesis and chemotherapy resistance through paracrine processes. However, the roles of circRNAs enriched in CAF-derived exosmes have not been reported.ObjectiveTo explore the mechanisms of how CAF affects ESCC proliferation and metastasis through paracrine processes and to investigate the role of circRNAs enriched in CAF-derived exosomes.MethodsExosomes were isolated from the conditional medium of CAF using differential ultracentrifugation, and then validated by Nanosight analysis. Exosome secretion inhibitor-GW4869 validates the pro-carcinogenic role of exosomes. The qRT-PCR showed the highest expression of circ_0076535 in the exosomal CircRNA, and knockdown of it confirmed its function. Online bioinformatics tool was utilized to predict the potential target gene of circ_0076535, and captured miR-145-5p as the target gene with high predictive value. The targeting association between miR-145-5p and circ_0076535 is further confirmed by the dual luciferase reporter experiment. The stimulation of tumour development and EMT by the CAF-derived exosome circ_0076535 is further validated <i>in vivo.</i>ResultsIn our research, we found that CAF-derived exosomes increased proliferation, migration, invasion and EMT in ESCC cells. Circ_0076535 was highly enriched in CAF-exosomes and transferred into ESCC cells directly depend on internalization of exosomes. CAF-exosomal circ_0076535 increased the level of circ_0076535 in ESCC cells and induced EMT. Mechanistic experiments revealed circ_0076535 acted as a sponge to absorb miR-145-5p and activated NF-κB signaling pathway.<b>Conclusions:</b> Conclusively, CAF-exosomal circ_0076535 promoted the ESCC progression via miR-145-5p/NF-κB axis and expected to be a potential biomarker for early diagnosis and treatment of ESCC.