Hypoxia combined with radiation reverses migration and invasion of head and neck squamous cell carcinoma by remodeling extracellular vesicle-mediated transfer of miR-23b-5p from cancer-associated fibroblasts

Background: Cancer-associated fibroblasts(CAFs), the main matrix components in the tumor microenvironment(TME), play a crucial role in tumor progression. Extracel ular vesicles(EVs) as main mediators in intercel ular communication can be regulated by hypoxia or radiation.Methods: CAFs were extracted from head and neck squamous cel carcinoma(HNSCC) tissues and CAF-derived EVs were col ected by ultracentrifugation.Bioinformatics analysis determined the role of poly(U)-specific endonuclease(ENDOU) on HNSCC progression and confirmed that ENDOU inhibited HNSCC progression by overexpressing ENDOU in HNSCC. Dual-luciferase activity report assay confirmed that miR-23b-5p was involved in the regulation of ENDOU expression. The migration and invasion of HNSCC cel s were verified by transwel assay. Furthermore, tumor-bearing mouse models were used to demonstrate the potential of EVs loaded with miR-23b-5p in HNSCC to promote tumor progression.Results: Our results showed that ENDOU was downregulated in HNSCC and inhibited HNSCC migration and invasion. Hypoxia and radiotherapy reversed CAF-derived EVs to promote migration and invasion of HNSCC.Mechanically, hypoxia and radiation downregulated miR-23b-5p in CAFderived EVs and then restored ENDOU expression in HNSCC. Finally,CAF-derived EVs carrying miR-23b-5p promoted the progression of HNSCC cells in vivo by regulating ENDOU expression.Conclusion: This study demonstrated that hypoxia combined with radiation reverses the promoting effect of CAFs on HNSCC migration and invasion by reducing the delivery of miR-23b-5p by CAF-derived EVs to decrease the inhibitory effect of ENDOU expression in HNSCC. The results provide a new perspective for better understanding the role of stromal components in TME in tumor regulation. Furthermore, the results provide a strong basis for the possibility of ENDOU as a biomarker for HNSCC.