Hypoxia induced changes in miRNAs and their target mRNAs in extracellular vesicles of esophageal squamous cancer cells

BACKGROUND: Extracellular vesicles (EVs) are endogenous membrane vesicles with a diameter of 30–200 nm. It has been reported that hypoxic cancer cells can release numerous EVs to mediate multiple regional and systemic effects in the tumor microenvironment. METHODS: In this study, we used ultracentrifugation to extract EVs secreted by TE‐13, an esophageal squamous carcinoma (ESCC) cell line during normoxia and hypoxia and performed high‐throughput sequencing to detect exosomal miRNAs. Gene ontology (GO) and KEGG pathway analyses were used to reveal pathways potentially regulated by the miRNAs. RESULTS: A total of 10 810 miRNAs were detected; 50 were significantly upregulated and 34 were significantly downregulated under hypoxic environment. GO analysis identified enrichment of protein binding, regulation of transcription (DNA‐templated), and membrane as molecular function, biological process, and cellular component, respectively. KEGG pathway analysis revealed cancer‐associated pathways, phospholipase D signaling pathway, autophagy, focal adhesion and AGE‐RAGE signaling as the key pathways. Further verification experiment from qRT‐PCR indicated that miR‐128‐3p, miR‐140‐3p, miR‐340‐5p, miR‐452‐5p, miR‐769‐5p and miR‐1304‐p5 were significantly upregulated in EVs from hypoxia TE‐13 cells while miR‐340‐5p was significantly upregulated in two other ESCC cells, ECA109 and TE‐1. CONCLUSION: This study, for the first time reveals changes in the expression of exosomal miRNAs in hypoxic ESCC cells and these findings will act as a resource to study the hypoxic tumor microenvironment and ESCC EVs.