Hypoxia-inducible factor-1α mediates reflux-induced epithelial-mesenchymal plasticity in Barrett's oesophagus patients

Introduction Epithelial-mesenchymal plasticity (EMP), the process through which epithelial cells acquire mesenchymal features, is needed for wound repair but also might contribute to cancer initiation. Earlier, in vitro studies showed that Barrett's cells exposed to acidic bile salt solutions (ABS) develop EMP. Now, we have (1) induced reflux oesophagitis in Barrett's oesophagus (BO) patients by stopping proton pump inhibitors (PPIs), (2) assessed their biopsies for EMP and (3) explored molecular pathways underlying reflux-induced EMP in BO cells and spheroids.Methods 15 BO patients had endoscopy with biopsies of Barrett's metaplasia while on PPIs, and 1 and 2 weeks after stopping PPIs; RNA-seq data were assessed for enrichments in hypoxia-inducible factors (HIFs), angiogenesis and EMP pathways. In BO biopsies, cell lines and spheroids, EMP features (motility) and markers (vascular endothelial growth factor (VEGF), ZEB1, miR-200a&b) were evaluated by morphology, migration assays, immunostaining and qPCR; HIF-1 alpha was knocked down with siRNA or shRNA.Results At 1 and/or 2 weeks off PPIs, BO biopsies exhibited EMP features and markers, with significant enrichment for HIF-1 alpha, angiogenesis and EMP pathways. In BO cells, ABS induced HIF-1 alpha activation, which decreased miR-200a&b while increasing VEGF, ZEB1 and motility; HIF-1 alpha knockdown blocked these effects. After ABS treatment, BO spheroids exhibited migratory protrusions showing nuclear HIF-1 alpha, increased VEGF and decreased miR-200a&b.Conclusions In BO patients, reflux oesophagitis induces EMP changes associated with increased HIF-1 alpha signalling in Barrett's metaplasia. In Barrett's cells, ABS trigger EMP via HIF-1 alpha signalling. Thus, HIF-1 alpha appears to play a key role in mediating reflux-induced EMP that might contribute to cancer in BO.Trial registration number NCT02579460.