Essential role of ALKBH5-mediated RNA demethylation modification in bile acid-induced gastric intestinal metaplasia

Reflux of bile acids and subsequent caudal-related homeobox 2 (CDX2) activation contribute to gastric intestinal metaplasia (IM), which is a precursor of gastric cancer. However, the underlying mechanism by which bile acids cause this is not entirely clear. Here we demonstrated that alkylation repair homolog protein 5 (ALKBH5), which is a major RNA N6-adenosine demethylase, was required for bile acid-induced gastric IM. Mechanistically, we revealed the N6-methyladenosine (m6A) modification profile in gastric IM for the first time and identified ZNF333 as a bona fide m6A target of ALKBH5. ALKBH5 was shown to demethylate ZNF333 mRNA, leading to enhanced ZNF333 expression by abolishing m6A-YTHDF2-dependent mRNA degradation. In addition, ALKBH5 activated CDX2 and downstream intestinal markers by targeting the ZNF333/CYLD axis and activating NF-?B signaling. Reciprocally, p65, which is the key transcription factor of the canonical NF-?B pathway, enhanced the transcription activity of ALKBH5 in the nucleus, thus forming a positive feed-forward circuit. In addition, ALKBH5 levels were positively correlated with ZNF333 and CDX2 in IM tissues, indicating a significant clinical relevance. Collectively, our findings suggest an m6A modification-associated positive feed-forward loop between ALKBH5 and NF-?B signaling is involved in the generation of the IM phenotype from gastric epithelial cells. Targeting the ALKBH5/ZNF333/CYLD/CDX2 axis might be a useful therapeutic strategy for gastric IM in patients with bile regurgitation. Overall design: We compared the RNA m6A sites in CDCA treated GES-1 cells and control, and input was analyzed for gene expression level.