EPHX1 enhances drug resistance to regorafenib by activating the JAK/STAT signaling pathway in hepatocellular carcinoma cell lines.

BACKGROUND: Regorafenib serves as a second-line treatment for patients with advanced hepatocellular carcinoma (HCC). Microsomal epoxide hydrolase 1 (EPHX1) is closely associated with tumorigenesis and drug resistance. However, the relationship between EPHX1 and regorafenib resistance, as well as the underlying mechanisms in HCC, remains unclear. OBJECTIVE: To investigate the role and mechanisms of EPHX1 in mediating regorafenib resistance in HCC. METHODS: We assessed the protein expression levels of EPHX1 in human HCC tissues and adjacent non-tumor tissues. Subsequently, we constructed HCC cell lines with EPHX1 overexpression and knockdown using lentiviral vectors and stimulated these cells with varying concentrations of regorafenib. We then measured cell proliferation and apoptosis using flow cytometry and Western blotting. Additionally, we established xenograft tumor models to explore the impact of EPHX1 on the in vivo efficacy of regorafenib. Furthermore, we employed digital gene expression sequencing (DGE-seq) to investigate and validate the specific molecular mechanisms by which EPHX1 mediates regorafenib resistance in HCC cells. RESULTS: We found that EPHX1 protein levels were significantly higher in HCC tissues compared to adjacent non-tumor tissues. EPHX1 inhibited the effects of regorafenib on cell proliferation and apoptosis. Consistently, the efficacy of regorafenib was enhanced in vivo following EPHX1 knockdown. Moreover, KEGG pathway enrichment analysis of DGE-seq data indicated that the JAK/STAT signaling pathway is crucial for EPHX1-induced regorafenib resistance. Finally, EPHX1 suppressed regorafenib-induced inactivation of the JAK/STAT signaling pathway and blocking this pathway with HY-N1447 alleviated EPHX1-induced regorafenib resistance. CONCLUSION: In summary, we conclude that EPHX1 enhances regorafenib resistance in HCC by activating the JAK/STAT signaling pathway. Our findings suggest that EPHX1 is a key resistance-related gene, which has significant implications for the application of regorafenib in advanced HCC.