Mechanistic investigation of microRNA-218 in regulating gastric cancer cell proliferation,migration and epithelial-mesenchymal transition

CHU Min; HUI Yihua; YUE Yiru; ZHANG Li; XIE Jianfang

doi:10.3969/j.issn.1009-0460.2025.07.003

Abstract：Objective To explore the mechanism by which microRNA-218(miR-218)regulates proliferation,migration,and epithelial-mesenchymal transition(EMT)in gastric cancer cells.Methods Functional studies were performed using human gastric cancer cell lines BGC823 and SGC7901,along with normal gastric epithelial cell line GES-1,by transfecting miR-218 mimics,miR-218 inhibitors,or scrambled miRNA control sequences.To verify whether B lymphoma Mo-MLV insertion region 1(BMI1)was involved in the antitumor effects of miR-218,a rescue experiment was conducted in SGC7901 cells by co-transfecting miR-218 mimics and a BMI1 overexpression plasmid.Expression levels of miR-218 and BMI1 mRNA were detected by quantitative real-time reverse transcription polymerase chain reaction.Western blot analysis was performed to examine the protein levels of EMT markers,including E-cadherin(E-cad),N-cadherin(N-cad),Vimentin(Vim),and Twist-related protien 1(TWIST1),as well as BMI1.Cell proliferation and migration abilities were assessed using the methyl thiazolyl tetrazolium assay and wound-healing assay,respectively.A dual-luciferase reporter gene assay confirmed the direct targeting of miR-218 to the 3′ untranslated region(3′UTR)of BMI1.Results Compared with normal gastric epithelial cells GES-1,miR-218 expression was significantly downregulated in gastric cancer cells SGC7901 and BGC823(P<0.001),while BMI1 was upregulated at both mRNA and protein levels(P<0.001).Functional experiments revealed that miR-218 acted as a tumor suppressor in gastric cancer.Overexpression of miR-218 significantly inhibited cell proliferation and migration(P<0.05),whereas inhibition of miR-218 promoted these malignant phenotypes.Additionally,miR-218 regulated the EMT process by upregulating epithelial marker E-cad and downregulating mesenchymal markers N-cad,Vim and TWIST1.Bioinformatics prediction combined with dual-luciferase reporter assays demonstrated that miR-218 directly bound to the 3′UTR of BMI1 mRNA and inhibited its protein expression(P<0.05)without affecting BMI1 mRNA levels.Rescue experiments further confirmed the critical role of BMI1 in miR-218-mediated tumor suppression.Exogenous BMI1 supplementation reversed miR-218's inhibitory effects on gastric cancer cell proliferation,migration and EMT.Conclusion The study reveals that miR-218,which shows reduced expression in gastric cancer,mediates tumor suppression by specifically inhibiting BMI1.These findings position the miR-218/BMI1 regulatory axis as a potential novel target for gastric cancer therapy.