Background and Aims:The long non-coding RNA SOX2 overlapping transcript(SOX2-OT)is involved in the regulation of cancer cell cycle and proliferation.Bioinformatics analysis has revealed potential binding sites among miR-409-3p,SOX2-OT,and membrane binding protein annexin A2(ANXA2).This study aims to investigate the expression and functional role of the SOX2-OT/miR-409-3p/ANXA2 axis in gastric cancer cells.Methods:qRT-PCR was used to measure the expression levels of SOX2-OT,miR-409-3p,and ANXA2 mRNA in gastric cancer tissues and cell lines.Gastric cancer cells were transfected with SOX2-OT shRNA plasmid(sh-SOX2-OT),co-transfected with sh-SOX2-OT and miR-409-3p inhibitor,or co-transfected with sh-SOX2-OT and ANXA2 overexpression plasmid.The control groups included blank,shRNA-negative control,inhibitor-negative control,and overexpression plasmid-negative control.Expression levels of SOX2-OT,miR-409-3p,and ANXA2 mRNA,cell proliferation,migration/invasion,apoptosis,and protein expression of Ki-67,cleaved caspase-3,Bax,MMP-9,and ANXA2 were assessed.Dual-luciferase reporter assays were conducted to confirm the targeting relationships among miR-409-3p,SOX2-OT,and ANXA2.A xenograft tumor model in nude mice was used to evaluate the effect of SOX2-OT on gastric cancer tumor growth in vivo.Results:SOX2-OT and ANXA2 expression levels were significantly upregulated,while miR-409-3p was downregulated in gastric cancer tissues(vs.adjacent non-cancerous tissues)and gastric cancer cell lines(vs.normal gastric epithelial cells)(all P＜0.05).In gastric cancer cels,knockdown of SOX2-OT led to decreased expression of SOX2-OT and ANXA2 mRNA and increased expression of miR-409-3p(all P＜0.05),and this was accompanied by reduced proliferation and migration/invasion abilities,and increased apoptosis(all P＜0.05);protein levels of ANXA2,Ki-67,and MMP-9 were significantly decreased,whereas cleaved caspase-3 and Bax levels were significantly increased(all P＜0.05).These effects were reversed by co-transfection with the miR-409-3p inhibitor or ANXA2 overexpression plasmid(all P＜0.05).Dual-luciferase assays confirmed the direct targeting relationships among miR-409-3p,SOX2-OT,and ANXA2.In vivo,knockdown of SOX2-OT significantly inhibited tumor growth in nude mice,with reduced SOX2-OT and increased miR-409-3p expression,as well as decreased ANXA2 and Ki-67 protein positivity in xenograft tissues(all P＜0.05).Conclusion:SOX2-OT is upregulated in gastric cancer cells and may promote malignant behaviors by competitively binding miR-409-3p,thereby relieving its inhibition on ANXA2.The SOX2-OT/miR-409-3p/ANXA2 axis may represent a potential molecular target for gastric cancer therapy.

Background and Aims:The long non-coding RNA SOX2 overlapping transcript(SOX2-OT)is involved in the regulation of cancer cell cycle and proliferation.Bioinformatics analysis has revealed potential binding sites among miR-409-3p,SOX2-OT,and membrane binding protein annexin A2(ANXA2).This study aims to investigate the expression and functional role of the SOX2-OT/miR-409-3p/ANXA2 axis in gastric cancer cells.Methods:qRT-PCR was used to measure the expression levels of SOX2-OT,miR-409-3p,and ANXA2 mRNA in gastric cancer tissues and cell lines.Gastric cancer cells were transfected with SOX2-OT shRNA plasmid(sh-SOX2-OT),co-transfected with sh-SOX2-OT and miR-409-3p inhibitor,or co-transfected with sh-SOX2-OT and ANXA2 overexpression plasmid.The control groups included blank,shRNA-negative control,inhibitor-negative control,and overexpression plasmid-negative control.Expression levels of SOX2-OT,miR-409-3p,and ANXA2 mRNA,cell proliferation,migration/invasion,apoptosis,and protein expression of Ki-67,cleaved caspase-3,Bax,MMP-9,and ANXA2 were assessed.Dual-luciferase reporter assays were conducted to confirm the targeting relationships among miR-409-3p,SOX2-OT,and ANXA2.A xenograft tumor model in nude mice was used to evaluate the effect of SOX2-OT on gastric cancer tumor growth in vivo.Results:SOX2-OT and ANXA2 expression levels were significantly upregulated,while miR-409-3p was downregulated in gastric cancer tissues(vs.adjacent non-cancerous tissues)and gastric cancer cell lines(vs.normal gastric epithelial cells)(all P＜0.05).In gastric cancer cels,knockdown of SOX2-OT led to decreased expression of SOX2-OT and ANXA2 mRNA and increased expression of miR-409-3p(all P＜0.05),and this was accompanied by reduced proliferation and migration/invasion abilities,and increased apoptosis(all P＜0.05);protein levels of ANXA2,Ki-67,and MMP-9 were significantly decreased,whereas cleaved caspase-3 and Bax levels were significantly increased(all P＜0.05).These effects were reversed by co-transfection with the miR-409-3p inhibitor or ANXA2 overexpression plasmid(all P＜0.05).Dual-luciferase assays confirmed the direct targeting relationships among miR-409-3p,SOX2-OT,and ANXA2.In vivo,knockdown of SOX2-OT significantly inhibited tumor growth in nude mice,with reduced SOX2-OT and increased miR-409-3p expression,as well as decreased ANXA2 and Ki-67 protein positivity in xenograft tissues(all P＜0.05).Conclusion:SOX2-OT is upregulated in gastric cancer cells and may promote malignant behaviors by competitively binding miR-409-3p,thereby relieving its inhibition on ANXA2.The SOX2-OT/miR-409-3p/ANXA2 axis may represent a potential molecular target for gastric cancer therapy.