miR-20b negatively regulates VEGF expression by targeting STAT3 in H22 hepatocellular carcinoma cells

Vascular endothelial growth factor (VEGF) promotes angiogenesis during tumor growth, and its expression involves multiple signaling pathways and transcription factors. In the present study, transforming growth factor (TGF)-beta 1 promoted upregulation of VEGF and downregulation of microRNA (miR)-20b expression in mouse H22 hepatocellular carcinoma cells. miR-20b negatively regulated both constitutive VEGF expression and TGF-beta 1-induced VEGF expression. The miRanda algorithm predicted that a binding site of the miR-20b GCAAUCUGGGCACUUU sequence was present in the signal transducer and activator of transcription (STAT)3 3'-untranslated region. Following transfection of miR-20b mimics into H22 cells, expression of STAT3 protein was downregulated. A dual-luciferase activity assay revealed that miR-20b directly targeted STAT3 to regulate its expression, and that interference with STAT3 expression significantly downregulated VEGF mRNA and protein expression. Interference with STAT3 expression resulted in increased VEGF expression in H22 cells overexpressing miR-20b, but expression was lower than that in quiescent H22 cells. This indicated that STAT3 was involved in the negative regulation of VEGF expression in H22 cells by miR-20b. The data demonstrated that miR-20b negatively regulated VEGF expression by directly targeting STAT3 in H22 cells.