Metformin Regulates the miR-205/VEGFA Axis in Renal Cell Carcinoma Cells: Exploring a Clinical Synergism with Tyrosine Kinase Inhibitors

Abstract

<b><i>Introduction:</i></b> Metformin (MF) intake could be associated with a favorable outcome in sunitinib (SUT)- and axitinib (AX)-treated clear cell renal cell carcinoma (ccRCC) patients. Functionally, MF induces miR-205, a microRNA serving as a tumor suppressor in several cancers. <b><i>Methods:</i></b> Real-time quantitative PCR, viability assays, and Western blotting analyzed MF and SUT/AX effects in RCC4 and 786-O cells. A tetracycline-inducible overexpression model was used to study the role of miR-205 and its known target gene, <i>VEGFA</i>. We analyzed miR-205 and <i>VEGFA</i> within a public and an in-house ccRCC cohort. Human umbilical vein endothelial cell (HUVEC) sprouting assays examined miR-205 effects on angiogenesis initiation. To determine the influence of the von Hippel-Lindau tumor suppressor (<i>VHL</i>), we examined <i>VHL</i>^<i>wt</i> reexpressing RCC4 and 786-O cells. <b><i>Results:</i></b> Viability assays confirmed a sensitizing effect of MF toward SUT/AX in RCC4 and 786-O cells. Overexpression of miR-205 diminished <i>VEGFA</i> expression – as did treatment with MF. Tumor tissue displayed a downregulation of miR-205 and an upregulation of <i>VEGFA</i>. Accordingly, miR-205 caused less and shorter vessel sprouts in HUVEC assays. Finally, <i>VHL</i>^<i>wt</i>-expressing RCC4 and 786-O cells displayed higher miR-205 and lower <i>VEGFA</i> levels. <b><i>Conclusion:</i></b> Our results support the protective role of MF in ccRCC and offer functional insights into the clinical synergism with tyrosine kinase inhibitors.