Mir-29b Regulates Oxidative Stress by Targeting SIRT1 in Ovarian Cancer Cells

Background: Metabolic abnormalities are frequently observed in multiple malignancies including epithelial ovarian cancer (EOC), among which imbalance between generation and elimination of reactive oxygen species (ROS) plays a critical role in EOC onset and progression. Here we investigated the role of miR-29b, a well-established tumor-suppressor miRNA in metabolic regulation of EOC cells.

Methods: cell viability and apoptosis in miR-29b inhibited and over-expressed EOC cells were evaluated by CCK8 and Annexin V-FITC/PI assays. Change in miR-29b was detected in EOC cells incubated in H2O2 culture by q-PCR. Relative ROS levels were also detected in different EOC cultures, including modified miR-29b and SIRT1 levels as well as H2O2 incubation. A luciferase reporter assay was employed to detect the direct binding of miR-29b to SIRT1 3' UTR. Changes in cell viability and ROS levels were assessed in SIRT1-knocked down EOC cells.

Results: miR-29b expression correlates with decreased EOC cell viability and increased apoptosis. H2O2 downregulated miR-29b in a time and dose-dependent manner. miR-29b expression negatively correlated with ROS levels, whereas SIRT1 significantly stimulated ROS formation. Luciferase reporter assays confirmed miR-29b downregulation of SIRT1by directly targeting its mRNA 3'-UTR. SIRT1 silencing rescues cell viability of H2O2 treated cells. Also, SIRT1 inhibition blocked cell apoptosis induced by H2O2 as well as reduced intracellular ROS levels.

Conclusion: Together, our findings indicated that the miR-29b/SIRT1 axis has a protective effect against H2O2-induced damage of cell viability and oxidative stress and may provide novel options for miR-29b-based therapeutic approaches for EOC treatment.