Metformin inhibits medulloblastoma cell growth and increases sensitivity to chemotherapy drugs

Abstract

Purpose: Medulloblastoma (MB) is the most common malignant pediatric brain tumor. Standard treatment is chemotherapy and radiation, both of which can be associated with long-term toxicity for pediatric patients. This project is focused on the use of metformin in the treatment of medulloblastoma. Metformin (MET) is an anti-diabetic drug with low toxicity that has been shown to have anti-cancer properties. We hypothesize that MET will inhibit MB cell growth and enhance the effect of chemotherapy and anti-cancer agents such as vincristine (VCR) and valproic acid (VPA) when used in combination, possibly by inhibiting the expression of survivin protein. Methods: MB cells (DAOY) were treated with increasing doses of MET (1-30 mM), VCR (1-16 nM), and VPA (1-30 mM). For combination treatment, DAOY cells were treated with selected doses of VCR (1, 2, 4 nM) and VPA (0.9, 1.8, 3.5 mM) alone or in the presence of MET (10 and 20 mM). Cell viability was assessed at 48 h post-treatment using the CellTiter-Glo cell viability assay kit. For western blot analysis, DAOY cells were treated with increasing doses of MET (0, 5, 10, 20 mM) for 24 and 48 h. Cells were harvested and protein extracts were prepared and used for determining survivin expression. Results: Treatment with MET, VCR, and VPA alone resulted in a decrease in cell viability in a dose and time dependent manner. The combination of MET+VCR resulted in greater inhibition of cell proliferation with 78.99% inhibition in comparison to MET alone (51.5%) or VCR alone (46.02%). The combination of MET+VPA resulted in greater inhibition of cell proliferation with 84.88% inhibition in comparison to MET alone (52.6%) or VPA alone (47.81%). Western blot analysis of MET treated cells showed a dose and time dependent decrease in survivin expression. Conclusion: Our experiments demonstrate the potential of MET as a novel therapeutic agent for the treatment of MB based on its ability to inhibit proliferation and enhance the activity of anti-cancer agents. These results also suggest that MET’s effect could be partially mediated by the down-regulation of survivin, a protein known to be involved in the inhibition of apoptosis and resistance of cells to chemotherapy. The low toxicity of metformin and its ability to sensitize medulloblastoma cells could potentially result in lowering chemotherapy associated toxicities, leading to improved quality of life for long-term survivors.