Abstract 5303: The role of the anti-hyperglycemic drug metformin in regulating tumor angiogenesis

Abstract

Abstract Metformin (dimethylbiguanide) is used as a first-line therapy for the management of type 2 diabetes. Recently, metformin has hit the headlines as anti-cancer drug. Metformin is known to work in part through activation of AMP-activated protein kinase (AMPK). AMPK is involved in cancer cell growth and metabolism by modulation of gene expression and translation through the AMPK/ mTOR/S6K1 axis. In order for a solid tumor to grow and to disseminate, an efficient angiogenesis is required, becoming in this way one of the most successful targets not only in cancer therapy but also in prevention. Angiogenesis is the formation of new blood vessels from pre-existing ones. Some evidences have been collected that metformin activates AMPK in human umbilical vein endothelial cells (HUVEC). We aimed to better characterize the mechanism of action by which metformin can affect neo-angiogenesis. We carried out HUVEC morphogenesis assay in matrigel in presence of metformin. We found that the compound affects normal tube formation. Moreover we assessed the effect of metformin on cell viability by a MTT assay in presence of different doses of the drug. We also observed that this compound affected endothelial cell proliferation. This finding was corroborated by real time PCR data showing that in HUVEC metformin treatment induced downregulation of Cyclin D1. The lower proliferation rate was not associated to the induction of apoptotic pathway, as indicated by Annexin V/7AAD staining and FACS analysis. In order to evaluate to what extent this compound can effect endothelial cell migration and invasion of a reconstitute basement membrane in vitro, HUVEC were cultured in a Boyden chamber and showed less invasiveness in presence of metformin compare to untreated cells. Futhertrmore we investigated the effect of the drug when administered to the cells along with other antiangiogenic compounds used in chemotherapy, e.g. the synthetic triterpenoid CDDO. The combination of two drugs demonstrated synergistic effects on cells organizing in tubule-like structures in a morphogenesis assay. Finally, we examined the activity of metformin on endothelial cells by microarray gene expression profiling. Although we are still in the validation process, preliminary results suggest that metformin decrease the expression of several genes involved in biosynthetic process and in the response to stimuli, supporting its anti-proliferative effect. On the other hand it also seems to induce a pro-inflammatory setting. This result hints that the effect of the chemotherapy can be potentiated by metformin, suggesting a possible use of metformin in combination with chemotherapeutic agent in order to lower the risk of side effect following high dosage treatments. Our results indicate an effective role of metformin in inhibiting neoangiogenesis by which it may exert or, at least, support its anti-tumor effect. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5303. doi:1538-7445.AM2012-5303