Modulation of the anti-tumor activity of VEGF blockade by metformin.

Abstract

e23009 Background: The payoff from first-generation angiogenesis inhibitors was commonly temporary, due to the development of intrinsic as well as acquired resistance. Apart from the vascular resistance due to circumventing VEGF blockade by proangiogenic factors, resistance has also been associated with assortment of resistant clones. Accordingly, a combination strategy was proposed to overcome such resistance. Metformin, as a potential candidate, has received considerable concern as an anticancer agent. Methods: IN-VITRO WORK;Cells were divided into normoxic and hypoxic groups. For both, four subgroups were developed; control, metformin, glucose deprivation and a subgroup in which cells were subjected to both glucose deprivation and metformin treatment. Cells were then subjected to analysis for Apoptosis, Cell cycle progression and western blot. IN-VIVO WORK; Tumor growth was assessed IGROV-1 subcutaneous xenografts. Animal were divided into four groups; control, Metformin, Bevacizumab and a fourth group receiving both drugs. Tumor growth was assessed along treatments and at time of sacrifice.After sacrificing animals, tumors were further analyzed for; necrosis, apoptosis, proliferative capacity, activation of AMPK and its downstream effectors. Results: Our in-vitro results suggested an anti-proliferative effect of metformin in terms of apoptosis, cell cycle arrest, AMPK activation and mTOR inhibition at various time points. In-vivo experiments revealed a significant decrease of tumor weight and proliferative capacity in tumors treated with both drugs and a trend toward a decrease in tumor growth along the treatment. Yet, there was no difference between the bevacizumab and the combination groups regarding AMPK activation suggesting another mechanism to exert the combination effect. The effect of Metformin on CSC percentage and viability was tested. Glucose deprivation plus hypoxia lead to increase in CSC population, while adding metformin to bevacizumab reverse this augmentation in CSC numbers. Conclusions: Study represents a proof of concept study demonstrating a positive modulatory effect of metformin addition to bevacizumab. Additional experimental work on a wider scale is running to ascertain the current results.