Metformin alters an anti-proliferative effect of Mitotane in a human adrenocortical cancer (H295R) cell line- preliminary results.pdf

Introduction: Metformin is used as a first-line treatment in type 2 diabetes. Several studies suggest that patients with type 2 diabetes treated with metformin may have a reduced cancer risk. Recently it has been shown that metformin acts directly on mitochondria to alter cellular bioenergetics and reduce tumorigenesis. We have shown that anti-proliferative effect of mitotane is related to changes in expression of the genes involved in mitochondrial metabolism in human adrenocortical (H295R), breast, lung and colon cancer (ENDO 2015). Aim: As both metformin and mitotane affect mitochondrial metabolism, the objective of the study was to assess the impact of combined treatment with metformin and mitotane on H295R cell line proliferation. Material and Methods: Human adrenocortical cancer cell lines (H295R) were cultured in 96 well plates, and cell proliferation rate was assessed by resazurin assay. Results: The maximum effect of metformin was observed at 48-hours of incubation, resulting in cytotoxicity of 6, 16, 28 and 55% at the concentration of 5, 10, 20 and 40mM, respectively. The maximum effect of mitotane (10uM) was observed at 24-hours of incubation, resulting in 30% of cytotoxicity and this concentration was used in combined treatments with metformin. Even though both compounds inhibited proliferation separately, combined treatment led to either total loss of their anti-proliferative effect (metformin at the concentration of 5 and 10mM) or a significant decrease in cytotoxicity to 9 (p<0.001) and 44% (p<0.001) for metformin at the concentration of 20 and 40mM, respectively. Conclusions: Those preliminary results shows that even though metformin alone can have an anti-proliferative effect on H295R cell line, it should be added to mitotane with caution as it can negatively alter the cytotoxic effect of mitotane. The studies require further exploration to understand this unexpected mechanism. - See more at http://press.endocrine.org/doi/abs/10.1210/endo-meetings.2016.AHPAA.3.SAT-411#sthash.qoPhRUpy.dpuf