Abstract 2090: Evaluation of the cytotoxic profile of Metformin and Y15 in platinum resistant ovarian cancer cells
Authors: Levy Arkene S. , Khan Zara , Batko Samuel , Thallapureddy Keerthi , Smith Robert , Kanagasabai Thanigaivelan , Torruellas Garcia Julie , Rathinavelu Appu 
Published: July 2016

Platinum resistance remains a major challenge in the chemotherapeutic management of ovarian cancer. The anti-diabetic drug metformin has been previously shown to induce cytotoxicity in platinum resistant ovarian cancer cells and overexpression and increased phosphorylation of a tyrosine kinase called Focal Adhesion Kinase (FAK) has been implicated in the development of this platinum resistance. Therefore, in the present study we evaluated the combined cytotoxic efficacy of Metformin and the focal adhesion kinase inhibitor 1,2,4,5-Benzenetetraamine tetrahydrochloride (Y15) in platinum resistant OVCAR3 ovarian cancer cells. Cells were initially treated with concentrations of Y15 ranging from 10-100 μM, and metformin from 10-100mM to determine 1C50 values. Subsequently, cells were treated with Y15 (80 μM) and metformin (26mM) alone and in combination. All treatments were triplicated with duration of 24hrs and control cells exposed to media only. The cytotoxic profile of each treatment was assessed using the automated trypan blue assay. DNA fragmentation and poly ADP ribose polymerase (PARP) cleavage assays were performed to evaluate the mechanism of cell death and we further evaluated the expression of phosphorylated FAK, p53 and p21 in response to treatments using western blot.

Y15 alone produced 48% cell death. In combination, Y15 significantly increased the cytotoxic efficacy of metformin by 22%, when compared to the metformin only treatment. Cell death by apoptosis was confirmed by PARP cleavage and the presence of DNA fragments in Y15, metformin, and metformin +Y15 treatment groups. The Metformin +Y15 combination significantly downregulated the expression of phosphorylated FAK when compared to the individual treatments and control and this confirmed reduced FAK activity. Reduced FAK auto phosphorylation also correlated with increased expression of p53 AND p21 in metformin and Y15 treatment groups.

Our findings show that Y15 significantly enhances the cytotoxic profile of metformin in platinum resistant OVCAR-3 cells. Furthermore, a FAK dependent apoptotic mechanism appears to underlie the cytotoxic effect of metformin as well as Y15 as both drugs significantly reduced the phosphorylation of FAK alone, and in combination. Reduced FAK activity also correlated with increased p53 and p21 expression. This study is the first to report a FAK dependent cytotoxic mechanism of metformin in ovarian cancer and in further work we will evaluate the mechanisms why which metformin cooperates with Y15 to inhibit FAK activity in platinum resistant ovarian cancer.

Citation Format: Arkene S. Levy, Zara Khan, Samuel Batko, Keerthi Thallapureddy, Robert Smith, Thanigaivelan Kanagasabai, Julie Torruellas Garcia, Appu Rathinavelu. Evaluation of the cytotoxic profile of Metformin and Y15 in platinum resistant ovarian cancer cells. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2090.