Abstract 2548: Metformin and everolimus act synergistically with paclitaxel against ovarian cancer

Abstract

Abstract Background: Epithelial ovarian cancer (EOC) is the most lethal gynecological malignancy, mostly due to the diagnosis of the disease at advanced stages and to chemoresistance to platinum- and taxane-based standard therapy. EOC comprises a heterogeneous group of diseases classified based on morphologic and molecular-genetic features. High grade serous ovarian cancer is the most prevalent EOC subtype, being followed by the clear cell subtype. Both EOC subtypes are vastly aggressive and frequently acquire the chemoresistant phenotype, thus challenging researchers and clinicians. Notably, hyperactivation of PI3K and MAPK pathways are frequently related to resistance to standard therapies in EOC, thus, metformin (MET) and everolimus (EVE) have emerged as novel therapeutic options against EOC. The present work aimed to investigate the action of MET and EVE, in vitro, in ES-2 (clear cell) and A2780 (serous) cell lines. Methods: Metabolic cell viability (MCV) assays were conducted after the treatment of the cells with MET or EVE in monotherapy and in association with paclitaxel (PAC) by the MTT method. Cell cycle progression was evaluated by flow cytometry/propidium iodide. Apoptosis was analyzed by the annexin V-FITC assay. Western blot was performed to investigate MEK/ERK and PI3K/AKT pathways. Findings: MCV of EOC lineages was reduced by MET and EVE in different concentrations. The combination of MET, at low and safe concentration (10uM), with PAC 100nM reduced the MCV in 56.55% for ES-2, and 71.38% for A2780. Similarly, EVE 0.06 nM and PAC 100 nM decreased the VCM in 66.4% and 73.38% for ES-2 and A2780, respectively. MET 10μm and EVE 0.06nM associated with PAC 12.5nM kept the MCV at levels comparable to PAC 100nM. These findings are of extreme clinical relevance as they reveal that the synergism between MET and EVE with PAC likely maintains the drug citotoxicity at lower concentrations than those associated to its severe and limiting side effects, as neurotoxicity. Annexin-FITC assay was conducted in ES-2 lineage treated with PAC alone and combined with MET or EVE. Low percentage of apoptotic/necrotic cells was observed, which suggests the occurrence of additional processes, such as autophagic cell death. EVE induced ES-2 cell cycle arrest; however, MET, at low concentration, did not cause the same effect. There were no significant cell cycle changes due to the combined treatment of ES-2 with PAC and MET or EVE. Western blot analysis demonstrated that the combination of EVE and PAC increased, whereas MET alone or in combination with PAC decreased the phosphorylation of ERK1/2 and AKT in ES2 cells. Conclusions: Our data suggest that MET or EVE exerts synergistic effect with PAC against EOC, thus opening an avenue to explore novel strategies against this highly lethal disease. Ongoing experiments are sought to elucidate the cellular pathways modulated by MET and EVE alone or in combination with PAC in EOC lineages, as well as the elicited cellular events and mechanisms. Citation Format: Nayara G. Tessarollo, Isabella S. Guimaraes, Taciane Ladislau, Ian Victor Silva, Leticia B. A. Rangel. Metformin and everolimus act synergistically with paclitaxel against ovarian cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2548. doi:10.1158/1538-7445.AM2015-2548