Abstract B57: Meclizine synergistically enhances anticancer effects of paclitaxel in A549 lung cancer cells

Abstract

Abstract Introduction: Lung cancer is the leading cause of cancer-related death worldwide. Despite all improvements in therapy, current standard care for patients with metastatic disease has reached a plateau in the overall response rate. A noteworthy strategy is combining standard anticancer therapy drugs and well-known drugs with novel application in cancer field, such as metformin, statins, and aspirin. This combination is advantageous due to therapeutic efficacy increase, by multiple molecular targeting, and toxicity reduction, by anticancer drug dosage decrease. In this scenario, besides meclizine use on prophylaxis against nausea and vertigo, meclizine was reported as a cellular respiration inhibitor by mechanisms independent of its antihistaminergic and anticholinergic activities. Driven by the importance of mitochondrial activity in cancer, this study aim was to evaluate meclizine anticancer activity and its interaction with placlitaxel in A549 human lung cancer cells. Methods: Meclizine and paclitaxel cytotoxic effects were evaluated in A549 cells by MTT assay. The data were analyzed by Compusyn software to evaluate the drug interaction and the combination index (CI) were determinate. As described by Chou and Talalay classical isobologram equation, CI values greater than 1.1 indicate antagonistic interactions, values between 0.9 and 1.1 indicate additive interactions, and values lower than 0.9 indicate synergistic interactions. Evaluation of apoptotic cells and mitochondrial membrane potential was performed by flow cytometry using Annexin V-Alexafluor488/propidium iodide and tetramethylrhodamine staining, respectively. Proteins expression were evaluated by Western blotting. All experiments were performed in quadruplicate in three independent experiments. All data are expressed as mean ± standard deviation (SD) and were analyzed by one-way ANOVA followed by the Tukey's test using GraphPad Prism software program, version 7. Results: Meclizine was cytotoxic to A549 cells (IC50=275 µM; 95% CI= 255 to 296 µM), leading to mitochondrial membrane depolarization (ratio of 0.35 of median fluorescence intensity reduction vs. control; p<0.001). Indeed, meclizine increased expression of apoptosis-inducing factor (AIF) and cathepsins D and B. In contrast, meclizine triggers a slight apoptosis rate (increase of 13.20% of Annexin V-positive population; p<0.01). Altogether, these results indicated that meclizine induces cell death in caspase-independent manner. Combination Index (CI) evaluation revels that meclizine (200 µM) combined with paclitaxel (40 µM) has stronger cytotoxic effect (CI=0.91). Interestingly, this combination produced an antiproliferative effect greater than the treatments with meclizine (200 µM) or paclitaxel (80 µM) alone. Therefore, meclizine allows a reduction of paclitaxel concentration with an increase of paclitaxel cytotoxic. Overall, these results indicate that in vitro meclizine plus paclitaxel have great cytotoxic effects against A549 cells. Conclusion: Meclizine is cytotoxic to A549 cells, inducing mitochondrial depolarization and caspase-independent cell death. Additionally, meclizine synergistically enhances anticancer effects of paclitaxel in A549 lung cancer cells; therefore, the dosage of paclitaxel can be reduced when associated to meclizine with no efficiency loss. Overall, the combination in vitro of meclizine and paclitaxel is an interesting strategy and may be an effective regimen for lung cancer treatment. Financial support: FAPESP (2015/18528-7 and 2016/09392-7). Citation Format: Sarah Fernandes Teixeira, Ricardo Alexandre De Azevedo, Salomão Dória Jorge, Emer Suavinho Ferro, José Alexandre Marzagão Barbuto, Adilson Kleber Ferreira. Meclizine synergistically enhances anticancer effects of paclitaxel in A549 lung cancer cells [abstract]. In: Proceedings of the AACR International Conference held in cooperation with the Latin American Cooperative Oncology Group (LACOG) on Translational Cancer Medicine; May 4-6, 2017; São Paulo, Brazil. Philadelphia (PA): AACR; Clin Cancer Res 2018;24(1_Suppl):Abstract nr B57.