Abstract 4539: Anti-leukemic activity of mitochondria-targeted asymmetrical 2,2′-binaphthoquinones

Abstract

Abstract Introduction: Binaphthoquinones are unique molecules consisting of two linked naphthoquinone units. By definition biquinones cause more effective oxidative stress than their monoquinone counterparts. Previously, we regiospecifically synthesized a series of asymmetrical binaphthoquinones, which possess HIV integrase inhibitory activity. Potent activity against HIV-uninfected CEM-T4 cells prompted us to investigate other cytotoxic mechanisms. A genome-wide yeast screen uncovered that mitochondria-related genes are required for sensitivity and resistance to these agents. Since mitochondria membrane permeabilization occurs early in the apoptotic program and is located downstream of most identified chemotherapy resistance mechanisms in hematological malignancies, we hypothesized that binaphthoquinones would be able to interfere with mitochondria function in leukemia cells and induce apoptosis by abrogating or bypassing other mechanisms of drug resistance. Materials and Methods: Seventeen of our biquinones were incubated with four leukemia cell lines (MV411, MOLM14, HL-60, U937) grown under standard conditions. A standard MTT cell proliferation assay was used to identify IC50 values. Two of the most potent compounds, biquinones #7 and #10 (BiQ7 & BiQ10), were assayed against MV411 cells and analyzed by flow cytometry for loss of mitochondria membrane potential (via rhodamine 123 staining), as well as a variety of apoptosis markers, such as phosphatidylserine, activated caspases, and sub-2n DNA increases by using Annexin V-PE (with 7AAD), a fluorescent caspase inhibitor reagent, and propidium iodide (PI), respectively. Results: The IC50 values for both compounds were less than 5 μM against all cell lines. A loss of mitochondria membrane potential was observed in 98-100% of the treated cells (control 5%). Loss of plasma membrane phosphatidylserine asymmetry was observed in 94-95% of the treated cells (control 18%). The cells showed increases in staining for activated caspases 3 & 7 (control 10%; BiQ7 98%; and BiQ10 96%). Finally, the cell cycle analyses showed increases in sub-2n DNA in the treated cells compared to the control (control 12%; BiQ7 34%; and BiQ10 54%). These assays were subsequently repeated to obtain triplicate results. Conclusion: Our study shows that this new class of compounds possesses promising in vitro anti-leukemic effects by targeting mitochondria membrane potential. In vivo experiments in a xenograft model and ex vivo experiments on primary human cells are in progress. The cytotoxicities of binaphthoquinones could vary widely as a result of the array of structural configurations available. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4539.