Abstract 2767: Nifurtimox and radiation for treating neuroblastoma: a preclinical study.

Proceedings: AACR 104th Annual Meeting 2013; Apr 6-10, 2013; Washington, DC Neuroblastoma (NB) is the most common extracranial solid malignancy in infants and children. NB is responsible for more than 15% of deaths due to childhood cancers. It is an aggressive malignancy and often requires intensive multimodality treatment that potentially causes extensive long term side-effects. Although radiation therapy (XRT) is an important part of the standard treatment plan in this malignancy, XRT is known to cause significant side effects and morbidity associated with XRT greatly impacts the lives of many patients. Therefore, new approaches to increase the efficacy of XRT while decreasing side effects could have a great impact in the use of this therapy in cancer. XRT-induced cell death is partially associated with the generation of reactive oxygen species (ROS). ROS production is implicated in cell apoptosis, and induction of ROS potentially serves as a promising strategy for inhibiting tumor growth. In this investigation we exploited a strategy to increase the response of XRT by adding a chemical agent, Nifurtimox (Nfx) that is known to induce the generation of ROS. Human NB cells, SH-SY5Y and LA1-55n were treated with vehicle (DMSO) or increasing (5/7.5/10/20 μl/ml) concentrations of Nfx or XRT (1/2/5/10 Gy) and cell viability was determined at 24, 48 and 72 hr post-treatment. Both Nfx and XRT inhibited NB cell growth following a dose and time-dependent response. In order to test the combination response, these cells were treated with selected doses of Nfx and/or XRT and the cell viability was measured at 48 h post-treatment. The combination of both agents resulted in significantly higher inhibition when compared to single agent. ROS levels and apoptosis were assessed in NB cells following individual and combination treatment. ROS levels were measured using flow cytometry. Activation of caspases was determined by Caspase Glo kits while apoptotic cells were measured by flowcytometry (Annexin-V staining). Consistent with cell viability results, combination of XRT and Nfx significantly up-regulated ROS, caspases and induced apoptotic cell population when compared to individual treatment. For the in vivo assay, athymic nude mice were subcutaneously injected with LA1-55n cells. When tumor growth volume reached 100 mm3, mice were treated with Nfx (25 mg/kg/day in corn oil through oral gavage for 3 wk), XRT (5 Gy 2 time/wk for 2 wk) or both and the tumor growth was measured. At the termination of the experiment, combination therapy (XRT and Nfx) caused more than 80% tumor growth inhibition while the individual treatment (XRT or Nfx) caused approximately 60% inhibition of tumor growth. Results of this investigation demonstrate that the combination of XRT and Nfx synergistically inhibits human neuroblastoma cell proliferation and tumor growth in mice. Citation Format: Don Eslin, Chris M. Lee, Giselle S. Sholler, Umesh T. Sankpal, Robert M. Sutphin, Riyaz M. Basha. Nifurtimox and radiation for treating neuroblastoma: a preclinical study. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2767. doi:10.1158/1538-7445.AM2013-2767