Abstract 3461: A chemical screen for the identification of novel therapeutics for pediatric brain tumors

Abstract

Abstract Treatment of brain tumors in children has greatly improved over the past decades, but current treatment protocols lack specificity, killing not only tumor cells, but also “healthy” normal brain cells. Moreover, current therapy still fails in approximately 20% of medulloblastoma patients, 50% of ependymomas and 80% of children suffering from high grade glioma. Treatment mostly consists of surgery, followed by chemotherapy and radiotherapy, and although this kind of therapy is among the most effective treatment options available, it is not sufficient. Therefore, new therapeutic drugs are required that specifically kill brain tumor cells and/or sensitize to irradiation, sparing normal brain tissue. In order to identify such novel compounds, drug screens were set up in a semi-high throughput format, using Gaussia luciferase (Gluc) activity as cell viability readout. As opposed to other forms of luciferase, Gluc is secreted in the medium, allowing the measurement of luciferase activity without lysing the cells. Since the Gluc signal has been shown to be linearly related to cell number, this assay can be used to determine cell viability at different points after drug treatment. In addition, an Acumen eX3 laser scanning cytometer was used in parallel, to determine cell number and cytometric parameters. We screened two small molecule libraries (2960 compounds) for cell growth inhibitory or radiosensitizing properties on pediatric high-grade glioma, ependymoma and medulloblastoma cell lines and primary patient material. Cells were incubated with a concentration of 1µM of the different compounds, either as single agent or in combination with 3 Gray irradiation, and cell viability was determined over a period of 4 days of incubation. A reduction of >75% of cell growth was considered to be significant. In general, 4 different groups of small molecules could be distinguished: 1) compounds that did not affect cell proliferation compared to controls, 2) compounds that block cell cycle progression, 3) compounds that induce cell death independently of irradiation, and 4) radiosensitizers. A total of 114 compounds was identified that inhibited cell growth and/or sensitized towards irradiation. Among the compounds that induced cell death were microtubule inhibitors, alkylating agents, topoisomerase inhibitors and anthracyclins. Besides these known anti-cancer agents we also identified a large number of cardiotonic drugs, benzimidazoles and limonoids that effectively killed brain tumor cells. We are currently investigating these hits and expanding our drug screens with additional primary pediatric brain tumor cells. In addition, we are repeating the screens on non neoplastic primary human cells, including astrocytes, to assess the therapeutic index of these drugs. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3461. doi:10.1158/1538-7445.AM2011-3461