Abstract 5497: Targeting glioblastoma stem cells with withaferin A

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Abstract Introduction. Glioblastoma multiforme (GBM) is the most common and aggressive form of primary brain cancer affecting 3 to 4 per 100,000 people annually in the United States. Despite aggressive therapy including surgical resection followed by both radiation and chemotherapy, overall survival remains dismal at approximately 14 months. Recent studies have determined that GBM's contain a small population of stem cells (GSCs), which promote tumor growth through unlimited self-renewal. Since GSCs are chemo- and radio-resistant and drive tumor regrowth following therapy, successful treatment depends on the elimination of these cells. Withaferin A (WA) is a bioactive compound derived from the plant Withonia somnifera which possesses anti-inflammatory and anti-cancer properties. Here we evaluated the effects of WA on patient derived GSCs. Methods. With IRB approval, GSC lines were generated. GSCs were propagated in neurosphere media and examined for the stem cell markers CD133, nestin, musashi and BMi1 by immunocytochemistry and western blot analysis. Effect of WA on cell viability was determined using MTS assay. The effect of WA on cell survival and stress pathways was evaluated by western blot analysis. Results. WA induced a significant decrease in cell viability at low micromolar concentrations. The IC50 for 3 patient derived GSC lines ranged between 0.96-1.78μM. WA induced ER stress and apoptosis in the GSCs as indicated by increased expression of ER stress markers grp78 and CHOP and increased levels of cleaved PARP. Furthermore, WA decreased survivin but increased phospho-ERK levels. However, inhibition of ERK activity with U0126 did not potentiate the effect of WA on cell death. Conclusion. Ashwagandha has been used safely for medicinal purposes for centuries and pharmacokinetic studies in mice indicate that micromolar plasma concentrations of WA are obtainable. Our studies indicate that very low concentrations of WA induce ER stress and cell death in GSC lines. Targeting GSC with WA may increase patient survival by hindering GSC mediated tumor regrowth following surgery. Our data demonstrates the efficacy of WA and supports additional studies toward the use of WA as an adjuvant GBM therapy. Citation Format: Baoyu Zhang, Branko Cuglievan, Nadia G. Myrthil, Steven Vanni, Ricardo J. Komotar, Regina M. Graham. Targeting glioblastoma stem cells with withaferin A. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 5497. doi:10.1158/1538-7445.AM2014-5497