Abstract 4266: Potential role of reactive oxygen species in affecting tumorigenicity of glioblastoma stem cells

Glioblastoma multiforme (GBM) is a common and highly aggressive primary brain tumor with poor prognosis due in part to drug resistance and high incidence of tumor recurrence. The drug resistant and cancer recurrence phenotype may be ascribed to the presence of cancer stem cells, which seem to reside in special stem-cell niches in vivo and require special culture conditions including certain growth factors and serum-free medium to maintain their stemness in vitro. In this study, we used two lines of stem-like cancer cells (GSC11 and GSC23) derived from the tumor tissues of two GBM patients by classical neurosphere culture system, and showed that addition of serum (FBS) to the medium induced an increase of ROS, leading to aberrant differentiation and eventual cell death. Although both GBM stem-like cell lines showed high percentage of CD133-positive cells (20% in GSC11 and 70% in GSC23), exposure to serum only caused a moderate decrease of CD133 expression at later time points. Several methods were used to further test the role of ROS in affecting the stemness of the GSC cells and their self-renewal capacity. Addition of 5% FBS or removal of the antioxidant supplements (B27) from the culture medium caused the spheroid GSC cells to attach to the culture surface, exhibit differentiation morphology, decrease expression of certain stem-cell markers, and eventually die within two weeks. Serum exposure also resulted in a decrease of the GSC ability to form colonies in soft agar assay and to grow tumors in a mouse xenograft model. Although an increase of general cellular ROS could be detected when GSC cells were exposed to FBS, the mitochondrial superoxide appeared to be prominent and likely to be a primary event, which led to a compensatory increase of the mitochondrial SOD2 expression and upregulation of glutathione synthesis. Interestingly, addition of the antioxidant N-Acetylcysteine to the FBS-containing medium partially blocked the FBS-induced aberrant differentiation and improved cell viability and self-renewal capacity, suggesting that ROS may play an important role in affecting stemness and differentiation status of the cancer stem cells. We postulate that during tumor development, only the progeny cells that acquire the ability to counteract the impact of ROS increase induced by serum may eventually proliferate and grow as the tumor bulk, and that proper redox-modulation may be a potential novel strategy to block tumor formation and possibly kill the stem-like cancer cells. 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 4266.