Arsenic trioxide treatment inhibits the expression of stem-cell markers in glioblastoma neurosphere cells. A) A representative experiment showing decreased transcript levels of the stem-cell marker CD133 in HSR-GBM1 cells following ATO treatment measured using quantitative real-time PCR. B) mRNA expression of the stem-cell markers CD133 and SOX2 was suppressed by ATO. C) Flow cytometric analysis of the CD133 positive fraction also revealed variable reductions in this stem-like subpopulation following ATO treatment. Representative flow cytometry plots of CD133-positive cells in vehicle and ATO treated HSR-GBM1 cultures are shown in the lower right panel.