(A) At 0.3 μg/ml D,L-methadone, cell viability is significantly increased in BTIC-18. (B) At concentrations of 1 μg/ml significant cell killing was observed only in U87. (C–E) At higher concentrations, BTIC-7 showed the highest and BTIC–12 the lowest susceptibility. The asterisk (*) indicates significant differences to untreated control (significance level 0.05).
BTIC: Brain tumor initiating cell.