Figure 1.

Effect of temozolomide alone (straight lines) or temozolomide with a 2-h pretreatment with O⁶-BG (O⁶-benzylguanine; dashed lines) on the clonogenic survival of the medulloblastoma cell lines DAOY (A), D341Med (B), and D425Med (C). Single cells were seeded into culture dishes and treated with the denoted concentrations of temozolomide in absence or presence of O⁶-BG and then allowed to further grow for 9 (DAOY), 14 (D341Med), or 12 (D425Med) days, respectively. Data are presented as the mean±standard deviation (s.d.) of three independent experiments performed in triplicates. The IC₅₀ values and their 95% confidence intervals were calculated from the regression curve and are indicated for each data set for temozolomide alone and temozolomide with a 2-h pretreatment with O⁶-BG for DAOY, D341Med, and D425Med cells. Differences between the two curves are represented by P-values (P<0.001, P<0.01, P<0.05; NS, not significant).