Effect of c-MYC expression on chemo-sensitivity of DAOY and UW228 MB cells. DAOY (c-MYC over-expressing) and to a lesser extent UW228 (c-MYC over-expressing) cells are more susceptible to etoposide, cisplatin, carboplatin, and doxorubicin, and are equally sensitive to methotrexate and vincristine, as determined by MTS assay compared with control cells (DAOY wt, V11; UW228 wt, V1). Values represent the mean percentage of viability (representative from two independent experiments) compared with non-treated cells ± standard deviation (n = 6). The IC50 values and their 95% confidence intervals were calculated from the regression curve and are indicated for each data set for c-MYC- and empty vector-transfected DAOY and UW228 cells. Differences between the two curves are represented by P-values (P < 0.001, P < 0.01, P < 0.05, n.s. not significant).