Hierarchical clustering of xenografts and their dexamethasone sensitivities in vivo and in vitro. (A) Unsupervised cluster dendrogram of the 37 879 probes across 19 BCP-ALL xenografts. The 10 framed xenografts are resistant to dexamethasone, according to their LGD in vivo and IC50 in vitro. The 9 unframed xenografts are sensitive to dexamethasone. (B-C) Kaplan-Meier curves of EFS following treatment with dexamethasone 15 mg/kg intraperitoneally Monday throughout Friday for 4 weeks (solid line) or vehicle control (dashed line) for (B) ALL-50 and (C) ALL-54. LGD calculated as the difference between median EFS of treated and control groups. (D) ALL-50 and ALL-54 were treated with increasing concentrations of dexamethasone, and viability was assessed by Alamar Blue assay after 48-hour incubation. Values are expressed as a percentage of the untreated control. Data represent mean ± standard error of the mean for n = 3 experiments. (E-G) ALL-50 and ALL-54 cultured cells in vitro were exposed to dexamethasone (1 µmol/L) and were harvested at times up to 16 hours and processed for real-time RT-PCR quantitation. Data are expressed relative (fold) to solvent-treated controls at each time point. Each data point represents the mean ± standard error of the mean from 3 independent experiments. Dex, dexamethasone; IC50, the dexamethasone half maximal inhibitory concentration; LGD, leukemia growth delay; ND, not determined.