In vitro susceptibility to doxorubicin- and dexamethasone-induced apoptosis in T-ALL: absence of cross-reactivity and differential dependence on maturation stage.

Primary T-ALL cells were incubated in the presence of either doxorubicin (1 μM) or dexamethasone (2 μM) for 24 hours at 37°C. After incubation, apoptotic cells were detected by flow cytometry using annexin V/PI staining, and the extent of drug-specific apoptosis was calculated by the formula described in “Patients, materials, and methods.” (A) Dexamethasone- versus doxorubicin-specific apoptosis in individual T-ALL samples (Spearman correlation coefficient, r_s = 0.22, P = .053). (B,C) Drug susceptibility in T-ALL subgroups. Subgroups were defined according to the EGIL criteria as pro–/pre– (CD1a⁻, sCD3⁻) T-ALL, cortical (CD1a⁺) T-ALL, and mature (CD1a⁻, sCD3⁺) T-ALL. Significant differences (Spearman analysis) were found: pro–/pre–T-ALL versus cortical (P = .002 and .02 for dexamethasone and doxorubicin) and cortical versus mature (P = .02 for doxorubicin).