Fresh bone marrow from 25 patients was taken at diagnosis and before therapy. After informed consent was obtained, marrow was extracted by aspiration from the posterior iliac crest. All patients studied had more than 90% blast cells. Patient ages, FAB classification, and cytogenetics are reported. To determine PD + ATO Cl, primary AML blasts from 25 patients were cultured (2.5 × 10⁵/mL in RPMI 1640 medium containing 10% FBS, 2 mM L-glutamine, penicillin G [100 U/mL], streptomycin [100 mg/mL]) in the presence of escalating doses of PD (0.1-10 μM), ATO (0.125-10 μM), or combinations of the 2 agents at a 1:1 ratio (0.25/0.25, 0.5/0.5, 1/1, 1.5/1.5, and 2/2). After 48 hours of treatment, the cells were harvested for sub-G₁ DNA content, annexin V, and mitochondrial transmembrane potential detection. Cl plots were then generated using the Chou-Talalay method and Calcusyn software. ++ indicates Cl ≤ 0.85 (indicating synergism); +, 0.85 < Cl < 1.10 (indicating additive effect); -, Cl ≥ 1.10 (indicating antagonistic effect). For TA-p73α, TA-p73β, and ΔN-p73, values indicate basal endogenous protein expression, detectable by Western blot analysis of whole cell lysates (100 μg), of p73 isoforms in AML blasts from 21 patients. Relative amounts of TA-p73α, TA-p73β, and ΔN-p73 isoforms in AML blasts were normalized to a positive control K562 cell line. TA-p73/ΔN-p73 ratio: TA-(p73α + p73β)/ΔN-p73 ratio expressed as fold increase in PD + ATO compared with ATO-treated cells. For p53 protein expression, - indicates fold increase ≤ 1.3 with respect to control; ±, fold increase between 1.4 and 1.9 with respect to control; +, fold increase between 2.0 and 4.0 with respect to control; ++, fold increase between 4.1 and 6.0 with respect to control; and +++, fold increase ≥ 6.1 with respect to control.

PD indicates PD184352; Cl, combination index; ND, not done; UL, undetectable levels; NA, not applicable.