Figure 1.

Synergistic anti-proliferative and cytotoxic effects of the various drug combinations in KBM3/Bu250⁶ (A) and OCI-AML3 (C) cell lines. Cells were exposed to drugs, alone or in combination, for 48 hrs then analyzed for cell proliferation by MTT assay and for apoptosis by Annexin V (Ann V) assay. The relationships between combination index (CI; y-axis) and fraction affected (Fa; x-axis) in each cell line are shown in panels B and D (representatives of two independent experiments). CI < 1 indicates synergism. (E) Comparison of the effects of the indicated drug combinations on OCI-AML3 (P53-wild type) and OCI-AML3/shP53 clone with downregulated P53 expression (inset shows Western blot for P53 protein level). (F) DNA demethylation of P16/INK4A gene promoter and its expression. OCI-AML3 cells were exposed to solvent (Control) or the indicated drug combinations for 48 hrs. Genomic DNA and total RNA were isolated and used for real-time PCR. The inset shows Western blot for the level of P16/INK4A protein. Signals were scanned and normalized relative to β-ACTIN. The numbers refer to fold difference in P16/INK4A relative to Control. Results (bar graphs) are the average ± SD of at least three independent experiments. Statistically significant differences are indicated by P values. Bu, busulfan; 4HC, 4-hydroperoxycyclophosphamide; DAC, decitabine.