Figure 1.

Sensitization of leukemia cells to As₂O₃-induced cytotoxicity with azacytidine (5′Aza) pre-treatment. (A) Dose-dependent cytotoxicity of As₂O₃ with or without 5′Aza treatment in the human AML cell lines, HL-60, K562, NB4, and OCI-AML3. As determined by MTT assay, all four cell lines pre-treated with 5′Aza exhibited significant decrease in cell viability as compared with their untreated controls. Data were acquired from three independent experiments, and relative survival of each individual cell line was normalized to its respective control. (B) Representative plot of flow cytometric analysis, showing a significant increase in As₂O₃-mediated cytotoxicity (annexin V-positive cells) in K562 cells pre-treatment with 5′Aza, as compared with control cells not treated with 5′Aza. (C) Bar charts showing the fold changes of As₂O₃-induced cell death (annexin V-positive cells) in each AML lines with or without 5′Aza pre-treatment. Quantitative analysis by flow cytometry further confirmed a significant increase in As₂O₃-induced apoptotic cell death after 5′Aza pre-treatment.