Growth inhibition and apoptosis induction by As₂O₃ in Jurkat and Raji cells. (A) Cell growth rate and viability. Jurkat and Raji cells were treated or untreated with the indicated concentrations of As₂O₃. Cell concentrations and percentages of viable cells after staining with trypan-blue were determined with the aid of a hematometer. Each value represents the mean ± SD of triplicates. (B) Apoptosis induction. Jurkat and Raji cells were untreated or treated with As₂O₃, 2 μM, for 3 days. Percentages of apoptotic cells were determined by staining with Annexin V and PI on flow cytometry, as described in “Materials and methods.” (C) Western blot analysis of PARP cleavage. Cells were untreated or were treated with As₂O₃, 2 μM, for 3 days. Anti-PARP antibody was used to detect the PARP cleavage product, as described in “Materials and methods.”