Western blot analysis for caspase-3 protein. Cells were treated with 1 μM As₂O₃, 25 μM DHA, or the combination of both substances for 24 hours. After treatment, the cells were lysed and analyzed by Western blot, as described in “Materials and methods.” Upper panel: Caspase-3 protein. Note that the antihuman caspase-3 antibody used in our experiments recognizes both the inactive proenzyme of caspase-3 (32 kDa) and its cleaved active fragment (17 kDa). Lower panel: β-actin, as internal control to verify equal protein loading.