I3C-induced apoptosis is caspase-dependent in HTLV-1-infected T-cell lines. (A) Effect of I3C on the cleavage of PARP in HUT-102 cells. Cells were treated with I3C (100 μM) for the indicated periods. Total SDS protein lysates (20 μg per lane) were prepared and immunoblotted against cleaved PARP. Representative data of three experiments with similar results. (B) I3C treatment activates caspase-3, -8 and -9 in HUT-102 cells. Cells were treated with or without I3C (100 μM) for 48 h. Caspase activity was assayed as described in "Methods" and expressed relative to untreated cells, which were assigned a value of 1. Values represent the mean ± SD of three experiments.