Honokiol induces PARP and caspase-3 cleavage and the release of cytochrome <i>c</i> in the cytoplasm in multidrug-sensitive and -resistant cells.

<p>(<b>a</b>) KB-3-1 cells and (<b>b</b>) KB-8-5 cells were treated with 5, 10, 15 µg/ml of honokiol for 24, 48 h. Full-length and cleaved PARP, cleaved caspase-3 and β-actin as a loading control were detected by immunoblotting using whole cell lysates. (<b>c</b>) KB-C1 and KB-V1 cells were treated with 5, 10, 15 µg/ml of honokiol for 48 h. Cleaved PARP was detected by immunoblotting using whole cell lysates. (<b>d</b>) Upper panel, KB-8-5 cells were treated with 5, 10, 15 µg/ml of honokiol for 48 h. Cytoplasmic and mitochondrial fractions were separated and immunoblotted with cytochrome c (Cyto C) antibody. COX4 (a mitochondrial protein) was used to show efficiency of cell fractionation. Lower panel, KB-8-5 cells were treated with 5, 10, 15 µg/ml of honokiol for 24 and 48 h. DR5 was detected by immunoblotting using whole cell lysates. All experiments were repeated at least three times, and representative data are presented.