Honokiol induces apoptotic cell death by oxidative burst and mitochondrial hyperpolarization of bladder cancer cells.

Bladder cancer is one of the most common types of malignant tumor worldwide. Current treatments, including chemo-/radiotherapy, only have limited efficacy on bladder cancer progression. Honokiol is an active component of Magnolia officinalis with multiple biological effects that may provide promising health benefits. In the present study, the anti-cancer properties of honokiol against bladder cancer cells were investigated by flow cytometric analysis. The results revealed that honokiol exhibited significant anti-proliferative effects on bladder cancer cell lines, particularly on BFTC-905 human transitional cell carcinoma cells. Furthermore, honokiol at low doses (≤25 µM) induced cell cycle arrest in G0/G1 phase, while it induced significant apoptotic cell death at high doses (≥50 µM; P<0.05). Furthermore, a significant accumulation of reactive oxygen species was identified in honokiol-treated cells. In addition, honokiol induced hyperpolarization of the mitochondrial membrane, which may lead to mitochondrial dysfunction. Finally, caspase-3/7 activation was identified in high-dose honokiol-treated bladder cancer cells. These results suggest that honokiol induces apoptosis via the mitochondrial pathway and honokiol-containing traditional herbal remedies may have a potential clinical application in the treatment of bladder cancer.