Honokiol, a natural biphenyl, inhibits in vitro and in vivo growth of breast cancer through induction of apoptosis and cell cycle arrest.

Honokiol (HNK), a naturally occurring biphenyl, possesses potent antineoplastic and antiangiogenic properties. We investigated the in vitro and in vivo activity of HNK against breast cancer. HNK exhibited potent anti-proliferative activity against breast cancer cell lines and enhanced the activity of other drugs used for the treatment of breast cancer. In vivo, HNK was highly effective against breast cancer in nude mice. We identified two different effects of HNK on breast cancer cells: cell cycle inhibition, observed at lower doses of HNK, and induction of apoptosis, observed at higher doses of the compound. Our data suggest that HNK is a systemically available, non-toxic inhibitor of breast cancer growth and should be examined for clinical applications.