Although the effects of
sanguinarine, a benzophenanthridine
alkaloid, on the inhibition of some kinds of
cancer cell growth have been established, the underlying mechanisms are not completely understood. This study investigated possible mechanisms by which
sanguinarine exerts its anticancer action in cultured human
bladder cancer cell lines (T24, EJ, and 5637).
Sanguinarine treatment resulted in concentration-response growth inhibition of the
bladder cancer cells by inducing apoptosis.
Sanguinarine-induced apoptosis was correlated with the up-regulation of Bax, the down-regulation of Bid and XIAP, the activation of
caspases (-3, -8, and -9), and the generation of increased
reactive oxygen species (ROS). The ROS scavenger N-acetyl
cysteine (NAC) completely reversed the
sanguinarine-triggered apoptotic events. In addition,
sanguinarine effectively increased the activation of the
c-Jun N-terminal kinase (JNK) and the expression of the early growth response gene-1 (Egr-1), which was recovered by pretreatment with NAC. Furthermore, knockdown of Egr-1 expression by
small interfering RNA attenuated
sanguinarine-induced apoptosis, but not the JNK inhibitor, indicating that the interception of ROS generation blocked the
sanguinarine-induced apoptotic effects via deregulation of the expression of Egr-1
proteins. Taken together, the data provide evidence that
sanguinarine is a potent
anticancer agent, which inhibits the growth of
bladder cancer cells and induces their apoptosis through the generation of
free radicals.