Sanguinarine-induced apoptosis is associated with an early and severe cellular glutathione depletion.

PURPOSE: The quaternary benzophenanthridine alkaloid sanguinarine exhibits a broad range of activity, including cytotoxicity against various human tumour and normal cell lines. Here, we examined its potency as an anticancer drug.
METHODS: The differential cytotoxicity against cancer versus normal cells was assessed in vitro by two fluorimetric assays (RRT and Hoechst 33342 dye DNA assays, respectively) in a panel of human solid cancer cell lines and a human fibroblast primary culture. The ability to induce apoptosis was demonstrated in PC3 human prostatic adenocarcinoma cells by analysis of morphological changes, internucleosomal DNA fragmentation, cellular poly(ADP-ribose) polymerase cleavage and caspase 3/7 activation. Production of reactive oxygen species was evaluated by the 2',7'-dichlorofluorescin diacetate assay. Depletion of cellular glutathione content was assessed with the monochlorobimane assay.
RESULTS: Sanguinarine markedly inhibited the growth of all tested cells (IC(50) 0.9-3.3 microM) without differential cytotoxicity against normal versus cancer cells. In PC3 cells, continuous treatment with 5 microM sanguinarine induced an early (within 10 min) cellular reduced glutathione depletion insensitive to dithiothreitol or N-acetylcysteine treatment, followed by a caspase 3/7-dependent apoptotic response within 2 h. Complementary assays suggested that the glutathione depletion was initiated by direct reactivity of sanguinarine with reduced glutathione.
CONCLUSIONS: Taken together, these results show that (1) sanguinarine exhibits no specificity for cancer cells, and (2) its strong cytotoxicity is probably due to a rapid apoptotic response induced by an early and severe glutathione-depleting effect. They also suggest that the clinical usefulness of this alkaloid as an anticancer drug is limited.