Purpose: We investigated the ability of pretreatment with buthionine sulfoximine (BSO) to overcome a priori resistance to arsenic trioxide (As2O3) in multiple myeloma (MM) cells and determine whether this was through an apoptotic mechanism that involves changes in the cellular redox state. Experimental Design: Using a panel of dexamethasone and chemotherapy-resistant MM cell lines, we examined growth inhibition, induction of apoptosis, and changes in the redox state by AS2O3 alone or after preincubation with BSO. Results: Whereas the sensitive cell lines showed 100% killing at 0.5 μmol/liter of As2O3, the resistant cell lines required BSO pretreatment to achieve 100% killing at this dose. By comparison, the peak As2O3 plasma concentration in acute promyelocytic leukemia in patients successfully treated was 5-7 μmol/liter with rapid decline to a sustained level of 1-2 μmol/liter. We demonstrated that BSO and As2O3-induced cytotoxicity was attributable to induction of apoptosis accompanied by activation of the death signals: caspases 3, 8, and 9. Conclusions: We have demonstrated that growth inhibition of highly resistant MM cell lines by As2O3 is facilitated by BSO and that this effect is accompanied by caspase activation, presumably leading to activation of apoptosis. These data indicate that steroid and chemotherapy-resistant MM cell lines can be overcome by manipulation of the cellular redox state. Because BSO and As2O3 can be used at clinically relevant concentrations, we believe that our observations may have important implications for the treatment of MM.
|Original language||English (US)|
|Number of pages||7|
|Journal||Clinical Cancer Research|
|State||Published - Mar 14 2002|
ASJC Scopus subject areas
- Cancer Research