Berbamine selectively induces apoptosis of human acute promyelocytic leukemia cells via survivin-mediated pathway.

BACKGROUND: Currently, resistance and relapse are still major problems in acute promyelocytic leukemia (APL) cases. Thus, new agents that override the resistance are crucial to the development of curative therapies for APL. In this study, we investigated the effects of berbamine on the proliferation of APL cell line NB4 and its possible mechanisms.

METHODS: NB4 cells were treated with berbamine at different concentrations (0-64 microg/ml) for 72 hours. MTT assay was used to determine proliferation inhibition of NB4 cells. Cell apoptosis was evaluated by both flow cytometry (FCM) and morphological examination. PML/RAR-alpha and survivin mRNAs were measured by nested-RT-PCR and RT-PCR, respectively. Activated-caspase 3 was determined by FCM.

RESULTS: Berbamine greatly inhibited the proliferation of NB4 cells in dose- and time-dependent manners, and its IC50 value was 3.86 microg/ml at 48 hours. Both morphological observations and FCM results showed that berbamine induced apoptosis of NB4 cells with concomitant increase of activated caspase-3 and decrease of survivin mRNA. After treatment with berbamine at 8 microg/ml for 48 hours, the percentage of apoptotic cells increased from 2.83% to 58.44% (P<0.01), and the percentage of cells with activated-caspase 3 elevated from 2.06% to 70.89% (P<0.01), whereas, level of survivin mRNA was reduced to 38.24% of control (P<0.01). However, no significant change was observed in PML/RAR-alpha mRNA.

CONCLUSIONS: Berbamine induces caspase-3-dependent apoptosis of leukemia NB4 cells via survivin-mediated pathway, suggesting that berbamine may be a novel potential agent against APL with a mechanism distinct from that of all-trans retinoic acid (ATRA) and arsenic trioxide (ATO).