Acta Pharmacologica Sinica (2009) 30: 451-457; doi: 10.1038/aps.2009.19; published online 9th March 2009

Aim: The aim of this study was to explore the effects and mechanism of berbamine on imatinib-resistant BCR-ABL-positive human leukemia K562 (K562-r) cells in vitro and in vivo.

Methods: Cell viability was measured by MTT assay, and apoptotic morphology changes were detected by fluorescence microscopy.  The apoptosis rate was measured by flow cytometric assay.  mdr-1 mRNA levels were determined by RT-PCR.  Bcl-2 family proteins, cytochrome c( cyt C), poly (ADP-ribose) polymerase (PARP), and P-glycoprotein were detected by Western blot.  BALB/c nu/nu mice were injected with K562-r cells subcutaneously.  Tumor-bearing mice were treated intravenously with berbamine. 

Results: MTT tests revealed that berbamine significantly inhibited K562-r cell proliferation and increased the chemo-sensitivity of K562-r cells to imatinib.  The apoptosis rate was significantly increased following treatment with 21.2 μmol/L berbamine; formation of typical apoptotic blebs was apparent, as observed by fluorescence microscopy.  Expression levels of mdr-1 mRNA and P-gp protein were high in untreated K562-r cells and significantly down-regulated by berbamine treatment.  Berbamine-treated K562-r cells also exhibited down-regulated expression of the anti-apoptotic proteins Bcl-2 and Bcl-x_L, up-regulated expression of the apoptotic proteins Bax and cytoplasmic cyt C, and stimulated proteolytic cleavage of PARP.  In addition, berbamine also suppressed the growth of K562-r xenotransplanted tumors in vivo.   

Keywords: berbamine; chronic myeloid leukemia; imatinib; mdr-1; Bcl-2