Berberine and a Berberis lycium extract inactivate Cdc25A and induce α-tubulin acetylation that correlate with HL-60 cell cycle inhibition and apoptosis

Berberis lycium Royle (Berberidacea) from Pakistan and its alkaloids berberine and palmatine have been reported to possess beneficial pharmacological properties. In the present study, the anti-neoplastic activities of different B. lycium root extracts and the major constituting alkaloids, berberine and palmatine were investigated in p53-deficient HL-60 cells.The strongest growth inhibitory and pro-apoptotic effects were found in the n-butanol (BuOH) extract followed by the ethyl acetate (EtOAc)-, and the water (H2O) extract.The chemical composition of the BuOH extract was analyzed by TLC and quantified by HPLC. 11.1 μg BuOH extract (that was gained from 1 mg dried root) contained 2.0 μg berberine and 0.3 μg/ml palmatine. 1.2 μg/ml berberine inhibited cell proliferation significantly, while 0.5 μg/ml palmatine had no effect. Berberine and the BuOH extract caused accumulation of HL-60 cells in S-phase. This was preceded by a strong activation of Chk2, phosphorylation and degradation of Cdc25A, and the subsequent inactivation of Cdc2 (CDK1). Furthermore, berberine and the extract inhibited the expression of the proto-oncogene cyclin D1. Berberine and the BuOH extract induced the acetylation of α-tubulin and this correlated with the induction of apoptosis. The data demonstrate that berberine is a potent anti-neoplastic compound that acts via anti-proliferative and pro-apoptotic mechanisms independent of genotoxicity.