Abstract: AimTo investigate the inhibitory effect of vitexicarpin on the proliferation of human cancer cells and its mechanism of action. MethodsThe inhibitory effect of vitexicarpin on the proliferation of human cancer cells was evaluated by the SRB method and its apoptosis-inducing effect was demonstrated by morphological observation under light microscope, flow cytometric analysis and agarose gel electrophoresis. The proteins related to apoptosis were examined by Western blotting analysis. Results Vitexicarpin significantly inhibited the proliferation of human cancer cells, A2780, HCT-15, HT-1080 and K562, with the IC₅₀ values of (19.1±2.4) μmol·L^-1 for A2780(48 h), (0.66±0.10) μmol·L^-1 for HCT-15(48 h), (0.44±0.06) μmol·L^-1 for HT-1080 (48 h) and (0.28±0.14) μmol·L^-1 for K562 (24 h). The cells treated with vitexicarpin showed characteristic morphology typical for apoptosis and gave dose-dependent sub-G0/G₁ peak in the flow cytometric analysis and DNA ladder on agarose gel electrophoresis. In Western blotting analysis, the cleavage of PARP and caspase-3, the release of cytochrome c from mitochondria into the cytosol, the decrease of Bcl-2 expression level, and the down-regulation of the ratio of Bcl-2/Bax expression level were examined in the K562 cells treated with vitexicarpin. ConclusionVitexicarpin induces apoptosis in K562 cells via mitochondria-controlled apoptotic pathway.