ABSTRACT
<p><b>OBJECTIVE</b>To investigate the anti-proliferation effect of oridonin on leukemic HL-60 cells and its mechanism.</p><p><b>METHODS</b>HL-60 cells in vitro in culture medium were given different concentrations of oridonin. The inhibitory rate of cells were measured by microculture tetrazolium (MTT) assay, cell apoptotic rate was detected by flow cytometry (FCM), morphology of cell apoptosis was observed by hoechst 33258 fluorescence staining, and the activity of telomerase was detected using telomere repeat amplification protocol (TRAP) PCR-ELISA before and after apoptosis occurred.</p><p><b>RESULTS</b>Oridonin could decrease telomerase activity, inhibit growth of HL-60 cells, and cause apoptosis significantly. The suppression was both in time- and dose-dependent manner. Marked morphological changes of cell apoptosis including condensation of chromatin and nuclear fragmentation were observed clearly by hoechst 33258 fluorescence staining especially after cells were treated 48-60 hours by oridonin.</p><p><b>CONCLUSIONS</b>Oridonin has apparent anti-proliferation and apoptotic effects on HL-60 cells in vitro, decreasing telomerase activity of HL-60 cells may be one of its most important mechanisms. These results will provide strong laboratory evidence of oridonin for clinical treatment of acute leukemia.</p>