Ponicidin, an extract from the Chinese herb Rabdosia rubescens, is currently one of the most important traditional Chinese
herbal medicines.
Ponicidin has been reported to have anti-
tumor effects on a large variety of malignant diseases. In this study, we investigated the anti-proliferation effects of
ponicidin on human myeloid K562 and HL-60 cells. Cell viability was measured by MTT assay; cell apoptosis was assessed by flow cytometry, DNA fragmentation analysis and
Hoechst 33258 staining.
Caspase-3 and
poly(ADP-ribose) polymerase (PARP) activation and Bax and Bcl-2 expression were detected by Western blot analysis. The results revealed that
ponicidin could significantly inhibit the growth of K562 and HL-60 cells by induction of apoptosis. The suppression was both time- and dose-dependent. Cell apoptosis was observed clearly after the cells were treated with
ponicidin for 48-72 h. Western blotting showed cleavage of the
caspase-3 zymogen protein (32 kDa) with the appearance of its 17 kDa subunit, together with a cleaved 89-kDa fragment of 116 kDa PARP when apoptosis occurred. Bcl-2 expression was down-regulated while Bax expression up-regulated concurrently when the cells were treated with
ponicidin for 24-48 h. Therefore, we conclude that
ponicidin has significant anti-proliferation effects by induction of apoptosis on
myeloid leukemia cells in vitro, down-regulation of Bcl-2, and up-regulation of Bax, and that activation of
caspase-3 and PARP may be an important apoptosis-inducing mechanism. The results suggest that
ponicidin may serve as a potential therapeutic agent for
leukemia.