Compound K, a metabolite of ginseng saponin, induces apoptosis via caspase-8-dependent pathway in HL-60 human leukemia cells.

Abstract

BACKGROUND:

Compound K [20-O-beta-(D-glucopyranosyl)-20(S)-protopanaxadiol], a metabolite of the protopanaxadiol-type saponins of Panax ginseng C.A. Meyer, has been reported to possess anti-tumor properties to inhibit angiogenesis and to induce tumor apoptosis. In the present study, we investigated the effect of Compound K on apoptosis and explored the underlying mechanisms involved in HL-60 human leukemia cells.

METHODS:

We examined the effect of Compound K on the viabilities of various cancer cell lines using MTT assays. DAPI assay, Annexin V and PI double staining, Western blot assay and immunoprecipitation were used to determine the effect of Compound K on the induction of apoptosis.

RESULTS:

Compound K was found to inhibit the viability of HL-60 cells in a dose- and time-dependent manner with an IC50 of 14 muM. Moreover, this cell death had typical features of apoptosis, that is, DNA fragmentation, DNA ladder formation, and the externalization of Annexin V targeted phosphatidylserine residues in HL-60 cells. In addition, compound-K induced a series of intracellular events associated with both the mitochondrial- and death receptor-dependent apoptotic pathways, namely, (1) the activation of caspases-3, -8, and -9; (2) the loss of mitochondrial membrane potential; (3) the release of cytochrome c and Smac/DIABLO to the cytosol; (4) the translocation of Bid and Bax to mitochondria; and (5) the downregulations of Bcl-2 and Bcl-xL. Furthermore, a caspase-8 inhibitor completely abolished caspase-3 activation, Bid cleavage, and subsequent DNA fragmentation by Compound K. Interestingly, the activation of caspase-3 and -8 and DNA fragmentation were significantly prevented in the presence of cycloheximide, suggesting that Compound K-induced apoptosis is dependent on de novo protein synthesis.

CONCLUSIONS:

The results indicate that caspase-8 plays a key role in Compound K-stimulated apoptosis via the activation of caspase-3 directly or indirectly through Bid cleavage, cytochrome c release, and caspase-9 activation.

• Authors: Sung-Hee Cho, Kyung-Sook Chung, Jung-Hye Choi, Dong-Hyun Kim, Kyung-Tae Lee
• Journal: BMC cancer (BMC Cancer) Vol. 9 Pg. 449 (Dec 18 2009) ISSN: 1471-2407 [Electronic] England
• PMID: 20017956 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Apoptosis Regulatory Proteins
• DIABLO protein, human
• Ginsenosides
• Intracellular Signaling Peptides and Proteins
• Mitochondrial Proteins
• Saponins
• Cytochromes c
• ginsenoside M1
• CASP8 protein, human
• Caspase 8

Topics

• Apoptosis (drug effects)
• Apoptosis Regulatory Proteins
• Caspase 8 (metabolism, physiology)
• Cytochromes c (metabolism)
• Drug Evaluation, Preclinical
• Ginsenosides (pharmacology)
• HL-60 Cells
• HeLa Cells
• Humans
• Intracellular Signaling Peptides and Proteins (metabolism)
• Leukemia (pathology)
• Membrane Potentials (drug effects)
• Mitochondrial Proteins (metabolism)
• Models, Biological
• Panax (chemistry, metabolism)
• Saponins (chemistry, metabolism)
• Signal Transduction (drug effects, physiology)
• Tumor Cells, Cultured
• U937 Cells