Downregulation of c-FLIP, XIAP and Mcl-1 protein as well as depletion of reduced glutathione contribute to the apoptosis induction of glycyrrhetinic acid derivatives in leukemia cells.

Abstract

The antiproliferative effects and apoptosis inducing abilities of four 18beta-glycyrrhetinic acid (GA) derivatives, methyl 2-cyano-3,11-dioxooleana-1,12-dien-30-oate (CDODO-Me-11), methyl 2-cyano-3,12-dioxooleana-1,12-dien-30-oate (CDODO-Me-12) and their non-esters were investigated in human leukemia cells. Methyl esterification and switching a keto group from position C(11) to C(12) significantly increased the antiproliferative effects. CDODO-Me-11 and CDODO-Me-12 were 10-fold more potent than their non-esters, respectively. CDODO-Me-12 was 10-fold more effective than CDODO-Me-11 in inducing apoptosis which was correlated with the activation of caspase-8 and caspase-9. Western blot analyses revealed that CDODO-Me-12 and CDODO-Me-11 downregulated the levels of anti-apoptosis proteins, c-FLIP, XIAP and Mcl-1, without altering the protein levels of Bcl-2 and the death receptors DR4 and DR5. Both agents decreased the levels of the mitochondrial membrane potential without altering the intracellular H(2)O(2) levels. Jurkat cells without expression of caspase-8 were not sensitive to CDODO-Me-12, but were somewhat responsive to CDODO-Me-11. K562 cells with higher intracellular reduced glutathione (GSH ) levels were less responsive to CDODO-Me-12 apoptosis induction than U937 cells even though both cell lines were equally sensitive to CDODO-Me-11 apoptosis induction. Both agents depleted intracellular GSH levels and exogenous GSH reversed apoptosis induction by either agent in HL-60 cells. N-acetylcysteine (NAC) significantly attenuated apoptosis induction by CDODO-Me-12, but only weakly, that by CDODO-Me-11. UV spectrophotometric analysis revealed that both agents interacted with GSH while only CDODO-Me-12 had high reactivity with NAC. These data suggest that both agents induce apoptosis requiring to bind to functional proteins with thiol groups and that GSH may play a protective role by forming inactive adducts with them.

• Authors: Dandan Song, Yuan Gao, Rui Wang, Dan Liu, Linxiang Zhao, Yongkui Jing
• Journal: Cancer biology & therapy (Cancer Biol Ther) Vol. 9 Issue 2 Pg. 96-108 (Jan 2010) ISSN: 1555-8576 [Electronic] United States
• PMID: 19949310 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Antineoplastic Agents, Phytogenic
• CASP8 and FADD-Like Apoptosis Regulating Protein
• CFLAR protein, human
• Myeloid Cell Leukemia Sequence 1 Protein
• Neoplasm Proteins
• Proto-Oncogene Proteins c-bcl-2
• X-Linked Inhibitor of Apoptosis Protein
• XIAP protein, human
• methyl 2-cyano-3,11-dioxooleana-1,12-dien-30-oate
• methyl 2-cyano-3,12-dioxooleana-1, 12-dien-30-oate
• Glutathione
• Glycyrrhetinic Acid

Topics

• Antineoplastic Agents, Phytogenic (pharmacology)
• Apoptosis (genetics)
• CASP8 and FADD-Like Apoptosis Regulating Protein (biosynthesis, genetics)
• Down-Regulation
• Drug Screening Assays, Antitumor
• Gene Expression Regulation, Leukemic (drug effects)
• Glutathione (metabolism)
• Glycyrrhetinic Acid (analogs & derivatives, pharmacology)
• HL-60 Cells (drug effects, metabolism)
• Humans
• Jurkat Cells (drug effects, metabolism)
• K562 Cells (drug effects, metabolism)
• Leukemia, Myeloid, Acute (pathology)
• Myeloid Cell Leukemia Sequence 1 Protein
• Neoplasm Proteins (biosynthesis, genetics)
• Oxidation-Reduction
• Proto-Oncogene Proteins c-bcl-2 (biosynthesis, genetics)
• U937 Cells (drug effects, metabolism)
• X-Linked Inhibitor of Apoptosis Protein (biosynthesis, genetics)