Ibulocydine sensitizes human hepatocellular carcinoma cells to TRAIL-induced apoptosis via calpain-mediated Bax cleavage.

Abstract

Tumor necrosis factor-related apoptosis-induced ligand (TRAIL) induces apoptosis selectively in cancer cells without affecting the majority of normal human cells. However, hepatocellular carcinoma (HCC) cells often display resistance to TRAIL-induced apoptosis. Ibulocydine (IB) is an isobutyrate ester pro-drug of a novel synthetic Cdk inhibitor that targets Cdk7 and Cdk9. In this study, we show that treatment with subtoxic doses of IB in combination with TRAIL displays potent cytotoxicity in TRAIL-resistant human HCC cells. Combination of IB and TRAIL was found to synergistically induce apoptosis through activation of caspases, which was blocked by a pan-caspase inhibitor (zVAD). Although the expression of Mcl-1 and survivin were reduced by IB plus TRAIL, overexpression of Mcl-1 and survivin did not block the cell death induced by co-treatment. Moreover, overexpression of Bcl-xL did not significantly interfere with the cell death induced by co-treatment of IB and TRAIL. Interestingly, the combination treatment induced cleavage of Bax, which was translocated to mitochondria upon induction of apoptosis. Furthermore, down-regulation of Bax by small interfering RNA effectively reduced the cell death and loss of mitochondrial membrane potential (MMP) caused by co-treatment with IB and TRAIL. Finally, pre-treatment of HCC cells with a calpain inhibitor effectively blocked IB plus TRAIL-induced cleavage of Bax and apoptosis. Collectively, our results demonstrate that IB increases the sensitivity of human HCC cells to TRAIL via mitochondria signaling pathway mediated by calpain-induced cleavage of Bax, suggesting that combined treatment with IB and TRAIL may offer an effective therapeutic strategy for human HCC.

• Authors: Seok Soon Park, Eunjin Jwa, Seol Hwa Shin, Eun Jin Ju, Intae Park, Jhang Ho Pak, Jung Jin Hwang, Dong-Hyung Cho, B Moon Kim, Sung-Bae Kim, Jung Shin Lee, Si Yeol Song, Seong-Yun Jeong, Eun Kyung Choi
• Journal: The international journal of biochemistry & cell biology (Int J Biochem Cell Biol) Vol. 83 Pg. 47-55 (02 2017) ISSN: 1878-5875 [Electronic] Netherlands
• PMID: 27923747 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: Copyright © 2016 Elsevier Ltd. All rights reserved.

Chemical References

• (5-(4-amino-6-bromo-5-carbamoyl-1H-pyrrolo(2,3-d)pyrimidin-1-yl)-3,4-dihydroxytetrahydrofuran-2-yl)methyl isobutyrate
• BAX protein, human
• BCL2L1 protein, human
• Prodrugs
• Pyrimidine Nucleosides
• RNA, Small Interfering
• TNF-Related Apoptosis-Inducing Ligand
• TNFSF10 protein, human
• bcl-2-Associated X Protein
• bcl-X Protein
• Calpain
• Caspases

Topics

• Apoptosis (drug effects, physiology)
• Calpain (metabolism)
• Carcinoma, Hepatocellular (drug therapy, metabolism, pathology)
• Caspases (metabolism)
• Cell Line, Tumor
• Drug Synergism
• Humans
• Liver Neoplasms (drug therapy, metabolism, pathology)
• Mitochondria (drug effects, metabolism)
• Prodrugs (administration & dosage, pharmacology)
• Pyrimidine Nucleosides (administration & dosage, pharmacology)
• RNA, Small Interfering (genetics)
• Signal Transduction (drug effects)
• TNF-Related Apoptosis-Inducing Ligand (administration & dosage, metabolism)
• Up-Regulation
• bcl-2-Associated X Protein (antagonists & inhibitors, genetics, metabolism)
• bcl-X Protein (genetics, metabolism)