title: 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.affiliation: Asan Institute for Life Sciences, University of Ulsan College of Medicine, Seoul, Republic of Korea; Institute for Innovative Cancer Research, University of Ulsan College of Medicine, Seoul, Republic of Korea.
authors.forename: Seok Soon
authors.initials: SS
authors.lastname: Park
authors.affiliation: Department of Radiation Oncology, University of Soonchunhyang College of Medicine, Cheonan, Republic of Korea.
authors.forename: Eunjin
authors.initials: E
authors.lastname: Jwa
authors.affiliation: Institute for Innovative Cancer Research, University of Ulsan College of Medicine, Seoul, Republic of Korea.
authors.forename: Seol Hwa
authors.initials: SH
authors.lastname: Shin
authors.affiliation: Institute for Innovative Cancer Research, University of Ulsan College of Medicine, Seoul, Republic of Korea.
authors.forename: Eun Jin
authors.initials: EJ
authors.lastname: Ju
authors.affiliation: Institute for Innovative Cancer Research, University of Ulsan College of Medicine, Seoul, Republic of Korea.
authors.forename: Intae
authors.initials: I
authors.lastname: Park
authors.affiliation: Asan Institute for Life Sciences, University of Ulsan College of Medicine, Seoul, Republic of Korea; Department of Convergence Medicine, University of Ulsan College of Medicine, Seoul, Republic of Korea.
authors.forename: Jhang Ho
authors.initials: JH
authors.lastname: Pak
authors.affiliation: Asan Institute for Life Sciences, University of Ulsan College of Medicine, Seoul, Republic of Korea; Institute for Innovative Cancer Research, University of Ulsan College of Medicine, Seoul, Republic of Korea; Center for Advancing Cancer Therapeutics, University of Ulsan College of Medicine, Seoul, Republic of Korea; Department of Convergence Medicine, University of Ulsan College of Medicine, Seoul, Republic of Korea.
authors.forename: Jung Jin
authors.initials: JJ
authors.lastname: Hwang
authors.affiliation: Graduate School of East-West Medical Science, Kyung Hee University, Yongin, Republic of Korea.
authors.forename: Dong-Hyung
authors.initials: DH
authors.lastname: Cho
authors.affiliation: Department of Chemistry, Seoul National University, Seoul, Republic of Korea.
authors.forename: B Moon
authors.initials: BM
authors.lastname: Kim
authors.affiliation: Department of Oncology, University of Ulsan College of Medicine, Seoul, Republic of Korea.
authors.forename: Sung-Bae
authors.initials: SB
authors.lastname: Kim
authors.affiliation: Asan Institute for Life Sciences, University of Ulsan College of Medicine, Seoul, Republic of Korea; Department of Internal Medicine,Asan Medical Center, University of Ulsan College of Medicine, Seoul, Republic of Korea.
authors.forename: Jung Shin
authors.initials: JS
authors.lastname: Lee
authors.affiliation: Institute for Innovative Cancer Research, University of Ulsan College of Medicine, Seoul, Republic of Korea; Center for Advancing Cancer Therapeutics, University of Ulsan College of Medicine, Seoul, Republic of Korea; Department of Radiation Oncology, University of Ulsan College of Medicine, Seoul, Republic of Korea. Electronic address: coocoori@amc.seoul.kr.
authors.forename: Si Yeol
authors.initials: SY
authors.lastname: Song
authors.affiliation: Asan Institute for Life Sciences, University of Ulsan College of Medicine, Seoul, Republic of Korea; Institute for Innovative Cancer Research, University of Ulsan College of Medicine, Seoul, Republic of Korea; Center for Advancing Cancer Therapeutics, University of Ulsan College of Medicine, Seoul, Republic of Korea; Department of Convergence Medicine, University of Ulsan College of Medicine, Seoul, Republic of Korea. Electronic address: syj@amc.seoul.kr.
authors.forename: Seong-Yun
authors.initials: SY
authors.lastname: Jeong
authors.affiliation: Institute for Innovative Cancer Research, University of Ulsan College of Medicine, Seoul, Republic of Korea; Center for Advancing Cancer Therapeutics, University of Ulsan College of Medicine, Seoul, Republic of Korea; Department of Radiation Oncology, University of Ulsan College of Medicine, Seoul, Republic of Korea. Electronic address: ekchoi@amc.seoul.kr.
authors.forename: Eun Kyung
authors.initials: EK
authors.lastname: Choi
mesh_terms: D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D002154:Calpain / Q000378:metabolism*; D006528:Carcinoma, Hepatocellular / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D020169:Caspases / Q000378:metabolism; D045744:Cell Line, Tumor; D004357:Drug Synergism; D006801:Humans; D008113:Liver Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D011355:Prodrugs / Q000008:administration & dosage / Q000494:pharmacology*; D011741:Pyrimidine Nucleosides / Q000008:administration & dosage / Q000494:pharmacology*; D034741:RNA, Small Interfering / Q000235:genetics; D015398:Signal Transduction / Q000187:drug effects; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000008:administration & dosage / Q000378:metabolism*; D015854:Up-Regulation; D051028:bcl-2-Associated X Protein / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D051020:bcl-X Protein / Q000235:genetics / Q000378:metabolism
chemical_list: C559897:(5-(4-amino-6-bromo-5-carbamoyl-1H-pyrrolo(2,3-d)pyrimidin-1-yl)-3,4-dihydroxytetrahydrofuran-2-yl)methyl isobutyrate; C494826:BAX protein, human; C494811:BCL2L1 protein, human; D011355:Prodrugs; D011741:Pyrimidine Nucleosides; D034741:RNA, Small Interfering; D053221:TNF-Related Apoptosis-Inducing Ligand; C505653:TNFSF10 protein, human; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein; D002154:Calpain; D020169:Caspases
keywords: Calpain; Caspase; Cleaved-Bax; Ibulocydine; Mitochondria