Critical role of Bid and Bax in indirubin-3'-monoxime-induced apoptosis in human cancer cells.
Indirubin-3'-monoxime (I3M) is a derivative of indirubin, an active component from a Chinese medicinal recipe with known anti-cancer function. I3M has been well established as a cyclin-dependent kinase (CDK) inhibitor, while the molecular mechanism underlying I3M-induced apoptosis has not been fully elucidated. In this study, we focused on the critical role of the pro-apoptosis Bcl-2 family members in I3M-induced apoptosis. We first observed I3M-induced apoptosis in a time- and dose-dependent manner in three different types of human cancer cells-cervical cancer HeLa, hepatoma HepG2 and colon cancer HCT116. Induction of the caspase cascade for both the extrinsic and intrinsic pathways was demonstrated, including caspase-8, -9 and -3 activation. Initiation of the death receptor pathway started with enhanced surface expression of DR4 and DR5, as well as increased total protein level, which correlated with the up-regulation of p53 and its transcriptional activity. Importantly, we found in HeLa cells that caspase-8 activation resulted in Bid cleavage, followed by Bax conformational change and hence the amplification of the apoptotic signals through the mitochondrial pathway. Consistently, stable knockdown of Bid abrogated I3M-induced Bax conformational change and cell death. Moreover, ectopic expression of a viral caspase inhibitor (CrmA) or Bcl-2 partially protected I3M-induced apoptosis. In conclusion, our results indicate that I3M mainly elicites apoptosis through extrinsic pathway with type II response mediated by the pro-apoptotic Bcl-2 family members (Bid and Bax).
Shi
Jie
J
Department of Community, Occupational and Family Medicine, Yong Loo Lin School of Medicine, National University of Singapore, 16 Medical Drive, MD3, Singapore 117597, Republic of Singapore.
Shen
Han-Ming
HM
D000970:Antineoplastic Agents / Q000737:chemistry / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D051023:BH3 Interacting Domain Death Agonist Protein / Q000378:metabolism*; D020169:Caspases / Q000378:metabolism; D045744:Cell Line, Tumor; D004305:Dose-Response Relationship, Drug; D049452:Green Fluorescent Proteins / Q000235:genetics; D006801:Humans; D007211:Indoles / Q000737:chemistry / Q000494:pharmacology*; D015394:Molecular Structure; D010091:Oximes / Q000737:chemistry / Q000494:pharmacology*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand / Q000096:biosynthesis; D018124:Receptors, Tumor Necrosis Factor / Q000096:biosynthesis; D013997:Time Factors; D014162:Transfection; D016159:Tumor Suppressor Protein p53 / Q000096:biosynthesis; D051028:bcl-2-Associated X Protein / Q000378:metabolism*
D000970:Antineoplastic Agents; C494826:BAX protein, human; D051023:BH3 Interacting Domain Death Agonist Protein; C494814:BID protein, human; D007211:Indoles; D010091:Oximes; D019253:Proto-Oncogene Proteins c-bcl-2; D034741:RNA, Small Interfering; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D018124:Receptors, Tumor Necrosis Factor; C105190:TNFRSF10A protein, human; D016159:Tumor Suppressor Protein p53; D051028:bcl-2-Associated X Protein; C474021:indirubin-3'-monoxime; D049452:Green Fluorescent Proteins; D020169:Caspases