title: Capsazepine, a TRPV1 antagonist, sensitizes colorectal cancer cells to apoptosis by TRAIL through ROS-JNK-CHOP-mediated upregulation of death receptors.
abstract: A major problem in clinical trials of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) as cancer therapy is the development of resistance to TRAIL. Therefore, agents that can overcome TRAIL resistance have great therapeutic potential. In this study, we evaluated capsazepine, a TRPV1 antagonist, for its ability to sensitize human colon cancer cells to TRAIL-induced apoptosis. Capsazepine potentiated the effect of TRAIL, as shown by its effect on intracellular esterase activity; activation of caspase-8,-9, and -3; and colony-formation assay. Capsazepine induced death receptors (DRs) DR5 and DR4, but not decoy receptors, at the transcriptional level and in a non-cell-type-specific manner. DR induction was dependent on CCAAT/enhancer-binding protein homologous protein (CHOP), as shown by (a) the induction of CHOP by capsazepine and (b) the abolition of DR- and potentiation of TRAIL-induced apoptosis by CHOP gene silencing. CHOP induction was also reactive oxygen species (ROS)-dependent, as shown by capsazepine's ability to induce ROS and by the quenching of ROS by N-acetylcysteine or glutathione, which prevented induction of CHOP and DR5 and consequent sensitization to TRAIL. Capsazepine's effects appeared to be mediated via JNK, as shown by capsazepine's ability to induce JNK and by the suppression of both CHOP and DR5 activation by inhibition of JNK. Furthermore, ROS sequestration abrogated the activation of JNK. Finally, capsazepine downregulated the expression of various antiapoptotic proteins (e.g., cFLIP and survivin) and increased the expression of proapoptotic proteins (e.g., Bax and p53). Together, our results indicate that capsazepine potentiates the apoptotic effects of TRAIL through downregulation of cell survival proteins and upregulation of death receptors via the ROS-JNK-CHOP-mediated pathway.
authors.affiliation: Cytokine Research Laboratory, Department of Experimental Therapeutics, The University of Texas M.D. Anderson Cancer Center, Houston, TX 77030, USA.
authors.forename: Bokyung
authors.initials: B
authors.lastname: Sung
authors.forename: Sahdeo
authors.initials: S
authors.lastname: Prasad
authors.forename: Jayaraj
authors.initials: J
authors.lastname: Ravindran
authors.forename: Vivek R
authors.initials: VR
authors.lastname: Yadav
authors.forename: Bharat B
authors.initials: BB
authors.lastname: Aggarwal
mesh_terms: D000111:Acetylcysteine / Q000378:metabolism; D017209:Apoptosis / Q000187:drug effects*; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism; D002211:Capsaicin / Q000031:analogs & derivatives* / Q000494:pharmacology; D053148:Caspase 3 / Q000378:metabolism; D053181:Caspase 8 / Q000378:metabolism; D053453:Caspase 9 / Q000378:metabolism; D045744:Cell Line, Tumor; D015179:Colorectal Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D005978:Glutathione / Q000378:metabolism; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D034622:RNA Interference; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species / Q000378:metabolism; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand / Q000096:biosynthesis; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000378:metabolism*; D050916:TRPV Cation Channels / Q000037:antagonists & inhibitors*; D051742:Transcription Factor CHOP / Q000235:genetics / Q000378:metabolism; D015854:Up-Regulation
chemical_list: D051017:Apoptosis Regulatory Proteins; C497249:DDIT3 protein, human; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D053221:TNF-Related Apoptosis-Inducing Ligand; C105190:TNFRSF10A protein, human; C505653:TNFSF10 protein, human; D050916:TRPV Cation Channels; C494482:TRPV1 protein, human; D051742:Transcription Factor CHOP; D048031:JNK Mitogen-Activated Protein Kinases; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D005978:Glutathione; C071423:capsazepine; D002211:Capsaicin; D000111:Acetylcysteine