title: Death receptor 5-mediated TNFR family signaling pathways modulate γ-humulene-induced apoptosis in human colorectal cancer HT29 cells.
abstract: A component from Emilia sonchifolia (L.) DC, γ-humulene, was investigated. Significantly decreased cell viability of human colorectal cancer HT29 cells in a dose-dependent manner with IC50 53.67±2.99 μM for 24-h treatment was found. γ-Humulene induced apoptotic cell death and apoptosis was confirmed by morphological assessment. The staining with propidium iodide (PI) and flow cytometric analysis also showed that γ-humulene significantly promoted the sub-G1 phase (an apoptotic population) in HT29 cells. Colorimetric assays indicated that pretreatment with a specific inhibitor of caspase-8 (Z-IETD-FMK) significantly reduced activities of caspase-8 and caspase-3 in examined HT29 cells. γ-Humulene stimulated the death receptor 5 (DR5), DR4, Fas-associated protein with death domain (FADD), the cleavage of caspase-8 and cleavage caspase-3, but reduced the protein levels of cellular Fas-associated death-domain-like IL-1ß-converting enzyme inhibitory protein (c-FLIP) by Western blot analysis. Consequently, γ-humulene-triggered cell death was significantly attenuated by DR5 siRNA and the caspase-8 inhibitor. Based on our results, we suggest that γ-humulene induced apoptotic cell death in HT29 cells through a DR5-mediated caspase-8 and -3-dependent signaling pathway. Therefore, this agent might be useful for developing new therapeutic regimens for treatment of colorectal cancer in the future.
authors.affiliation: School of Pharmacy, Department of Pharmacology, China Medical University, Taichung 404, Taiwan, ROC.
authors.forename: Yu-Hsuan
authors.initials: YH
authors.lastname: Lan
authors.forename: Yang-Chang
authors.initials: YC
authors.lastname: Wu
authors.forename: Kai-Wei
authors.initials: KW
authors.lastname: Wu
authors.forename: Jing-Gung
authors.initials: JG
authors.lastname: Chung
authors.forename: Chi-Cheng
authors.initials: CC
authors.lastname: Lu
authors.forename: Yuan-Liang
authors.initials: YL
authors.lastname: Chen
authors.forename: Tian-Shung
authors.initials: TS
authors.lastname: Wu
authors.forename: Jai-Sing
authors.initials: JS
authors.lastname: Yang
mesh_terms: D000230:Adenocarcinoma / Q000378:metabolism / Q000473:pathology*; D017209:Apoptosis / Q000187:drug effects*; D020169:Caspases / Q000378:metabolism; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D015179:Colorectal Neoplasms / Q000378:metabolism / Q000473:pathology*; D004305:Dose-Response Relationship, Drug; D004353:Drug Evaluation, Preclinical; D019073:HT29 Cells; D006801:Humans; D008954:Models, Biological; D000081222:Monocyclic Sesquiterpenes; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand / Q000378:metabolism / Q000502:physiology*; D018124:Receptors, Tumor Necrosis Factor / Q000378:metabolism* / Q000502:physiology; D012717:Sesquiterpenes / Q000494:pharmacology*; D015398:Signal Transduction / Q000502:physiology
chemical_list: D000081222:Monocyclic Sesquiterpenes; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D018124:Receptors, Tumor Necrosis Factor; D012717:Sesquiterpenes; C042686:humulene; D020169:Caspases