title: Silibinin sensitizes human glioma cells to TRAIL-mediated apoptosis via DR5 up-regulation and down-regulation of c-FLIP and survivin.
abstract: Silibinin, a flavonoid isolated from Silybum marianum, has been reported to have cancer chemopreventive and therapeutic effects. Here, we show that treatment with subtoxic doses of silibinin in combination with tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) induces rapid apoptosis in TRAIL-resistant glioma cells, but not in human astrocytes, suggesting that this combined treatment may offer an attractive strategy for safely treating gliomas. Although the proteolytic processing of procaspase-3 by TRAIL was partially blocked in glioma cells, cotreatment with silibinin efficiently recovered TRAIL-induced caspase activation in these cells. Silibinin treatment up-regulated DR5, a death receptor of TRAIL, in a transcription factor CHOP-dependent manner. Furthermore, treatment with silibinin down-regulated the protein levels of the antiapoptotic proteins FLIP(L), FLIP(S), and survivin through proteasome-mediated degradation. Taken together, our results show that the activity of silibinin to modulate multiple components in the death receptor-mediated apoptotic pathway is responsible for its ability to recover TRAIL sensitivity in TRAIL-resistant glioma cells.
authors.affiliation: Department of Molecular Science and Technology, Institute for Medical Sciences, Ajou University School of Medicine, Suwon, Korea.
authors.forename: Yong-Gyu
authors.initials: YG
authors.lastname: Son
authors.forename: Eun Hee
authors.initials: EH
authors.lastname: Kim
authors.forename: Jin Yeop
authors.initials: JY
authors.lastname: Kim
authors.forename: Seung U
authors.initials: SU
authors.lastname: Kim
authors.forename: Taeg Kyu
authors.initials: TK
authors.lastname: Kwon
authors.forename: A-Rum
authors.initials: AR
authors.lastname: Yoon
authors.forename: Chae-Ok
authors.initials: CO
authors.lastname: Yun
authors.forename: Kyeong Sook
authors.initials: KS
authors.lastname: Choi
mesh_terms: D000975:Antioxidants / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D001253:Astrocytes / Q000187:drug effects; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein / Q000235:genetics*; D020169:Caspases / Q000378:metabolism; D004338:Drug Combinations; D004353:Drug Evaluation, Preclinical; D004357:Drug Synergism; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D005910:Glioma / Q000235:genetics / Q000473:pathology*; D006801:Humans; D051034:Inhibitor of Apoptosis Proteins; D008869:Microtubule-Associated Proteins / Q000235:genetics*; D009363:Neoplasm Proteins / Q000235:genetics*; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand / Q000235:genetics*; D000077385:Silybin; D012838:Silymarin / Q000494:pharmacology; D000077022:Survivin; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000494:pharmacology*; D051742:Transcription Factor CHOP / Q000378:metabolism; D014407:Tumor Cells, Cultured