title: The cyclin-dependent kinase inhibitor flavopiridol sensitizes human hepatocellular carcinoma cells to TRAIL-induced apoptosis.
abstract: Flavopiridol was one of the first cyclin-dependent kinase inhibitors demonstrated to have an antitumor effect in several cancer types. Here, we investigated the effects of flavopiridol on TNF-related apoptosis-inducing ligand (TRAIL) in the human hepatocellular carcinoma (HCC) cell lines HLE and HepG2, and evaluated the role of flavopiridol in apoptosis. To better understand the mechanism of increased TRAIL sensitivity in HCC cells, we determined the effect of flavopiridol on cell surface expression of TRAIL and TRAIL receptors using flow cytometry analysis. The levels of survivin, FLIP, Bcl-xL and X-chromosome-linked IAP (XIAP) in treated and untreated cells was also determined. Flavopiridol decreased cell viability in a dose-dependent manner in the two HCC cell lines tested. The pan-caspase inhibitor z-VAD-FMK did not inhibit the effect. However, subtoxic levels of flavopiridol dramatically enhanced TRAIL-induced apoptosis in both cells. Flavopiridol up-regulated TRAIL, TRAIL-R1 and TRAIL-R2 in both cell lines. In addition, flavopiridol down-regulated expression of survivin in both cell lines, and expression of FLIP and Bcl-xL were down-regulated in HLE cells. In summary, flavopiridol augmented TRAIL sensitivity by up-regulation of TRAIL receptors and down-regulation of survivin, FLIP and Bcl-xL. Thus, combining flavopiridol with a TRAIL agonist may prove to be an effective new strategy for treatment of HCC.
authors.affiliation: First Department of Internal Medicine, Mie University School of Medicine, Tsu, Mie 514-8507, Japan.
authors.forename: Kazumi
authors.initials: K
authors.lastname: Miyashita
authors.forename: Katsuya
authors.initials: K
authors.lastname: Shiraki
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Fuke
authors.forename: Tomoko
authors.initials: T
authors.lastname: Inoue
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Yamanaka
authors.forename: Yumi
authors.initials: Y
authors.lastname: Yamaguchi
authors.forename: Norihiko
authors.initials: N
authors.lastname: Yamamoto
authors.forename: Keiichi
authors.initials: K
authors.lastname: Ito
authors.forename: Kazushi
authors.initials: K
authors.lastname: Sugimoto
authors.forename: Takeshi
authors.initials: T
authors.lastname: Nakano
mesh_terms: D000970:Antineoplastic Agents / Q000378:metabolism*; D017209:Apoptosis / Q000502:physiology*; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein / Q000378:metabolism; D006528:Carcinoma, Hepatocellular / Q000378:metabolism*; D045744:Cell Line, Tumor; D002470:Cell Survival; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors*; D005419:Flavonoids / Q000378:metabolism / Q000494:pharmacology*; D006801:Humans; D051034:Inhibitor of Apoptosis Proteins; D008113:Liver Neoplasms / Q000378:metabolism*; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D009363:Neoplasm Proteins / Q000378:metabolism; D010880:Piperidines / Q000378:metabolism / Q000494:pharmacology*; D047428:Protein Kinase Inhibitors / Q000378:metabolism; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand / Q000378:metabolism; D000077022:Survivin; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D051020:bcl-X Protein / Q000378:metabolism; D019014:fas Receptor / Q000378:metabolism
chemical_list: D000970:Antineoplastic Agents; C494811:BCL2L1 protein, human; C107489:BIRC5 protein, human; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D005419:Flavonoids; D051034:Inhibitor of Apoptosis Proteins; D008869:Microtubule-Associated Proteins; D009363:Neoplasm Proteins; D010880:Piperidines; D047428:Protein Kinase Inhibitors; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D000077022:Survivin; D053221:TNF-Related Apoptosis-Inducing Ligand; C505653:TNFSF10 protein, human; D014409:Tumor Necrosis Factor-alpha; D051020:bcl-X Protein; D019014:fas Receptor; C077990:alvocidib; D018844:Cyclin-Dependent Kinases