title: IFN-gamma enhances paclitaxel-induced apoptosis that is modulated by activation of caspases 8 and 3 with a concomitant down regulation of the AKT survival pathway in cultured human keratinocytes.
abstract: The aim of this study was to investigate the molecular effects of paclitaxel and IFN-gamma on cultured human keratinocyte cells (HaCaT) assessing the induction of both the apoptotic pathway and cell survival signals. Cellular cytotoxicity assays were performed by MTT dye assay. Caspases 8, 3 and AKT (Ser473 and Thr308 residues) were assessed by Western blot analysis. Morphological characteristics were examined by Wright stain analysis. Paclitaxel reduced keratinocyte growth in a 3-day bioassay with an effective ED(50) of 6-600 ng/ml. A large variation in ED(50) can be attributed to the asynchronous population of cells. Paclitaxel treatment induced activation of the AKT survival pathway in a time-dependent manner. The down-regulation of AKT signal was preceded by the subsequent activation of caspases 8 and 3 leading to apoptosis. These results indicate that paclitaxel activates both the PI3-K/AKT cell survival pathway followed by induction of apoptotic signals in cultured human keratinocytes. The induction of apoptosis in paclitaxel-treated cells is enhanced by coadministration of IFN-gamma. The synergistic effect of these two agents on HaCaT cells relies on a pathway involving caspases 8 and 3, with activity increasing by 48 h. Collectively, our data indicate that i) paclitaxel-induced apoptosis is enhanced by IFN-gamma; ii) the down-regulation of PI3-K/AKT survival pathway may help potentiate the apoptotic effects of paclitaxel and iii) the apoptotic signaling pathways are initiated with the activation of caspases 8 and 3 activities.
authors.affiliation: Department of Pathobiology, Brown University, Providence, RI, USA.
authors.forename: K
authors.initials: K
authors.lastname: Hokeness
authors.forename: L H
authors.initials: LH
authors.lastname: Qiu
authors.forename: M
authors.initials: M
authors.lastname: Vezeridis
authors.forename: B F
authors.initials: BF
authors.lastname: Yan
authors.forename: S
authors.initials: S
authors.lastname: Mehta
authors.forename: Y S
authors.initials: YS
authors.lastname: Wan
mesh_terms: D000328:Adult; D017209:Apoptosis / Q000187:drug effects*; D053148:Caspase 3; D053181:Caspase 8; D020169:Caspases / Q000378:metabolism*; D016923:Cell Death / Q000187:drug effects; D002461:Cell Line, Transformed; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D006801:Humans; D007371:Interferon-gamma / Q000494:pharmacology*; D015603:Keratinocytes / Q000166:cytology* / Q000187:drug effects / Q000502:physiology; D017239:Paclitaxel / Q000494:pharmacology*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D012867:Skin
chemical_list: D011518:Proto-Oncogene Proteins; D007371:Interferon-gamma; D011505:Protein-Tyrosine Kinases; C494918:AKT1 protein, human; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; C505407:CASP3 protein, human; C505530:CASP8 protein, human; D053148:Caspase 3; D053181:Caspase 8; D020169:Caspases; D017239:Paclitaxel