title: Differential regulation of the cytotoxicity activity of paclitaxel by orobol and platelet derived growth factor in human ovarian carcinoma cells.
abstract: Paclitaxel (PX) binds to and stabilizes tubulin, preventing depolymerization, and resulting in cell death. Based on a previous report showing the activity of phosphatidylinositol kinase (PIK) on tubulin, we investigated the effect of the PI4K inhibitor orobol and the PI3K activator platelet derived growth factor (PDGF) on PX sensitivity. Drug sensitivity was examined by classical colony forming assay. Tubulin isotype expression was determined by semi-quantitative RT-PCR. Microtubule texture was observed by laser confocal microscope using anti-beta-tubulin antibody. Apoptotic activity was estimated by frequency of condensed nuclear chromatin with Hoechst 33342 stain. Orobol enhanced PX sensitivity of human ovarian carcinoma 2008 cells by 18.9+/-1.2-fold (N=3; P<0.01). In contrast, pretreatment with PDGF rendered cells resistant to PX by 2.3+/-0.4-fold (N=3; P<0.01). Neither orobol nor PDGF showed any effect on cell growth. Orobol produced a 2.5-fold sensitization in cisplatin-resistant 2008/C13*5.25 (C13) cells, and PDGF rendered the cells 2.3-fold resistant to PX. Orobol suppressed the beta 4a-tubulin isotype expression by 85% and other isotypes by 20%. In contrast, PDGF induced beta 4a-tubulin isotype expression by 1.3-fold, while it supressed all the other isotypes by 20-40%. Orobol produced thick microtubules and PDGF generated ring condensed microtubules. Orobol promoted PX-induced apoptosis, while PDGF caused 50% reduction of apoptosis. These results indicate that orobol and PDGF regulate PX sensitivity by reciprocally altering the proportion of tubulin isotype expression and PX-induced apoptotic signaling.
authors.affiliation: Department of Obstetrics and Gynecology, Jikei University School of Medicine, Tokyo 125-8506, Japan. isonishi@jikei.ac.jpc
authors.forename: Seiji
authors.initials: S
authors.lastname: Isonishi
authors.forename: Motoaki
authors.initials: M
authors.lastname: Saitou
authors.forename: Misato
authors.initials: M
authors.lastname: Saitou
authors.forename: Makoto
authors.initials: M
authors.lastname: Yasuda
authors.forename: Tadao
authors.initials: T
authors.lastname: Tanaka
mesh_terms: D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D053148:Caspase 3 / Q000378:metabolism; D018284:Cystadenocarcinoma, Serous / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D019008:Drug Resistance, Neoplasm; D005260:Female; D005419:Flavonoids / Q000494:pharmacology*; D006801:Humans; D018613:Microscopy, Confocal; D010051:Ovarian Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D017239:Paclitaxel / Q000494:pharmacology*; D010982:Platelet-Derived Growth Factor / Q000378:metabolism*; D011485:Protein Binding; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012334:RNA, Neoplasm / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014404:Tubulin / Q000235:genetics / Q000378:metabolism; D014407:Tumor Cells, Cultured
chemical_list: D000972:Antineoplastic Agents, Phytogenic; D005419:Flavonoids; D010982:Platelet-Derived Growth Factor; D012333:RNA, Messenger; D012334:RNA, Neoplasm; D014404:Tubulin; D053148:Caspase 3; C059811:orobol; D017239:Paclitaxel