title: Potential antagonism of tubulin-binding anticancer agents in combination therapies.
abstract: ZD6126 is a vascular targeting agent, developed for the treatment of solid tumors. In vivo, ZD6126 is rapidly converted into the tubulin-binding agent N-acetylcolchinol. We have previously reported that in vitro N-acetylcolchinol disrupts microtubules and induces rapid changes in endothelial cell morphology, which in a tumor would lead to a rapid loss of tumor vessel integrity and subsequent extensive tumor necrosis. The aim of this study was to investigate the effect of cytotoxic antineoplastic drugs-cisplatin, doxorubicin, vincristine, paclitaxel, and docetaxel-on endothelial cell response to N-acetylcolchinol. We found that cisplatin and doxorubicin did not interfere with the ability of N-acetylcolchinol to cause morphologic changes in human umbilical vein endothelial cells, whereas vincristine showed additive effects. In contrast, the microtubule-stabilizing agents paclitaxel (1-10 micromol/L) and docetaxel (0.1-1 micromol/L) prevented the morphologic changes induced by N-acetylcolchinol in human umbilical vein endothelial cells. The effect was observed when cells were exposed to paclitaxel and N-acetylcolchinol together or when paclitaxel was given shortly before N-acetylcolchinol. Paclitaxel and N-acetylcolchinol interacted at the level of microtubule organization, as shown in immunofluorescence analysis of the cytoskeleton. The protective effect was reversible because 4 hours after paclitaxel wash out, cells recovered the sensitivity to N-acetylcolchinol. In vivo, pretreatment of mice with paclitaxel inhibited the vascular targeting activity of ZD6126 on newly formed vessels in the Matrigel plug assay and ZD6126-induced necrosis in tumors. These findings indicate that paclitaxel, depending on the timing and schedule of administration, can affect the vascular targeting activity of ZD6126, which may have an effect on the optimal scheduling of therapies based on the combined use of microtubule-stabilizing and microtubule-destabilizing agents.
authors.affiliation: Laboratory of Biology and Treatment of Metastasis, Department of Oncology, Mario Negri Institute for Pharmacological Research, Bergamo Italy.
authors.forename: Giulia
authors.initials: G
authors.lastname: Taraboletti
authors.forename: Gianluca
authors.initials: G
authors.lastname: Micheletti
authors.forename: Romina
authors.initials: R
authors.lastname: Dossi
authors.forename: Patrizia
authors.initials: P
authors.lastname: Borsotti
authors.forename: Michele
authors.initials: M
authors.lastname: Martinelli
authors.forename: Fabio
authors.initials: F
authors.lastname: Fiordaliso
authors.forename: Anderson J
authors.initials: AJ
authors.lastname: Ryan
authors.forename: Raffaella
authors.initials: R
authors.lastname: Giavazzi
mesh_terms: D020533:Angiogenesis Inhibitors / Q000008:administration & dosage / Q000494:pharmacology; D000818:Animals; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use*; D002448:Cell Adhesion / Q000187:drug effects; D002460:Cell Line; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002945:Cisplatin / Q000008:administration & dosage / Q000494:pharmacology; D003078:Colchicine / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology*; D003599:Cytoskeleton / Q000187:drug effects / Q000378:metabolism; D000077143:Docetaxel; D004305:Dose-Response Relationship, Drug; D004317:Doxorubicin / Q000008:administration & dosage / Q000494:pharmacology; D004347:Drug Interactions; D042783:Endothelial Cells / Q000187:drug effects / Q000378:metabolism; D005260:Female; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D008819:Mice, Nude; D008856:Microscopy, Fluorescence; D009336:Necrosis / Q000517:prevention & control; D009943:Organophosphorus Compounds / Q000008:administration & dosage / Q000494:pharmacology; D017239:Paclitaxel / Q000008:administration & dosage / Q000494:pharmacology; D011485:Protein Binding; D043823:Taxoids / Q000008:administration & dosage / Q000494:pharmacology; D014404:Tubulin / Q000378:metabolism*; D014471:Umbilical Veins / Q000166:cytology; D014750:Vincristine / Q000008:administration & dosage / Q000494:pharmacology; D023041:Xenograft Model Antitumor Assays / Q000379:methods*
chemical_list: D020533:Angiogenesis Inhibitors; C455219:N-acetylcochinol-O-phosphate; D009943:Organophosphorus Compounds; D043823:Taxoids; D014404:Tubulin; D000077143:Docetaxel; C017815:N-acetylcolchinol; D014750:Vincristine; D004317:Doxorubicin; D017239:Paclitaxel; D002945:Cisplatin; D003078:Colchicine