title: Differential cytotoxic effects of docetaxel in a range of mammalian tumor cell lines and certain drug resistant sublines in vitro.
abstract: The in vitro cytotoxic effects of docetaxel (Taxotere; RP56976, NSC688503) proved both time and concentration dependent. Amongst thirteen human cell lines from various tumor types, exposure to increasing concentrations of docetaxel over 24 hrs resulted in a plateau-shaped dose response curve, suggesting that increased cell kill becomes more dependent on increased exposure duration than on concentration. IC50 concentrations (reducing survival by 50%) ranged from 0.13-3.3 ng/ml, with three neuroblastoma lines proving most sensitive and three breast and two colon carcinoma lines showing least sensitivity. There was significant cross-resistance to docetaxel in the classic multidrug resistant (MDR) Chinese hamster ovarian (CHO) CHRC5 line and the human lymphoblastoid CCRF-CEMVLB1000 line, as well as in two vincristine (VCR)-selected MDR MCF-7 sublines. All four of these MDR sublines overexpress P-glycoprotein (Pgp), as did a 6-fold docetaxel-selected resistant CHO subline. As an apparent corollary, in two human teratoma lines selected for etoposide resistance and showing some cross-resistance to VCR and in two CHO sublines expressing low levels of VCR resistance, yet all proving Pgp positive, no docetaxel cross-resistance was identified. Verapamil modulated docetaxel resistance only in sublines expressing resistance to the drug and overexpressing Pgp. Four other human tumor sublines selected for resistance to 5-fluorouracil, cisplatin or teniposide, showed a lack of cross-resistance to docetaxel. Furthermore, cross-resistance to docetaxel was not apparant in four epipodophyllotoxin-selected resistant sublines with alterations in topoisomerase II, indicating its effectiveness against tumor cells expressing the topoisomerase II-related MDR phenotype. Our observation that docetaxel cross-resistance was not automatically expressed by classic MDR tumour cells appears of interest and of potential clinical relevance.
authors.affiliation: Laboratory of Cellular Chemotherapy, Imperial Cancer Research Fund, London, England.
authors.forename: B T
authors.initials: BT
authors.lastname: Hill
authors.forename: R D
authors.initials: RD
authors.lastname: Whelan
authors.forename: S A
authors.initials: SA
authors.lastname: Shellard
authors.forename: S
authors.initials: S
authors.lastname: McClean
authors.forename: L K
authors.initials: LK
authors.lastname: Hosking
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000032:analysis*; D000818:Animals; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D016466:CHO Cells / Q000187:drug effects; D006224:Cricetinae; D004250:DNA Topoisomerases, Type II / Q000378:metabolism*; D000077143:Docetaxel; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D004351:Drug Resistance; D004354:Drug Screening Assays, Antitumor; D006801:Humans; D017239:Paclitaxel / Q000031:analogs & derivatives* / Q000494:pharmacology; D043823:Taxoids; D014407:Tumor Cells, Cultured / Q000187:drug effects; D014700:Verapamil / Q000494:pharmacology
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000972:Antineoplastic Agents, Phytogenic; D043823:Taxoids; D000077143:Docetaxel; D014700:Verapamil; D004250:DNA Topoisomerases, Type II; D017239:Paclitaxel