title: Alterations of beta-tubulin isotypes in breast cancer cells resistant to docetaxel.
abstract: Docetaxel is one of the most active drugs used to treat breast cancer. The cellular target of docetaxel is the microtubule, specifically the beta-tubulin subunit, that comprises a series of isotypes and that can modulate function. This study has examined the role of alteration in beta-tubulin isotypes in vitro and has sequenced the beta-tubulin gene to determine if there were mutations, both of which may represent important mechanisms of acquired resistance to docetaxel. Breast cancer cells, MCF-7 (oestrogen-receptor positive) and MDA-MB-231, (oestrogen-receptor negative) were made resistant to docetaxel in vitro. Expression of beta-tubulin isotypes (class I, II, III, IVa, IVb, and VI) was determined at the RNA and protein level using RT-PCR and western analysis, respectively. DNA sequencing evaluated the beta-tubulin gene. At the mRNA level, class I, II, III, and IVa beta-tubulin mRNA isotypes were over-expressed in docetaxel-resistant MCF-7 cells when compared with the docetaxel-sensitive parental cells. However, class VI beta-tubulin mRNA isotype expression was decreased in resistant cells. In MDA-MB-231 cells, there was a decrease in expression of the class I and class IVa beta-tubulin mRNA. However, there were increased expressions in class II, IVb, and VI beta-tubulin mRNA isotypes in resistant cells. Western analysis has confirmed corresponding increases in beta-tubulin protein levels in MCF-7 cells. However, in MDA-MB-231 cells, there were decreased protein levels for class II and class III beta-tubulin. This study demonstrates that altered expression of mRNA beta-tubulin isotypes and modulation of beta-tubulin protein levels are associated with acquired docetaxel resistance in breast cancer cells. This allows further understanding and elucidation of mechanisms involved in resistance to docetaxel.
authors.affiliation: School of Medicine, College of Life Sciences and Medicine, University of Aberdeen, Medical School, Foresterhill, Aberdeen, UK.
authors.forename: Kawan
authors.initials: K
authors.lastname: Shalli
authors.forename: Iain
authors.initials: I
authors.lastname: Brown
authors.forename: Steven D
authors.initials: SD
authors.lastname: Heys
authors.forename: Andrew C
authors.initials: AC
authors.lastname: Schofield
mesh_terms: D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D001943:Breast Neoplasms / Q000737:chemistry* / Q000188:drug therapy / Q000473:pathology; D045744:Cell Line, Tumor; D000077143:Docetaxel; D019008:Drug Resistance, Neoplasm; D005260:Female; D006801:Humans; D009154:Mutation; D020033:Protein Isoforms; D012333:RNA, Messenger / Q000032:analysis; D011960:Receptors, Estrogen / Q000032:analysis; D017422:Sequence Analysis, DNA; D043823:Taxoids / Q000494:pharmacology*; D014404:Tubulin / Q000032:analysis / Q000145:classification* / Q000235:genetics
chemical_list: D000972:Antineoplastic Agents, Phytogenic; D020033:Protein Isoforms; D012333:RNA, Messenger; D011960:Receptors, Estrogen; D043823:Taxoids; D014404:Tubulin; D000077143:Docetaxel