Alterations of β‐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.

Cytoskeleton and paclitaxel sensitivity in breast cancer: The role of β‐tubulins

“…This evidence is in agreement with previous studies, which analyzed Class I b-tubulin mutations in ovarian and lung cancer. 23,30,31 Among other factors suggested as potentially influencing paclitaxel chemosensitivity, microtubule dynamics, 32 presence of stabilizing/destabilizing factors 33 and specific b-tubulin isotype expression 16 Previous papers showed increased expression of selected btubulin isotypes in paclitaxel resistant murine, 34 human lung and ovarian cancer, 17 prostate cancer 8 and breast cancer 21,35 cell lines. Other AA.…”

Melanoma cell sensitivity to Docetaxel‐induced apoptosis is determined by class III β‐tubulin levels

“…For example, the increased expression of classes III and IVa btubulin has also been associated with the Paclitaxel-resistance in non-small lung carcinoma cell lines [10] and in K562 erythroleukemia cells [24]. Docetaxel-resistant MCF-7 breast cancer cells also exhibited increased expression of classes I, II, III and IV b-tubulin isotypes whereas all isotypes examined except for class IV were decreased in Docetaxel-resistant MB-MDA-231 breast cancer cells [25]. Notwithstanding the differences observed between various cancer cell lines, increased levels of b-tubulins do appear to have significance for clinical outcomes with taxanes.…”

Synuclein γ Compromises Spindle Assembly Checkpoint and Renders Resistance to Antimicrotubule Drugs

“…Although general mechanisms of drug resistance may apply to AMD resistance (3,4), more specifically, the current research paradigm on AMD resistance focus on acquired b-tubulin mutations and altered expression of b-tubulin isotypes (5,6). Because tubulin is the structural protein of microtubule and is supposed to be the main target of docetaxel action, alternations of tubulin expression are thought to induce docetaxel resistance.…”