Expression of oncogenic epidermal growth factor receptor family kinases induces paclitaxel resistance and alters beta-tubulin isotype expression.
Oncogenic transformation confers resistance to chemotherapy through a variety of mechanisms, including suppression of apoptosis, increased drug metabolism, and modification of target proteins. Oncogenic epidermal growth factor receptor family members, including EGFRvIII and HER2, are expressed in a broad spectrum of human malignancies. Cell lines transfected with EGFRvIII and HER2 are more resistant to paclitaxel-mediated cytotoxicity, and tubulin polymerization induced by paclitaxel is suppressed compared with cells expressing wild type epidermal growth factor receptor. Because differential expression of beta-tubulin isotypes has been proposed to modulate paclitaxel resistance, we analyzed beta-tubulin isotypes expressed in cell lines transfected with different oncogenes. EGFRvIII- and HER2-expressing cells demonstrated equivalent total beta-tubulin protein compared with cells transfected with wild type receptor or untransfected controls. EGFRvIII-expressing cells demonstrated increases in class IVa (2.5-fold) and IVb (3.1-fold) mRNA, and HER2-expressing cells showed increases in class IVa (2. 95-fold) mRNA. Expression of oncogenic Ha-Ras did not change class IV RNA levels significantly. Inhibition of EGFRvIII kinase activity using a mutant allele with an inactivating mutation in the kinase domain decreased expression of class IVa by 50% and partially reversed resistance to paclitaxel. Expression of oncogenic epidermal growth factor receptor family members is associated with modulation of both beta-tubulin isotype expression and paclitaxel resistance in cells transformed by expression of the receptor. This effect on tubulin expression may modulate drug resistance in human malignancies that express these oncogenes.
Montgomery
R B
RB
Department of Medicine and Oncology, Veterans Affairs Puget Sound Health Care System, University of Washington, Seattle, Washington 98108, USA. rbmontgo@u.washington.edu
Guzman
J
J
O'Rourke
D M
DM
Stahl
W L
WL
D016475:3T3 Cells; D000818:Animals; D002471:Cell Transformation, Neoplastic; D019008:Drug Resistance, Neoplasm; D066246:ErbB Receptors / Q000235:genetics* / Q000502:physiology; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D051379:Mice; D017239:Paclitaxel / Q000633:toxicity*; D020033:Protein Isoforms / Q000235:genetics; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000235:genetics / Q000502:physiology; D011994:Recombinant Proteins / Q000096:biosynthesis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014162:Transfection; D014404:Tubulin / Q000235:genetics*
D066246:ErbB Receptors; D017239:Paclitaxel; D020033:Protein Isoforms; D018719:Erb-b2 Receptor Tyrosine Kinases; D011994:Recombinant Proteins; D014404:Tubulin; C410723:epidermal growth factor receptor VIII