Modulation of drug resistance by alpha-tubulin in paclitaxel-resistant human lung cancer cell lines

Beta(beta)-tubulin isotype Variation has recently been implicated in the mo dulation of resistance to paclitaxel in human lung cancer cells and in prim ary human ovarian tumour samples. Whether alpha-tubulin is involved in drug resistance has not been reported. We have generated a paclitaxel-resistant cell line (H460/T800) from the sensitive human lung carcinoma parental cel l line NCI-H460. The resistant cells are more than 1000-fold resistant to t axol and overexpress beta-glycoprotein. Interestingly, H460/T800 cells also overexpress alpha- and beta-tubulin as detected by Western blot analysis. From Northern blot analysis, the mechanism of tubulin overexpression appear s to be post-transcriptional. To understand whether alpha-tubulin plays a r ole in drug resistance, we transfected antisense human k alpha 1 cDNA const ruct into the H460/T800 paclitaxel-resistant cells. The antisense clones di splayed a reduced alpha-tubulin expression, and the cells were 45-51% more sensitive to paclitaxel and other known antimitotic drugs, compared with ve ctor transfected controls. Complementary experiments of transfecting the se nse k alpha 1 cDNA into H460 cells conferred a 1.8- to 3.3-fold increase in the IC50 Of several antimitotic agents. Our study suggests that alpha-tubu lin is one of the factors that contributes to drug resistance. (C) 2000 Els evier Science Ltd. All rights reserved.