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Modulation of drug resistance by alpha-tubulin in paclitaxel-resistant human lung cancer cell lines
E K Han1, E Kyu-Ho Han, L Gehrke
1Pharmaceutical Products Division, Cancer Research, Dept. 4N6, Bldg. AP9, Abbott Laboratories, IL 60064-3500, Abbott Park, USA.
Abstract:
Beta(beta)-tubulin isotype variation has recently been implicated in the modulation of resistance to paclitaxel in human lung cancer cells and in primary 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 cell line NCI-H460. The resistant cells are more than 1000-fold resistant to taxol and overexpress P-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 appears to be post-transcriptional. To understand whether alpha-tubulin plays a role in drug resistance, we transfected antisense human kalpha1 cDNA construct into the H460/T800 paclitaxel-resistant cells. The antisense clones displayed a reduced alpha-tubulin expression, and the cells were 45-51% more sensitive to paclitaxel and other known antimitotic drugs, compared with vector transfected controls. Complementary experiments of transfecting the sense kalpha1 cDNA into H460 cells conferred a 1.8- to 3.3-fold increase in the IC(50) of several antimitotic agents. Our study suggests that alpha-tubulin is one of the factors that contributes to drug resistance.
Insights
Alpha-tubulin contributes to paclitaxel resistance in lung cancer cells. Reducing alpha-tubulin expression increases sensitivity to antimitotic drugs, suggesting it is a factor in drug resistance.
Area of Science:
- Oncology
- Molecular Biology
- Cell Biology
Background:
- Beta-tubulin isotype variation is linked to paclitaxel resistance in lung and ovarian cancers.
- The role of alpha-tubulin in drug resistance remains uninvestigated.
Purpose of the Study:
- To investigate the role of alpha-tubulin in paclitaxel resistance in human lung cancer cells.
- To determine if modulating alpha-tubulin expression affects sensitivity to antimitotic drugs.
Main Methods:
- Generated a paclitaxel-resistant human lung carcinoma cell line (H460/T800).
- Utilized Western blot and Northern blot analysis to detect tubulin expression and mechanism.
- Transfected antisense human kalpha1 cDNA into resistant cells to reduce alpha-tubulin expression.
- Transfected sense kalpha1 cDNA into sensitive cells to assess its effect on drug sensitivity.
Main Results:
- H460/T800 cells exhibited over 1000-fold resistance to paclitaxel and overexpressed P-glycoprotein, alpha-tubulin, and beta-tubulin.
- Tubulin overexpression was found to be post-transcriptional.
- Reducing alpha-tubulin expression via antisense transfection increased sensitivity to paclitaxel and other antimitotic drugs by 45-51%.
- Increasing alpha-tubulin expression via sense transfection conferred a 1.8- to 3.3-fold increase in drug resistance.
Conclusions:
- Alpha-tubulin plays a significant role in modulating paclitaxel resistance in lung cancer.
- Alpha-tubulin is a contributing factor to drug resistance, alongside beta-tubulin and P-glycoprotein.
- Targeting alpha-tubulin may represent a potential therapeutic strategy to overcome antimitotic drug resistance.
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