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Non-P-glycoprotein-mediated multidrug-resistant human KB cells selected in medium containing adriamycin,
T Sumizawa1, Y Chuman, H Sakamoto
1Department of Cancer Chemotherapy, Faculty of Medicine, Kagoshima University, Japan.
Abstract:
Human epidermoid KB cell lines resistant to high levels of adriamycin, C-A90, C-A120, C-A500, and C-A1000, were isolated in selection medium containing increasing concentrations of adriamycin, 1 microgram/ml of cepharanthine, a multidrug-resistance (MDR) reversing agent, and 100 nM of mezerein, a protein kinase C activating agent. One of the adriamycin-resistant KB cell lines, C-A500, was cross-resistant to drugs that typify the classical multidrug resistance phenotype, such as vincristine, actinomycin D, VP-16, and colchicine. The accumulation of adriamycin and vincristine was decreased in C-A500 cells and the efflux of adriamycin from C-A500 was enhanced compared with parental KB-3-1 cells. These adriamycin-resistant KB cells did not contain detectable levels of P-glycoprotein or overexpress MDR1. Multidrug-resistance-associated protein (MRP) and MRP mRNA were expressed in the adriamycin-resistant KB cells, C-A120, C-A500, and C-A1000, but not in parental KB-3-1 and revertant C-AR cells. The MRP gene was amplified in all the MDR cells that overexpressed MRP mRNA. DNA topoisomerase II levels were markedly decreased in C-A500 and C-A1000 cells but only slightly decreased in C-A120 cells. These results indicate that MRP overexpressed in the resistant cells may be responsible for the reduced accumulation of adriamycin and vincristine and that both the increased expression of MRP and decreased levels of topoisomerase II underlie the drug resistance in C-A120, C-A500, and C-A1000 cell lines.
Insights
Multidrug resistance in human cancer cells is linked to increased multidrug-resistance-associated protein (MRP) and decreased DNA topoisomerase II. These factors contribute to reduced drug accumulation and enhanced efflux, impacting chemotherapy effectiveness.
Area of Science:
- Molecular Biology
- Cancer Research
- Pharmacology
Background:
- Human epidermoid KB cell lines were developed to study adriamycin resistance.
- Multidrug resistance (MDR) is a significant challenge in cancer chemotherapy.
- Identifying mechanisms of MDR is crucial for improving treatment outcomes.
Purpose of the Study:
- To investigate the mechanisms underlying adriamycin resistance in human KB cell lines.
- To determine the role of multidrug-resistance-associated protein (MRP) and DNA topoisomerase II in MDR.
- To explore the relationship between drug accumulation, efflux, and resistance phenotypes.
Main Methods:
- Isolation of adriamycin-resistant KB cell lines (C-A90, C-A120, C-A500, C-A1000).
- Assessment of cross-resistance to various chemotherapeutic agents.
- Measurement of adriamycin and vincristine accumulation and efflux.
- Analysis of P-glycoprotein, MDR1, MRP, and MRP mRNA expression.
- Evaluation of DNA topoisomerase II levels.
Main Results:
- Adriamycin-resistant cell lines showed cross-resistance to vincristine, actinomycin D, VP-16, and colchicine.
- Reduced intracellular accumulation and enhanced efflux of adriamycin and vincristine were observed.
- P-glycoprotein and MDR1 were not overexpressed; however, MRP and MRP mRNA were expressed in resistant cells.
- MRP gene amplification correlated with MRP mRNA overexpression.
- Markedly decreased DNA topoisomerase II levels were found in highly resistant cell lines.
Conclusions:
- Overexpression of MRP is implicated in the reduced accumulation of adriamycin and vincristine.
- Both increased MRP expression and decreased DNA topoisomerase II levels contribute to multidrug resistance in these KB cell lines.
- These findings highlight the complex mechanisms of MDR and suggest potential therapeutic targets.
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