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Amplification of specific DNA sequences correlates with multi-drug resistance in Chinese hamster cells
Abstract:
Mammalian cells selected for resistance to certain cytotoxic drugs frequently develop cross-resistance to a broad spectrum of other drugs unrelated in structure to the original selective agent. This phenomenon constitutes a major problem in cancer chemotherapy. Multi-drug resistance arises from decreased intracellular drug accumulation, apparently due to an alteration of the plasma membrane. The observation of double minute chromosomes or homogeneously staining regions in some of the multi-drug-resistant cell lines suggests that gene amplification underlies this phenomenon. We have used the technique of DNA renaturation in agarose gels to detect, compare and clone amplified DNA sequences in Adriamycin- and colchicine-resistant sublines of Chinese hamster cells. We show that both Adriamycin- and colchicine-resistant cells contain amplified DNA fragments, some of which are amplified in both of these independently derived cell lines. Furthermore, loss of the multi-drug resistance phenotype on growth in the absence of drugs correlates with the loss of amplified DNA. These results strongly suggest that the DNA sequences which are amplified in common in multi-drug-resistant cell lines include the gene(s) responsible for a common mechanism of multi-drug resistance in these cells. We have cloned one of the commonly amplified DNA fragments and show that the degree of amplification of this fragment in the cells correlates with the degree of their drug resistance.
Insights
Multi-drug resistance in cancer chemotherapy is linked to gene amplification. Researchers found that amplified DNA fragments in drug-resistant cells correlate with resistance levels, suggesting a common resistance mechanism.
Area of Science:
- Molecular Biology
- Genetics
- Cancer Research
Background:
- Mammalian cells can develop multi-drug resistance (MDR), a significant obstacle in cancer chemotherapy.
- MDR is characterized by decreased intracellular drug accumulation, often due to plasma membrane alterations.
- Gene amplification, indicated by chromosomal abnormalities, is a suspected underlying mechanism for MDR.
Purpose of the Study:
- To investigate the role of gene amplification in MDR using Adriamycin- and colchicine-resistant Chinese hamster cells.
- To detect, compare, and clone amplified DNA sequences associated with MDR.
- To establish a correlation between amplified DNA and the MDR phenotype.
Main Methods:
- Utilizing DNA renaturation in agarose gels to analyze DNA from drug-resistant cell lines.
- Comparing amplified DNA fragments in independently derived resistant cell lines.
- Correlating the loss of amplified DNA with the loss of drug resistance upon drug withdrawal.
Main Results:
- Both Adriamycin- and colchicine-resistant cells exhibited amplified DNA fragments.
- Some amplified DNA fragments were common to both independently derived resistant cell lines.
- Loss of drug resistance correlated with the loss of amplified DNA.
- Cloning of a commonly amplified DNA fragment showed its amplification level correlates with drug resistance.
Conclusions:
- Gene amplification is strongly implicated in the common mechanism of multi-drug resistance.
- Commonly amplified DNA sequences likely contain genes responsible for MDR.
- The degree of amplification of specific DNA fragments directly relates to the level of drug resistance.