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The multidrug resistance phenotype: 31P nuclear magnetic resonance characterization and 2-deoxyglucose toxicity
O Kaplan1, J W Jaroszewski, R Clarke
1Medicine Branch, National Cancer Institute, NIH, Bethesda, Maryland 20892.
Abstract:
In order to identify changes in 31P nuclear magnetic resonance (NMR) spectra associated with multiple drug resistance (MDR), a number of wild type and drug-resistant cancer cell lines were studied. The resistant cells included cells selected with various drugs, mainly Adriamycin, as well as cells transfected with the human multidrug resistance gene (MDR1 gene), which encodes P-glycoprotein. In most cases, 31P NMR spectra were significantly different from those of parental, drug-sensitive lines. The spectra of resistant cells generally indicated increased levels of ATP and phosphocreatine in the cytoplasm. These changes are compatible with the increased glucose utilization rate previously described for resistant cells. Major changes were also observed in the levels of glycerophosphocholine and glycerophosphoethanolamine. Changes in cellular metabolism reflected by 31P NMR spectra depend on the drug used to select the cells for MDR. The direction of these changes was not consistent for all cell lines studied and could not be directly attributed to expression of P-glycoprotein, suggesting that the changes may be related to alterations in metabolism and membrane function associated with other mechanisms of MDR. The results demonstrate the suitability of 31P NMR for studies of biochemical changes associated with MDR. The toxicity of 2-deoxyglucose, a glucose antimetabolite, was investigated in addition to the NMR studies and was found to be consistently higher in multidrug-resistant cells than in the parental drug-sensitive lines. For MCF-7 breast cancer cells, where several sublines with different levels of resistance were available, the toxicity was highest for the most resistant lines.
Insights
31P nuclear magnetic resonance (NMR) reveals distinct metabolic shifts in multidrug-resistant (MDR) cancer cells, including higher ATP and phosphocreatine levels. These biochemical changes, identified via NMR, correlate with increased toxicity of 2-deoxyglucose in resistant cell lines.
Area of Science:
- Biochemistry
- Cell Biology
- Medical Physics
Background:
- Multiple drug resistance (MDR) is a major challenge in cancer chemotherapy.
- Understanding the biochemical underpinnings of MDR is crucial for developing effective treatments.
Purpose of the Study:
- To investigate biochemical alterations associated with MDR using 31P nuclear magnetic resonance (NMR) spectroscopy.
- To explore the relationship between MDR, cellular metabolism, and the toxicity of 2-deoxyglucose.
Main Methods:
- Studied 31P NMR spectra of various wild-type and drug-resistant cancer cell lines, including those selected with Adriamycin and transfected with the MDR1 gene.
- Assessed the toxicity of 2-deoxyglucose in sensitive and resistant cell lines.
Main Results:
- 31P NMR spectra of resistant cells differed significantly from sensitive cells, showing increased cytoplasmic ATP and phosphocreatine levels.
- Observed notable changes in glycerophosphocholine and glycerophosphoethanolamine levels.
- Multidrug-resistant cells exhibited consistently higher toxicity to 2-deoxyglucose, with MCF-7 cells showing increased toxicity correlating with resistance levels.
Conclusions:
- 31P NMR is a suitable technique for studying biochemical changes in MDR.
- Metabolic alterations in MDR are complex and influenced by the selection drug, not solely by P-glycoprotein expression.
- Increased 2-deoxyglucose toxicity in MDR cells suggests metabolic vulnerabilities exploitable for therapy.