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Updated: Aug 2, 2026
Implementation of In Vitro Drug Resistance Assays: Maximizing the Potential for Uncovering Clinically Relevant Resistance Mechanisms
Published on: December 9, 2015
cDNA microarray analysis of multidrug resistance: doxorubicin selection produces multiple defects in apoptosis
G S Watts1, B W Futscher, R Isett
1Arizona Cancer Center, University of Arizona, Tucson, 85724, USA. gwatts@azcc.arizona.edu
Abstract:
Doxorubicin plays an important role in the treatment of leukemias, lymphomas, and a variety of carcinomas. Tumor cell resistance to doxorubicin is often associated with expression of the multidrug resistance gene MDR1, which codes for the drug efflux pump P-glycoprotein, and a multidrug-resistant phenotype. Evidence from multiple sources suggests, however, that additional genes besides MDR1 are involved in development of multidrug resistance. To identify genes involved in the multidrug resistance phenotype, we created a 5760-gene cDNA microarray to search for differentially expressed genes between the human multiple myeloma cell line RPMI 8226 and its doxorubicin-selected sublines 8226/Dox6 and 8226/Dox40, both of which express MDR1 and are multidrug-resistant. The cDNA microarray results identified a set of differentially expressed genes, which included MDR1 as expected. Thirty Northern analyses were used to confirm the results of the cDNA microarrays; comparison with the microarray results showed a 90% agreement between the two techniques. Within the set of differentially expressed genes identified by the cDNA microarrays, 29 were of particular interest as they can participate in apoptotic signaling, particularly as mediated by ceramide and the mitochondrial permeability transition. The functional importance of these changes in gene expression is supported by their explanation of the 8226/Dox cell lines' cross-resistance to substances that are not P-glycoprotein substrates, such as Fas/CD95 ligand and staurosporine. We conclude that doxorubicin selection led to changes in gene expression that reduce the apoptotic response to death-inducing stimuli and thus contribute to the multidrug resistance phenotype.
Insights
Doxorubicin resistance in cancer cells involves more than just the MDR1 gene. New gene expression changes reduce the cell
Area of Science:
- Molecular Biology
- Cancer Research
- Genomics
Background:
- Doxorubicin is a key chemotherapy drug for various cancers.
- Multidrug resistance (MDR) is often linked to the MDR1 gene and P-glycoprotein.
- Evidence suggests other genes contribute to MDR beyond MDR1.
Purpose of the Study:
- To identify novel genes involved in multidrug resistance.
- To investigate gene expression changes in doxorubicin-selected cancer cells.
- To understand the mechanisms of doxorubicin resistance.
Main Methods:
- Utilized a 5760-gene cDNA microarray to compare gene expression.
- Analyzed human multiple myeloma cell lines (RPMI 8226 and doxorubicin-selected sublines).
- Confirmed microarray findings using Northern blot analysis.
Main Results:
- Identified differentially expressed genes, including the expected MDR1 gene.
- Confirmed 90% agreement between microarray and Northern blot results.
- Discovered 29 genes involved in apoptotic signaling, particularly ceramide and mitochondrial pathways.
Conclusions:
- Doxorubicin selection induces gene expression changes that impair apoptotic signaling.
- These alterations contribute to a multidrug-resistant phenotype.
- Identified genes explain cross-resistance to non-P-glycoprotein substrates, highlighting broader MDR mechanisms.
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