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.
Footnotes
-
This work was supported by National Institutes of Health T32 CA 09213, Core Grant 3P30CA23074-19 (to the Arizona Cancer Center), and CA65662 (to B.W.F.).
- Abbreviations:
- D40
- Dox40
- TNF
- tumor necrosis factor
- PCR
- polymerase chain reaction
- SSC
- standard saline citrate
- FAN
- neutral sphingomyelinase-activating protein
- CAPK
- ceramide-activated protein kinase
- MEK
- mitogen-activated protein kinase/extracellular signal-regulated kinase kinase
- KSR
- kinase suppressor of ras
- JNK
- c-jun N-terminal kinase
- N-SMase
- neutral sphingomyelinase
- BAD
- BCL-2 antagonist of cell death
- DISC
- death-inducing signaling complex
- CLARP
- caspase-like apoptosis-regulatory protein
- Received May 23, 2001.
- Accepted July 24, 2001.
- The American Society for Pharmacology and Experimental Therapeutics
JPET articles become freely available 12 months after publication, and remain freely available for 5 years.Non-open access articles that fall outside this five year window are available only to institutional subscribers and current ASPET members, or through the article purchase feature at the bottom of the page.
|