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Modulation of drug resistance in a daunorubicin resistant subline with oligonucleoside methylphosphonates
1Molecular Biology Section, Southern Research Institute, Birmingham, AL 35255-5305.
Abstract:
Human K562 erythroleukemia cells were selected in sequential steps for resistance to daunorubicin (K562/III) and found to be cross-resistant to a number of drugs, including vincristine, dactinomycin, doxorubicin, etoposide, and teniposide. In this paper, we report that the K562/III subline showed amplification of an mdr1 gene and its 4.5 kb transcript. Our results also show that non-ionic oligonucleoside methylphosphonates, complementary to the initiation codon and 15 bases upstream of the mdr1 gene, can completely inhibit the synthesis of P-glycoprotein and partially increase the toxicity of daunorubicin.
Insights
Researchers developed drug-resistant K562/III cells, finding mdr1 gene amplification. Oligonucleotides targeting the mdr1 gene inhibited P-glycoprotein synthesis and enhanced daunorubicin toxicity.
Area of Science:
- Molecular Biology
- Cancer Research
- Pharmacology
Background:
- Human K562 erythroleukemia cells (K562/III) exhibit cross-resistance to multiple chemotherapy drugs.
- This resistance is often associated with the multidrug resistance (MDR) phenotype.
- The P-glycoprotein (P-gp) transporter, encoded by the mdr1 gene, is frequently implicated in MDR.
Purpose of the Study:
- To investigate the molecular mechanisms underlying daunorubicin resistance in K562/III cells.
- To explore the role of the mdr1 gene and its transcript in conferring drug resistance.
- To evaluate the potential of antisense oligonucleotides in overcoming MDR.
Main Methods:
- Sequential selection of K562 cells for daunorubicin resistance.
- Analysis of gene amplification and transcript levels of the mdr1 gene.
- Treatment with non-ionic oligonucleoside methylphosphonates complementary to the mdr1 gene.
- Assessment of P-glycoprotein synthesis and cellular toxicity of daunorubicin.
Main Results:
- The K562/III subline demonstrated amplification of the mdr1 gene and its 4.5 kb transcript.
- Non-ionic oligonucleoside methylphosphonates effectively inhibited P-glycoprotein synthesis.
- These oligonucleotides partially restored daunorubicin sensitivity, increasing its toxicity.
Conclusions:
- Amplification of the mdr1 gene is a key mechanism for daunorubicin resistance in K562/III cells.
- Targeting the mdr1 gene with antisense oligonucleotides can overcome P-glycoprotein-mediated multidrug resistance.
- Oligonucleotide-based strategies hold promise for enhancing chemotherapy efficacy in resistant cancers.