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Diagnostic Microdosing Approach to Study Gemcitabine Resistance
Tiffany M Scharadin1, Hongyong Zhang1, Maike Zimmermann1,2
1Department of Internal Medicine, Division of Hematology and Oncology, University of California Davis , Sacramento, California 95817, United States.
Abstract:
Gemcitabine metabolites cause the termination of DNA replication and induction of apoptosis. We determined whether subtherapeutic "microdoses" of gemcitabine are incorporated into DNA at levels that correlate to drug cytotoxicity. A pair of nearly isogenic bladder cancer cell lines differing in resistance to several chemotherapy drugs were treated with various concentrations of 14C-labeled gemcitabine for 4-24 h. Drug incorporation into DNA was determined by accelerator mass spectrometry. A mechanistic analysis determined that RRM2, a DNA synthesis protein and a known resistance factor, substantially mediated gemcitabine toxicity. These results support gemcitabine levels in DNA as a potential biomarker of drug cytotoxicity.
Insights
Subtherapeutic gemcitabine microdoses incorporate into DNA, correlating with cytotoxicity. Ribonucleotide reductase M2 (RRM2) significantly mediates gemcitabine toxicity, suggesting DNA gemcitabine levels as a biomarker.
Area of Science:
- Biochemistry
- Molecular Biology
- Cancer Research
Background:
- Gemcitabine is a chemotherapy drug that induces apoptosis by terminating DNA replication.
- The relationship between low-dose gemcitabine incorporation into DNA and its cytotoxic effects is not fully understood.
- Ribonucleotide reductase M2 (RRM2) is implicated as a resistance factor in chemotherapy.
Purpose of the Study:
- To investigate the incorporation of subtherapeutic gemcitabine microdoses into DNA.
- To determine if DNA gemcitabine levels correlate with drug cytotoxicity.
- To elucidate the role of RRM2 in gemcitabine-mediated toxicity.
Main Methods:
- Utilized nearly isogenic human bladder cancer cell lines.
- Treated cells with various concentrations of 14C-labeled gemcitabine for 4-24 hours.
- Quantified gemcitabine incorporation into DNA using accelerator mass spectrometry.
- Performed mechanistic analysis to identify mediating factors of gemcitabine toxicity.
Main Results:
- Gemcitabine was incorporated into DNA at levels that correlated with cytotoxicity.
- RRM2 was identified as a key mediator of gemcitabine toxicity.
- The study demonstrated a link between DNA gemcitabine levels and drug efficacy.
Conclusions:
- Subtherapeutic gemcitabine microdoses can be incorporated into DNA, impacting cytotoxicity.
- RRM2 plays a significant role in mediating gemcitabine toxicity in cancer cells.
- Gemcitabine levels within DNA may serve as a predictive biomarker for gemcitabine treatment response.
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