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Two mechanisms of adriamycin-DNA interaction in L1210 cells
Abstract:
Among the effects exerted by adriamycin (ADR), interaction with DNA is closely related to cytotoxicity. The interaction results in the formation of protein-associated DNA single-strand breaks (PA-SSB) and, at drug levels greater than or equal to 2.8 X 10(-6) M, also in "direct" (nonenzymatic) DNA single-strand breaks (D-SSB). To characterize the two types of DNA lesions, euoxic mouse leukemia L1210 cells were treated with various antioxidant agents in the presence of 2.8 X 10(-6), X 10(-5), or X 10(-4) M concentrations of ADR. The enzymes superoxide dismutase (200 micrograms/ml) or catalase (250 micrograms/ml), the OH' scavengers dimethyl sulfoxide (70 mM) or ethanol (70 mM), and an inhibitor of superoxide production, 2-deoxy-glucose (1 and 10 mM), reduced the frequency of D-SSB to 18.3 to 68.2% of its level in ADR-treated controls, while the frequency of PA-SSB remained unchanged. These observations seem to indicate that ADR-mediated free radicals cause discernible DNA damage in euoxic cells only at very high drug concentrations, greater than the peak plasma level achievable clinically following i.v. bolus. At lower ADR levels, relevant to clinical use, another type of interaction between the drug and DNA prevails, which apparently does not involve a free-radical mechanism.
Insights
Adriamycin (ADR) can cause DNA damage through free radicals at high concentrations, leading to direct DNA single-strand breaks (D-SSB). However, at clinically relevant levels, ADR-DNA interactions do not appear to involve free radicals.
Area of Science:
- Molecular Biology
- Cancer Research
- Pharmacology
Background:
- Adriamycin (ADR) is a potent chemotherapeutic agent whose cytotoxicity is linked to DNA interactions.
- ADR induces two types of DNA damage: protein-associated DNA single-strand breaks (PA-SSB) and direct DNA single-strand breaks (D-SSB).
Purpose of the Study:
- To investigate the role of free radicals in ADR-induced DNA damage.
- To differentiate the mechanisms underlying PA-SSB and D-SSB formation at various ADR concentrations.
Main Methods:
- Mouse leukemia L1210 cells were treated with ADR at concentrations of 2.8 X 10(-6) M, 10(-5) M, and 10(-4) M.
- Cells were co-treated with antioxidant agents, including superoxide dismutase, catalase, dimethyl sulfoxide, ethanol, and 2-deoxy-glucose.
- The frequency of D-SSB and PA-SSB was quantified to assess the impact of antioxidants.
Main Results:
- Antioxidant agents significantly reduced the frequency of D-SSB (18.3% to 68.2% reduction) at high ADR concentrations.
- PA-SSB formation remained unaffected by the presence of antioxidant agents.
- Free radical-mediated DNA damage (D-SSB) was observed only at very high ADR concentrations, exceeding clinically achievable levels.
Conclusions:
- ADR-induced D-SSB in euoxic cells is mediated by free radicals, but only at supra-therapeutic concentrations.
- At clinically relevant ADR concentrations, DNA damage likely occurs via a non-free radical mechanism, predominantly involving PA-SSB.