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Photosensitization of human leukemic cells by anthracenedione antitumor agents
J A Hartley1, S M Forrow, R L Souhami
1Department of Oncology, University College and Middlesex School of Medicine, London, United Kingdom.
Abstract:
1,4-Diamino-substituted anthraquinone antitumor agents (mitoxantrone and ametantrone) and structurally related 1,5- and 1,8-diamino-substituted compounds (AM1 and AM2) were tested for their ability to photosensitize human leukemic cells in culture. Viability was measured using the 3,4,5-dimethylthiazol-2,5-diphenyl tetrazolium bromide assay, and DNA and membrane damage were assessed. Following a 1-h exposure to AM2, a dose of drug required to give 50% loss of cell viability (53 microM) was obtained in the dark, which was reduced to approximately 2.4 microM following illumination for 2 min (lambda greater than 475 nm), a dose of light that was completely nontoxic to the cells in the absence of drug. A shift in the cell viability curve was also observed for AM1 but, under identical conditions, the dose modification was only 8.9. In contrast, neither ametantrone nor mitoxantrone gave a decreased viability upon illumination. DNA single-strand breaks as measured by alkaline elution correlated with cell viability. Frank DNA single-strand breaks were produced by AM2 and light, suggesting the production of free radicals. The strand breaks produced by AM2 in the dark and by mitoxantrone (with or without illumination) were protein concealed. No evidence of photo-induced membrane damage, as determined by transport of the model amino acid cycloleucine, could be observed even at supralethal doses.
Insights
New photosensitizing agents, AM1 and AM2, show potential for photodynamic therapy in leukemia treatment. AM2 demonstrated significant photosensitizing activity, reducing required drug dosage upon illumination, unlike ametantrone and mitoxantrone.
Area of Science:
- Biochemistry
- Pharmacology
- Oncology
Background:
- Anthraquinone derivatives like mitoxantrone and ametantrone are used as antitumor agents.
- Investigating novel diamino-substituted anthraquinones for enhanced therapeutic effects is crucial.
Purpose of the Study:
- To evaluate the photosensitizing potential of 1,4-, 1,5-, and 1,8-diamino-substituted anthraquinones against human leukemic cells.
- To assess the impact of light exposure on the efficacy and toxicity of these compounds.
Main Methods:
- Cell viability was measured using the MTT assay.
- DNA damage was assessed via alkaline elution, and membrane integrity was evaluated through amino acid transport assays.
- Compounds were tested in the presence and absence of light (λ > 475 nm).
Main Results:
- AM2 exhibited significant photosensitization, reducing the drug concentration for 50% cell viability loss from 53 μM in the dark to 2.4 μM with light.
- AM1 showed a lesser dose modification (8.9) upon illumination.
- Ametantrone and mitoxantrone did not demonstrate photosensitizing effects.
- Light-induced DNA single-strand breaks by AM2 suggested free radical production, while breaks induced by AM2 in the dark and mitoxantrone were protein-concealed.
- No photo-induced membrane damage was observed.
Conclusions:
- AM2 is a potent photosensitizer with potential for photodynamic therapy in leukemia.
- The mechanism of AM2 likely involves light-activated free radical generation leading to DNA damage.
- Ametantrone and mitoxantrone lack photosensitizing properties relevant to this therapeutic approach.