Related Experiment Videos
Toxicity of [PtCl2(NH3)L] in hypoxia; L = misonidazole or metronidazole
K A Skov1, H Adomat, D J Chaplin
1Medical Biophysics Unit, BC Cancer Research Centre, Vancouver, Canada.
Abstract:
There is increasing interest in compounds which show selective toxicity to the resistant hypoxic portions of tumors. Cisplatin does not generally show preferential toxicity in hypoxic cells, as do nitroimidazoles. It is proposed that attachment of a nitroimidazole could add a degree of hypoxic selectivity to Pt agents. Platinum complexes containing one nitroimidazole ligand bind to DNA and show higher toxicity in hypoxic than aerobic CHO cells. Cis and trans isomers of complexes with misonidazole (a 2-nitroimidazole) and metronidazole (a 5-nitroimidazole) are compared with respect to binding to DNA (approximately the same), reduction potential (trans miso greater than cis miso greater than cis metro greater than trans metro), and toxicity (trans greater than cis miso, cis greater than trans metro, with trans miso approximately cis metro in hypoxia, despite significantly different reduction potentials). The effect of platination on nitroimidazole toxicity is not entirely explained by DNA binding and increased reduction potential. These compounds do not exhibit cross resistance with cisplatin in L1210 resistant cells. This factor, their selectivity for hypoxia, and preliminary results in vivo indicating potentiation of anti-tumor activity by the vasoactive compound, hydralazine, which increases tumor hypoxia, suggest further development of these compounds for use in tumors with resistant hypoxic portions.
Insights
New platinum (Pt) agents with nitroimidazole ligands show selective toxicity towards hypoxic tumor cells. These compounds are effective against cisplatin-resistant cells and show potential for treating resistant hypoxic tumors.
Area of Science:
- Oncology
- Medicinal Chemistry
- Tumor Biology
Background:
- Hypoxic tumor cells are resistant to conventional chemotherapy, including cisplatin.
- Nitroimidazoles exhibit selective toxicity towards hypoxic cells.
- Combining platinum agents with nitroimidazoles may enhance tumor targeting in hypoxic regions.
Purpose of the Study:
- To synthesize and evaluate platinum complexes functionalized with nitroimidazole ligands.
- To assess the hypoxic selectivity and efficacy of these novel platinum-nitroimidazole compounds.
- To investigate their potential in overcoming cisplatin resistance in tumors.
Main Methods:
- Synthesis of platinum complexes with misonidazole (2-nitroimidazole) and metronidazole (5-nitroimidazole) ligands.
- Comparison of cis and trans isomers regarding DNA binding, reduction potential, and cytotoxicity in hypoxic and aerobic conditions.
- Evaluation of cross-resistance with cisplatin in resistant cell lines.
- In vivo studies with hydralazine to assess anti-tumor activity potentiation.
Main Results:
- Platinum complexes with nitroimidazole ligands demonstrated higher toxicity in hypoxic versus aerobic conditions.
- DNA binding was similar across isomers, but toxicity varied.
- Reduction potentials influenced toxicity, but not entirely.
- Compounds showed no cross-resistance with cisplatin.
- Preliminary in vivo data suggested potentiation of anti-tumor activity with hydralazine.
Conclusions:
- Platinum complexes incorporating nitroimidazole ligands offer a strategy for targeting hypoxic tumor cells.
- These agents possess potential for treating resistant hypoxic tumors.
- Further development is warranted due to their selective toxicity and lack of cross-resistance with cisplatin.