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Evaluation of various types of new hypoxic cell sensitizers using the EMT6 single cell-spheroid-solid tumour system
Abstract:
Eleven new hypoxic cell sensitizers representative of those developed in Japan between 1980 and 1985 were evaluated in vitro and in vivo in comparison with misonidazole (MISO), SR-2508, Ro 03-8799, and ANT (2-amino-5-nitrothiazole). The new compounds included 2-nitroimidazole nucleoside analogues, nitrotriazoles and other nitroaromatics, non-nitro compounds, and electron-affinic compounds that readily intercalate DNA. The sensitizing activity in the EMT6 single cells correlated not only with the reduction potential but, for some compounds, also with the reactivity with non-protein sulphydryls. The sensitizers were also tested using the EMT6 spheroids and solid tumours. The patterns of changes in sensitizer enhancement ratios (SERs) for single cells, spheroids, and solid tumours were classified into two types: (1) SERs for the three testing systems were similar; and (2) SERs decreased in the order of: single cells, spheroids, and solid tumours. Only nitroimidazole and nitrotriazole derivatives belonged to the former type. RK-28 and RK-29, 2-nitroimidazoles with sugar analogue components, had in vivo effects almost equal to those of MISO. Also 3- and 4-nitrotriazole derivatives had definite in vivo effects.
Insights
New hypoxic cell sensitizers were evaluated for their effectiveness in cancer treatment. Nitroimidazole and nitrotriazole derivatives showed promising in vivo effects, comparable to existing treatments.
Area of Science:
- Pharmacology
- Oncology
- Medicinal Chemistry
Background:
- Hypoxic cell sensitizers are crucial for enhancing radiation therapy efficacy in solid tumors.
- Development of novel sensitizers is ongoing to overcome limitations of existing agents like misonidazole.
Purpose of the Study:
- To evaluate the in vitro and in vivo efficacy of eleven new hypoxic cell sensitizers developed between 1980-1985.
- To compare their performance against established sensitizers including misonidazole (MISO), SR-2508, Ro 03-8799, and 2-amino-5-nitrothiazole (ANT).
Main Methods:
- In vitro and in vivo assays using EMT6 single cells, spheroids, and solid tumors.
- Assessment of sensitizing activity based on reduction potential and reactivity with non-protein sulphydryls.
- Classification of sensitizer enhancement ratios (SERs) across different testing systems.
Main Results:
- Sensitizing activity in single cells correlated with reduction potential and reactivity with sulphydryls.
- Two patterns of SERs were observed: similar across all systems, or decreasing from single cells to solid tumors.
- Nitroimidazole and nitrotriazole derivatives exhibited similar SERs across all systems.
- RK-28 and RK-29 (2-nitroimidazoles) showed in vivo efficacy similar to MISO.
- 3- and 4-nitrotriazole derivatives demonstrated significant in vivo effects.
Conclusions:
- Nitroimidazole and nitrotriazole derivatives represent a promising class of hypoxic cell sensitizers.
- RK-28, RK-29, and nitrotriazole derivatives possess potent in vivo anti-cancer activity.
- These novel compounds warrant further investigation for clinical application in cancer therapy.