Is Fenbendazole a Radiosensitizer?

Fenbendazole is a moderate microtubule destabilizer and causes cell death by modulating multiple pathways. It is a broad spectrum benzimidazole anthelmintic that has been found to be effective against gastrointestinal parasites such as Giardia, roundworms, hookworms, whipworms (including the tapeworm genus Taenia, but not Dipylidium caninum, a common dog tapeworm), pinworms, aelurostrongylus, and Strongyloides. It is also used as a treatment for various tapeworm infections in pets, including dogs, cats, rabbits, fish, reptiles and birds.

Cell viability in monolayer cultures of EMT6 cells was determined in the presence and absence of fenbendazole. 2-h treatments with varying doses of fenbendazole had no effect on the number of viable cells in the cultures, but the addition of fenbendazole for 24 h significantly decreased clonogenic survival. The yield-corrected surviving fractions were substantially lower than the corresponding untreated control values (Figure 1).

Severe hypoxia, however, increased the sensitivity of cultures to the toxic effects of 2-h treatments with fenbendazole (Figure 2). Hypoxia was produced by sealing culture bottles with rubber gaskets and inserting needles for the influx and efflux of gases, with a mixture of 95% nitrogen and 5% carbon dioxide containing 1 ppm oxygen (8, 9).

The results show that fenbendazole interferes with cell viability and reduces tumor growth in the presence and absence of radiation. This interference is not due to a direct inhibition of tumor growth by fenbendazole, but rather through the indirect effect of the drug on radiation response. This is a novel finding that indicates that fenbendazole is a potential radiosensitizer. fenben lab fenbendazol

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