Can Fenbendazole Be Used As an Inhibitor of Tumor Growth?

 

The anthelmintic drug fenbendazole binds to and inhibits microtubule polymerization in helminthes. It also displays cytostatic activity when administered at high concentrations, a property that may explain its utility in parasitic diseases. However, it has not previously been investigated as a potential inhibitor of tumor growth.

In a series of experiments described in Table 1, the viability of EMT6 cells was measured in a colony formation assay after 2- or 24-h treatments with different concentrations of fenbendazole. The cell number was then compared with the number of cells in cultures treated with the same dose of docetaxel. The results show that the addition of fenbendazole significantly reduced the surviving fraction, but did not change the shape of the dose-response curve for docetaxel, suggesting that the two drugs had additive toxicities.

In contrast, a previous experiment using a 3-injection fenbendazole regimen in BALB/cRw mice found that fenbendazole did not affect the time to four-fold tumor volume (data not shown) or the radiation response of the tumors. These findings are consistent with our in vitro data, which showed that the anthelmintic drug had cytostatic rather than cytotoxic properties at the concentrations used in these experiments.

In an effort to understand the discrepancy between our in vitro and in vivo results, we tested fenbendazole at the concentrations found in this study in an established human lymphoma xenograft model in C.B-17/Icr-prkdcscid/Crl (SCID) mice. This well-established xenograft model typically produces successful tumor growth in 20 to 40% of mice during the 21-d observation period. We found that the fenbendazole diet was not effective in suppressing tumor growth in these mice, but that a subsequent facility treatment for rodent pinworms with a fenbendazole and supplemental vitamins-containing diet was. The supplemental vitamin-fenbendazole diet had a higher concentration of vitamins than the standard vendor-supplied irradiated control diet used in this study.  sanare lab fenbendazole