Fenben (tradename for a compound mixture of several different drugs) is an antiparasitic agent used to treat parasitic infections in animals. Research has shown that this class of medications can also kill cancer cells. However, turning this potential into a clinical treatment has been slow. Health Canada lists anthelmintic medications such as fenben for veterinary use only and no peer-reviewed study has found evidence of them curing cancer in humans.
In our experiments, fenbendazole showed time-dependent anti-proliferative effects in SNU-C5 and 5-FU sensitive/resistant CRC cells, with IC50 values of 0.5 mM and 5 mM respectively. In addition, fenbendazole significantly reduced the number of colony-forming units (CFU) in a standard colony formation assay.
To elucidate the mechanism of fenbendazole-induced cell death, we measured the expression of various proteins involved in necroptosis and ferroptosis by immunoblot analysis. Compared with untreated cells, fenbendazole treatment significantly increased the expression of LC3, Atg7, and active caspase-8 in 5-FU-sensitive/resistant SNU-C5 cells. It also enhanced p53-mediated apoptosis in both cells and induced the formation of reactive oxygen species, leading to lipid peroxidation via decreased expression of SLC7A11 and GPX4 in the resistant cell.
To determine whether fenbendazole exhibits similar cytotoxicity in hypoxic conditions, cells were treated with varying doses of fenbendazole under hypoxia. As expected, 2-h treatments with fenbendazole at the lowest drug concentration tested in hypoxia significantly increased the toxicity of the drug compared to the same treatment in air. Moreover, the survival curves in cultures treated under hypoxia showed a steeper decline in cell viability at lower drug doses and a more gradual increase with higher drug concentrations.