Benzimidazole anthelmintic drugs are frequently used to treat genitourinary malignancies and have promising anti-cancer effects . Several studies show that benzimidazoles enhance the cytotoxicity of radiation or docetaxel in metastatic or resistant cancers. However, the role of benzimidazoles in overcoming multidrug resistance remains to be fully evaluated. Our previous study showed that fenbendazole significantly inhibited the growth of 5-FU-resistant SNU-C5/5-FUR cells and reduced their multidrug resistance mediated by p53-p21 pathways compared with wild type SNU-C5 cells. Therefore, we hypothesized that fenbendazole might induce the cell death through a combination of mechanisms including ferroptosis and autophagy.
To test this hypothesis, we treated SNU-C5/5-FUR and SNU-C5/5-FUR plus SNU-C5/5-FUR MGMT/MDM2 cells with fenbendazole in the presence or absence of iron chelators (ferostatin-1 and deferoxamine mesylate, DFOM) at the concentrations close to their IC50 values for 3 days. We found that fenbendazole significantly decreased the proliferation of both cells and that this effect was more potent in MGMT/MDM2 cells than in SNU-C5 cells.
In addition, we found that fenbendazole inhibited tubulin polymerization and caused cell cycle arrest at G2/M phase in both SNU-C5 and MGMT/MDM2 cells. Furthermore, fenbendazole significantly increased the expression of p53, p21, caspase-8 and MLKL in MGMT/MDM2 cells.
Finally, we found that fenbendazole induced the expression of necroptosis-related proteins in both SNU-C5 and SNU-C5/5-FUR cancer cells. The induction of necroptosis is associated with oxidative stress, mitochondrial dysfunction, and mitochondrial release of pro-apoptotic proteins. We also found that fenbendazole enhanced both p53-independent and ferroptosis-augmented apoptosis in SNU-C5/5-FUR tumor cells. fenbendazole stage 4 cancer