The anthelmintic drug fenben was recently repurposed to overcome resistant cancers by triggering various cell death pathways. The anti-cancer activity of fenben on wild-type and 5-fluorouracil-resistant SNU-C5 colorectal cancer cells was analyzed by flow cytometry assays to measure cell viability, apoptosis, cell cycle arrest, and necroptosis. Fenbendazole significantly inhibited cell viability, activated apoptosis via p53, and caused G2/M cell cycle arrest in both SNU-C5 and SNU-C5/5-FUR cells. However, fenbendazole did not activate the necroptosis pathway via MLKL activation. This suggests that fenbendazole does not stimulate the necroptotic machinery by decreasing expression of GPX4.
Time-dependent anti-proliferative effects of fenbendazole were assessed in both SNU-C5 and SNU-C5/5-FUR CRC cells. Proliferation was reduced 4.07 + 0.18-fold and 1.63 + 0.11-fold with 0.5 and 10 mM fenbendazole, respectively, in comparison with control cells. Moreover, fenbendazole induced apoptosis and cell cycle arrest in both CRC cells (Figure 1A).
The results indicated that the most effective treatment was to administer fenbendazole for 12 days to mice with established EMT6 tumors. These animals were then irradiated at a dose of 10 Gy and re-treated with three daily i.p. injections of fenbendazole (Figure 2A). Three tumors were irradiated in each group and the growth of the tumors was monitored by measuring the tumor volume. After reaching a total tumor volume of 1000 mm3, mice were euthanized and the number of lung metastases was counted. In the fenbendazole-treated groups, there was significantly less lung metastasis than in unirradiated mice and the effect was maintained after x-ray radiation (Figure 2B).
The authors thank Dr. Tsuyuki Miwa for providing the RNA-seq data used in this study and Dr. Hiroshi Nagasawa for technical assistance.