Antiproliferative Activity of Niclosamide Against Melanoma and Colorectal Cancer Cells

Studies of the actions of niclosamide against tumor cells and normal human cells (human embryo kidney cells and pulmonary embryo fibroblast cells) showed higher levels of cytotoxic activity against tumor cells, including melanoma (the Mel-8, Mel-10, MS lines) and colorectal cancer (the Caco-2, COLO 320 HSR, and SW827 cells). Niclosamide was shown to have a high level of cytotoxic activity against cells with the multidrug resistance phenotype due to high levels of expression of MDR1 protein on the plasma membrane (the Mel-8 and MCF-7Adr lines). The proportion of tumor stem cells (TSC) was measured by flow cytometry as the proportion of cells forming side populations (SP). Niclosamide was found to act on TSC cells either more effectively (colorectal cancer line SW 837, (decreases in SP fraction size) or with the same effectiveness as the main population of tumor cells (SP fraction size unaltered).