Ivermectin as an inhibitor of cancer stem-like cells

: The aim of the present study was to demonstrate that ivermectin preferentially inhibited cancer stem‑like cells (CSC) in breast cancer cells and downregulated the expression of 'stemness' genes. Computational searching of DrugBank, a database of approved drugs, was performed using the principles of two‑dimensional similarity searching; the chemical structure of salinomycin was used as a query. Growth inhibition of the breast cancer cell lin e MDA‑MB‑231 by ivermectin was investigated in the total cell population, in cell spheroids and in sorted cells that expressed cluster of differentiation (CD)44+/CD24‑. The effects of ivermectin treatment on the expression of pluripotency and self‑renewal transcription factors, such as homeobox protein nanog (nanog), octamer‑binding protein 4 (oct‑4) and SRY‑box 2 (sox‑2), were evaluated by reverse transcription‑quantitative polymerase chain reaction and western blotting. Ivermectin exhibited a similarity value of 0.78 in reference to salinomycin. Ivermectin demonstrated an inhibitory effect upon the growth of MDA‑MB‑231 cells in the range of 0.2‑8 µM. Ivermectin preferentially inhibits the viability of CSC‑enriched populations (CD44+/CD24‑ and cells growing in spheroids) compared with the total cell population. The opposite pattern was observed with paclitaxel treatment. Ivermectin exposure reduced the expression of nanog, oct‑4 and sox‑2 at the mRNA and protein levels. Ivermectin preferentially inhibited the CSC subpopulation in the MDA‑MB‑231 cells and downregulated the expression of genes involved in the maintenance of pluripotency and self‑renewal.