ObjectivesDrug repurposing studies enable shorter routes to the clinic by skipping the steps like in vitro in vivo screening, chemical optimization and toxicological studies. In our study, we investigated the potent anti-cancer effect of Alzheimer's drug Memantine on 4T1 breast cancer cells.MethodsMemantine's effect on proliferation of 4T1 cells was evaluated by using the MTT assay. Memantine inhibited 4T1 cell proliferation in a concentration- dependent manner at 24 and 48 hours. We investigated the drug's effect on the protein expressions of Bax, Bcl-2, Casp-3, Casp-9, E-Cad, Vimentin, B-Cat, GSK3B, p-ERK, ERK, p-GS, GS that are involved in apoptosis, metastasis and cell survival.ResultsMemantine altered the Bcl-2, Bax, Casp3, Casp-9 apoptotic protein expression levels. We found that memantine inhibited p-Erk expression and that result suggested a plausible mechanism of action for memantine's antineoplastic effect. Memantine also inhibited wound closure at 24 h, significantly (p = 0.0055).ConclusionsMemantine inhibited 4T1 breast cancer cell proliferation at significantly lower doses than mostly studied re-purposed drug Metformin. Therefore, we believe that memantine might hold a great promise as a new repositioned drug in cancer treatment and it is our further interest to investigate its effects in vivo (Fig. 3, Ref. 22).