Re-188-magnetoferritin nanoparticles (NPs) provide an attractive platform for localized radiation therapy due to their magnetic targeting capability while enhancing contrast in magnetic resonans imaging (MRI) signals. In this study, cellular uptake, in vitro cytotoxicity, apoptotic potential of a non-radioactive isotope of rhenium in the form of Re-187-magnetoferritin NPs were evaluated in both human normal mammary epithelial and breast metastatic adenocarcinoma cell lines. The results showed that, NP administration into the cells is through receptor mediated endocytosis and cancer cells displayed significantly higher uptake and cytotoxicity compared to normal cells. IC50 values of nanoparticles were calculated as 0.96 mg/mL for cancer and 1.73 mg/mL for normal cells. Annexin V/ Propidium Iodide (PI) staining also showed that, NPs induced higher apoptotic rates in cancer cells compared to normal cells. Gene expression analyses confirming the results showed that, pro-apoptotic PUMA and BAX genes were significantly up-regulated while anti-apoptotic BCL-2 and SURVIVIN genes were down-regulated in cancer cells compared to normal cells. Overall, these in vitro results suggest that, Re-187-magnetoferritin NPs have a promising potential for cancer therapy and can be used for imaging and diagnostic purposes for breast cancer at concentrations lower than 0.96 mg/mL. At concentrations above 1 mg/mL, NPs induce apoptosis which can also be used for cancer treatments.