Antitumor effects of seleno-β-lactoglobulin on human breast cancer MCF-7 and MDA-MB-231 cells in vitro.

Seleno-β-lactoglobulin (Se-β-Lg) was synthesized using seleninic acid, an organoselenium compound, and β-lactoglobulin (β-Lg), an important component of milk. Previously, we have studied the effects of Se-β-Lg on hepatocellular carcinoma and gastric cancer cells. In this study, we investigated the antitumor effects of Se-β-Lg and its potential mechanisms of action against human breast cancer cells (MCF-7 and MDA-MB-231). The results showed that the half-maximal inhibitory concentrations (IC50) of Se-β-Lg were 40.84 μg/mL for MCF-7 cells and 46.04 μg/mL for MDA-MB-231 cells at 24 h, while the compound showed no cytotoxicity to normal breast cells. The involvement of reactive oxygen species (ROS) in the activation of the apoptotic signaling pathway by Se-β-Lg was demonstrated by the incubation of cells with 80 μg/mL Se-β-Lg and determination of the rates of apoptosis and intracellular ROS levels after the addition of 10 mM N-acetyl-l-cysteine, a ROS inhibitor. Our findings revealed highly potent anticancer activities of Se-β-Lg against breast cancer cells and suggested that the compound may be used as a chemopreventive agent for breast cancer. Furthermore, we thoroughly elucidated the antitumor mechanism of Se-β-Lg.