The Effects of Silibinin on the Induction of Apoptosis and Inhibition of Cell Growth in MCF-7 Breast Cancer Cell Line

Breast cancer is one of the most common leading causes of cancer–related mortality in women. Silibinin, a natural flavonolignane and the main component of milk thistle (Silybum maianum), has conventionally been overlooked as anti-hepatotoxic and anti-cancer agent. In this study, we assessed the effects of Silibinin on breast cancer cell viability, growth, apoptotsis and expression level of P53 gene in MCF-7 cells. The MCF-7 cells were treated in the medium of RPMI1640 and silibinin (control and 25–800 μM) for 24, 48 and 72 hours. Cell proliferation was assessed by MTT (Methyl-Thiazol-Tetrazolium) assay. The percentage of apoptosis was determined by flow cytometry analysis using Annexin-V fluorecence isothiocyanat (FITC). The fold changes of P53 expression were determined by Real-Time PCR. The results showed the maximum inhibitory effect of silibinin on the inhibition of cell growth and induction of apoptosis at a concentration of 200 μM after 24 hour incubation (p<0.05). Incubation of the cells with silibinin for 48 hours descended IC50 value to 148 μM (p<0.05). The flowcytometric analysis showed that silibinin-induced apoptosis is independent of its cytotoxic effects on the cells. Increase in the percentage of apoptosis was associated with significant increase in P53 mRNA level. Silibinin inhibited cell growth and induced apoptosis in a time-dose depending effect. Furthermore, Silibinin treatment resulted in apoptotic effects on MCF-7 cells. These results sug-gested that Silibinin could be an affective component to induce cell cycle arrest and apoptosis in vitro.