Effects of rapamycin on cell apoptosis in MCF-7 human breast cancer cells.

BACKGROUND Rapamycin is an effective anti-angiogenic drug. However, the mode of its action remains unclear. Therefore, in this study, we aimed to elucidate the antitumor mechanism of rapamycin, hypothetically via apoptotic promotion, using MCF-7 breast cancer cells. MATERIALS AND METHODS MCF-7 cells were plated at a density of 15105 cells/well in 6-well plates. After 24h, cells were treated with a series of concentrations of rapamycin while only adding DMEM medium with PEG for the control regiment and grown at 37oC, 5% CO2 and 95% air for 72h. Trypan blue was used to determine the cell viability and proliferation. Untreated and rapamycin-treated MCF-7 cells were also examined for morphological changes with an inverted-phase contrast microscope. Alteration in cell morphology was ascertained, along with a stage in the cell cycle and proliferation. In addition, cytotoxicity testing was performed using normal mouse breast mammary pads. RESULTS Our results clearly showed that rapamycin exhibited inhibitory activity on MCF-7 cell lines. The IC50 value of rapamycin on the MCF-7 cells was determined as 0.4μg/ml (p<0.05). Direct observation by inverted microscopy demonstrated that the MCF-7 cells treated with rapamycin showed characteristic features of apoptosis including cell shrinkage, vascularization and autophagy. Cells underwent early apoptosis up to 24% after 72h. Analysis of the cell cycle showed an increase in the G0G1 phase cell population and a corresponding decrease in the S and G2M phase populations, from 81.5% to 91.3% and 17.3% to 7.9%, respectively. CONCLUSIONS This study demonstrated that rapamycin may potentially act as an anti-cancer agent via the inhibition of growth with some morphological changes of the MCF-7 cancer cells, arrest cell cycle progression at G0/G1 phase and induction of apoptosis in late stage of apoptosis. Further studies are needed to further characterize the mode of action of rapamycin as an anti-cancer agent.