Relations Between Autophagy And Apoptosis On Qercetin-induced Death Of Human Breast Cancer Cell Line MCF-7

Objective: To study the effects of qercetin-induced death of human breast cancer cell line MCF-7, and the relations between the mechanism of autophagy and apoptasis on qercetin-induced death of MCF-7.Methods: After treatment with different concentration of Que, the growth inhibition of the MCF-7 cells was assessed by MTT colorimetric assay. The MDC,Hochest and AO/EB staining were applied to identify the autophagy and the apoptosis after Que treatment. With ALLN to inhibit the m-calpain, z-IETD-FMK to inhibt the caspase 8,E64 to inhibt the cathepsins , the combination of MTT assay and LDH leakage , the fluorescent staining and the Flow cytometry were performed to analyze the relations between autophagy and apoptasis on qercetin-induced death of human breast cancer cell line MCF-7 cells .Results: The proliferation of MCF-7 cells was significantly inhibited in a dose- and time-dependent manner after Que treatment. Apoptosis was induced in MCF-7 cells as detected by Hochest 33258 staining and AO/EB staining in the late phase of Que treatment. Autophagy was also induced in MCF-7 cells as detected by MDC staining and Fluorescent staining in the early phase. LC3, the autophagic protein in mammalian cells, was activated; Que-induced MCF-7 cells cytotoxicity enhanced, after alkalization lysosome, the flow cytometry detected that the apoptosis peak of MCF-7 was advanced, and the immune assay in LC3 expression was reduced. The inhibition of caspase 8 can enhance the suppression of Que on MCF-7 cells in vitro, but the cathepsins inhibitor, E64d can reduce the growth inhibition of Que on MCF-7.Conclusions: Que can significantly inhibt the growth of the MCF-7 cells, and it can induce the autophagy and apoptosis which have different contribution to Que-induced death of MCF-7 cells. The autophagic mechanism is a protection mechanism, and it can reduce the cytotoxicity in the death of MCF-7 cells induced by Que. Maybe Que promote the MCF-7 cells to take place the autophagy, apoptosis and some other death path with the activation of the lysosomal protease .So the lysosome is a hinge of the autophagy and the apoptosis.