Study On Qercetin-induced Autophagic Death Of Human Breast Cancer Cell Line MCF-7

AIM To study the effects and the mechanisms of autophagy on quercetin(Que)-induced death of MCF-7 cells.METHODS After treatment with Que, the inhibition of cell growth was assessed by MTT colorimetric assay. Observe the morphological changes of MCF-7 cells with microscope. Hochest33258 staining, AO/EB staining and MDC staining were used to detect apoptosis and autophagy induced by Que. To examine the effects of Que on autophagy activation, 3-methyadenine (3-MA), an autophagy specific inhibitor, was used after Que treatment. And the cytotoxicity of Que was measured by lactose dehydrogenase (LDH) leakage. The lysosomal membrane alkalizing agent - chloroquines (Chlo) was added after Que and the growth inhibition of MCF-7 cells was assessed by MTT colormetric assay. Immunohistochemistry and mitochondria membrane potential detection were excerted to study the apoptotic and autophagic mechanisms involved in the death of MCF-7 cells.RESULTS The proliferation of MCF-7 cells was significantly inhibited in a dose-and time-dependent manner when treated with Que. The morphology of MCF-7 cells also changed significantly after being exposed to Que as detected by microscope. Apoptosis was induced in MCF-7 cells as detected by Hochest33258 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 in the early phase. The cytotoxicity of Que on MCF-7 cells increased either before or after blocking autophagy as the result of LDH leakage showed. The proliferation of MCF-7 cells was significantly inhibited when treated with Chlo. What's more, once autophagy was induced by Que, LC3, the autophagic protein in mammalian cells, was activated. Moreover, the mitochondrial membrane potential collapsed in MCF-7 cells after Que treatment. CONCLUSION Que significantly inhibited the proliferation of MCF-7 cells and it triggered autophagy followed by apoptosis in MCF-7 cells. In Que-induced death of MCF-7 cells, autophagy promoted an autophagic cell death and through triggereing lysosome and mitochondria to promoting MCF-7 cells into another deadth style. Propabley, both of these two types programmed cell death (PCD) promoted MCF-7 cells to death and the activation of cathepsins was probably involved in the mechanism of it.