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  • Title: The role of Beclin 1 in SDT-induced apoptosis and autophagy in human leukemia cells.
    Author: Su X, Wang X, Liu Q, Wang P, Xu C, Leung AW.
    Journal: Int J Radiat Biol; 2015 Jun; 91(6):472-9. PubMed ID: 25758178.
    Abstract:
    PURPOSE: To prove the occurrence of autophagy after treatment by protoporphyrin IX (PpIX)-mediated sonodynamic therapy (SDT) of human chronic myelogenous leukemia K562 cells as well as its relationship with apoptosis. MATERIALS AND METHODS: The 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenylter-trazolium bromide tetrazolium (MTT) assay was adopted to examine cytotoxicity of different treatments. Nuclear morphology changes were observed under a fluorescence microscopy with 4'-6-Diamidino-2-Phenylindole (DAPI) staining. Western blotting was used to analyze the expression of caspase-3, Beclin 1 (BECN 1) and the conversion of LC3- phosphatidylethanolamine conjugate/a cytosolic form of LC3 (LC3 II/I). Fluorescence microscope was used to identify the formation of autophagic vacuoles (AVO) during autophagy. RESULTS: Under optimal conditions, SDT was shown to induce autophagy in K562 cells, which caused the up-regulation of Beclin-1 and the formation of AVO. In addition, pre-treatment of cancer cells with Beclin 1-targeted short hairpin RNA (Beclin 1 shRNA) was shown to reduce the level of LC3-II accumulation and staining with punctate spots of monodansylcadaverine (MDC) staining. Besides, the cytotoxic effect of SDT was significantly increased by Beclin 1 shRNA. Furthermore, studies showed a marked effect on the apoptosis of cells by Beclin 1 shRNA to sonodamage with increased DAPI staining and caspase-3 cleavage. CONCLUSIONS: These results demonstrated that SDT significantly induced autophagy of K562 cells, probably to protect the K562 cells from sonodamage.
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