To investigate the mechanism of oridonin (ORI)-induced autophagy in prostate cancer PC-3 cells, PC-3 cells cultured in vitro were treated with ORI, and the inhibitory ratio of ORI on PC-3 cells was assayed by 3-4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide. The ultrastructural changes of the cells were observed under light microscope, scanning electron microscope (SEM), and transmission electron microscope (TEM). Acridine orange (AO) staining was used to observe the acidic vesicular organelles (AVOs). The level of autophagy-related proteins, MAP1-LC3, was detected by Western Blot, and RT-PCR was used to detect the level of mRNA of beclin 1. After ORI treatment, the proliferation of PC-3 cells was inhibited significantly in a concentration and time-dependent manner. SEM examination revealed cellular shrinkage and disappearance of surface microvilli in ORI-treated cells. Under TEM examination, the nuclei exhibited chromatin condensation and the appearance of a large number of autophagosomes with double-membrane structure in cytoplasm. AO staining showed the existence of AVOs. The expression of LC3 and the mRNA level of beclin 1 was increased by ORI. Furthermore, autophagy inhibitor 3-methyladenine reversed the increase of beclin 1 mRNA. The growth of PC-3 cells was inhibited, and autophagy was induced by ORI, indicating ORI may have a potential antitumor effect.
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