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Pentagalloylglucose(PGG) is a natural polyphenolic compound derived from a large number of medicine herbals. Accumulative studies have demonstrated PGG expresses multiple pharmaceutical potentials including anti-cancer; anti-diabetes and cytoprotection whit low toxicity. Ovarian carcinoma is a main gynecologic neoplasm and no effective therapeutics. The study here researched the proliferation inhibition of ovarian carcinoma cells by PGG and the molecular mechanism. Several ovarian carcinoma cells ware used as experimental models.Methods:1. MTT assay was employed to investigate the effects of PGG on the proliferations of ovarian cancer HO-8910, HO-8910PM, SKOV-3 cells. The morphology changes induced by PGG were observed under a light microscope.2. Cells treated with PGG were stained with PI and the cell cycle distribution was detected through a flow cytometer. To observe the change of nucleus induced by PGG, cells were stained with Hoechst and observed under a fluorescence microscope. Cells treated with PGG were stained AnnexinV-FITC/PI, then the cell apoptosis were detected through a flow cytometer.3. Western blot was employed to detect the PGG-induced cleaved caspases(c-caspases), that indicate the activity of caspase pathway of apoptosis. Western blot was also employed to detect the distribution of P65 and relative inhibitory protein IκB in cytoplasm and nucleus, the decreased nucleus distribution of P65 and increased cytoplasm distribution of IκB indicate a inhibited NF-κB transcription activity.4. RT-PCR was used to research the PGG-induced transcription alteration of NF-κB target genes, including bcl-2, bcl-xl, ciap-1, ciap-2, survivin, niap, xiap, cyclinD1, all were prosurvival genes in tumor cells.Results:1. PGG inhibited proliferation of ovarian cancer HO-8910, HO-8910PM and SKOV-3 cells. The inhibitory effects appear a time-and–does dependent manner when the treatment exceeded 48 hours or the does of PGG exceeded 20μM(P<0.05).2. PGG treatment changed cell cycle distribution of three ovarian cancer HO-8910, HO-8910PM and SKOV-3 cells, and induced apoptosis in HO-8910, HO-8910PM , but not in SOV-3 cells. PGG induced S- phase enrichment in three ovarian cancer cells in a time-and–does dependent manner. The PGG-induced apoptosis-like change of nucleus was observed in HO-8910 and HO-8910PM, but not in SKOV-3 cells, all treated with PGG and then stained with Hoechst. The apoptosis induced by PGG was also confirmed by AnnexinV-FITC positive of HO-8910 and HO-8910PM cells, that indicates cell membrane eversion in apoptosis.3. PGG treatment induced activated caspases of caspase firmly, that are c-Caspase-9, 3,7. The cleavage o f caspase-8 was inhibited by PGG treatment, though PGG up-regulated the upstream tumor necrosis factor receptor.4. PGG treatment repressed nuclear translocation of P65 NF-κB and enriched IκB, the inhibitory protein, in cytoplasm. Accordingly, the mRNA of target genes of NF-κB, bcl-2, bcl-xl, surviving, niap, xiap, cyclinD1, but not ciap-1 or ciap-2, was down-regulated. PGG treatment had no effects on the mRNA expression of bax. Conclusion:Through inducing cell cycle retardation in cell cycle and apoptosis, PGG can inhibit proliferation of ovarian carcinoma cells. PGG could have repressed the transcription activity of oncogenic transcription factor NF-κB to down-regulate the expression of apoptosis-inhibitory genes, finally triggered endogenous caspase apoptosis pathway death in ovarian cancer cells.
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