protopanaxadiol and Liver-Neoplasms

Diol-type ginsenosides, such as protopanaxadiol (PPD), exhibit antioxidation, anti-inflammation, and antitumor effects. However, the antitumor effect of these ginsenosides and the mechanism of PPD remain unclear. In this work, the antitumor effects of several derivatives, including PPD, Rg5, Rg3, Rh2, and Rh3, were evaluated in five different cancer cell lines. PPD demonstrated the best inhibitory effects on the proliferation and migration of the five cancer cell lines, especially the hepatocellular carcinoma (HCC) cell lines. Therefore, the mechanism of action of PPD in HCC cells was elucidated. PPD inhibited the proliferation, migration, and invasion ability of HepG2 and PLC/PRF/5 cells in a dose-dependent manner. Western blot and immunofluorescence assay showed that PPD can alter the expression of epithelial-mesenchymal transition markers, increase E-cadherin expression, and decrease vimentin expression. Docking and biacore experiments revealed that STAT3 is the target protein of PPD, which formed hydrogen bonds with Gly583/Leu608/Tyr674 at the SH2 domain of STAT3. PPD inhibited the phosphorylation of STAT3 and its translocation from the cytosol to the nucleus, thereby inhibiting the expression of Twist1. PPD also inhibited tumor volume and tumor lung metastasis in PLC/PRF/5 xenograft model. In conclusion, PPD can inhibit the proliferation and metastasis of HCC cells through the STAT3/Twist1 pathway.

Topics: Animals; Antineoplastic Agents, Phytogenic; Carcinoma, Hepatocellular; Cell Line, Tumor; Epithelial-Mesenchymal Transition; Female; Hep G2 Cells; Humans; Liver Neoplasms; MCF-7 Cells; Mice; Mice, Inbred BALB C; Mice, Nude; Sapogenins; Signal Transduction; STAT3 Transcription Factor; Transfection; Xenograft Model Antitumor Assays

20(S)-Protopanaxadiol (PPD), a metabolite of ginsenosides, has been demonstrated to possess cytotoxic effects on several cancer cell lines. The molecular mechanism is, however, not well understood. In this study, we have shown that PPD inhibits cell growth and induces apoptosis in human hepatocarcinoma HepG2 cells. PPD-treated cells showed a massive cytoplasmic vacuolization and a dramatic change of endoplasmic reticulum (ER) morphology. The induction of ER stress is associated with the upregulation of ER stress-associated genes and proteins. PPD activates the unfolded protein response (UPR) through the phosphorylation of PERK and eIF2α, the splicing of XBP1 mRNA, and the cleavage of AFT6. PPD also induces the intrinsic and extrinsic apoptotic pathways. It activates DR5, caspase-8, -9, -3, and promotes the cleavage of PARP while it downregulates Bcl-2, Bcl-x(L) and mitochondrial membrane potential. Knockdown of one of the three UPR limbs by specific siRNAs did not affect PPD-induced apoptosis, which was however, significantly suppressed by the downregulation of CHOP. Western blot analysis showed that PPD-stimulated downregulation of Bcl-2 protein, increase of DR5 protein, activation of caspase-8 and cleavage of PARP were significantly inhibited in CHOP siRNA-transfected cells. Taken together, we have identified ER as a molecular target of PPD and our data support the hypothesis that PPD induces HepG2 cell apoptosis through the ER stress pathway.

Topics: Apoptosis; Endoplasmic Reticulum Stress; Extracellular Signal-Regulated MAP Kinases; Ginsenosides; Hep G2 Cells; Humans; Liver Neoplasms; MAP Kinase Signaling System; Mitochondria; p38 Mitogen-Activated Protein Kinases; Receptors, TNF-Related Apoptosis-Inducing Ligand; Sapogenins; Transcription Factor CHOP; Unfolded Protein Response; Up-Regulation; Vacuoles

To investigate the antioxidative effects of ginsenosides [protopanaxadiol derivatives (PD):protopanaxatriol derivatives (PT) = 1:1] from the roots of Korean ginseng, cell viability, malondialdehyde (MDA) production, antioxidant enzyme activities, and expressions of apoptosis were analyzed after pretreatment of human hepatoma HepG2 cells with H(2)O(2). Cell death was increased through H(2)O(2) treatment dose dependently, and a dose of ginseng extract (PD:PT = 1:1) of 18.6 microg/mL was enough to derive it in reverse. MDA production was reduced through the administration of ginseng extracts even with more intensive H(2)O(2) treatments. Through the use of even low levels of ginseng extract (e.g., 1.86 microg/mL), catalase (CAT) activity was easily reduced from the plateau induced by H(2)O(2). The glutathione peroxidase activity was no better than that of CAT. We assume that ginseng extract acts as an antioxidant even when effective levels of ginseng differ. A ginseng extract dose of 18.6 microg/mL increased the apoptotic expression of oxidative stressed signals, such as c-Jun-N-terminal kinase and stress-activated protein kinase expressions, and mitochondrial cytochrome c released caspase-3 activation; however, these expressions changed with higher doses of ginseng.

Topics: Antioxidants; Apoptosis; Blotting, Western; Carcinoma, Hepatocellular; Caspase 3; Catalase; Cell Line, Tumor; Cell Proliferation; Cell Survival; Chromatography, High Pressure Liquid; Dose-Response Relationship, Drug; Glutathione Peroxidase; Humans; Hydrogen Peroxide; Korea; Liver Neoplasms; Malondialdehyde; Mitogen-Activated Protein Kinases; Oxidants; Panax; Plant Extracts; Sapogenins; Saponins