Previous studies revealed that polydatin, a natural small compound, possessed protective effect against ischemia/reperfusion injury and inflammation. However, the action and molecular mechanism of its potent anti-cancer activity remain poorly understood. In the present study, polydatin significantly killed several human tumor cell lines in a dose- and time-dependent manner. The compound also dose-dependently caused mitochondrial apoptosis in human nasopharyngeal carcinoma CNE cells. In addition, polydatin triggered endoplasmic reticulum (ER) stress and down-regulated the phosphorylation of Akt in CNE cells, while knock-down of CCAAT/enhancer-binding protein homologous protein (CHOP) dramatically abrogated the inactivation of Akt and reversed the pro-apoptotic effect of polydatin. Furthermore, polydatin provoked the generation of reactive oxygen species in CNE cells, while the antioxidant N-acetyl cysteine almost completely blocked the activation of ER stress and apoptosis, suggesting polydatin-induced reactive oxygen species is an early event that triggers ER stress mitochondrial apoptotic pathways in CNE cells. Taken together, these findings strongly suggest that polydatin might be a promising anti-tumor drug and our data provide the molecular theoretical basis for clinical application of polydatin.

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Rapid increases in incidence and mortality of human malignant melanoma are observed worldwide; thus, the development of new effective chemicals to control melanoma is urgent. In this study, the cytotoxic effect of oxymatrine, a natural quinolizidine alkaloid, against three human melanoma cell lines (A375, Sk-Mel-28, MM96L) and the underlying mechanisms were investigated. Oxymatrine killed all three human melanoma cell lines in a dose-dependent manner. The compound also dose-dependently caused apoptosis in human melanoma A375 cells. In addition, oxymatrine induced a remarkable change in mitochondrial membrane potential and triggered the release of cytochrome c from mitochondria to cytosol. Furthermore, this small compound resulted in a marked activation of capase-3, caspase-9, and poly (ADP-ribose) polymerase, while caspase-3 inhibitor Z-DEVD-FMK significantly reversed the proapoptotic effect of oxymatrine in A375 cells. Moreover, oxymatrine also dose-dependently increased the generation of reactive oxygen species in A375 cells, and N-acetylcysteine, a reactive oxygen species production inhibitor, almost completely blocked oxymatrine-induced apoptosis. In conclusion, our findings suggest that oxymatrine triggers oxidative stress, resulting in the collapse of the mitochondrial transmembrane potential, which in turn leads to cytochrome c release and apoptosis through the intrinsic caspase-9/caspase-3 pathway in human melanoma A375 cells.

The pathogenic mechanisms underlying pituitary somatotroph adenoma formation, progression are poorly understood. To identify candidate tumor suppressor genes involved in pituitary somatotroph adenoma tumorigenesis, we used HG18 CpG plus Promoter Microarray in 27 human somatotroph adenomas and 4 normal human adenohypophyses. RASSF3 was found with frequent methylation of CpG island in its promoter region in somatotroph adenomas but rarely in adenohypophyses. This result was confirmed by pyrosequencing analysis. We also found that RASSF3 mRNA level correlated negatively to its gene promoter methylation level. RASSF3 hypermethylation and downregulation was also observed in rat GH3 and mouse GT1.1 somatotroph adenoma cell lines. 5-Aza-2′ deoxycytidine and trichostatin-A treatment induced RASSF3 promoter demethylation, and restored its expression in GH3 and GT1.1 cell lines. RASSF3 overexpression in GH3 and GT1.1 cells inhibited proliferation, induced apoptosis accompanied by increased Bax, p53, and caspase-3 protein and decreased Bcl-2 protein expression. We also found that the antitumor effect of RASSF3 was p53 dependent, and p53 knockdown blocked RASSF3-induced apoptosis and growth inhibition. Taken together, our results suggest that hypermethylation-induced RASSF3 silencing plays an important role in the tumorigenesis of pituitary somatotroph adenomas.

The contribution of complement to the development of autoimmune diabetes has been proposed recently. The underlying mechanisms, however, remain poorly understood. We hypothesize that myeloid-derived suppressor cells (MDSC), which act as regulators in autoimmunity, play a role in resistance to diabetes in absence of complement C3. Indeed, MDSC number was increased significantly in STZ-treated C3−/− mice. These cells highly expressed arginase I and inducible nitric oxide synthase (iNOS). Importantly, depletion of MDSC led to the occurrence of overt diabetes in C3−/− mice after STZ. Furthermore, C3−/− MDSC actively suppressed diabetogenic T cell proliferation and prevented/delayed the development of diabetes in arginase and/or iNOS-dependent manner. Both Tregs and transforming growth factor-β (TGF-β) are crucial for MDSC induction in STZ-treated C3−/− mice as depletion of Tregs or blocking TGF-β bioactivity dramatically decreased MDSC number. These findings indicate that MDSC are implicated in resistance to STZ-induced diabetes in the absence of complement C3, which may be helpful for understanding of mechanisms underlying preventive effects of complement deficiency on autoimmune diseases.

Background/Aims: Nasopharyngeal cancer (NPC) is one of the common human malignant diseases all over the world, and chemotherapy remains the main therapy for NPC. However, the survival and life quality of NPC patients are still very poor. Thus, novel and selective anti-tumor agents are pressingly needed. Our previous study identified pectolinarigenin as a novel effective anti-tumor drug candidate for NPC. In this study, we further investigated its anti-tumor activities and explored the potential molecular mechanism. Methods: NPC C666-1 cells were cultured and treated by pectolinarigenin. Cell proliferation assay, colony formation assay, Transwell assay and wound healing assay were conducted and cell apoptosis was detected by flow cytometry. Mitochondrial transmembrane potential and ROS were also observed. NPC subcutaneous xenograft mice model was established to evaluate the anti-tumor effect of pectolinarigenin in vivo. Results: We observed that treatment of pectolinarigenin inhibited cell viability and cell migration of NPC C666-1 cells in concentration- and time-dependent manner. Pectolinarigenin induced cell apoptosis in C666-1 cells detected by flow cytometry analysis, which was associated with the activation of mitochondrial-related apoptosis and the accumulation of reactive oxygen species (ROS). Pectolinarigenin also activated caspase signaling pathway. The in vivo experiment of subcutaneous xenograft mice model also indicated that the administration of pectolinarigenin could decrease the tumor growth of NPC and no severe toxicity was observed. Conclusions: Based on our findings, we conclude that pectolinarigenin could suppress the tumor growth of NPC, which verifies it as a new therapeutic agent for treating this devastating disease.