Baicalin inhibits the TGF-ß1/p-Smad3 pathway to suppress epithelial-mesenchymal transition-induced metastasis in breast cancer.

TGF-ß1 is an epithelial-mesenchymal transition (EMT)-inducing factor that is critical in tumor progression. However, whether the effect of TGF-ß1 on breast cancer is through the EMT pathway remains to be determined, and drug development based on this mechanism needs to be improved. Results of this study showed that TGF-ß1 dysregulation significantly correlated with the expression levels of EMT-associated markers and transcriptional factors. Exogenous expression of TGF-ß1 promoted breast cancer cell metastasis and EMT progression. In addition, direct binding of baicalin to TGF-ß1 caused its inactivation, which subsequently blocked signal transduction and inhibited breast cancer cell metastasis. In vivo experiment results further invalidated the inhibitory effect of baicalin on TGF-ß1-induced tumor metastasis. These results suggest that baicalin, an active ingredient used in traditional Chinese medicine, exhibits a potential therapeutic effect on breast cancer metastasis by regulating TGF-ß1-dependent EMT progression.

Olaquindox-induced apoptosis is suppressed through p38 MAPK and ROS-mediated JNK pathways in HepG2 cells.

We investigated mitogen-activated protein kinase (MAPK) pathways as well as reactive oxygen species (ROS) in olaquindox-induced apoptosis. Exposure of HepG2 cells to olaquindox resulted in the phosphorylation of p38 MAPK and c-Jun N-terminal kinases (JNK). To confirm the role of p38 MAPK and JNK, HepG2 cells were pretreated with MAPKs-specific inhibitors prior to olaquindox treatment. Olaquindox-induced apoptosis was significantly potentiated by the JNK inhibitor (SP600125) or the p38 MAPK inhibitor (SB203580). Furthermore, we observed that olaquindox treatment led to ROS generation and that olaquindox-induced apoptosis and ROS generation were both significantly reduced by the antioxidants, superoxide dismutase and catalase. In addition, the levels of phosphorylation of JNK, but not p38 MAPK, were significantly suppressed after pretreatment of the antioxidants, while inhibition of the activations of JNK or p38 MAPK had no effect on ROS generation. This result suggested that ROS may be the upstream mediator for the activation of JNK. Conclusively, our results suggested that apoptosis in response to olaquindox treatment in HepG2 cells might be suppressed through p38 MAPK and ROS-JNK pathways.

c-Myc influences olaquindox-induced apoptosis in human hepatoma G2 cells.

Olaquindox, a synthetic antimicrobial compound, was banned as feed additives in the U.S. and the EU. In China, the use of olaquindox is banned in poultry and aquaculture feed, restricted in livestock feed for growth promotion. Olaquindox's safety is the object of increasing attention. The present study was undertaken to investigate whether and how olaquindox elevates expression of c-Myc, which influences olaquindox-induced apoptosis in HepG2 cells. For a better understanding of c-Myc's role in susceptibility of human hepatoma G2 cells to olaquindox-induced apoptosis, two vectors (the pSilencer-cmyc(Si-cmyc) and the control vector) were transfected to HepG2 cells. The cells were pretreated with Si-cmyc, which expressed only 35-65% c-Myc protein levels compared to those of the parental cells and the control cells. We examined effects of olaquindox on reactive oxygen species (ROS) production in these c-Myc low-expressing cells, and on apoptosis. Our data revealed that ROS production induced by olaquindox treatment was partially blocked by Si-cmyc transfection and partly inhibited olaquindox-induced apoptosis through decreased ROS generation. Further data showed that olaquindox induced decreased ROS by Si-cmyc transfection through decreased cytochrome c release to cytosol, which inhibited apoptosis of the cells. These results suggest that c-Myc might be important during olaquindox-induced apoptosis in human hepatoma G2 cells.

Investigation of quinocetone-induced genotoxicity in HepG2 cells using the comet assay, cytokinesis-block micronucleus test and RAPD analysis.

Quinocetone, a new quinoxaline 1,4-dioxide derivative, has been approved as an animal growth promoter in China since 2003. To investigate the genotoxicity of quinocetone in vitro, its effects on the extent of DNA injury in human hepatoma (HepG2) cells accompanied by chromosomal damage and genomic DNA alterations were tested. The cell viability test indicated that quinocetone inhibited cell proliferation as a function of dose and time. In the comet assay, significant DNA fragment migration was observed in a dose-dependent manner. A dose-dependent increase of the micronucleated (MN) cell frequency was shown in cytokinesis-block micronucleus (CBMN) test. The gain/loss of randomly amplified polymorphic DNA (RAPD) bands and the change of band intensity in RAPD profiles were obtained after HepG2 cells were exposed to quinocetone at concentrations of 1.25, 2.5 and 5 microg/mL. The results demonstrated that quinocetone exerted genotoxic effects on HepG2 cells. Thus, the use of quinocetone as a growth promoter in animal feed should be seriously considered.