Ursolic acid,a naturally occurring triterpenoid,suppresses migration and invasion of human breast cancer cells by modulating c‐Jun N‐terminal kinase,Akt and mammalian target of rapamycin signaling

Metastasis is one of the most important factors related to breast cancer therapeutic efficacy. Ursolic acid, a naturally occurring triterpenoid, has various anticancer activities. In this study, we first observed that ursolic acid exerted a dose‐ and time‐dependent inhibitory effect on the migration and invasion of highly metastatic breast MDAMB231 cells at non‐cytotoxic concentrations. This effect was associated with reduced activities of metalloproteinase‐2 (MMP‐2) and u‐PA, which correlated with enhanced expression of tissue inhibitor of MMP‐2 and plasminogen activator inhibitor‐1, respectively. Ursolic acid suppressed the phosphorylation of Jun N‐terminal kinase, Akt and mammalian target of rapamycin, but had no effect on the phosphorylation of ERK and p38. Ursolic acid also strongly reduced the levels of NFκB p65, c‐Jun and c‐Fos proteins in the nucleus of MDAMB231 cells. A time‐dependent inhibition of the protein levels of Rho‐like GTPases, growth factor receptor‐bound protein 2, Ras and vascular endothelial growth factor in cytosol by ursolic acid treatment was also observed. In conclusion, we demonstrated that the anti‐invasive effects of ursolic acid on MDAMB231 cells might be through the inhibition of Jun N‐terminal kinase, Akt and mammalian target of rapamycin phosphorylation and a reduction of the level of NFκB protein in the nucleus, ultimately leading to downregulation of MMP‐2 and u‐PA expression. These results suggest that ursolic acid has potential as a chemopreventive agent for metastatic breast cancer.     

Soy isoflavone genistein induces cell death in breast cancer cells through mobilization of endogenous copper ions and generation of reactive oxygen species

Scope: Worldwide geographical variation in cancer incidence indicates a correlation between dietary habits and cancer risk. Epidemiological studies have suggested that populations with high isoflavone intake through soy consumption have lower rates of breast, prostate, and colon cancer. Isoflavone genistein in soybean is considered a potent chemopreventive agent against cancer. Although several mechanisms have been proposed, a clear anticancer action mechanism of genistein is still not known. Methods and results: Here, we show that the cytotoxic action of genistein against breast cancer cells involves mobilization of endogenous copper. Further, whereas the copper specific chelator neocuproine is able to inhibit the apoptotic potential of genistein, the molecules which specifically bind iron (desferroxamine mesylate) and zinc (histidine) are relatively ineffective in causing such inhibition. Also, genistein‐induced apoptosis in these cells is inhibited by scavengers of reactive oxygen species (ROS) implicating ROS as effector elements leading to cell death. Conclusions: As copper levels are known to be considerably elevated in almost all types of cancers, in this proof‐of‐concept study we show that genistein is able to target endogenous copper leading to prooxidant signaling and consequent cell death. We believe that such a mechanism explains the anticancer effect of genistein as also its preferential cytotoxicity towards cancer cells.     

The effects of green tea (–)‐epigallocatechin‐3‐gallate on reactive oxygen species in 3T3‐L1 preadipocytes and adipocytes depend on the glutathione and 67 kDa laminin receptor pathways

Green tea (–)‐epigallocatechin‐3‐gallate (EGCG) is known as to regulate obesity and fat cell activity. However, little information is known about the effects of EGCG on oxidative reactive oxygen species (ROS) of fat cells. Using 3T3‐L1 preadipocytes and adipocytes, we found that EGCG increased ROS production in dose‐ and time‐dependent manners. The concentration of EGCG that increased ROS levels by 180–500% was approximately 50 μM for a range of 8–16 h of treatment. In contrast, EGCG dose‐ and time‐dependently decreased the amount of intracellular glutathione (GSH) levels. EGCG was more effective than (–)‐epicatechin, (–)‐epicatechin‐3‐gallate, and (–)‐epigallocatechin in changing ROS and GSH levels. This suggests a catechin‐specific effect. To further examine the relation of GSH to ROS as altered by EGCG, we observed that exposure of preadipocytes and adipocytes to N‐acetyl‐L ‐cysteine (a GSH precursor) blocked the EGCG‐induced increases in ROS levels and decreases in GSH levels. These observations suggest a GSH‐dependent effect of EGCG on ROS production. While EGCG was demonstrated to alter levels of ROS and GSH, its signaling was altered by an EGCG receptor (the so‐called 67 kDa laminin receptor(67LR)) antiserum, but not by normal rabbit serum. These data suggest that EGCG mediates GSH and ROS levels via the 67LR pathway.     

Gallic acid induces G2/M phase cell cycle arrest via regulating 14‐3‐3β release from Cdc25C and Chk2 activation in human bladder transitional carcinoma cells

Scope: Cell cycle regulation is a critical issue in cancer treatment. Previously, gallic acid (GA) has been reported to possess anticancer ability. Here, we have evaluated the molecular mechanism of GA on cell cycle modulation in a human bladder transitional carcinoma cell line (TSGH‐8301 cell). Methods and results: Using flow cytometer analysis, exposure of the cells to 40 μM GA resulted in a statistically significant increase in G2/M phase cells, which was accompanied by a decrease in G0/G1 phase cells. GA‐treated cells resulted in significant growth inhibition in a dose‐dependent manner accompanied by a decrease in cyclin‐dependent kinases (Cdk1), Cyclin B1, and Cdc25C, but significant increases in p‐cdc2 (Tyr‐15) and Cip1/p21 by western blotting. Additional mechanistic studies showed that GA induces phosphorylation of Cdc25C at Ser‐216. This mechanism leads to its translocation from the nucleus to the cytoplasm resulting in an increased binding with 14‐3‐3β. When treated with GA, phosphorylated Cdc25C can be activated by ataxia telangiectasia‐mutated checkpoint kinase 2 (Chk2). This might be a DNA damage response as indicated by Ser‐139 phosphorylation of histine H2A.X. Furthermore, treatment of the cells with a Chk2 inhibitor significantly attenuated GA‐induced G2/M phase arrest. Conclusion: These results indicate that GA can induce cell cycle arrest at G2/M phase via Chk2‐mediated phosphorylation of Cdc25C in a bladder transitional carcinoma cell line.