No abstract

Matrix metalloproteinase (MMP)-9 plays a key role in tumor invasion. Inhibitors of MMP-9 were screened from Metasequoia glyptostroboides (Dawn redwood) and one potent inhibitor, isoginkgetin, a biflavonoid, was identified. Noncytotoxic levels of isoginkgetin decreased MMP-9 production profoundly, but up-regulated the level of tissue inhibitor of metalloproteinase (TIMP)-1, an inhibitor of MMP-9, in HT1080 human fibrosarcoma cells. The major mechanism of Ras-dependent MMP-9 production in HT1080 cells was phosphatidylinositol 3-kinase (PI3K)/Akt/nuclear factor-KB (NF-KB) activation. Expression of dominant-active H-Ras and p85 (a subunit of PI3K) increased MMP-9 activity, whereas dominant-negative forms of these molecules decreased the level of MMP-9. H-Ras did not increase MMP-9 in the presence of a PI3K inhibitor, LY294002, and a NF-KB inhibitor, SN50. Further studies showed that isoginkgetin regulated MMP-9 production via PI3K/Akt/NF-KB pathway, as evidenced by the findings that isoginkgetin inhibited activities of both Akt and NF-KB. PI3K/Akt is a well-known key pathway for cell invasion, and isoginkgetin inhibited HT1080 tumor cell invasion substantially. Isoginkgetin was also quite effective in inhibiting the activities of Akt and MMP-9 in MDA-MB-231 breast carcinomas and B16F10 melanoma. Moreover, isoginkgetin treatment resulted in marked decrease in invasion of these cells. In summary, PI3K/ Akt is a major pathway for MMP-9 expression and isoginkgetin markedly decreased MMP-9 expression and invasion through inhibition of this pathway. This suggests that isoginkgetin could be a potential candidate as a therapeutic agent against tumor invasion. [Mol Cancer Ther 2006;5(11):2666 -75]

No abstract

Selenium, an essential biological trace element, reduces the incidence of cancer. Our previous studies show that selenite inhibits tumor invasion by suppressing the expression of matrix metalloproteinases (MMP) -2 and -9. Methylseleninic acid (MSeA), an immediate precursor of methylselenol, inhibits tumor cell growth in vitro and mammary carcinogenesis in vivo. In this study, we demonstrate that MSeA suppresses pro-MMP-2 activation in a dose-dependent manner induced by 12-O-tetradecanoylphorbol-13-acetate (PMA), and further decreases the invasiveness of HT1080 tumor cells. Membrane type-1-MMP (MT1-MMP) is a crucial element in the process of pro-MMP-2 activation. Pro-MMP-2 binds MT1-MMP, using tissue inhibitor of metalloproteinase-2 (TIMP-2) as an adaptor, by forming a trimolecular complex on the cell surface. MSeA blocked MT1-MMP in a dose-dependent manner, but not TIMP-2 expression. MMP-9 and TIMP-1 levels were not affected by MSeA. Selenite induced a decrease in protein levels of both pro-MMPs -9 and -2, but not active forms of pro-MMP-2. MT1-MMP expression is regulated by NF-kappaB. Our data show that the effect of MSeA on MT1-MMP expression is mediated through suppression of NF-kappaB activity. Methylselenol generated by selenomethionine (SeMet) and methioninase (METase) inhibited pro-MMP-2 activation induced by PMA, confirming the effect of MSeA on pro-MMP-2 activity. Moreover, ROS production induced by PMA was partly decreased in the presence of MSeA. This suppression of ROS production may be related to diminished NF-kappaB activity. Thus, our results suggest that MSeA blocks tumor invasion in vitro via inhibiting pro-MMP-2 activation mediated by suppression of MT1-MMP expression, which is regulated by the NF-kappaB signal pathway.

Matrix Metalloproteinases (MMPs) are crucial enzymes for ultraviolet irradiation-induced photoaging in human skin. Ultraviolet B (UVB) stimulates dermal fibroblasts to increase MMP-1 and -3 expression and extracellular matrix (ECM) degradation in photoaging. We investigated whether phosphatase and tensin homolog (PTEN)/Akt pathway is involved in secretions of MMP-1 and -3 in human dermal fibroblasts. The increase in MMP-1 and -3 expression and secretion occurred along with the increase in PTEN and Akt phosphorylation by UVB irradiation in a dose- and time-dependent manner. However, treatment with a casein kinase 2 inhibitor, 5,6-dichloro-1-beta-D-ribofuranosyl-benzimidazole, inhibited their phosphorylations and MMP-1 and -3 secretions. Transfection of wild-type PTEN (Wt-PTEN) decreased basal and UVB-induced MMP-1 and -3 secretions, as well as activator protein-1 (AP-1) activity, while transfection of small interference RNA of PTEN (siRNA-PTEN), phosphatase-inactive PTEN (C124S-PTEN), or lipid phosphatase-inactive PTEN (G129E-PTEN) increased basal or UVB-induced MMP-1 and -3 secretions and AP-1 activity. Transfection of constitutively active Akt (Myr-Akt) also increased basal or UVB-induced MMP-1 and -3 secretions, as well as AP-1 activity. However, transfection of kinase-inactive Akt (K179M-Akt) decreased their secretions, but showed no significant change of AP-1 activity without UVB irradiation, and a significant increase of AP-1 activity with UVB irradiation. Treatment with the phosphatidylinositol 3-kinase inhibitors, LY294002 or wortmannin, downregulated basal and UVB-induced MMP-1 and -3 secretions. In conclusion, UVB irradiation increases PTEN and Akt phosphorylation in human dermal fibroblasts, and these inhibition of PTEN and activation of Akt by phosphorylation are involved in UVB-induced MMP-1 and -3 secretions partly through upregulation of AP-1 activity.

Peroxisome proliferator-activated receptor c (PPARc) is a nuclear receptor modulating a variety of biological functions including cancer cell proliferation and differentiation. However, the role of PPARc and its ligands in tumor invasion is unclear. To evaluate a possible role for PPARc ligands in tumor invasion, we examined whether PPARc agonists including pioglitazone, troglitazone, rosiglitazone, and ciglitazone could affect the activity of matrix metalloproteinases (MMPs) in the HT1080 cell line, a well-studied and well-characterized cell line for MMP research. The gelatin zymography assay showed that ciglitazone activated pro-MMP-2 significantly. In addition, ciglitazone increased the expression of MMP-2, which was accompanied by an increase of membrane type 1-MMP (MT1-MMP) expression. The PPARc antagonist, GW9662 attenuated the ciglitazone-induced PPARc activation but it did not affect the pro-MMP2 activation by ciglitazone, suggesting that the action of ciglitazone on the pro-MMP-2 activation bypassed the PPARc pathway. Antioxidants and various inhibitors of signal transduction were used to investigate the mechanism of ciglitazone-induced pro-MMP-2 activation. We found that the sustained production of reactive oxygen species (ROS) was required for pro-MMP-2 activation by ciglitazone. We also found that PB98059, an inhibitor of MEK-ERK, significantly blocked ciglitazone-induced pro-MMP-2 activation and that extracellular signal-regulated kinase (ERK) was hyperphosphorylated by ciglitazone. Moreover, cell invasion was significantly increased by ciglitazone in the HT1080 cell lines, whereas cell motility was not affected. This study suggests that ciglitazone-induced pro-MMP-2 activation increases PPARc-independent tumor cell invasion through ROS production and ERK activation in some types of cancer cells.

Functions of selenium are diverse as antioxidant, anti-inflammation, increased immunity, reduced cancer incidence, blocking tumor invasion and metastasis, and further clinical application as treatment with radiation and chemotherapy. These functions of selenium are mostly related to oxidation and reduction mechanisms of selenium metabolites. Hydrogen selenide from selenite, and methylselenol (MSeH) from Se-methylselenocyteine (MSeC) and methylseleninicacid (MSeA) are the most reactive metabolites produced reactive oxygen species (ROS); furthermore, these metabolites may involve in oxidizing sulfhydryl groups, including glutathione. Selenite also reacted with glutathione and produces hydrogen selenide via selenodiglutathione (SeDG), which induces cytotoxicity as cell apoptosis, ROS production, DNA damage, and adenosine-methionine methylation in the cellular nucleus. However, a more pronounced effect was shown in the subsequent treatment of sodium selenite with chemotherapy and radiation therapy. High doses of sodium selenite were effective to increase radiation therapy and chemotherapy, and further to reduce radiation side effects and drug resistance. In our study, advanced cancer patients can tolerate until 5000 μg of sodium selenite in combination with radiation and chemotherapy since the half-life of sodium selenite may be relatively short, and, further, selenium may accumulates more in cancer cells than that of normal cells, which may be toxic to the cancer cells. Further clinical studies of high amount sodium selenite are required to treat advanced cancer patients.

Activin/Nodal signaling is essential for germ-layer formation and axial patterning during embryogenesis. Recent evidence has demonstrated that the intra-or extracellular inhibition of this signaling is crucial for ectoderm specification and correct positioning of mesoderm and endoderm. Here, we analyzed the function of Xenopus serum response factor (XSRF) in establishing germ layers during early development. XSRF transcripts are restricted to the animal pole ectoderm in Xenopus early embryos. Ectopic expression of XSRF RNA suppresses mesoderm induction, both in the marginal zone in vivo and caused by Activin/Nodal signals in animal caps. Dominant-negative mutant or antisense morpholino oligonucleotide-mediated inhibition of XSRF function expands the expression of mesendodermal genes toward the ectodermal territory and enhances the inducing activity of the Activin signal. SRF interacts with Smad2 and FAST-1, and inhibits the formation of the Smad2-FAST-1 complex induced by Activin. These results suggest that XSRF might act to ensure proper mesoderm induction in the appropriate region by inhibiting the mesoderm-inducing signals during early embryogenesis.