v-Src activates the expression of 92-kDa type IV collagenase gene through the AP-1 site and the GT box homologous to retinoblastoma control elements. A mechanism regulating gene expression independent of that by inflammatory cytokines

Overexpression of membrane sialic acid-specific sialidase Neu3 inhibits matrix metalloproteinase-9 expression in vascular smooth muscle cells

The ganglioside-specific sialidase Neu3 has been suggested to participate in cell growth, migration, and differentiation. Recent reports suggest that sialidase may be involved in intimal thickening, an early stage in the development of atherosclerosis. However, the role of the Neu3 gene in vascular smooth muscle cells (VSMC) responses has not yet been elucidated. To determine whether a Neu3 is able to modulate VSMC growth, the effect of overexpression of the Neu3 gene on cell proliferation was examined. However, the results show that the overexpression of this gene has no effect on DNA synthesis and ERK phosphorylation in cultured VSMC in the presence of TNF-alpha. Because atherogenic effects need not be limited to proliferation, we decided to examine whether Neu3 exerted inhibitory effects on matrix metalloproteinase-9 (MMP-9) activity in TNF-alpha-induced VSMC. The expression of the Neu3 gene led to the inhibition of TNF-alpha-induced matrix metalloproteinase-9 (MMP-9) expression in VSMC as determined by zymography and immunoblot. Furthermore, Neu3 gene expression strongly decreased MMP-9 promoter activity in response to TNF-alpha. This inhibition was characterized by the down-regulation of MMP-9, which was transcriptionally regulated at NF-kappaB and activation protein-1 (AP-1) sites in the MMP-9 promoter. These findings suggest that the Neu3 gene represents a physiological modulator of VSMC responses that may contribute to plaque instability in atherosclerosis.

Activating Transcription Factor 2 Mediates Matrix Metalloproteinase-2 Transcriptional Activation Induced by p38 in Breast Epithelial Cells

Mounting evidence suggests a role for matrix metalloproteinase (MMP)-2 in the malignant progression of breast cancer cells. We showed previously that H-Ras, but not N-Ras, induced invasion of MCF10A human breast epithelial cells through Rac-MKK3/6-p38 pathway resulted in MMP-2 up-regulation. Activation of p38 pathway by MKK6 caused a selective up-regulation of MMP-2. In this study, we aimed to elucidate the transcriptional regulation of MMP-2 by p38 pathway leading to the invasive phenotype of MCF10A cells. By using 5' deletion mutant constructs of MMP-2 promoter, we showed that deletion of the region containing activator protein-1 (AP-1) site caused the greatest reduction of MMP-2 promoter activity both in MKK6- and H-Ras-activated MCF10A cells, suggesting that the AP-1 binding site is critical for the MMP-2 promoter activation. DNA binding and transcriptional activities of AP-1 were increased by MKK6 or H-Ras as evidenced by electrophoretic mobility shift assay and luciferase assay using an AP-1-driven plasmid. By doing immunoinhibition assay and chromatin immunoprecipitation assay, we revealed the activating transcription factor (ATF) 2 as a transcription factor for MMP-2 gene expression through binding to the functional AP-1 site. Activation of ATF2, which depended on p38 activity, was crucial for MMP-2 promoter activity as well as induction of invasive and migrative phenotypes in MCF10A cells. This is the first report revealing ATF2 as an essential transcription factor linking MKK3/6-p38 signaling pathway to MMP-2 up-regulation, providing evidence for a direct role of ATF2 activation in malignant phenotypic changes of human breast epithelial cells.

Wild-type p53 inhibits nuclear factor-kappaB-induced matrix metalloproteinase-9 promoter activation: implications for soft tissue sarcoma growth and metastasis

Human soft tissue sarcoma (STS) is a highly lethal malignancy in which control of metastasis determines survival. Little is known about the molecular determinants of STS dissemination. Here, we show that human STS express high levels of matrix metalloproteinase-9 (MMP-9) and that MMP-9 expression levels correlate with sequence analysis-defined p53 mutational status. Reintroduction of wild-type p53 (wtp53) into mutant p53 STS cell lines decreased MMP-9 mRNA and protein levels, decreased zymography-assessed MMP-9 proteolytic activity, and decreased tumor cell invasiveness. Reintroduction of wtp53 into STS xenografts decreased tumor growth and MMP-9 protein expression. Luciferase reporter studies showed that reintroduction of wtp53 into mutant p53 STS cells decreased MMP-9 promoter activity. Deletion constructs of the MMP-9 promoter identified a region containing a p53-responsive element that lacked a p53 consensus binding site but did contain a nuclear factor-kappaB (NF-kappaB) site. Mutating this NF-kappaB binding site eliminated the wtp53-repressive effect. Electrophoretic mobility shift assays confirmed decreased NF-kappaB binding in STS cells in the presence of wtp53. Our findings suggest a role for MMP-9 in STS progression and expand the role of p53 in molecular control of STS growth and metastasis. Therapeutic interventions in human STS targeting MMP-9 activity directly or via reintroduction of wtp53 merit further investigation.

Mechanisms underlying TGF-beta1-induced expression of VEGF and Flk-1 in mouse macrophages and their implications for angiogenesis

TGF-beta induces vascular endothelial growth factor (VEGF), a potent angiogenic factor, at the transcriptional and protein levels in mouse macrophages. VEGF secretion in response to TGF-beta1 is enhanced by hypoxia and by overexpression of Smad3/4 and hypoxia-inducible factor-1alpha/beta (HIF-1alpha/beta). To examine the transcriptional regulation of VEGF by TGF-beta1, we constructed mouse reporters driven by the VEGF promoter. Overexpression of HIF-1alpha/beta or Smad3/4 caused a slight increase of VEGF promoter activity in the presence of TGF-beta1, whereas cotransfection of HIF-1alpha/beta and Smad3/4 had a marked effect. Smad2 was without effect on this promoter activity, whereas Smad7 markedly reduced it. Analysis of mutant promoters revealed that the one putative HIF-1 and two Smad-binding elements were critical for TGF-beta1-induced VEGF promoter activity. The relevance of these elements was confirmed by chromatin immunoprecipitation assay. p300, which has histone acetyltransferase activity, augmented transcriptional activity in response to HIF-1alpha/beta and Smad3/4, and E1A, an inhibitor of p300, inhibited it. TGF-beta1 also increased the expression of fetal liver kinase-1 (Flk-1), a major VEGF receptor, and TGF-beta1 and VEGF stimulated pro-matrix metalloproteinase 9 (MMP-9) and active-MMP-9 expression, respectively. The results from the present study indicate that TGF-beta1 can activate mouse macrophages to express angiogenic mediators such as VEGF, MMP-9, and Flk-1.

H-Ras selectively up-regulates MMP-9 and COX-2 through activation of ERK1/2 and NF-kappaB: an implication for invasive phenotype in rat liver epithelial cells

One of the most frequent events in carcinogenesis is uncontrolled activation of Ras signaling pathway. A previous study demonstrated that the introduction of H-Ras into the normal WB-F344 rat liver epithelial (WB) cell line and adult male F344 rats resulted in tumorigenicity. The present study investigated whether H-Ras induced the invasive and migrative phenotypes in WB cells, and subsequently aimed at characterizing the underlying mechanisms. H-Ras induced the invasive and migrative phenotypes of WB cells with a selective up-regulation of matrix metalloproteinase (MMP)-9, but not MMP-2. Cyclooxygenase (COX)-2 and the subsequent production of prostaglandin E2 (PGE2) were also induced by H-Ras. Treatment of H-Ras WB cells with GM6001 and NS398, the inhibitors of MMPs and COX-2, respectively, significantly inhibited the H-Ras-induced invasive and migrative phenotypes. DNA binding activity of nuclear factor (NF)-kappaB, but not that of activator protein (AP)-1, was increased by H-Ras. Caffeic acid phenethyl ester and Bay 11-7082, specific inhibitors of NF-kappaB and IKK, respectively, significantly inhibited the expression of MMP-9 and COX-2, invasion and migration of H-Ras WB cells, revealing NF-kappaB as a transcriptional factor responsible for H-Ras-induced malignant phenotypic conversion of WB cells. Activation of ERKs pathway was critical for H-Ras-induced invasive and migrative phenotypes, up-regulation of MMP-9 and COX-2 as well as enhanced DNA binding activity of NF-kappaB in WB cells. Taken together, these results demonstrate that H-Ras up-regulates MMP-9 and COX-2 through activation of ERKs and IKK-IkappaBalpha-NF-kappaB signal pathway which may contribute to the malignant progression of WB rat liver epithelial cells.

Expression Cloning Identifies Transgelin (SM22) as a Novel Repressor of 92-kDa Type IV Collagenase (MMP-9) Expression

The 92-kDa gelatinase (MMP-9) expression is prerequisite for tissue remodeling in physiology and cancer. However, there are few known regulators of MMP-9 expression. Using an expression cloning strategy, we identified transgelin (SM22), a 22-25-kDa actin-binding protein localized to the cell membrane and cytoplasm, as a novel regulator of MMP-9 expression. Overexpression of a SM22 cDNA in HT1080 cells decreased MMP-9 mRNA/protein levels and diminished in vitro invasion of the latter rescued with exogenous MMP-9. Conversely, small interfering RNA-mediated knockdown of SM22 elevated MMP-9 synthesis, and uterus from SM22-null mice showed strong MMP-9 immunoreactivity compared with wild type animals. The ability of SM22 to repress MMP-9 expression required an intact amino terminus calponin homology domain. MMP-9 expression is driven by ERK signaling and SM22 targeted this pathway as evidenced by (a) the transience in MAPK activation and (b) blunted stimulation of the MMP-9 promoter by a constitutively active MEK expression vector. Progressive deletion analysis located the SM22 responsive region of the MMP-9 promoter to the proximal 90-bp region harboring an AP-1 motif subsequently implicated by site-directed mutagenesis. Furthermore, nuclear extract from the SM22 transfectants showed diminished c-Fos binding to this motif and SM22 expression reduced the activity of an AP-1-driven reporter by 75%. Thus, SM22 adds to a short list of repressors of MMP-9 expression, achieving this by reducing AP-1-dependent trans-activation of the gene by way of compromised ERK activation. Diminished transgelin expression in several cancers may thus partly account for the elevated MMP-9 expression evident in these tumors.

Effects of hormone replacement therapy type and route of administration on plasma matrix metalloproteinases and their tissue inhibitors in postmenopausal women

BACKGROUND

Matrix metalloproteinases (MMPs) are implicated in numerous disease states including cardiovascular disease and cancer. Because recent studies have shown a detrimental effect of hormone replacement therapy on cardiovascular disease and breast cancer, we investigated whether there are any differences in the concentrations of MMPs and their tissue inhibitors (TIMPs) in women receiving various forms of postmenopausal therapy.

MATERIAL AND METHODS

A total of 195 healthy postmenopausal women were assessed: 46 were taking tibolone, 47 were taking transdermal estradiol, 46 were taking conjugated equine estrogens (CEE), and 56 were not taking any menopausal therapy (CTR). Plasma levels of MMP-2 and -9 and TIMP-1 and TIMP-2 were measured by ELISA methods.

RESULTS

MMP-9 levels were significantly higher in the CEE group in comparison with healthy women not receiving menopausal therapy (P < 0.05). In contrast, MMP-9 levels in the tibolone group were significantly lower than in any other group (P < 0.01, compared with transdermal estradiol and CTR, and P < 0.001, compared with CEE). MMP-9 to TIMP-1 ratio was also significantly higher in the CEE, compared with CTR (P < 0.05), and lower in the tibolone group (P < 0.01, compared with all groups). MMP-2 levels were higher in the CEE group, compared with healthy women not receiving any menopausal therapy, and women taking tibolone (P < 0.05).

CONCLUSIONS

Our study demonstrates differential effects of various forms of postmenopausal therapy on serum levels of MMP-9 and MMP-2. It remains to be established whether these differences might be associated with differences in risks of cardiovascular disease and cancer in these women.

Differential functions of Ras for malignant phenotypic conversion

Among the effector molecules connected with the group of cell surface receptors, Ras proteins have essential roles in transducing extracellular signals to diverse intracellular events, by controlling the activities of multiple signaling pathways. For over 20 years since the discovery of Ras proteins, an enormous amount of knowledge has been accumulated as to how the proteins function in overlapping or distinct fashions. The signaling networks they regulate are very complex due to their multiple functions and cross-talks. Much attention has been paid to the pathological role of Ras in tumorigenesis. In particular, human tumors very frequently express Ras proteins constitutively activated by point mutations. Up to date, three members of the Ras family have been identified, namely H-Ras, K-Ras (A and B), and N-Ras. Although these Ras isoforms function in similar ways, many evidences also support the distinct molecular function of each Ras protein. This review summarizes differential functions of Ras and highlights the current view of the distinct signaling network regulated by each Ras for its contribution to the malignant phenotypic conversion of breast epithelial cells. Four issues are addressed in this review: (1) Ras proteins, (2) membrane localization of Ras, (3) effector molecules downstream of Ras, (4) Ras signaling in invasion. In spite of the accumulation of information on the differential functions of Ras, much more remains to be elucidated to understand the Ras-mediated molecular events of malignant phenotypic conversion of cells in a greater detail.

Src oncogene activates MMP-2 expression via the ERK/Sp1 pathway

Previous studies demonstrated that activation of Src oncogene increased matrix metalloproteinase-2 (MMP-2) expression in various types of cells. In this study, we elucidated the underlying mechanism of Src-induced MMP-2. We first used murine fibroblast cell line C3H10T1/2 and its v-Src transfectant IV5 to address this issue. RT-PCR and promoter activity assay indicated that Src stimulated MMP-2 via transcriptional activation. Transfection of constitutively active Src into C3H10T1/2 cells also stimulated MMP-2 mRNA expression. Deletion and mutation analysis indicated that the Sp1 site located within the -91/-84 region of human MMP-2 promoter is the major responsive element for Src. Electrophoresis mobility shift assays showed that Src enhanced the binding of Sp1 to this consensus site to stimulate MMP-2 gene expression. We next investigated the signaling pathway that mediated the effect of Src on MMP-2. Our data showed that extracellular signal-regulated kinase (ERK) pathway inhibitor PD98059, but not the c-Jun N-terminal kinase (JNK) inhibitor SP600125, p38 kinase inhibitor SB203580, and PI3K inhibitor wortmannin, attenuated Src-induced MMP-2 promoter activity. These inhibitors did not show significant effect on basal MMP-2 promoter activity in C3H10T1/2 cells. In addition, the dominant negative mutant of ERK-2 suppressed the activation of MMP-2 by Src. Treatment of PD98059 or an Src specific inhibitor PP1 reduced Sp1 DNA binding activity in IV5 cells. Taken together, our results strongly suggest that Src induces MMP-2 expression via transcription activation and the ERK/Sp1 signaling pathway is involved in this process.

Hirsutenone inhibits phorbol ester-induced upregulation of COX-2 and MMP-9 in cultured human mammary epithelial cells: NF-kappaB as a potential molecular target

Inappropriate upregulation of cyclooxygenase-2 (COX-2) and matrix metalloproteinases (MMPs) has been implicated in the pathogenesis of various types of cancer. In the present study, we investigated the effects of hirsutenone, a diarylheptanoid isolated from the medicinal plant Alnus hirsuta var. sibirica, on the expression of COX-2 and MMP-9 induced by the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) in MCF10A human breast epithelial cells. Treatment of MCF10A cells with TPA led to the expression of COX-2 and MMP-9. Hirsutenone at 12 microM inhibited the TPA-induced COX-2 expression at both the transcriptional and posttranscriptional levels. Hirsutenone also suppressed the synthesis of prostaglandin E(2), one of the major products of COX-2, and its catalytic activity. The upregulation of MMP-9 by TPA was also significantly reduced by hirsutenone. Likewise, hirsutenone attenuated the invasiveness and motility of MCF10A cells stimulated with TPA. Hirsutenone blocked the TPA-induced DNA binding of nuclear factor kappa B (NF-kappaB) and translocation of p65, the functionally active NF-kappaB subunit, to the nucleus. The luciferase reporter gene assay revealed that hirsutenone abrogated the transcriptional activity of NF-kappaB. Treatment of MCF10A cells with N-alpha-Tosyl-l-phenylalanine chloromethyl ketone, a specific inhibitor of NF-kappaB, reduced the TPA-induced expression of COX-2 and MMP-9. In summary, hirsutenone inhibits the TPA-induced upregulation of COX-2 and MMP-9 in human breast epithelial cells, possibly by targeting NF-kappaB, which may contribute to its chemopreventive effects.

Transcriptional induction of matrix metalloproteinase-9 in the chondrocyte and synoviocyte cells is regulated via a novel mechanism: evidence for functional cooperation between serum amyloid A-activating factor-1 and AP-1

Increased expression of matrix metalloproteinase-9 (MMP-9) by IL-1beta and TNF-alpha is regarded as a key factor in the degradation of cartilage during arthritis. However, the underlying molecular mechanism of this induction process especially in the cells of the joint capsule remains elusive. Chondrocytes and synoviocytes, the resident cells of joint capsule, markedly increase transcription of MMP-9 in response to IL-1beta- and TNF-alpha-mediated stimulation. Using progressively deleted and mutant promoter constructs of MMP-9, we show that serum amyloid A-activating factor (SAF)-1, a novel transcription factor, and the AP-1 family of proteins cooperatively regulate cytokine-mediated induction of MMP-9 in the resident cells of the joint capsule. In the MMP-9 promoter, SAF-1 and AP-1 DNA-binding elements are present in close proximity with only 14 nucleotides apart. SAF-1 DNA-binding activity is increased in both cytokine-stimulated cells as well as in osteoarthritic cartilage tissues. Although overexpression of SAF-1 could increase expression of the MMP-9 promoter and endogenous MMP-9 gelatinolytic activity, for maximal induction of MMP-9 gene concurrent participation of SAF-1 and AP-1 is required. Mutation of either one of these two elements resulted in a severe reduction in cytokine responsiveness of MMP-9 promoter and compromised the transactivation potential of both SAF-1 and AP-1. Simultaneous requirement for two distinct DNA-binding elements suggests that SAF-1 and AP-1 function in a mutually beneficial manner acting as essential coactivators to drive cytokine-mediated transcriptional activation of MMP-9.

Ascochlorin inhibits matrix metalloproteinase-9 expression by suppressing activator protein-1-mediated gene expression through the ERK1/2 signaling pathway: inhibitory effects of ascochlorin on the invasion of renal carcinoma cells

The expression of matrix metalloproteinases (MMPs) has been implicated in the invasion and metastasis of cancer cells. Here we examined the effect of ascochlorin, a prenyl-phenol anti-tumor compound from the fungus Ascochyta viciae, on the regulation of signaling pathways that control MMP-9 expression in human renal carcinoma (Caki-1) cells. Ascochlorin reduced the invasive activity of Caki-1 cells and inhibited phorbol 12-myristate 13-acetate-induced increases in MMP-9 expression and activity in a dose-dependent manner. Reporter gene, electrophoretic mobility shift, kinase inhibitor assays, and in vitro kinase assay showed that ascochlorin inhibits MMP-9 gene expression by suppressing activation of the nuclear transcription factor activator protein-1 (AP-1) via the extracellular signal-regulated kinase 1 and 2 pathway. The AP-1 family member most specifically affected by ascochlorin was Fra-1. Ascochlorin did not affect the activation of the c-Jun N-terminal or p38 kinase pathways. Moreover, transfection of Caki-1 cells with AP-1 decoy oligodeoxynucleotides resulted in the suppression of phorbol 12-myristate 13-acetate-induced MMP-9 expression and invasion. In conclusion, ascochlorin represents a unique natural anti-tumor compound that specifically inhibits MMP-9 activity through suppression of AP-1-dependent induction of MMP-9 gene expression.

TNFalpha-mediated extracellular matrix remodeling is required for multiple division cycles in rat hepatocytes

During liver regeneration, hepatocytes proliferate under the control of both proinflammatory cytokines such as tumor necrosis factor alpha (TNFalpha) and growth factors, in parallel to extracellular matrix remodeling. This study investigated mechanisms by which mitogen and extracellular matrix signals are linked for inducing proliferation of differentiated hepatocytes. The authors used adult rat hepatocytes in coculture with liver biliary cells, because cells are stably differentiated for several weeks, capable of extracellular matrix deposition, and unable to divide in response to growth factor alone. This work demonstrated that hepatocytes could undergo several proliferation waves without loss of differentiation by using alternating periods of TNFalpha/growth factor stimulation and deprivation. Three days after stimulation with TNFalpha and epidermal growth factor (EGF), up to 35% of hepatocytes divided. Demonstration was also provided that EGF alone only promoted cell progression up to late G(1), whereas TNFalpha was necessary for G(1)/S transition and Cdk1 induction. TNFalpha promoted an extracellular matrix (ECM) degradation that involved the matrix metalloproteinase MMP-9 induction through activation of NF-kappaB pathway. Finally, the authors showed that ECM remodeling signal was required for initiating any new hepatocyte division wave, in presence of mitogen. In conclusion, these results highlight that hepatocyte division is dependent on ECM deposition associated with differentiation status, and that ECM degradation signal is critical in controlling G(1)/S transition and Cdk1 induction. These results provide new insights for understanding the unique hepatocyte proliferation control and improving regeneration in patients suffering from liver damage.

22-Oxa-1alpha,25-dihydroxyvitamin D3 inhibits metastasis and angiogenesis in lung cancer

1alpha,25-Dihydroxyvitamin D(3) (1alpha,25-D(3)) has potent antiproliferative and anti-invasive properties in vitro in cancer cells. However, its calcemic effect in vivo limits its therapeutic applications. Here, we report the efficacy of 22-oxa-1alpha,25-dihydroxyvitamin D(3) (22-oxa-1alpha,25-D(3)), a low calcemic analog of vitamin D, against the development of metastatic lung carcinoma after an intravenous injection of green fluorescent protein-transfected Lewis lung carcinoma (LLC-GFP) cells in C57BL/6 mice. The mice injected with tumor cells were implanted simultaneously with osmotic minipumps containing either 1alpha,25-D(3), 22-oxa-1alpha,25-D(3) or vehicle. The 1alpha,25-D(3) treatment group had been hypercalcemic, but the 22-oxa-1alpha,25-D(3) and vehicle treatment groups remained normocalcemic for the duration of the experiment. The total number of lung metastases, lung weight and the expression of GFP mRNA in the lung were markedly decreased in 1alpha,25-D(3) and 22-oxa-1alpha,25-D(3)-treated mice. In the in vitro experiment, 1alpha,25-D(3) and 22-oxa-1alpha,25-D(3) reduced the expression of matrix metalloproteinase (MMP)-2, MMP-9, vascular endothelial growth factor and parathyroid hormone-related protein in LLC-GFP cells. Furthermore, in the angiogenesis assay, the number of tumor cells or basic fibroblast growth factor-induced angiogenesis was reduced in 1alpha,25-D(3) and 22-oxa-1alpha,25-D(3)-treated mice. Moreover, using a new experimental model of vitamin D receptor (VDR) null mutant (VDR(-/-)) mice with corrected hypocalcemia and hypervitaminosis D, we examine the anti-cancer effect of 22-oxa-1alpha,25-D(3) without other functions induced by 22-oxa-1alpha,25-D(3) in the host. In the VDR(-/-) mice, 22-oxa-1alpha,25-D(3) directly inhibited the metastatic activity of LLC-GFP cells in a dose-dependent manner without exerting a direct influence on the calcemic activity or other actions regulated by 22-oxa-1alpha,25-D(3) in the host. These results indicate that the inhibition of metastasis and angiogenesis-inducing activity in cancer cells seemed to be a major mechanism responsible for the anti-cancer effects of 22-oxa-1alpha,25-D(3). Our findings show that 22-oxa-1alpha,25-D(3) is beneficial for the prevention of metastasis in lung carcinoma.

Leptomycin B Reduces Matrix Metalloproteinase-9 Expression and Suppresses Cutaneous Inflammation

Matrix metalloproteinase-9 (MMP-9), a type of gelatinase, plays many roles in tissue metabolism, especially in inflammation, and many regulatory elements have been reported in the promoter region of its encoding gene. Leptomycin B, which regulates the nucleo-cytoplasmic trafficking of proteins, including transcription-factor-related ones, has the potential to exert important biological effects. The addition of leptomycin B to keratinocytes in culture had no effect on matrix metalloproteinase-2 (another gelatinase) but caused the selective down-regulation of MMP-9 during the stimulation of differentiation with high Ca(2+) or transforming growth factor-beta, as well as during the stimulation of inflammation by tumor necrosis factor-alpha or interleukin-1alpha. This down-regulation depended on multiple regulatory elements in the promoter of MMP-9 including KRE-M9 (which we have recently identified), and a classical 12-o-tetradecanoyl-phorbol-13-acetate-responsive element. The topical application of leptomycin B to murine skin also effectively suppressed inflammation, including MMP-9 expression, after ultraviolet B irradiation. These results suggest that the application of leptomycin B and/or its derivatives could be useful for treating many inflammatory conditions.

Dipyridamole selectively inhibits inflammatory gene expression in platelet-monocyte aggregates

BACKGROUND

Drugs that simultaneously decrease platelet function and inflammation may improve the treatment of cardiovascular disorders. Here, we determined whether dipyridamole and aspirin, a combination therapy used to prevent recurrent stroke, regulates gene expression in platelet-monocyte inflammatory model systems.

METHODS AND RESULTS

Human platelets and monocytes were pretreated with dipyridamole, aspirin, or both inhibitors. The cells were stimulated with thrombin or activated by adhesion to collagen, and gene expression was measured in the target monocytes. Thrombin-stimulated platelets increased monocyte chemotactic protein-1 (MCP-1) expression by monocytes. Dipyridamole but not aspirin attenuated nuclear translocation of NF-kappaB and blocked the synthesis of MCP-1 at the transcriptional level. Dipyridamole delayed maximal synthesis of interleukin-8 but did not alter cyclooxygenase-2 accumulation. Adherence to collagen and platelets also increased the expression of matrix metalloproteinase-9 (MMP-9) in monocytes, a response that was inhibited by dipyridamole. In this case, however, dipyridamole did not block transcription or distribution of MMP-9 mRNA to actively translating polysomes, indicating that it regulates the expression of MMP-9 protein at a postinitiation stage of translation. Dipyridamole also blocked MCP-1 and MMP-9 generated by lipopolysaccharide-treated monocytes, indicating that at least part of its inhibitory action is unrelated to its antiplatelet properties.

CONCLUSIONS

These results indicate that dipyridamole has selective antiinflammatory properties that may contribute to its actions in the secondary prevention of stroke.

The role of Osteopontin in tumor metastasis

Osteopontin (OPN) is a glyco-phosphoprotein that is expressed and secreted by numerous human cancers. OPN functions in cell adhesion, chemotaxis, macrophage-directed interleukin-10 (IL-10) suppression, stress-dependent angiogenesis, prevention of apoptosis, and anchorage-independent growth of tumor cells by regulating cell-matrix interactions and cellular signaling through binding with integrin and CD44 receptors. While constitutive expression of OPN exists in several cell types, induced expression has been detected in T-lymphocytes, epidermal cells, bone cells, macrophages, and tumor cells in remodeling processes such as inflammation, ischemia-reperfusion, bone resorption, and tumor progression. Recently, substantial evidence has linked OPN with the regulation of metastatic spread by tumor cells. However, the molecular mechanisms that define the role of OPN in tumor metastasis are incompletely understood. Transcriptional regulators that contribute to the induction of OPN expression have received significant attention as potential modulators of the OPN-mediated metastatic phenotype. The following review will discuss the molecular structure of OPN, the evidence for its functional role in tumor cell metastasis, the downstream signals that activate invasive mechanisms, and the recent reports concerning regulation of OPN transcription.

CEACAM6 is a determinant of pancreatic adenocarcinoma cellular invasiveness

Pancreatic adenocarcinoma is among the most aggressively invasive malignancies. The immunoglobulin superfamily member carcinoembryonic antigen-related cell adhesion molecule 6 (CEACAM6) is emerging as an important determinant of the malignant phenotype in a range of cancers. We sought to define the role of CEACAM6 in pancreatic adenocarcinoma cellular invasiveness. CEACAM6 was stably overexpressed in Capan2 cells, which inherently express low levels of CEACAM6. Retrovirally mediated RNA interference was used to silence CEACAM6 expression in BxPC3 cells, which inherently overexpress CEACAM6. Cellular invasiveness was quantified using a modified Boyden chamber assay. Overexpression of CEACAM6 increased Capan2 cellular invasiveness, whereas CEACAM6 knockdown attenuated BxPC3 invasiveness. A role for the c-Src tyrosine kinase in mediating CEACAM6-dependent invasiveness was defined using constitutively active and dominant-negative c-Src expression constructs. c-Src-dependent modulation of matrix metalloproteinase-9 activity contributes significantly to the increased cellular invasiveness induced by CEACAM6 overexpression. Levels of CEACAM6 expression can modulate pancreatic adenocarcinoma cellular invasiveness in a c-Src-dependent manner. This pathway warrants further investigation as a target for therapy.

Combination of an SRC kinase inhibitor with a novel pharmacological antagonist of the urokinase receptor diminishes in vitro colon cancer invasiveness

PURPOSE

The urokinase-type plasminogen activator receptor (u-PAR) contributes to colon cancer invasion and metastases. We have shown previously that u-PAR expression in colon cancer is driven by the Src tyrosine kinase. In the current study, we determined the ability of PP2 (4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine), a Src kinase inhibitor, to reduce u-PAR expression and colon cancer invasion.

EXPERIMENTAL DESIGN

Western blotting, Northern blotting, and u-PAR promoter-reporter assays were performed to determine whether PP2 represses u-PAR expression. In vitro invasion assays were used to determine whether this kinase inhibitor, with or without a novel u-PAR antagonist, diminished cultured colon cancer invasiveness.

RESULTS

A constitutively active c-Src increased in vitro invasiveness of SW480 cells, whereas HT-29 cells expressing antisense c-Src showed diminished invasiveness, validating c-Src as a target for low molecular weight compound(s). The Src inhibitor PP2 reduced u-PAR transcription in HT-29 cells over the concentration range that blocked Src kinase activity. PP2 also reduced u-PAR protein amounts in three other colon cancer cell lines with modest to high constitutive Src activity. Treatment of HT-29 cells and 2C8 cells (a SW480 clone expressing a constitutively active Src) with PP2 diminished their in vitro invasiveness. Furthermore, combination of the Src inhibitor with a novel u-PAR peptide antagonist (NI-5.12) proved superior to the individual agents in suppressing invasiveness.

CONCLUSIONS

A c-Src kinase inhibitor represses u-PAR expression and, alone or in combination with a u-PAR antagonist, diminishes colon cancer invasiveness. Thus, concurrent targeting of c-Src expression and pharmacological blockade of the u-PAR may represent a novel means of controlling colon cancer spread.

Induction of myofibroblast MMP-9 transcription in three-dimensional collagen I gel cultures: regulation by NF-kappaB, AP-1 and Sp1

Chronic liver injury leads to a progressive wound healing response that eventually results in hepatic fibrosis characterised by net deposition of fibrillar extracellular matrix (ECM) and a qualitative shift from type IV to type I/III collagen. The pivotal cellular event underlying this response is hepatic stellate cell (HSC) activation towards a myofibroblast-like phenotype. Activated HSC contribute to ECM remodelling via secretion of type I/III collagens and matrix metalloproteinases (MMPs). Previous studies showed that three-dimensional (3D) contact of activated HSC with type I collagen further stimulates the ECM remodelling properties of HSC by inducing the type IV gelatinase, MMP-9. The aim of the current study was to confirm transcriptional activation of the MMP-9 gene and identify transcription factors regulating this response. Gelatin zymography and Northern blotting were used to confirm induction of MMP-9 protein and mRNA expression in primary rat HSC cultured in a three-dimensional collagen I gel lattice. MMP-9 promoter studies in transfected HSC and electrophoretic mobility shift assay (EMSA) were employed to study transcriptional events. Both NF-kappaB and AP-1 DNA were induced in HSC cultured in 3D collagen I gels and binding sites for these factors in the MMP-9 promoter were crucial for induction of transcription. By contrast removal of an Sp1 site in the promoter enhanced transcription, while over-expression of either Sp1 or Sp3 repressed transcription. It is concluded that 3D contact of activated HSC with collagen I stimulates MMP-9 expression by elevating NF-kappaB and AP-1 activities which are able to overcome the repressive influence of Sp1/Sp3 on MMP-9 gene transcription.

Age-related changes in matrix metalloproteinase-9 regulation in cultured mouse aortic smooth muscle cells

We previously reported that aortic smooth muscle cells (SMC) from aged mice have an age-related decline in proliferative capacity compared with those derived from young mice. Here we investigated matrix metalloproteinase-9 (MMP-9) regulation in both young and aged SMC. Zymography, immunoblot, and northern blot analysis showed that MMP-9 expression is significantly reduced in response to tumor necrosis factor-alpha stimulation with increasing in vitro age. Mutational analysis, gel shift assays and supershift assays demonstrated that the lower MMP-9 expression in aged SMC is associated with lower activities of NF-kappaB and AP-1. Since mitogen-activated protein kinase ERK1/2 induce MMP-9 expression, we examined whether U0126, an ERK1/2 inhibitor, influenced MMP-9 expression in aged SMC. Treatment with U0126 successfully inhibited MMP-9 expression in both young and aged SMC. Finally, to analyze the causal relationship between replicative senescence and MMP-9 expression, we stably overexpressed the MMP-9 gene in aged SMC and we showed no alteration of the proliferative capacity of the transduced cells. Taken together, these results suggest that down-regulation of MMP-9 expression in SMC may play a role in vascular remodeling during in vitro aging.

Resveratrol inhibits phorbol myristate acetate-induced matrix metalloproteinase-9 expression by inhibiting JNK and PKC delta signal transduction

Proteolytic degradation of the extracellular matrix and tumor metastasis correlate with the expression of endopeptidases known as matrix metalloproteinases (MMPs). The expression of MMPs is regulated by cytokines and signal transduction pathways, including those activated by phorbol myristate acetate (PMA). We found that resveratrol, a phytoalexin present in grapes, significantly inhibits the PMA-induced increase in MMP-9 expression and activity. These effects of resveratrol are dose dependent and correlate with the suppression of MMP-9 mRNA expression levels. PMA caused about a 23-fold increase in MMP-9 promoter activity, which was suppressed by resveratrol. Transient transfection utilizing MMP-9 constructs, in which specific transcriptional factors were mutagenized, indicated that the effects of PMA and resveratrol were mediated via an activator protein-1 and nuclear factor-kappaB response element. Resveratrol inhibited PMA-mediated activation of c-Jun N-terminal kinase (JNK) and protein kinase C (PKC)-delta activation. Therefore, we conclude that the MMP-9 inhibition activity of resveratrol and its inhibition of JNK and PKC-delta may have a therapeutic potential, given that a novel means of controlling growth and invasiveness of tumors.

Ets-1 regulates TNF-alpha-induced matrix metalloproteinase-9 and tenascin expression in primary bronchial fibroblasts

Increased subepithelial deposition of extracellular matrix proteins is a key feature in bronchial asthma. Matrix metalloproteinase-9 (MMP-9) is a proteolytic enzyme that degrades the extracellular matrix. Tenascin is an extracellular matrix glycoprotein that is abundant in thickened asthmatic subbasement membrane. The expression of MMP-9 and tenascin reflects disease activity in asthma and airway remodeling. The molecular mechanisms regulating the expression of these proteins remain unknown. Both MMP-9 and tenascin promoters contain an Ets binding site, suggesting control by Ets-1. Thus, we hypothesized that Ets-1 expression is increased in asthma and that it contributed to enhanced MMP-9 and tenascin expression. To test this hypothesis, we determined the expression of Ets-1 in bronchial biopsies obtained from asthmatic subjects and determined the expression of Ets-1, MMP-9, and tenascin by bronchial fibroblasts activated ex vivo. We observed that nuclear extracts from TNF-alpha-activated fibroblasts showed increased Ets-binding activity. In addition, TNF-alpha-activated fibroblasts had increased expression of Ets-1 mRNA and protein, which preceded an increase in MMP-9 and tenascin mRNA. Furthermore, treatment of fibroblasts with Ets-1 antisense oligonucleotides down-regulated TNF-alpha-induced Ets-1, MMP-9, and, to a lesser extent, tenascin protein expression or activity. Taken together, these data demonstrate that TNF-alpha increases MMP-9 and tenascin expression in bronchial fibroblasts via the transcription factor Ets-1, and suggest a role for Ets-1 in airway remodeling in asthma.

PTEN induces G1 cell cycle arrest and inhibits MMP-9 expression via the regulation of NF-kappaB and AP-1 in vascular smooth muscle cells

The tumor suppressor PTEN is one of the most commonly inactivated genes in human cancer. PTEN, an inositol phosphatase specific for the products of PI 3-kinase, is known to inhibit PDGF-mediated vascular smooth muscle cell (VSMC) proliferation and migration. However, little is known about the molecular mechanisms by which this tumor suppressor regulates cell growth and migration in VSMC. Here, we show that PTEN expression has the potent inhibitory effect on DNA synthesis of cultured VSMC in the presence of PDGF. The growth suppression of PTEN was mediated by its ability to block cell cycle progression in the G1 phase. Such an arrest correlated with down-regulation of cyclins and CDKs and up-regulation of the CDK inhibitor p21 and p27 expression, whereas up-regulation of p53 by PTEN expression was not observed. Expression of PTEN also led to the inhibition of TNF-alpha-induced matrix metalloproteinase-9 (MMP-9) expression in VSMC as determined by zymography and immunoblot. Furthermore, PTEN expression strongly decreased MMP-9 promoter activity in response to TNF-alpha. This inhibition was characterized by down-regulation of MMP-9, which was transcriptionally regulated at NF-kappaB and activation protein-1 (AP-1) sites in the MMP-9 promoter. These findings indicate the efficacy of PTEN in inhibiting cell proliferation, G1-S phase cell cycle progress, and MMP-9 expression through the transcription factors NF-kappaB and AP-1 in VSMC.

Matrix Metalloproteinase 9 Expression is Coordinately Modulated by the KRE-M9 and 12-O-Tetradecanoyl-Phorbol-13-Acetate Responsive Elements

To investigate the pathophysiologic role of matrix metalloproteinase 9 (MMP-9), we analyzed the mechanism of its transcriptional regulation in keratinocytes and in HT1080 fibrosarcoma cells in culture. The KRE-M9 element, which is located between the 12-O-tetradecanoyl-phorbol-13-acetate responsive element (TRE) and the transcription initiation site in the MMP-9 promoter, is essential for MMP-9 transcription in the absence of the TRE. The KRE-M9 binding protein, however, is shown to be a repressor of transcription rather than an activator; we found several times higher transcriptional activity when the KRE-M9 element was mutated. In contrast, activator protein 1 proteins (AP-1) are shown to activate transcription of MMP-9 by binding to the TRE, which is located adjacent to the KRE-M9 element. Moreover, we found that the KRE-M9 binding protein could serve as a differentiation repressing factor 1 (DRF-1) as shown by the decrease in levels of this protein with differentiation. In addition, the TRE binding protein is able to bind to the KRE-M9 to some extent. These results indicate that the coordinated modulation of MMP-9 transcription via the TRE and the KRE-M9 elements is important in epidermal and mesenchymal tissues. Our findings could facilitate consideration of the molecular mechanism in a variety of pathophysiologic conditions with which MMP-9 is involved.

ERK1/2 mediates TNF-?-induced matrix metalloproteinase-9 expression in human vascular smooth muscle cells via the regulation of NF-?B and AP-1: Involvement of the ras dependent pathway

The expression of matrix metalloproteinase-9 (MMP-9) has been implicated in progression of atherosclerotic lesions. The role and importance of the signaling pathway in the transcriptional regulation of MMP-9 in human aortic smooth muscle cells (HASMC) was examined. Tumor necrosis factor-alpha (TNF-alpha) stimulated the secretion of MMP-9 in HASMC, as shown by zymography and immunoblot analysis. At the transcriptional levels, TNF-alpha also stimulated the 5'-flanking 710-bp promoter activity of MMP-9. Transcription factors NF-kappaB binding site (-601) and AP-1 binding site (-82) were identified as the cis-elements for TNF-alpha activation, as determined by gel shift assay and mutation analysis. Treatment with U0126, an inhibitor of the extracellular signal-regulated kinase (ERK), significantly downregulated TNF-alpha-induced MMP-9 expression and promoter activity, whereas the inactive analog U0124 had no effect. Furthermore, the transactivation of TNF-alpha-stimulated NF-kappaB and AP-1 was inhibited by U0126 treatment. Finally, the transient transfection of HASMC with dominant negative Ras (RasN17) suppressed TNF-alpha-induced ERK activity, MMP-9 production, and promoter activity. Overexpression of RasN17 also abolished the TNF-alpha-stimulated NF-kappaB and AP-1 activity. In conclusion, the findings herein indicate the activation of the Ras/ERK pathway contributes to the induction of MMP-9 expression in HASMC. In addition, the transcription factors NF-kappaB and AP-1 that are involved in the Ras/ERK-mediated control of MMP-9 regulation on HASMC in response to TNF-alpha have now been identified.

In vitro cellular aging is associated with enhanced proliferative capacity, G1 cell cycle modulation, and matrix metalloproteinase-9 regulation in mouse aortic smooth muscle cells

Cellular and molecular events in young (passage 1-3) and aged (passage 25-30) primary mouse aortic smooth muscle cells (MASMC) were investigated. Immunoblot and immunofluorescence analyses indicated that smooth muscle alpha-actin (SM alpha-actin) levels were significantly reduced with increasing in vitro age. Aged MASMC showed an increased proliferative capacity in response to fetal bovine serum (FBS) in comparison with young MASMC. The cell cycle-associated proteins such as cyclin D1, cyclin E, CDK2, and CDK4, and kinase activities associated with CDK2 and CDK4 were increased in aged MASMC. In addition, CDK inhibitor p21 was elevated in aged cell, whereas p27 was decreased. These changes of G1 cell cycle machinery could be explained by the increased proliferative capacity. Matrix metalloproteinase-9 (MMP-9) expression was also increased in response to tumor necrosis factor-alpha (TNF-alpha) in aged MASMC, as evidenced by zymography and immunoblot analysis. Transient transfection assays showed an age-dependent increase in transcription from MMP-9 promoter activity in response to TNF-alpha. In addition, the transcription factors NF-kappaB and AP-1 that are involved in the MMP-9 regulation of aged MASMC in response to TNF-alpha were identified by means of mutation analysis and gel shift assays. These results suggest that the age-associated increase in SMC proliferative capacity, accumulative cell cycle regulators, and MMP-9 expression may play a role in vascular remodeling during in vitro aging.

DEP-induced fra-1 expression correlates with a distinct activation of AP-1-dependent gene transcription in the lung

Recent studies indicate a potential role for Fra-1, a heterodimeric partner of activator protein (AP)-1, in toxicant-induced epithelial injury, repair, and cellular transformation. Here we have investigated the effects of diesel exhaust particles (DEP) on fra-1 expression in C10 cells, a murine lung epithelial cell line. DEP markedly upregulated fra-1, but not fra-2, expression. The increase in fra-1 mRNA expression correlated well with its protein- and DNA-binding activity. DNA-binding assays also revealed a predominant presence of Jun-B and Jun-D in the AP-1 complex. Interestingly, DEP did not alter Jun-B and Jun-D protein levels. Transcriptional analysis revealed that fra-1 induction is regulated in part at the transcriptional level. The -379 to +32 bp 5'-flanking region mediated this induction. Furthermore, inhibitors of ERK1/2, JNK1, and p38 mitogen-activated protein kinases (MAPKs) significantly suppressed DEP-stimulated fra-1 transcription, suggesting their involvement in the induction process. Consistent with this finding, DEP stimulated phosphorylation of ERK1/2, JNK1, and p38 MAPKs with a distinct activation pattern. Overexpression of Fra-1 downregulated c-Jun and Nrf2 enhanced AP-1- and ARE-mediated reporter gene expression, respectively. In contrast, Fra-1 had the opposite effect on matrix metalloproteinase (MMP)-9 promoter activity. In particular, it bound to the functional AP-1 site of the MMP-9 promoter after DEP stimulation. Consistent with this result, DEP also markedly upregulated MMP-9 promoter activity. Collectively, these findings suggest that fra-1 induction by DEP may play a role in selectively regulating gene expression involved in alveolar epithelial cell injury and repair.

Pyrrolopyrimidine c-Src inhibitors reduce growth, adhesion, motility and invasion of prostate cancer cells in vitro

Two bona fide c-Src inhibitors, denominated CGP77675 and CGP76030, reduced in a time- and concentration-dependent manner (i) the proliferation of the PC3 prostate carcinoma cell line, as assessed by the [3H]-thymidine incorporation test, (ii) the capacity of PC3 cells to adhere and spread on Matrigel substrate, as determined by crystal violet staining, (iii) the ability of PC3 cells to migrate through a gelatine boundary and invade a Matrigel substrate. The latter effect was not due to a decrease of urokinase-type plasminogen activator (uPA), nor of metalloproteinase-2 (MMP-2) activities. The MMP-9 activity, along with the expression of the Tissue Inhibitor of Metalloproteinases (TIMP)-1 and TIMP-2, were reduced by the two inhibitors, consistent with the ability of c-Src to enhance MMP-9 and TIMP expression levels. Collectively, these data demonstrate that the pyrrolopyrimidine-derived c-Src inhibitors significantly reduced PC3 cell activities associated with their malignant phenotype.

Synergistic cooperation between the AP-1 and LEF-1 transcription factors in activation of the matrilysin promoter by the src oncogene: implications in cellular invasion

The matrix metalloprotease matrilysin is expressed in premalignant polyps and plays a key role in local invasion during the progression of digestive tumors. In the present work, we investigated the possible relationships between the activity of the mouse and human matrilysin promoters (Mp), endogenous matrilysin protein expression, and two early oncogenetic defects frequently observed in human colonic cancers, namely activation of the src oncogene and impairment of the Wnt/APC/beta-catenin pathway. Using transient transfection assays, we report here that src signaling and the HMG-box transcription factor LEF-1 act synergistically with the proximal (-61 to -67) AP-1 binding site to transactivate the Mp in premalignant and tumorigenic kidney and colonic epithelial cells, through beta-catenin- and axin-independent signaling pathways. This synergism involves the -109 and -194 Tcf/LEF-1 binding sites in the Mp and a physical interaction between LEF-1 and c-Jun. Furthermore, src coordinates accumulation of the c-Jun factor and matrilysin transcripts. Conversely, the c-Jun dominant negative mutant TAM67 and the src tyrosine kinase inhibitor M475271 impaired src-induced Mp activation, matrilysin protein accumulation, and invasion of type I collagen gels. This mechanism may thereby contribute to cellular invasion during the early-stage adenoma/adenocarcinoma conversion and the metastatic process of digestive tumors.

Sinusoidal obstruction syndrome (veno-occlusive disease) in the rat is prevented by matrix metalloproteinase inhibition

BACKGROUND & AIMS

The mechanical origins of the obstruction in sinusoidal obstruction syndrome are initiated by dehiscence of sinusoidal endothelial cells from the space of Disse. The biochemical changes that permit the dehiscence of the sinusoidal endothelial cells were investigated.

METHODS

In vitro and in vivo studies examined changes induced by monocrotaline, a pyrrolizidine alkaloid that induces sinusoidal obstruction syndrome in both humans and experimental animals.

RESULTS

In the monocrotaline-induced rat model of sinusoidal obstruction syndrome, there was an early increase of matrix metalloproteinase-9 and a later, lower-magnitude increase of matrix metalloproteinase-2 in the liver. In vitro studies of sinusoidal endothelial cells, hepatocytes, stellate cells, and Kupffer cells showed that sinusoidal endothelial cells are the major source of both basal and monocrotaline-induced matrix metalloproteinase-9/matrix metalloproteinase-2 activity. Monocrotaline caused depolymerization of F-actin in sinusoidal endothelial cells, and blocking of F-actin depolymerization prevented the increase in matrix metalloproteinase activity. Administration of matrix metalloproteinase inhibitors prevented the signs and histological changes associated with sinusoidal obstruction syndrome.

CONCLUSIONS

Monocrotaline causes depolymerization of F-actin in sinusoidal endothelial cells, which leads to increased expression of metalloproteinase-9 and matrix metalloproteinase-2 by sinusoidal endothelial cells. Inhibition of matrix metalloproteinase-9 and matrix metalloproteinase-2 prevents the development of sinusoidal obstruction syndrome, establishing that matrix metalloproteinase inhibitors may be a therapeutically viable strategy for prevention.

High glucose alters matrix metalloproteinase expression in two key vascular cells: potential impact on atherosclerosis in diabetes

Diabetes is a major risk factor for atherosclerosis. Hyperglycemia is an underlying contributing factor; however, the mechanisms that mediate the vascular complications are not yet fully understood. In the present study, we provide evidence that elevated glucose induces discordant matrix metalloproteinase (MMP) expression from two key vascular cells, endothelial cells and macrophages. Our results clearly indicate that high glucose (25 mM) induced endothelial cell expression and activity of the collagenase, MMP-1 and the gelatinase, MMP-2, whilst reducing expression of the stromelysin, MMP-3 (P<0.05). Similarly, our results show that high glucose (25 mM) induces expression and activity of MMP-9 from monocyte-derived macrophages (P<0.05). High glucose culture did not affect metalloproteinase inhibitor (TIMP-1) expression. Our results suggest for the first time that high glucose exposure induced discordant regulation of the MMP/TIMP system in vascular cells. The increased MMP-1, MMP-2 and MMP-9 activities induced by high glucose exposure could promote matrix degradation thereby accelerating atherogenesis and potentially reducing plaque stability in diabetes.

Tendon cells produce gelatinases in response to type I collagen attachment

Cells that carry out wound healing must be able to perform catabolic as well as anabolic functions. As the tendon is a tissue rich in extracellular matrix (ECM) proteins, we hypothesized that cells which participate in tendon healing should be able to produce proteases that would allow the remodeling of such a tissue. To this end, we assessed the ability of endotenon cells isolated from canine flexor digitorum profundus tendon and from surrounding parietal sheath to produce the gelatinases MMP-2 and MMP-9. Endotenon and sheath cells cultured in vitro on polystyrene produced small amounts of MMP-2 and MMP-9 was not detectable. When cultured on polystyrene coated with type I collagen, the cells upregulated MMP-2 production and MMP-9 production was induced. No other ECM protein elicited this response nor did other cell lines respond in this way after attachment to type I collagen. The two gelatinases were identified by immunological methods, ability to bind gelatin, size, metal ion requirement, serine protease inhibitor insensitivity, and APMA activation. For cells grown on collagen-coated plastic, gelatinase upregulation was proportional to the amount of ligand present until saturation was reached. For any group of fresh tendon cells, MMP-2 and MMP-9 upregulation was greater in a three dimensional collagen gel than the highest response from the same group under two dimensional culture conditions. Attachment of the cells to type I collagen increased the ratio of active to inactive MMP-2. Dexamethasone inhibited the upregulation of both MMP-2 and MMP-9. These results show that ECM proteins can influence both the production and the state of activation of these matrix metalloproteinases.

Increased surgical stress promotes tumor metastasis

BACKGROUND

Although it is well-known that excessive surgical stress augments the growth of residual cancer and metastasis, whether surgical stress is increased according to the degree of surgical manipulation and can consequently lead to the enhancement of cancer metastasis has not been thoroughly examined. Moreover, the molecules associated with response for stress-enhanced metastasis have not been well-analyzed. The aim of this study was to examine whether cancer metastasis is enhanced with an increase of surgical stress with an experimental lung metastasis model and to analyze the related molecules responsible for stress-enhanced metastasis.

METHODS

Colon 26-L5 carcinoma cells (1.5 x 10(4)/mouse) were injected intravenously into 6-week-old female BALB/c mice (Japan SLC, Hamamatsu, Japan). Two hours later, the mice were divided into 5 groups: untreated controls (the C group); mice given anesthesia only (the A group); mice given anesthesia and laparotomy (the AL group); mice given anesthesia, laparotomy, and appendectomy (the ALAp group); and mice given anesthesia, laparotomy, appendectomy, and left hepatic lobectomy (the ALApH group). The anesthesia procedures were the same in all groups (intraperitoneal administration of 0.8 mg/mouse sodium pentobarbital). In the AL, ALAp, and ALApH groups, a 3-cm long laparotomy was performed, and the time of the whole operation was just 5 minutes. All mice were killed 14 days after the procedures, and the number of lung metastases on the lung surface was counted manually. At the same time, BALB/c mice without tumor burden were given the same 5 kinds of surgical stress, and the messenger RNA expression of various metastasis-related molecules in the lung was measured with reverse transcriptase-polymerase chain reaction at 6, 24, and 48 hours after surgical stress. We also examined the effect of ONO-4817 (an inhibitor of matrix metalloproteinases ([MPs]) on lung metastasis in the mice with the 5 kinds of surgical stress.

RESULTS

The numbers of lung metastases on the lung surface and the messenger RNA expression of MMP-9, membrane type IBMMP, and urokinase-type plasminogen activator at 24 hours after surgery were enhanced in proportion to the degree of surgical stress. Moreover, ONO-4817 significantly inhibited lung metastasis.

CONCLUSION

These results strongly suggest that increased surgical stress augments cancer metastasis via surgical stress-induced expression of proteinases in the target organ of metastasis.

Liver X receptor-dependent repression of matrix metalloproteinase-9 expression in macrophages

Matrix metalloproteinases (MMPs) are zinc endopeptidases that degrade extracellular matrix (ECM) components during normal and pathogenic tissue remodeling. Inappropriate expression of these enzymes contributes to the development of vascular pathology, including atherosclerosis. MMP-9 is expressed in its active form in atherosclerotic lesions and is believed to play an important role in vascular remodeling, smooth muscle cell migration, and plaque instability. We demonstrate here that the liver X receptors (LXRs) LXRalpha and LXRbeta inhibit basal and cytokine-inducible expression of MMP-9. Treatment of murine peritoneal macrophages with the synthetic LXR agonists GW3965 or T1317 reduces MMP-9 mRNA expression and blunts its induction by pro-inflammatory stimuli including lipopolysaccharide, interleukin-1beta, and tumor necrosis factor alpha. In contrast, macrophage expression of MMP-12 and MMP-13 is not altered by LXR ligands. We further show that the ability of LXR ligands to regulate MMP-9 expression is strictly receptor-dependent and is not observed in macrophages obtained from LXRalphabeta null mice. Analysis of the 5'-flanking region of the MMP-9 gene indicates that LXR/RXR heterodimers do not bind directly to the MMP-9 promoter. Rather, activation of LXRs represses MMP-9 expression, at least in part through antagonism of the NFkappaB signaling pathway. These observations identify the regulation of macrophage MMP-9 expression as a mechanism whereby activation of LXRs may impact macrophage inflammatory responses.

Constitutive exclusion of Csk from Hck-positive membrane microdomains permits Src kinase-dependent proliferation of Theileria-transformed B lymphocytes

Infection of bovine T cells and B cells with the intracellular protozoan parasite Theileria parva induces a transformed phenotype with characteristics comparable to leukemic cells. The transformed phenotype reverts on drug-induced parasite death, and the cured lymphocytes acquire a resting phenotype and eventually die by apoptosis if not further stimulated. Here, we show that both lymphocyte proliferation and activation of the transcription factor AP-1 are mediated by Src-family protein tyrosine kinases (PTKs) in a parasite-dependent fashion. Src-family PTKs are known to be present in glycolipid-enriched microdomains (GEMs), also called lipid rafts, and to be negatively regulated by PTK Csk complexed to tyrosine-phosphorylated transmembrane adapter protein PAG (phosphoprotein associated with GEMs) also called Cbp (Csk-binding protein). We, therefore, purified GEMs from proliferating infected B cells and from growth-arrested cells that had been drug-cured of parasites. Proliferation arrest led to a striking increase of PAG/Cbp expression; correspondingly, the amount of Csk associated with PAG/Cbp in GEMs increased markedly, whereas PTK Hck accumulation in GEM fractions did not alter on growth arrest. We propose that Theileria-induced lymphocyte proliferation and permanent activation of Hck stems from down-regulation of PAG/Cbp and the concomitant constitutive loss of the negative regulator Csk from the GEMs of transformed B cells.

Quercetin exerts multiple inhibitory effects on vascular smooth muscle cells: role of ERK1/2, cell-cycle regulation, and matrix metalloproteinase-9

The French paradox has been attributed to the antioxidant properties of flavonoids present in the red wine. Quercetin, a bioflanoid present in the human diet, is known to inhibit angiotensin II-induced hypertrophy and serum-induced smooth muscle cell proliferation. However, it is not known whether quercetin exerts similar cardioprotective effects in cells treated with TNF-alpha. In this study, we investigated whether quercetin exerts the multiple suppressive effects on cytokine TNF-alpha-induced human aortic smooth muscle cells (HASMC). Treatment of quercetin showed potent inhibitory effects on the DNA synthesis of cultured HASMC in the presence of TNF-alpha. These inhibitory effects were associated with reduced extracellular signal-regulated kinase (ERK)1/2 activity and G1 cell-cycle arrest. Treatment of quercetin, which induced a cell-cycle block in G1-phase, induced down-regulation of cyclins and CDKs and up-regulation of the CDK inhibitor p21 expression, whereas up-regulation of p27 or p53 by quercetin was not observed. Because anti-atherogenic effects need not be limited to antiproliferation, we decided to examine whether quercetin exerted inhibitory effects on matrix metalloproteinase-9 (MMP-9) activity in TNF-alpha-induced HASMC. Quercetin inhibited TNF-alpha-induced MMP-9 secretion on HASMC in a dose-dependent manner. This inhibition was characterized by down-regulation of MMP-9, which was transcriptionally regulated at NF-kappaB site and activation protein-1 (AP-1) site in the MMP-9 promoter. These findings indicate the efficacy of quercetin in inhibiting cell proliferation, G1- to S-phase cell-cycle progress, and MMP-9 expression through the transcription factors NF-kappaB and AP-1 on TNF-alpha-induced HASMC.

Repression of 92-kDa type IV collagenase expression by MTA1 is mediated through direct interactions with the promoter via a mechanism, which is both dependent on and independent of histone deacetylation

Although the expression of the metastases-associated gene MTA1 correlates with tumor metastases, its role in regulating type IV collagenase expression is unknown. Enforced MTA1 expression in HT1080 cells reduced basal and 12-myristate 13-acetate-induced 92-kDa type IV collagenase (MMP-9) protein/mRNA levels. DNase I hypersensitivity and PstI accessibility assays revealed multiple regions of the MMP-9 promoter (-650/-450 and -120/+1), showing reduced hypersensitivity in the MTA1-expressing cells. Chromatin immunoprecipitation assays demonstrated MTA1 binding to the distal region, which spans several regulatory cis elements. Co-immunoprecipitation and chromatin immunoprecipitation assay experiments revealed histone deacetylase 2 (HDAC2)-MTA1 protein-protein interactions and the MTA1-dependent recruitment of HDAC2 to the distal MMP-9 promoter region, yielding diminished histone H3/H4 acetylation. However, HDAC2 binding and H3/H4 acetylation at the proximal MMP-9 region were unaffected by MTA1 expression. Furthermore, trichostatin treatment only partially relieved MTA1-repressed MMP-9 expression, indicating a HDAC-insensitive component possibly involv ing the nucleosome-remodeling Mi2 activity, which was recruited to the promoter by MTA1. In summary, (a) MMP-9 adds to a short list of MTA1-regulated genes, which so far only includes c-myc and pS2, and (b) MTA1 binds to the MMP-9 promoter, thereby repressing expression of this type IV collagenase via histone-dependent and independent mechanisms.

Evidence for the role of promoter methylation in the regulation of MMP-9 gene expression

Several studies have reported that elevated MMP-9 expression in lymphoma tissues correlated with tumor stage, grade, or prognosis. Because the DNA methylation pattern is critical for gene expression, detailed methylation analysis using genomic bisulfite sequencing was performed on a series of lymphoma cell lines. We found an inverse correlation between level of methylation of the MMP-9 promoter and the level of MMP-9 expression. Treating lymphoma cells with a DNA methylation inhibitor decreased MMP-9 promoter methylation and increased MMP-9 messenger RNA and protein secretion. This increased expression was potentiated by PMA, a known stimulus of MMP-9 in lymphoma cells. Finally, experiments using in vitro methylated MMP-9 promoter constructs confirmed the fact that DNA methylation exerts suppression on transcriptional activity. The results thus indicate that methylation may contribute to the transcriptional activity of the MMP-9 promoter.

Interferons inhibit tumor necrosis factor-alpha-mediated matrix metalloproteinase-9 activation via interferon regulatory factor-1 binding competition with NF-kappa B

Enhanced expression of matrix metalloproteinase-9 (MMP-9) correlates with invasion during tumor progression. Interferons (IFNs) inhibit MMP-9 activation in response to tumor necrosis factor-alpha (TNF-alpha), and the latter activates the MMP-9 gene through NF-kappaB. Understanding the molecular basis for MMP-9 inhibition may provide tools to control cell invasion. The data reported here show the critical role of interferon regulatory factor-1 (IRF1) in the inhibition of MMP-9. (i) IFN treatment suppresses TNF-alpha-induced MMP-9 reporter activity in STAT1(+/+) cells but not in STAT1(-/-) cells. (ii) IRF1 transfection blocks TNF-alpha-mediated MMP-9 activation. (iii) IFNs phosphorylate STAT1 and induce IRF1 but do not affect Ikappa-B degradation nor NF-kappaB nuclear translocation. (iv) Nuclear NF-kappaB (p50/p65) and IRF1, but not STAT1, bind to the MMP-9 promoter region containing an IFN-responsive-like element overlapping the NF-kappaB-binding site. (v) Recombinant IRF1, although unable to bind to an NF-kappaB consensus sequence, competes with NF-kappaB proteins for binding to the MMP-9 promoter. (vi) Conversely recombinant p50/p65 proteins reduce IRF1-DNA binding. (vii) In cells cotransfected with IRF1 and/or p65 expression vectors, an excess of IRF1 reduces MMP-9 reporter activity, whereas an excess of p65 blocks the inhibitory effect of IFN-gamma. Thus, in contrast to the known synergism between IRF1 and NF-kappaB, our data identify a novel role for IRF1 as a competitive inhibitor of NF-kappaB binding to the particular MMP-9 promoter context.

Downregulation of MMP-9 in ERK-mutated stable transfectants inhibits glioma invasion in vitro

We previously showed that enhanced expression of MMP-9, an endopeptidase that digests basement-membrane type IV collagen, is related to tumor progression in vitro and in vivo; antisense-MMP-9 stably transfected clones were less invasive than untransfected parental cells and did not form tumors in nude mice. In this study, we examined the role of ERK-1 in the regulation of MMP-9 production and the invasive behavior of the human glioblastoma cell line SNB19, in which ERK1 is constitutively activated. SNB19 cells were stably transfected with mt-ERK, a vector encoding ERK-1 cDNA in which the conserved lysine at codon 71 was changed to arginine, thus impairing the catalytic efficiency of this enzyme. Gelatin zymography showed reduced levels of MMP-9 in the mt-ERK-transfected cell lines relative to those in vector-transfected and parental control cells. Reductions in MMP-9 protein mRNA levels were also detected in the mt-ERK-transfected cells by Western and Northern blotting. The mt-ERK-transfected cells were much less invasive than parental or vector control cells in a Matrigel invasion assay and in a spheroid coculture assay. Thus an ERK-dependent signaling pathway seems to regulate MMP-9 mediated glioma invasion in SNB19 cells; interfering with this pathway could be developed into a therapeutic approach, which aims at a reduction of cancer cell invasion.

Glucocorticoid-mediated suppression of cytokine-induced matrix metalloproteinase-9 expression in rat mesangial cells: involvement of nuclear factor-kappaB and Ets transcription factors

Glucocorticoids and their synthetic analogs exert potent antiinflammatory actions that, in most cases, are due to an inhibition of the expression of inflammatory genes. In this study, we elucidated the mechanisms of dexamethasone-mediated suppression of matrix metalloproteinase-9 (MMP-9) expression triggered by IL-1beta in rat mesangial cells. Treatment of mesangial cells with dexamethasone markedly reduced the gelatinolytic content of conditioned media due to a decrease in MMP-9 expression. Cloning of a 1.3-kb fragment of the rat MMP-9 gene promoter and subsequent site- directed mutagenesis revealed that a nuclear factor kappaB (NF-kappaB) site at -561 to -550 and a region from -511 to -497 bearing a distal activator protein 1 site adjacent to an Ets-binding site are essentially involved in the IL-1beta-mediated transactivation of MMP-9. Inhibition of MMP-9 expression by dexamethasone resides in a promoter region downstream of -597. The IL-1beta-caused increase in DNA binding of both NF-kappaB and Ets-1 immunopositive complexes was substantially suppressed by dexamethasone as shown by EMSA. This was paralleled with a reduced abundance of p65 and Ets-1 proteins in cell nuclei concomitantly with a reduced inhibitor of kappaB (IkappaB) degradation. In addition to NF-kappaB, we suggest a pivotal role for the Ets binding site, in concert with a distal activator protein-1 element, in the transcriptional suppression of cytokine-induced MMP-9 expression by glucocorticoids.

U0126, a mitogen-activated protein kinase kinase inhibitor, inhibits the invasion of human A375 melanoma cells

The anti-invasive ability of the mitogen-activated protein kinase (MAPK) kinase inhibitor, U0126, was examined in human A375 melanoma cells in vitro. The effect was compared to that of PD98059, another commonly used MEK (MAPK kinase) inhibitor. U0126 or PD98059 showed a dose-dependent inhibition of A375 cell invasion through growth factor-reduced Matrigel. U0126 was more potent than PD98059 in suppressing tumor cell invasion. Both compounds significantly decreased urokinase plasminogen activator (uPA) and matrix metalloproteinases-9 (MMP-9) concentrations in conditioned media. At 5 microM, U0126 inhibited phosphorylation of the MEK 1/2 to a non-detectable level within 24 h. The phosphorylation of extracellular signal-related kinase 1/2 was also dramatically suppressed by the treatment with 10 microM U0126 or 40 microM PD98059. Both compounds suppressed the protein expression of c-Jun, but not c-Fos. The expression of uPA and MMP-9 was also inhibited. Our data suggest that U0126 is an effective agent in inhibiting human A375 melanoma cell invasion and that the effect is partially due to the decreased production of uPA and MMP-9.

An inhibitor of c-jun aminoterminal kinase (SP600125) represses c-Jun activation, DNA-binding and PMA-inducible 92-kDa type IV collagenase expression

The 92-kDa type IV collagenase (MMP-9) contributes to tumor invasion and metastases and strategies to down-regulate its expression could ultimately be of clinical utility. Although the expression of this collagenase is regulated by numerous growth factors, the signaling pathways that transduce these signals are fewer in number and therefore represent pharmacological targets. In this regard, we previously reported that MMP-9 expression was regulated by the c-jun amino terminal kinase (JNK) signaling cascade. Therefore, we undertook a study to determine the efficacy of a novel compound (SP600125), which binds to the ATP binding site of all known JNKs, in repressing MMP-9 expression. In OVCAR-3 cells, SP600125 inhibited the PMA-dependent secretion of MMP-9 in a time-dependent manner and over a dose range that blocked c-Jun phosphorylation and AP-1 binding. SP600125 repressed the activity of a PMA-stimulated MMP-9 promoter-driven luciferase reporter, suggesting that diminished secretion of this collagenase reflected reduced transcription. Further, the activity of a GAL4-driven reporter in PMA-treated cells, co-transfected with an expression construct encoding the trans-activation domain of c-Jun fused to the DNA binding domain of GAL4, was repressed by SP600125. These findings indicate the efficacy of SP600125 in inhibiting c-Jun activation, DNA-binding and the PMA-dependent induction of MMP-9 expression.

Control of MMP-9 expression at the maternal-fetal interface

Cytotrophoblastic cells (CTB) from first trimester placenta form columns of invasive CTB. This invasive behaviour is due to the ability of CTB to secrete matrix metalloproteinases (MMPs) since tissue inhibitor of MMP (TIMP) inhibits their invasiveness. Although CTB behave like metastatic cells, in vivo they are only transiently invasive (first trimester) and their invasion is normally limited only to the endometrium and to the proximal third of the myometrium. This temporal and spatial regulation of trophoblast invasion is believed to be mediated in an autocrine way by trophoblastic factors and in a paracrine way by uterine factors. Several types of regulators have been investigated: hormones, extra-cellular matrix glycoproteins and cytokines or growth factors. This review is not intended to be an exhaustive catalogue of potential regulators of trophoblastic MMP-9 secretion but is aimed at summarising the most important signalling pathways involved in MMP-9 regulation.

Macrophage migration inhibitory factor up-regulates matrix metalloproteinase-9 and -13 in rat osteoblasts. Relevance to intracellular signaling pathways

Neutral matrix metalloproteinases (MMPs) play an important role in bone matrix degradation accompanied by bone remodeling. We herein show for the first time that macrophage migration inhibitory factor (MIF) up-regulates MMP-13 (collagenase-3) mRNA of rat calvaria-derived osteoblasts. The mRNA up-regulation was seen at 3 h in response to MIF (10 microg/ml), reached the maximum level at 6-12 h, and returned to the basal level at 36 h. MMP-13 mRNA up-regulation was preceded by up-regulation of c-jun and c-fos mRNA. Tissue inhibitor of metalloproteinase (TIMP)-1 and MMP-9 (92-kDa type IV collagenase) were also up-regulated, but to a lesser extent. The MMP-13 mRNA up-regulation was significantly suppressed by genistein, herbimycin A and 4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine. Similarly, a selective mitogen-activated protein kinase (MAPK) kinase (MEK)1/2 inhibitor (PD98059) and c-jun/activator protein (AP)-1 inhibitor (curcumin) suppressed MMP-13 mRNA up-regulation induced by MIF. The mRNA levels of c-jun and c-fos in response to MIF were also inhibited by PD98059. Consistent with these results, MIF stimulated phosphorylation of tyrosine, autophosphorylation of Src, activation of Ras, activation of extracellular signal-regulated kinases (ERK) 1/2, a MAPK, but not c-Jun N-terminal kinase or p38, and phosphorylation of c-Jun. Osteoblasts obtained from calvariae of newborn JunAA mice, defective in phosphorylation of c-Jun, or newborn c-Fos knockout (Fos -/- ) mice, showed much less induction of MMP-13 with the addition of MIF than osteoblasts obtained from wild-type or littermate control mice. Taken together, these results suggest that MIF increases the MMP-13 mRNA level of rat osteoblasts via the Src-related tyrosine kinase-, Ras-, ERK1/2-, and AP-1-dependent pathway.

Paracrine regulation of matrix metalloproteinase expression in endometriosis

Following retrograde menstruation, shed endometrial tissue fragments attach to and invade the peritoneal surface to form established endometriotic lesions. With disease progression, the biochemically active lesions undergo remodeling and become fibrotic. Matrix metalloproteinase enzymes (MMPs) and the tissue inhibitors of metalloproteinases (TIMPs) play a significant role in normal endometrial remodeling during menses. Anomalous expression of MMPs and TIMPs has been identified in endometriotic lesions as compared to their highly regulated expression in eutopic endometrium. The paracrine mechanisms regulating misexpression of MMPs and TIMPs by endometriotic lesions are, however, not well defined. Misexpression of the MMPs and TIMPs may be due to innate anomalies in the eutopic endometrium from women with endometriosis, in the resident immune cells and peritoneal cells that juxtapose the ectopic endometrium, and/or numerous substances present in peritoneal fluid of women with endometriosis. The majority of MMPs are under strict transcriptional regulation. Steroid hormones and cytokines appear to act on the MMP promoter, either independently or in consort, to provide both positive and negative regulation of these genes. Misregulated expression of MMPs and TIMPs is associated with a more aggressive phenotype and a cascade of events facilitating peritoneal extracellular matrix degradation and establishment or remodeling of endometriotic lesions. The mechanisms by which MMP and TIMP expression are misregulated warrant further investigation as such information may provide insight into novel therapeutic modalities for endometriosis.

Activation of Src kinase in primary colorectal carcinoma: an indicator of poor clinical prognosis

BACKGROUND

The specific activity of the non-receptor protein tyrosine kinase, Src, is increased in the majority of colon and rectal adenocarcinomas compared to normal mucosa. However, the prognostic significance of this difference is unknown. The objective of the current study was to determine if Src activity is a marker for poor clinical prognosis in colon carcinoma patients. As Src activation leads to expression of urokinase/plasminogen activator receptor (u-PAR), expression of Src and u-PAR were correlated with patient survival.

METHODS

Tumors and adjacent normal colonic mucosae from 45 patients with colorectal carcinoma were screened for Src activity by the immune complex kinase assay. Expression of u-PAR was determined by enzyme linked immunoabsorbent assay. The primary tumor-to-normal mucosa ratios of activity were compared following classification and regression tree (CART) analysis to determine the prognostic significance of elevated specific Src activity. Expression of u-PAR was correlated with Src activity.

RESULTS

By CART analysis, Src activity in tumors elevated more than twofold over normal mucosa was significant. Increased Src activity significantly correlated with Dukes stage, pT and pN classification, and increased u-PAR levels (P < 0.001). Kaplan Meier analysis showed a significant association between elevated Src activity and shorter overall survival of all patients (P = 0.0004) and of Dukes Stage A-C patients (P = 0.0037). In patients who underwent curative resection, a significant correlation with a decreased disease-free survival rate was found (P < 0.0001). Multivariate analysis revealed that elevated Src activity was a prognostic parameter independent of M classification (P = 0.0125, relative risk 3.54, 95% confidence interval 1.31 - 9.76).

CONCLUSIONS

Src activity is an independent indicator of poor clinical prognosis in all stages of human colon carcinoma. These data suggest that Src-specific inhibitors may have a therapeutic role in inhibiting tumor progression and metastasis, and that measurement of Src activity may aid in selection of early stage patients for adjuvant therapy.

The p38 SAPK pathway regulates the expression of the MMP-9 collagenase via AP-1-dependent promoter activation

The invasive phenotype of cancers critically depends on the expression of proteases such as the M(R) 92,000 type IV collagenase (MMP-9). Several growth factors and oncogenes were found to increase promoter activity and as a consequence protease expression. This frequently requires the activation of the transcription factor AP-1 by signal transduction cascades such as the ERK and JNK pathways. We have previously demonstrated that the tumor promoter TPA can induce MMP-9 expression via a third signaling cascade, the p38 pathway. Considering that TPA is a potent activator of AP-1, we hypothesized that this transcription factor might also be required for p38 pathway-dependent MMP-9 regulation. While dominant negative p38 and MKK-6 mutants reduced MMP-9 promoter activity in CAT assays, a construct encoding an activating mutation in the MKK-6 protein potently stimulated it. This was mediated via 144 bp of the 5'flanking region of the wild-type promoter, which contains an AP-1 site at -79. Both point mutations in this motif and the expression of a c-jun protein lacking its transactivation domain and therefore acting as a dominant negative AP-1 mutant abrogated MKK-6-dependent promoter stimulation. Finally SB 203580, a specific p38 pathway inhibitor, reduced MMP-9 expression/secretion and in vitro invasion of cancer cells. Thus, our results provide evidence that also the third SAPK/MAPK signaling cascade, the p38 signal transduction pathway, stimulates MMP-9 expression in an AP-1-dependent fashion.