Epidermal growth factor stimulation of stromelysin mRNA in rat fibroblasts requires induction of proto-oncogenes c-fos and c-jun and activation of protein kinase C

Phosphocitrate inhibits a basic calcium phosphate and calcium pyrophosphate dihydrate crystal-induced mitogen-activated protein kinase cascade signal transduction pathway

Calcium deposition diseases caused by calcium pyrophosphate dihydrate (CPPD) and basic calcium phosphate (BCP) crystals are a significant source of morbidity in the elderly. We have shown previously that both types of crystals can induce mitogenesis, as well as metalloproteinase synthesis and secretion by fibroblasts and chondrocytes. These responses may promote degradation of articular tissues. We have also shown previously that both CPPD and BCP crystals activate expression of the c-fos and c-jun proto-oncogenes. Phosphocitrate (PC) can specifically block mitogenesis and proto-oncogene expression induced by either BCP or CPPD crystals in 3T3 cells and human fibroblasts, suggesting that PC may be an effective therapy for calcium deposition diseases. To understand how PC inhibits BCP and CPPD-mediated cellular effects, we have investigated the mechanism by which BCP and CPPD transduce signals to the nucleus. Here we demonstrate that BCP and CPPD crystals activate a protein kinase signal transduction pathway involving p42 and p44 mitogen-activated protein (MAP) kinases (ERK 2 and ERK 1). BCP and CPPD also cause phosphorylation of a nuclear transcription factor, cyclic AMP response element-binding protein (CREB), on serine 133, a residue essential for CREB's ability to transactivate. Treatment of cells with PC at concentrations of 10(-3) to 10(-5) M blocked both the activation of p42/p44 MAP kinases, and CREB serine 133 phosphorylation, in a dose-dependent fashion. At 10(-3) M, a PC analogue, n-sulfo-2-aminotricarballylate and citrate also modulate this signal transduction pathway. Inhibition by PC is specific for BCP- and CPPD-mediated signaling, since all three compounds had no effect on serum-induced p42/P44 or interleukin-1beta induced p38 MAP kinase activities. Treatment of cells with an inhibitor of MEK1, an upstream activator of MAPKs, significantly inhibited crystal-induced cell proliferation, suggesting that the MAPK pathway is a significant mediator of crystal-induced signals.

A dominant negative mutant of jun blocking 12-O-tetradecanoylphorbol-13-acetate-induced invasion in mouse keratinocytes

We previously reported that induced activator protein-1 (AP-1) transcriptional activity appears to be required for tumor promoter-induced transformation in mouse epidermal JB6 cells. To extend this investigation to a keratinocyte culture model and a transgenic mouse model, we constructed K14TAM67, a keratin 14 promoter-controlled version of the dominant negative jun mutant to directly block AP-1 activity and possibly indirectly block NF kappa B activity in basal squamous epithelia. This study was directed at characterizing TAM67 expression and biological activity in the mouse cell line 308, a keratinocyte model for studying carcinogenesis. Cotransfection of K14TAM67 with luciferase plasmid reporter DNAs produced inhibition of basal and 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced AP-1 and NF kappa B activity but had no effect on p53-dependent transcriptional activity. In an in vitro invasion assay, stable expression of TAM67 in 308 cells blocked TPA-induced Matrigel invasion. This suggests that blocking TPA-induced AP-1- or NF kappa B-regulated gene expression by TAM67 inhibits TPA-induced progression. Recombinant tissue inhibitor of metalloproteinase 1 reduced TPA-induced in vitro invasion, thus implicating metalloproteinases at least in part in the transcription factor-dependent process. Analysis of mRNA levels for members of the matrix metalloproteinase (MMP) family, however, revealed that the expression of any single MMP family member did not correlate with regulation of AP-1 or NF kappa B activity. However, the combination of substantial levels of mRNA for stromelysin-1, stromelysin-2, collagenase, membrane type 1 MMP, and gelatinase A occurred only in TPA-treated cells in the absence of TAM67. These results suggest that the action of the dominant negative jun mutant on AP-1 and NF kappa B gene regulation results in complex alterations in the levels of downstream effector genes, such as the metalloproteinases, that effect TPA-induced cellular invasion.

Stromelysin-3 induction and interstitial collagenase repression by retinoic acid. Therapeutical implication of receptor-selective retinoids dissociating transactivation and AP-1-mediated transrepression

Human stromelysin-3 and interstitial collagenase are matrix metalloproteinases whose expression by stromal cells in several types of carcinomas has been associated with cancer progression. We compared here the regulation of the expression of both proteinases by retinoids in human fibroblasts. Physiological concentrations of retinoic acid were found to simultaneously induce stromelysin-3 and repress interstitial collagenase. In both cases, the involvement of a transcriptional mechanism was supported by run-on assays. Furthermore, in transient transfection experiments, the activity of the stromelysin-3 promoter was induced by retinoic acid through endogenous receptors acting on a DR1 retinoic acid-responsive element. The ligand-dependent activation of the receptors was also investigated by using selective synthetic retinoids, and we demonstrated that retinoic acid-retinoid X receptor heterodimers were the most potent functional units controlling both stromelysin-3 induction and interstitial collagenase repression. However, specific retinoids dissociating the transactivation and the AP-1-mediated transrepression functions of the receptors were found to repress interstitial collagenase without inducing stromelysin-3. These findings indicate that such retinoids may represent efficient inhibitors of matrix metalloproteinase expression in the treatment of human carcinomas.

Regulation of matrix metalloproteinase-1 and tissue inhibitor of metalloproteinase-1 in MCF-7 cells: comparison with regulatory mechanisms of pS2 expression

Regulation of two genes involved in tumor invasion, the matrix metalloproteinase (MMP)-1 and the tissue inhibitor of MMP (TIMP)-1, by activators of protein kinase C (PKC) or protein kinase A (PKA) was studied in MCF-7 mammary adenocarcinoma cells. The basal mRNA expression was undetectable for MMP-1 and low for TIMP-1. Treatment of MCF-7 cells with the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) (100 nM) was associated with a high expression of MMP-1 mRNA, as well as an induction of the level of TIMP-1 mRNA (5- to 10-fold). In the presence of actinomycin D (AMD, 4.0 microM), an inhibitor of transcription, these stimulatory effects of TPA were abolished. Similar responses were observed when protein synthesis was inhibited by cycloheximide (CHX, 50 microM). In the presence of the cyclic AMP (cAMP) analogue N6-benzoyl (N6-Bzl)-cAMP (500 microM), the MMP-1 mRNA was unaffected and still below the level of detection, whereas a non-significant increase (< 2-fold) in TIMP-1 mRNA was observed. The level of pS2 mRNA, of which the induction by TPA in MCF-7 cells is a primary transcriptional event, was up-regulated (10- to 15-fold) by TPA (100 nM), whereas a much weaker increase (2- to 3-fold) was observed by treatment with N6-Bzl-cAMP (500 microM). Again, these stimulatory effects were counteracted by AMD (4.0 microM) and CHX (50 microM). These data suggest that activation of PKC but not of PKA may induce transcription of MMP-1 and TIMP-1, possibly by the synthesis of transcription factor(s), in transformed cells of epithelial origin.

Vitamin D3 regulation of stromelysin-1 (MMP-3) in chondrocyte cultures is mediated by protein kinase C

Matrix metalloproteinases (MMPs) are a group of enzymes with the potential to degrade extracellular matrix proteins. One of the MMPs, stromelysin-1 (MMP-3) has been localized to extracellular matrix vesicles in growth plate chondrocyte cultures, suggesting involvement of this enzyme in remodeling of the extracellular matrix during endochondral development, a process which is regulated by the vitamin D metabolites, 1,25-(OH)2D3 and 24,25-(OH)2D3. To determine whether stromelysin-1 is regulated by vitamin D as well, confluent cultures of cells derived from growth zone (GC) and resting zone (RC) rat costochondral cartilage were treated with 1 alpha, 25-(OH)2D3 (1,25) and 24R,25-(OH)2D3 (24,25), respectively, and the effect on stromelysin-1 assessed by casein gel zymography and Western blots. Although stromelysin-1 activity was enriched in the matrix vesicle fraction, only the plasma membrane enzyme was affected by the treatment; 1, 25 and 24,25 caused a marked decrease in plasma membrane stromelysin-1 activity in their target cells. Since plasma membrane protein kinase C (PKC) activity is stimulated by 1,25 and 24,25, we hypothesized that stromelysin-1 activity was regulated by the vitamin D metabolites via PKC-dependent phosphorylation. To test this, membrane fractions (containing endogenous PKC alpha and zeta as well as stromelysin-1) were incubated in the presence of purified rat brain PKC and/or recombinant human (rh) stromelysin-1 and [gamma 32 P]-ATP and anti-stromelysin-1 immunoprecipitates were analyzed by autoradiography and Western blots. Immuno-phospho-stromelysin-1 was localized to a 52-kDa band in the plasma membrane fraction only; no phosphorylation was observed in the matrix vesicle fraction. Selective inhibitors of PKC activity demonstrated that phosphorylation was inhibited by H7 and low concentrations of H8, but not by HA1004, indicating that PKC, not PKA, was responsible. Protein phosphatase 2A1 (PP2A), a serine/threonine-specific phosphatase, selectively removed the radiolabel in a time-dependent manner, providing further support for a PKC-dependent phosphorylation mechanism. Incubation of resting zone cell plasma membranes with 24,25 but not 1, 25, resulted in phosphorylation of stromelysin-1, demonstrating that the nongenomic effect was metabolite-specific. This suggests that this may be one mechanism by which vitamin D metabolites regulate stromelysin-1 activity and that PKC-dependent phosphorylation inhibits the metalloproteinase.

Opposite, binary regulatory pathways involved in IL-1-mediated stromelysin gene expression in rat mesangial cells

Glomerular mesangial cells express matrix metalloproteinase sromelysin in response to the proinflammatory cytokine IL-1 beta. The present study was conducted to identify intracellular machinery involved in this IL-1 action, especially focusing on the role of the TPA response element (TRE) located in the 5'-flanking region of the stromelysin gene. Using transient transfection with a pTRE-LacZ reporter plasmid, we detected no obvious up-regulation of TRE activity in rat mesangial cells following the IL-1 stimulation. However, the basal activity of TRE was found to be essential to the stromelysin induction, since (i) mesangial cells stably expressing a transdominant negative mutant of c-Jun, which effectively suppressed both basal and inducible TRE activity, exhibited the blunted expression of stromelysin in response to IL-1 beta, whereas (ii) transfection with a c-fos antisense gene, which suppressed only the inducible TRE activity, did not affect the stromelysin induction. To seek cooperative pathways required for the IL-1 action, we next focused on protein kinases, the potential regulators of the stromelysin gene. Stimulation of mesangial cells with a protein kinase C (PKC) activator, phorbol 12-myristate 13-acetate (PMA), induced the stromelysin transcript without affecting TRE activity. Depletion of intracellular PKC by high-dose PMA or inhibition of PKC activity with calphostin C suppressed the stromelysin induction by IL-1 beta, suggesting the crucial contribution of a PKC-mediated, but TRE-independent pathway. In contrast, either cAMP inducer forskolin or dibutyryl cAMP suppressed the IL-1-mediated stromelysin expression. An inhibitor of cAMP-dependent protein kinase A (PKA), HA1004, enhanced the IL-1 effect in a dose-dependent manner. Unexpectedly, the inhibitory action of PKA was not through cAMP response element (CRE) but through TRE, because (i) activation of CRE was not induced by IL-1 beta, and (ii) cAMP-mediated activation of PKA suppressed the basal TRE activity. These findings elucidated the unique, binary regulation of stromelysin by IL-1 beta; that is, IL-1 up-regulated the transcript via the PKC-dependent pathway under the cooperation with constitutively active TRE, and this stimulatory effect was in part counterbalanced by the IL-1-inducible PKA which down-regulated the basal TRE activity.

Cross-talk between different enhancer elements during mitogenic induction of the human stromelysin-1 gene

Platelet-derived growth factor (PDGF) induces the expression of human stromelysin-1, a matrix metalloproteinase involved in tumor invasion and metastasis. Here it is shown that stromelysin-1 gene induction by PDGF depends on Ras and involves three previously identified promoter elements (the stromelysin-1 PDGF-responsive element (SPRE) site, the two head-to-head polyomavirus enhancer A-binding protein-3 (PEA3) sites, and the activator protein-1 (AP-1) binding site). During mitogenic induction, these responsive elements appear to be organized in two independent transcriptional units, SPRE-AP-1 and PEA3-AP-1, which result from specific element cross-talking. Interestingly, expression of a dominant negative mutant of Raf-1 significantly interfered with the induction through PEA3-AP-1 but not with that operating through SPRE-AP-1. Conversely, only the induction operating through SPRE-AP-1 was affected significantly by the expression of a dominant negative mutant of the atypical lambda/iota protein kinase C (lambda/iotaPKC). These data strongly suggest that the signal triggered by PDGF flows through Ras and bifurcates toward two distinct pathways, one operating through Raf and involving PEA3-AP-1 and the other one Raf-independent, operating through lambda/iotaPKC and SPRE-AP-1. Furthermore, we present evidence suggesting that the novel SPRE-binding transcription factor SPBP cross-couples with c-Jun to transactivate the SPRE site.

The significance of epidermal growth factor receptor and matrix metalloproteinase-3 in squamous cell carcinoma of the oral cavity

Surgical specimens from 65 patients with squamous cell carcinoma (SCC) of the oral cavity were examined immunohistochemically. The clinicopathological significance of the expression of epidermal growth factor receptor (EGFR) and matrix metalloproteinase-3 (MMP-3) was assessed. Among the 65 tumours, 20(30.8%) and 37(56.9%) tested positively for EGFR and MMP-3, respectively. A positive correlation between the expression of EGFR and MMP-3 was found. The expression of EGFR in oral SCCs was associated with an advanced T stage of the primary tumour, an advanced pathological stage, and a high incidence of neck metastasis. In addition, MMP-3 was primarily expressed at the advancing front of cancer with a diffuse invasive mode. Thus, overexpression of MMP-3 was associated with an advanced pathological stage, a diffuse invasive mode, and a high incidence of neck metastasis. The analysis of MMP-3 expression is useful to evaluate the pathological status of tumours. Because EGFR-overexpressed tumour should produce larger amounts of MMP-3 in vivo, a close examination of oral SCC for expression of EGFR and MMP-3 should be helpful to predict their malignant potential.

Expression of c-fos gene inhibits proteoglycan synthesis in transfected chondrocyte

The effect of expression of c-fos gene on proteoglycan synthesis, one of the important markers of cartilage metabolism, was examined by introducing the c-fos DNA into HCS 2/8 chondrocytes. The [35S]sulfate incorporation into proteoglycan was decreased in the c-fos transfectants expressing exogenous c-fos mRNA, when compared to a control transfectant. A significant increase in transcription of MMP-3 with the suppressed transcription of aggrecan and TIMP-1 were also observed in the c-fos transfectants. Moreover, analysis of the effect of AP-1 proteins on the collagenase and TIMP-1 promoters in gastric carcinoma KKLS cells revealed that c-Fos combined with any of the Jun-related proteins failed to stimulate the TIMP-1 promoter, though collagenase promoter was effectively activated by any Fos/Jun-related protein heterocomplex. These findings indicate that the c-fos expression may govern the cartilage metabolism and hence may play an important role in the pathogenesis of joint destruction in arthritis.

Specific inhibition of basic calcium phosphate and calcium pyrophosphate crystal-induction of metalloproteinase synthesis by phosphocitrate

Calcium pyrophosphate dihydrate (CPPD) and basic calcium phosphate (BCP) crystal deposition diseases are a group of heterogeneous arthritides which are a significant source of morbidity in the elderly. Both crystals induced mitogenesis and metalloproteinase (MP) synthesis and secretion by fibroblasts and chondrocytes which may promote degradation of intra-articular tissue. We have previously shown that phosphocitrate (PC), an inhibitor of hydroxyapatite crystallization, specifically blocks BCP crystal-induced mitogenesis in 3T3 cells. This led us to examine the effect of PC on BCP and CPPD crystal induction of MP synthesis in human fibroblasts. PC (10(-3) to 10(-4) M) specifically inhibited the crystal-induced collagenase and stromelysin mRNA accumulation while having no effect on epidermal growth factor-induced or basal levels of mRNA for both enzymes. Western blots (collagenase) of conditioned media confirmed that PC blocked crystal-induced proteinase secretion as well. Moreover, PC (10(-3) M) also blocked the crystal induction of c-fos and c-jun. Since FOS and JUN proteins form a transacting activator (AP-1) for expression of collagenase and stromelysin genes, PC may block the synthesis of both enzymes by inhibiting the transcription of c-fos and c-jun.

Translational augmentation of pro-matrix metalloproteinase 3 (prostromelysin 1) and tissue inhibitor of metalloproteinases (TIMP)-1 mRNAs induced by epidermal growth factor in human uterine cervical fibroblasts

The mechanisms by which epidermal growth factor (EGF) enhances the production of pro-matrix metalloproteinase 3 (proMMP-3/prostromelysin 1) and tissue inhibitor of metalloproteinases (TIMP)-1 were investigated using human uterine cervical fibroblasts. The treatment of the cells with EGF for 24 h resulted in about 5-6-fold increase in the production of proMMP-3 and TIMP-1 compared with the untreated control cells. This increase was accompanied by an increase of proMMP-3 and TIMP-1 mRNAs. However, an about 3- and 2-fold increase in the production of proMMP-3 and TIMP-1, respectively, was observed as early as 1 h after the treatment of the cells with EGF, and it was not accompanied by any apparent increase in proMMP-3 and TIMP-1 mRNAs. This early effect of EGF on the enhanced production of proMMP-3 and TIMP-1 was not inhibited by actinomycin D, even though actinomycin D inhibited the synthesis of the total RNA in both the EGF-treated and untreated cells. These results indicate that EGF enhances the apparent production of proMMP-3 and TIMP-1 by two mechanisms: one by the accelerated translation of their mRNAs; and the other by the enhanced transcription of their genes. The former event takes place much earlier than the latter.

Protein kinase C isotypes required for phorbol-ester induction of stromelysin-1 in rat fibroblasts

The phorbol-ester tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) is a potent inducer of the metalloproteinase stromelysin in fibroblasts in vivo and in several cultured cell lines. Rat-1 and Rat-2 fibroblasts, however, do not respond to TPA stimulation by induction of stromelysin gene activity, although collagenase promoter-mediated activity is induced threefold by TPA treatment in these cells. We determined that rat fibroblasts expressed protein kinase C(PKC)alpha, PKCdelta, PKCepsilon, and PKCzeta but neither the mRNA nor the protein for PKCbeta. When Rat-2 fibroblasts were stably transfected with an expression vector producing PKCbeta, however, TPA treatment of these variants resulted in a 3.1-fold induction of stromelysin promoter-mediated luciferase activity compared with a 1.3-fold induction in parental Rat-2 cells (P<0.002). Transient transfection of PKCepsilon produced a small but significant increase in TPA-stimulation of both stromelysin- and collagenase-mediated gene expression. These results suggest that there are PKC isotype-specific signaling pathways that can differentially regulate matrix metalloproteinase gene expression.

Synergistic transcriptional activation of the tissue inhibitor of metalloproteinases-1 promoter via functional interaction of AP-1 and Ets-1 transcription factors

The tissue inhibitor of metalloproteinases-1 (TIMP-1) is an inhibitor of the extracellular matrix-degrading metalloproteinases. We characterized response elements that control TIMP-1 gene expression. One contains a binding site that selectively binds c-Fos and c-Jun in vitro and confers a response to multiple AP-1 family members in vivo. Adjacent to this is a binding site for Ets domain proteins. Although c-Ets-1 alone did not activate transcription from this element, it enhanced transcription synergistically with AP-1 either in the context of the natural promoter or when the sequence was linked upstream of a heterologous promoter. Furthermore, a complex of c-Jun and c-Fos interacted with c-Ets-1 in vitro. These results suggest that AP-1 tethers c-Ets-1 to the TIMP-1 promoter via protein-protein interaction to achieve Ets-dependent transcriptional regulation. Collectively, our results indicate that TIMP-1 expression is controlled by several DNA response elements that respond to variations in the level and activity of AP-1 and Ets transcriptional regulatory proteins.

Differential effects of transforming growth factor-beta 1 on the expression of matrix metalloproteinases and tissue inhibitors of metalloproteinases in young and old human fibroblasts

The balance between the activities of matrix metalloproteinases (MMPs) and the tissue inhibitors of metalloproteinases (TIMPs) is an important control point in tissue remodeling. Previous studies have demonstrated elevated expression of the MMPs collagenase and stromelysin-1 by aged human diploid fibroblasts compared to early-passage cultures. We show here that aging cells display an altered response to transforming growth factor-beta 1 (TGF beta 1) that selectively affects MMP mRNA expression. In both young and old cells, phorbol myristoyl-13 acetate (PMA) induced the expression of transcripts of collagenase, stromelysin-1, gelatinase-B, TIMP-1, and TIMP-3. In young cells, TGF beta 1 reciprocally modulated PMA-induced MMP and TIMP gene expression leading to reduced levels of transcripts for the MMPs and augmented accumulation of TIMP-1 and TIMP-3 mRNAs. However, repressing effects of TGF beta 1 on collagenase, stromelysin-1, and gelatinase-B RNA expression were not apparent in old cells, though induction of the TIMP genes was unimpaired. By electrophoretic mobility shift analysis the nuclear transcription factors AP1 and serum response factor (SRF) showed reduced levels of DNA binding activities in old fibroblasts compared to young cells. A probe for the TGF beta-inhibitory element (TIE) gave equivalent levels of complexes with nuclear extracts from both types of cells, though of different mobilities. We conclude that the effects of TGF beta 1 on MMP and TIMP gene expression involve different cellular intermediaries, and suggest that altered composition or modification of TIE binding factors in aging cells may underlie the failure of TGF beta 1-mediated transcription repression. This mechanism may contribute to elevated constitutive expression of MMPs in old cells and to the connective tissue deterioration that accompanies the aging process.

Contributions of tumor and stromal matrix metalloproteinases to tumor progression, invasion and metastasis

The malignant progression of tumors is driven by the expression of oncogenes and loss of expression of tumor suppressor genes; factors that are intrinsic to cancer cells. The phenotypic changes brought about by the gain or loss of expression of oncogenes and tumor suppressor genes lead to the acquisition of malignant traits, namely, the ability to invade into and grow in ectopic tissue environments. Recently, however, focus in cancer research has widened from the cancer cell to include the surrounding tumor stroma as an integral player in the process of tumor progression. One of the areas in cancer research contributing to this enhanced appreciation of stromal involvement in tumor progression and metastasis is that of matrix metalloproteinases (MMPs). This review provides an overview of the characteristics of MMPs and discusses their role in the progression and metastasis of tumors. Initially, attention will focus on the regulation of MMPs in tumor cells but will switch to discourse on stromal expression of MMPs in tumors and speculation on the functional consequences of stromal expression of MMPs.

Modulation of expression of genes encoding nuclear proteins following exposure to JANUS neutrons or gamma-rays

Previous work has shown that exposure of cells to ionizing radiations causes modulation of a variety of genes, including those encoding c-fos, interleukin-1, tumor necrosis factor, cytoskeletal elements, and many more. The experiments reported herein were designed to examine the effects of either JANUS neutron or gamma-ray exposure on expression of genes encoding nucleus-associated proteins (H4-histone, c-jun, c-myc, Rb, and p53). Cycling Syrian hamster embryo cells were irradiated with varying doses and dose rates of either JANUS fission-spectrum neutrons or gamma-rays; after incubation of the cell cultures for 1 h following radiation exposure, mRNA was harvested and analyzed by Northern blot. Results revealed induction of transcripts for c-jun, H4-histone, and (to a lesser extent) Rb following gamma-ray but not following neutron exposure. Interestingly, expression of c-myc was repressed following gamma-ray but not following neutron exposure. Radiations at different doses and dose rates were compared for each of the genes studied.

Structure and promoter characterization of the human stromelysin-3 gene

In the present study, we have isolated the human stromelysin-3 (ST3) gene which encodes a matrix metalloproteinase (MMP) expressed in fibroblastic cells of tissues associated with intense remodeling. The gene was found to span 11.5 kilobases (kb) including 8 exons and 7 introns. The genomic organization of ST3 gene exons is well conserved compared to other members of the MMP family, except for the 3 last exons corresponding to the hemopexin-like domain and to a long 3'-untranslated region. The transcription initiation site was located 31 nucleotides downstream of a TATA box. Analysis of 1.4 kb of 5'-flanking DNA sequence in the ST3 gene promoter revealed the presence of putative regulatory elements, but no consensus sequence for AP1-binding site in contrast to other MMP promoters. However, a specific cis-acting retinoic acid responsive element of the DR1 type was identified in the proximal region (-385) of the ST3 gene promoter. Transient transfection experiments demonstrated that a minimal promotor activity could be modulated by various sequences within the 3.4 kb of 5'-flanking region, and that the ST3 promoter was transactivated by retinoic acid receptors in the presence of retinoic acid. These findings indicate that the human ST3 gene promoter is characterized by structural and functional features which differ from those previously described in other MMP promoters, and further supports the possibility that ST3 gene expression is controlled by specific factors during tissue remodeling.

Molecular cloning of the rat intestinal trefoil factor gene. Characterization of an intestinal goblet cell-associated promoter

Intestinal trefoil factor (ITF) is a small peptide bearing the unique motif of intrachain disulfide bonds characteristic of the trefoil family. Previous work had localized expression of ITF primarily within goblet cells in the small and large bowel, making it a candidate gene for the study of the molecular basis of intestinal and goblet cell-specific gene expression. In order to study the regulation of ITF expression, we have cloned the rat ITF gene and sequenced 1.7 kilobases of the 5'-flanking region. RNase protection analysis demonstrated a single transcriptional start site. Various lengths of the 5'-flanking region were linked to the reporter gene luciferase and transfected into the colon cancer cell lines LS174T and Caco-2, representing, respectively, cells with and without goblet cell-like phenotype. Expression in the goblet cell-like LS174T colon cancer cell line was nearly 10-fold greater than expression in Caco-2 cells which exhibit columnar enterocyte-like phenotype. The pattern of goblet cell-associated selective transcription required only 153 base pairs of the rat ITF 5'-flanking sequence. Transfection of a construct of human growth hormone under the control of the rat ITF promoter in the N2 subclone of HT-29 cells demonstrated expression of the reporter gene only in those cells exhibiting a goblet cell phenotype as assessed by expression of immunoreactive mucin. These initial studies of the 5'-flanking region of the ITF gene demonstrate the presence of cis-regulatory elements capable of directing goblet cell specific expression.

The human stromelysin promoter contains a previously unreported 1.0-kb sequence

Cloning and characterization of the promoter region controlling the gene encoding human stromelysin (Str) has been previously reported [Quinones et al., J. Biol. Chem. 264 (1989) 8339-8344]. We have characterized independently isolated genomic clones of the STR promoter, designated pSKStrB and 682, that are considerably different from the published sequence. Although the sequences up to an XbaI site at -480 of the 5' regions are identical, a novel 1.0-kb segment exists upstream from -480. This sequence is absent from the published clone, but its presence in the genomic DNA from twelve individuals has been confirmed by both PCR analysis and restriction mapping. Upstream of the novel 1-kb segment, the sequence of the published clone reappears, but in pSKStrB exists in inverse orientation.

Gene expression of interstitial collagenase (matrix metalloproteinase 1) in gastrointestinal tract cancers

Collagenolytic proteinases play an important pathological role in the invasion and metastasis of cancer cells. However, little is known about the role of interstitial collagenase (matrix metalloproteinase-1; MMP-1) in this process. To investigate the expression of the MMP-1 gene in cancer tissues, an in situ hybridization study was carried out in gastrointestinal tract cancers (one esophageal cancer, five gastric cancers, and four colorectal cancers), using a 35S-labeled MMP-1 cDNA probe. The MMP-1 gene was expressed in the stromal cells of fibrous tissue around cancer nests, especially at the margin of invasion and/or within the cancer nest; however, no definite expression within cancer cells was observed. Expression of the MMP-1 gene in the stromal cells was more common in well differentiated gastric adenocarcinoma than in poorly differentiated adenocarcinomas. These findings indicate that expression of the MMP-1 gene is greater in stromal cells that are closely associated with cancer cells, suggesting a pathophysiological role of MMP-1 in the invasion and metastasis of cancer cells.

Induction of stromelysin-1 and collagenase synthesis in fibrochondrocytes by tumor necrosis factor-alpha

Stromelysin-1 and collagenase mRNA levels were assayed in fibrochondrocytes by Northern blot analysis at 0, 2, 4, 8 and 24 h after stimulation with tissue necrosis factor-alpha (TNF-alpha). Peak collagenase mRNA levels occurred 24 h after stimulation and were increased nine-fold over the level at time 0. Stromelysin-1 mRNA levels peaked 8 h after stimulation, with a five-fold increase over the level at time 0. A TNF-alpha dose-related response to both collagenase and stromelysin-1 mRNA accumulation was also demonstrated. Confirmation of the presence of secreted metallo-proteinases in the conditioned media was established by immunoprecipitation of stromelysin-1 and Western blotting of collagenase. Both enzymes were secreted in latent forms. Consistent with stromelysin-1 activity, substrate gels demonstrated a doublet of caseinase activity with molecular masses at 57 kDa and 59 kDa in TNF-alpha stimulated samples. Collagenase assays of conditioned media also demonstrated a significant increase in collagenase activity after stimulation by TNF-alpha. While epidermal growth factor had a minimal effect on stromelysin-1 and collagenase expression, transforming growth factor-beta, and insulin-like growth factor-1 did not induce either enzyme activity.

Inhibition of glycogen synthesis by epidermal growth factor in hepatocytes. The role of cell density and pertussis toxin-sensitive GTP-binding proteins

Epidermal growth factor (EGF) counteracts the stimulation of glycogen synthesis by insulin in hepatocytes, but it is not known whether this is due to inhibition of glycogen synthesis or to inhibition of the insulin-signalling mechanism. This study investigates the mechanisms by which EGF affects the basal rate and the insulin stimulation of glycogen synthesis. The basal rate of glycogen synthesis is higher at low than at high cell density. EGF inhibits the basal rate of glycogen synthesis at low cell density but not in confluent cultures and abolishes the difference due to density. However, EGF inhibits the stimulation of glycogen synthesis by insulin irrespective of cell density. Increasing glycogen synthesis by increasing the [glucose] does not abolish the difference in rates of glycogen synthesis due to cell density, neither does it induce responsiveness to EGF at high cell density, establishing that responsiveness to EGF is a function of cell density and not of the basal rate and that inhibition of the insulin stimulation also cannot be accounted for by the higher rate of glycogen synthesis. Cytochalasin D and phalloidin, which alter cell morphology through interactions with the microfilament cytoskeleton, mimic the cell-density-dependent inhibition of glycogen synthesis by EGF. The inhibition of glycogen synthesis by EGF and cytochalasin D is additive and cytochalasin D potentiates the inhibition of glycogen synthesis by EGF, suggesting involvement of a cytoskeletal mechanism. Exogenous phospholipase C inhibits glycogen synthesis at both low and high cell density and the inhibition at low cell density is not additive with that caused by either EGF or cytochalasin D, suggesting that these agonists inhibit glycogen synthesis through changes in Ca2+ and/or diacylglycerol. The inhibition of glycogen synthesis by EGF in the absence of insulin stimulation is blocked by neomycin, which inhibits Ca2+ release from intracellular stores but not by antagonists of protein kinase C. It was also inhibited by pertussis toxin (50%), suggesting that it may involve GTP-binding-protein-mediated release of Ca2+ from intracellular stores. The inhibition of the stimulation of glycogen synthesis by insulin was not affected by neomycin and was only marginally inhibited by pertussis toxin or guanosine 5'-O-[3-thio]triphosphate (GTP[S]). We infer from these findings that the inhibition by EGF of the basal rate of glycogen synthesis and of the insulin stimulation are mediated by different mechanisms. The latter is pertussis toxin insensitive and independent of cell density, whereas the former is expressed only at low cell density, it is potentiated by cytochalasin D and inhibited by pertussis toxin.

Increase of c-jun mRNA upon hypo-osmotic cell swelling of rat hepatoma cells

c-jun mRNA levels were increased in rat hepatoma cells (H4-II-E-C3) when exposed to hypotonic medium (205 mosmol/l) with a maximal induction observed after 1 h of hypotonic exposure. At this time point an approximate 5-fold increase in c-jun expression could be detected in relation to normotonic control incubations (305 mosmol/l). Hypertonic exposure (405 mosmol/l) had only a slight effect on c-jun expression. In contrast to the increased c-jun mRNA levels under hypotonic conditions, expression of the c-fos proto-oncogene was unaffected by changes in the osmolarity. The hypotonicity-induced increase in c-jun expression was also detectable in the presence of a protein kinase C (PKC) inhibitor. This indicates that PKC is not involved in the signal transduction pathway leading to c-jun expression upon hypotonic cell swelling in these cells.

Identification of serum-inducible genes: different patterns of gene regulation during G0-->S and G1-->S progression

We have identified, by differential cDNA library screening, 15 serum inducible genes in the human diploid fibroblast cell line WI-38. The genes fall into two classes that are distinguished by their dependence on protein synthesis for the induction by serum, i.e., primary and secondary genes. While 11 of these genes encode known proteins, 4 other genes have not been described to date. The former genes encode proteins of diverse functions, including the monocyte-derived neutrophil chemotactic factor (MONAP), calmodulin, tropomyosin, tenascin, collagenase, plasminogen activator inhibitor-2a, the ‘sperm-specific’ cleavage signal-1 protein, metallothionein IIa and the mitochondrial chaperonin hsp-60. Interestingly, one of the unknown genes contains a large open reading frame for a polypeptide that is highly homologous to a previously unidentified long open reading frame in the opposite strand of the gene coding for the transcription factor HTF-4. We also studied the regulation of these serum-induced genes during cell cycle progression in normally cycling WI-38 and HL-60 cells separated by counterflow elutriation as well as in serum-stimulated HL-60 cells. Our results clearly show that, in contrast to the prevailing opinion, the expression of most genes induced after mitogen stimulation is not subject to a significant regulation in normally proliferating cells. This supports the hypothesis that the progression into S from either G0 or G1 are distinct processes with specific patterns of gene expression.

Involvement of protein kinase C in the interleukin 1 alpha-induced gene expression of matrix metalloproteinases and tissue inhibitor-1 of metalloproteinases (TIMP-1) in human uterine cervical fibroblasts

The role of protein kinase C in the interleukin 1 (IL-1)-mediated production of pro-matrix metalloproteinases (proMMPs) and tissue inhibitor-1 of metalloproteinases (TIMP-1) in human uterine cervical fibro-blasts has been investigated. IL-1 and a protein kinase C activator, 12-O-tetradecanoylphorbol 13-acetate (TPA) augmented the production of proMMP-1 (interstitial procollagenase), proMMP-3 (prostromelysin-1) and TIMP-1, but their effects were inhibited by the protein kinase C inhibitors 1-(5-isoquinolinesulfonyl)-2-methylpiperazine dihydrochloride (H-7) and staurosporine in a dose-dependent manner. The suppressive effect of H-7 and staurosporine on the IL-1-induced production of proMMPs-1 and -3 and TIMP-1 resulted from the decrease in the steady-state levels of their mRNAs. When protein kinase C was down-regulated by treating the cells with a high level of TPA, the inductive effect of IL-1 upon proMMP-3 production was reduced considerably. These results indicate that protein kinase C mediates the IL-1-induced production of proMMPs-1 and -3 and TIMP-1 at the pretranslational level in human uterine cervical fibroblasts. On the other hand, neither IL-1 nor TPA modulated the production of proMMP-2 (progelatinase A). Both IL-1 and TPA also accelerated the production of prostaglandin E2 (PGE2) by cervical fibroblasts. However, the treatment of the cells with staurosporine in the presence of IL-1 or TPA further augmented PGE2 synthesis, suggesting that the increased synthesis of PGE2 by IL-1 treatment is mediated via signalling pathways distinct from those of proMMPs-1 and -3 and TIMP-1.

Transcriptional interactions of transforming growth-factor-β with pro-inflammatory cytokines

BACKGROUND

Inflammation and tissue injury are characterized by a massive infiltration of mononuclear cells. These pro-inflammatory cells, which are the precursors of an inflammatory response by the immune system, secrete a variety of cytokines and growth factors that alter the biosynthetic repertoire of the resident connective tissue cells. Specifically, expression of connective tissue matrix metalloproteinases, such as stromelysin and interstitial collagenase, is enhanced, together with the expression of chemoattractants for leukocytes, such as interleukin-8 (IL-8). These events lead to increased connective tissue degradation. We have examined the growth factor regulation of expression in cultured fibroblasts of the prototypic pro-inflammatory factors interstitial collagenase and IL-8.

RESULTS

We demonstrate that transforming growth factor-beta (TGF-beta) does not interfere with cytokine-induced IL-8 gene expression, nor does it affect the activity of NF-kappaB-driven promoters. In contrast, TGF-beta down-regulates collagenase gene expression through the induction of the jun-B proto-oncogene. Jun-B is a negative regulator of c-jun, which mediates cytokine activation of collagenase gene expression through its action as a component of the AP-1 transcription factor.

CONCLUSION

Our data suggest that TGF-beta may attenuate the deleterious events that occur in inflammation by preventing cytokine-induced extracellular matrix degradation, although it does not affect cytokine-induced recruitment of pro-inflammatory cells. Furthermore, our data suggest a potential therapeutic use for jun-B, which may be a candidate for gene therapy in disease states that are characterized by excessive connective tissue degradation.

Cytokine regulation of metalloproteinase gene expression

Matrix metalloproteinases belong to a family of zinc-dependent enzymes capable of degrading extracellular matrix and basement membrane components. Their expression is greatly modulated by cytokines and growth factors and involves the gene products of the Fos and Jun families of oncogenes. After extra(peri)cellular activation, their activity can be further controlled by specific tissue inhibitors of metalloproteinases. A correct balance between these regulatory mechanisms is necessary to ensure matrix remodeling in normal physiological processes such as embryonic development, but the overexpression of these enzymes may initiate or contribute to pathological situations such as cartilage degradation in rheumatoid arthritis or to tumor progression and metastasis. Delineation of the mechanisms of metalloproteinase and metalloproteinase inhibitors gene expression, understanding of their mode of interactions, and characterization of their patterns of expression in various tissues in normal and pathological states will lead to new therapeutic strategies to counteract the deleterious effects of matrix metalloproteinases in human disease.

Role of cytokines and inflammatory mediators in tissue destruction

Colonization or emergence of microbial pathogens may result in tissue destruction by activation of one or more of five distinct host degradative pathways (matrix metalloproteinase pathway, plasminogen-dependent pathway, phagocytic pathway, PMN-serine proteinase pathway and osteoclastic bone resorption) or by direct cleavage of extracellular matrix constituents by microbial proteinases. Activation of endogenous destructive pathways may be mediated by immune responses resulting in expression of degradative cellular phenotypes among both immigrant and resident cell populations. In addition, expression of degradative phenotypes may be triggered by direct influences on host cells of microbial products (LPS, enzymes, toxins). A body of evidence suggests that each of these mechanisms involves local production of proinflammatory cytokines and growth factors. The matrix metalloproteinase pathway is centrally involved in dissolution of all unmineralized connective tissues and perhaps in resorption of bone as well. The matrix metalloproteinase family consists of nine or more genetically distinct Zn++ endopeptidases which collectively cleave all of the constituents of the extracellular matrix. Recent studies have uncovered many essential elements of a complex, but still incomplete, regulatory network that governs tissue destruction. Proinflammatory cytokines and growth factors induce signalling pathways several of which are dependent on protein kinase C and result in transient expression of the transcription factors c-jun and c-fos. Initiation of transcription of most matrix metalloproteinase genes requires binding of the transcription factor AP-1 (c-jun/c-fos) to a specific promoter sequence but attainment of maximal transcription rates is dependent on interaction with other promoter elements as well. Several matrix metalloproteinases have been detected in crevicular fluids and tissues of inflamed human gingiva as have the proinflammatory cytokines (IL-1 and TNF-alpha) which regulate their transcription. Although the mere presence of enzymes and cytokines does not necessarily impart function per se, these observations suggest that some level of spatial or temporal linkage exists between metalloproteinase/cytokine expression and gingival inflammation.

The role of growth regulatory aberrations in progression of human colon carcinoma

Colon carcinoma is a multistage disease. Most malignancies arise from pre-existing benign tumors. Multiple chromosomal defects affecting oncogene and tumor suppressor gene function are associated with disease progression. These aberrations result in an imbalance between the normal positive and negative growth effectors, which contribute further to disease progression. We have studied how changes in the expression of TGF alpha and TGF beta affect colon carcinoma cell behavior. Overexpression of the stimulatory factor TGF alpha in a relatively benign cell line with weak TGF alpha autocrine activity converted the cell type to an aggressive, progressed phenotype in vivo and in vitro. In contrast, disruption of TGF alpha expression by constitutive expression of TGF alpha antisense RNA in a progressed cell line with a strong, internalized autocrine loop resulted in the development of clones with decreased tumorigenicity in vitro and in vivo. Suppression of the inhibitory effects of TGF beta by constitutive expression of TGF beta antisense RNA increased the tumorigenicity of the cell lines in vitro and in vivo. None of these alterations in TGF alpha or TGF beta expression affected the doubling time of the cells. The changes in tumorigenicity were due to effects on the lag phase of growth. We conclude that TGF beta functions to maintain the cells in a quiescent state while TGF alpha drives reentry into the cell cycle. We have identified a unique cis-element that mediates TGF alpha autoregulation. The transcription factor binding this element is also involved in the cell-cycle regulation of TGF alpha expression. We hypothesize that this factor may be a convergent point TGF alpha and TGF beta interact in controlling movement into and out of quiescence.

Activation of protein kinase C inhibits human keratinocyte migration

The involvement of protein kinase C (PKC) in epidermal growth factor (EGF)-induced human keratinocyte migration was studied with the phagokinetic assay. It was concluded that PKC activation does not mediate, but rather inhibits, EGF-induced keratinocyte migration. The following experimental observations support these conclusions: 1) The PKC inhibitor H-7 did not inhibit EGF-induced migration but instead led to a modest enhancement. 2) PKC activators such as phorbol-12-myristate-13-acetate (PMA), phorbol-12,13-dibutyrate (PDBu), and 1,2-dioctanoly-sn-glycerol inhibited migration, but biologically inactive 4 alpha-PMA had no effect. 3) PMA did not inhibit keratinocyte attachment and spreading but blocked migration almost immediately after addition. 4) Migration of PKC-depleted cells, which were produced by prolonged treatment with PDBu, was enhanced similarly to normal cells by EGF. 5) PKC-depleted cells were not susceptible to the inhibitory effects of phorbol esters on migration. Additional experiments, in which cells were preactivated with EGF, suggested that PKC inhibits the EGF effect at a post-receptor level. The inhibitory effect of PKC on keratinocyte migration was not restricted to EGF-induced migration; PKC activation also inhibited keratinocyte migration induced by bovine pituitary extract, insulin, insulin-like growth factor-1, and keratinocyte growth factor.

Role of matrix metalloproteinases in human periodontal diseases

Matrix metalloproteinases (MMP) are a family of proteolytic enzymes that mediate the degradation of extracellular matrix macromolecules, including interstitial and basement membrane collagens, fibronectin, laminin, and proteoglycan core protein. The enzymes are secreted or released in latent form and become activated in the pericellular environment by disruption of a Zn(++)-cysteine bond which blocks the reactivity of the active site. The major cell types in inflamed and healthy periodontal tissues (fibroblasts, keratinocytes, endothelial cells, and macrophages) are capable of responding to growth factors and cytokines, as well as to products released from the microbial flora by induction of transcription of 1 or more MMP genes. Cytokines that are likely to regulate expression of MMP genes in periodontal tissues include IL-1, TNF-alpha, and TGF-alpha. In addition, triggered PMN leukocytes which express only 2 MMP (PMN-CL and Mr 92K GL) release these enzymes from specific granule storage sites in response to a number of stimuli. The evidence that MMP are involved in tissue destruction in human periodontal diseases is still indirect and circumstantial. Cells isolated from normal and inflamed gingiva are capable of expressing a wide complement of MMP in culture and several MMP can be detected in cells of human gingiva in vivo. In addition, PMN-CL and Mr 92K GL are readily detected in gingival crevicular fluid from gingivitis and periodontitis patients. Osteoclastic bone resorption does not appear to directly involve MMP, but a body of evidence suggests that bone resorption is initiated by removal of the osteoid layer by osteoblasts by means of a collagenase-dependent process.

Matrix metalloproteinases: a review

Matrix metalloproteinases (MMPs) are a family of nine or more highly homologous Zn(++)-endopeptidases that collectively cleave most if not all of the constituents of the extracellular matrix. The present review discusses in detail the primary structures and the overlapping yet distinct substrate specificities of MMPs as well as the mode of activation of the unique MMP precursors. The regulation of MMP activity at the transcriptional level and at the extracellular level (precursor activation, inhibition of activated, mature enzymes) is also discussed. A final segment of the review details the current knowledge of the involvement of MMP in specific developmental or pathological conditions, including human periodontal diseases.

Role of matrix metalloproteinases in invasion and metastasis: biology, diagnosis and inhibitors

The processes of tumour invasion and subsequent metastasis are the most lethal aspects of cancer. Whilst many factors are involved, the matrix metalloproteinases (MMPs) have been implicated as key-rate limiting enzymes in the invasive process. This family consisting of eight members of similar structure, can be roughly divided into three groups based on substrate specificity. All are secreted in a latent form and require proteolytic cleavage for activation. The expression of these enzymes is regulated at the transcriptional level by a variety of growth factors and oncogenes. They are also regulated at the protein level by a family of specific inhibitors called the tissue inhibitors of metalloproteinases (TIMPs). Studies in human tumour samples have shown a positive correlation between metalloproteinase expression and metastatic potential. The levels of metalloproteinase expression have been manipulated using molecular biology techniques in several cell lines and shown a similar correlation. These results suggest that an understanding of metalloproteinase expression and proteolytic activity may lead to the development of effective therapeutic agents with the potential to reduce the incidence of metastatic cancer.

Correlation between lack of bone Gla protein mRNA expression in rat transplantable osteosarcomas and expression of both c-fos and c-jun proto-oncogenes

Alkaline phosphatase (AP) activity and expression of bone Gla protein (BGP), c-fos, and c-jun were compared in two transplantable osteosarcomas with high potentials for metastasis to the lung. The original spontaneous osteosarcoma (SOS) gradually became histologically undifferentiated, losing its osteogenic activity during serial transfer, whereas the chemical (4-hydroxyaminoquinoline 1-oxide)-induced osteosarcoma (COS) retained osteogenesis. The two osteosarcomas showed similar doubling times and levels of lung metastasis, and strong AP activity was detected on the cell membranes of both. Northern blot analysis revealed that lack of BGP mRNA expression was associated with expression of both c-fos and c-jun proto-oncogenes in SOS. In contrast, neither c-fos nor c-jun mRNAs were detected but BGP mRNA was expressed in the case of COS. These results suggest that the c-fos and c-jun genes may suppress the expression of BGP mRNA relevant to differentiation and osteoid formation in rat osteosarcomas. However, this does not appear to be directly related to proliferative or metastatic biological behavior.

Post-transcriptional regulation of collagenase and stromelysin gene expression by epidermal growth factor and dexamethasone in cultured human fibroblasts

Epidermal growth factor (EGF) is a ubiquitous fibroblast mitogen which also stimulates the synthesis of the extracellular matrix degrading metalloproteinases, collagenase, and stromelysin. Using primary cultures of human skin fibroblast, we show that these metalloproteinase mRNAs are coordinately up-regulated by EGF; and that dexamethasone, a potent inhibitor of collagenase and stromelysin synthesis, coordinately down-regulates these EGF-induced mRNAs. Nuclear run-on assays showed that EGF increased transcription of collagenase and stromelysin approximately 2-fold over the untreated control, while repression by dexamethasone was difficult to detect. However, steady state mRNA levels were induced approximately 10-fold by EGF and co-treatment with dexamethasone decreased them to below control levels, suggesting modulation of mRNA stability. Thus, we measured the half-life of these mRNAs using "pulse-chase" methodology. Typically, the half-life of EGF-induced collagenase and stromelysin mRNAs was approximately 30 h, and co-treatment with dexamethasone decreased the half-life of these mRNAs by 30-50%. Additionally, we found that the transcription inhibitor DRB stabilized EGF-induced metalloproteinase mRNAs, suggesting an mRNA degradation pathway which requires transcription. Thus our data demonstrate that collagenase and stromelysin are coordinately regulated by EGF and by dexamethasone, primarily at the level of metalloproteinase mRNA stability.

Involvement of AP1 and PEA3 binding sites in the regulation of murine tissue inhibitor of metalloproteinases-1 (TIMP-1) transcription

Transcription of tissue inhibitor of metalloproteinases-1 (TIMP-1), a secreted protein that regulates the activities of the metalloproteinases, collagenase and stromelysin, is activated by serum growth factors. Transient transfection experiments have revealed several regions of cis-acting regulatory sequences involved in the response of the murine TIMP-1 gene to serum. One area is in the vicinity of the promoter, consisting of a non-consensus binding site (5'-TGAGTAA-3' at -59/-53) for transcription factor AP1 and an adjacent 24 bp region of dyad symmetry that contains a PEA3-binding site. A second is an upstream region (-1020 to -780) that acts as an enhancer when linked to a heterologous promoter, and contains a consensus AP1 binding site (at -803/ -797). Gel retardation assays revealed differences between nuclear factors in mouse C3H10T1/2 cells that bound to the TIMP(-59/ -53)AP1 site and a consensus collagenase TRE (TPA-response element). The TIMP(-59/ -53)AP1 site is a promiscuous motif that binds c-Fos/c-Jun AP1 translated in vitro and is an effective competitor for binding of nuclear AP1 factors to the consensus TRE, but in addition it binds factors that do not associate with the consensus TRE. The TIMP(-59/ -53)AP1 motif and the dyad symmetry region stimulated expression from a thymidine kinase promoter in an additive fashion, and competition experiments showed that excess copies of these factor binding sites reduced expression from a reporter plasmid driven by the TIMP-1 promoter. Our data show that binding sites for AP1 and PEA3 transcription factors are involved in the regulation of TIMP-1 transcription, which suggests that the coordinated induction of TIMP-1, collagenase and stromelysin may be achieved through the actions of a shared set of nuclear transcription factors. However, the properties of the TIMP-1(-59/ -53)AP1 motif likely reflect an additional type of transcriptional regulation restricted to TIMP-1.

Basic calcium phosphate crystals cause coordinate induction and secretion of collagenase and stromelysin

Synovial fluid basic calcium phosphate crystals (BCP) are often found in severely degenerated joints. Crystalline BCP is a growth factor stimulating fibroblast mitogenesis and acting as a competence factor similar to platelet-derived growth factor. In human fibroblasts (HF), the synthesis of collagenase and stromelysin is coordinately induced after stimulation with a variety of cytokines and growth factors. We sought to determine whether BCP, like other growth factors, might induce proteases that would damage articular tissue. Northern blot analysis of mRNA for collagenase and stromelysin in HF stimulated with BCP was performed. Secreted enzymes were analyzed by immunoblot using a monoclonal antibody to collagenase and by immunoprecipitation using a polyclonal antibody to stromelysin. Stromelysin activity was confirmed using casein substrate gels. A significant, dose-dependent accumulation of collagenase and stromelysin message was evident after 4 h and continued for at least 24 h in BCP-stimulated cultures. Forty-nine and 54 kD proteins immunoreacting with collagenase antibody were identified in the conditioned media (CM) from BCP-stimulated cultures while 50 and 55 kD proteins were identified by immunoprecipitation with stromelysin antibody. Collagenase activity was increased significantly in the CM from BCP treated cells; casein substrate gels showed casein degrading bands at molecular weights consistent with stromelysin. BCP stimulates coordinate induction of collagenase and stromelysin which may mediate the joint destruction associated with these crystals.

Negative regulation of gene expression by TGF-beta

Stromelysin gene expression is transcriptionally activated by a number of growth factors (e.g., EGF and PDGF), tumor promoters (e.g., TPA), and oncogenes (e.g., ras, src) through an AP-1-dependent mechanism. TGF-beta repression of stromelysin induction is mediated at the level of transcription by an element located at position -709 in the rat stromelysin promoter referred to as the TGF-beta inhibitory element (TIE). A TIE-binding protein complex is induced by treatment of rat fibroblasts with TGF-beta. This protein complex contains the protooncogene c-fos, and induction of c-fos by TGF-beta is required for the repressive effects of TGF-beta on stromelysin gene expression. Interestingly, c-fos induction is also required for stimulation of stromelysin expression by EGF in rat fibroblasts. Preliminary studies suggest that differential regulation of members of the jun family of early-response genes may explain this apparent paradox and determine whether stromelysin is induced or repressed by growth factors. TGF-beta stimulation therefore initiates a cascade of events that results in a specific pattern of gene expression: the direct stimulation of early-response genes can lead to subsequent induction or repression of other genes. Growth factor regulation of matrix metalloproteinases appears to play a role in embryonic development in the morphogenesis of the murine lung. Treatment of embryonic lungs in organ culture with the growth factors EGF or TGF-alpha results in stimulation of growth and inhibition of branching morphogenesis. A similar inhibition of branching was observed when these lung rudiments were treated with the matrix metalloproteinase collagenase. Most interestingly, the effects of EGF and TGF-alpha can be completely reversed by the tissue inhibitor of metalloproteinases, TIMP. TGF-beta has the opposite effect on growth of murine lung rudiments--growth is inhibited in a dose-dependent manner. This example illustrates a potential role for growth factor regulation of matrix-degrading metalloproteinases in complex developmental processes.

Secretion of stromelysin by cultured dermal papilla cells: differential regulation by growth factors and functional role in mitogen-induced cell proliferation

To understand better the molecular nature of the epithelial-mesenchymal interactions that govern folliculogenesis and hair growth, we have studied the behavior of cultured rat dermal papilla cells (rDP), the mesenchymal component of the hair follicle. Basic fibroblast growth factor (bFGF) and platelet-derived growth factor (PDGF) both potentiated the growth of rDP in culture, and transforming growth factor-beta (TGF-beta) inhibited rDP proliferation. Biosynthetic labeling studies demonstrated that both PDGF and bFGF induced synthesis of a major secreted protein(s) with Mr = 55-60 kD. It was noted that PDGF and bFGF differentially regulated synthesis of this major secreted protein; PDGF-mediated induction was found to be transient, while bFGF allowed prolonged synthesis of the protein. Sodium dodecyl sulfate (SDS)-substrate gel analysis of rDP-conditioned media revealed that this protein is a metalloproteinase with casienolytic activity and Mr approximately 51 kD (unreduced). We have identified the growth factor-regulated rDP protein as the matrix metalloproteinase stromelysin by immunoprecipitation. Northern analysis established that increased secretion of stromelysin was accompanied by an increased expression of stromelysin-specific mRNA. Remarkably, stromelysin antisera interfere with stimulation of dermal papilla cell growth, demonstrating that stromelysin production serves a functional role in mitogen-induced proliferation in these cells. These findings provide insight into the mechanism by which the connective tissue remodeling required for formation of hair embryonically and the postembryonic hair cycle may be regulated.

Effects of epidermal growth factor on glycolysis in A431 cells

A431 cells were treated with epidermal growth factor (EGF) to study the mechanism by which this factor accelerates the glycolytic flux. After EGF treatment, fructose-2,6-bisphosphate (Fru-2,6-P2) levels rose up to 2-fold. This change correlated with an increase in phosphofructokinase-2 activity, which was not due to a change in the transcription or translation of the enzyme, neither in the amount of enzyme. PK-C does not appear to be involved in the signalling mechanism since EGF was equally potent in PK-C depleted cells than in control cells. The increase in Fru-2,6-P2 levels was lower and more transient in cells treated with EGF in a calcium-free medium than in the presence of the cation, and it was restored by the addition of calcium to the medium. These results suggest a possible role for calcium-mediated pathways in the control of Fru-2,6-P2 levels in A431 cells.