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

Histone deacetylase inhibitors upregulate MMP11 gene expression through Sp1/Smad complexes in human colon adenocarcinoma cells

MMP-11 (stromelysin-3) is a matrix metalloproteinase associated with tumor progression and poor prognosis. Its expression was initially described exclusively in stromal cells surrounding tumors, but more recently it has also been detected in macrophages and hepatocarcinoma cells. Here we show MMP-11 expression in human epithelial colon adenocarcinoma cell lines (Caco-2, HT-29 and BCS-TC2). Treatment of BCS-TC2 cells with butyrate and trichostatin A (TSA) (histone deacetylase inhibitors) increases MMP11 promoter activity and protein expression. Using electrophoretic mobility shift assay (EMSA) and supershift assays, we demonstrate for the first time that Sp1 is able to bind to the GC-boxes within the MMP11 proximal promoter region; this binding has been confirmed by chromatin immunoprecipitation. Sp1 is involved in MMP11 basal expression and it is essential for the upregulation of transcription by histone deacetylase inhibitors as deduced from mutant constructs lacking the Sp1 sites and by inhibition of its binding to the promoter with mithramycin. This regulation requires the formation of Sp1/Smad2 heterocomplexes, which is stimulated by an increase in the acetylation status of Smad after butyrate or TSA treatments. We have also found that ERK1/2-mitogen-activated protein kinase (MAPK), but not p38-MAPK or JNK, is involved in the upregulation of MMP11 by HDAC inhibitors.

Transcriptional activities of retinoic acid receptors

Vitamin A derivatives plays a crucial role in embryonic development, as demonstrated by the teratogenic effect of either an excess or a deficiency in vitamin A. Retinoid effects extend however beyond embryonic development, and tissue homeostasis, lipid metabolism, cellular differentiation and proliferation are in part controlled through the retinoid signaling pathway. Retinoids are also therapeutically effective in the treatment of skin diseases (acne, psoriasis and photoaging) and of some cancers. Most of these effects are the consequences of retinoic acid receptors activation, which triggers transcriptional events leading either to transcriptional activation or repression of retinoid-controlled genes. Synthetic molecules are able to mimic part of the biological effects of the natural retinoic acid receptors, all-trans retinoic acid. Therefore, retinoic acid receptors are considered as highly valuable therapeutic targets and limiting unwanted secondary effects due to retinoid treatment requires a molecular knowledge of retinoic acid receptors biology. In this review, we will examine experimental evidence which provide a molecular basis for the pleiotropic effects of retinoids, and emphasize the crucial roles of coregulators of retinoic acid receptors, providing a conceptual framework to identify novel therapeutic targets.

Tumor cell-mediated induction of the stromal factor stromelysin-3 requires heterotypic cell contact-dependent activation of specific protein kinase C isoforms

Stromelysin-3 (ST3, MMP-11) has been shown to be strongly overexpressed in stromal fibroblasts of most invasive human carcinomas. However, the molecular mechanisms leading to ST3 expression in nonmalignant fibroblasts remain unknown. The aim of the present study was to analyze the signaling pathways activated in normal pulmonary fibroblasts after their interaction with non-small cell lung cancer (NSCLC) cells and leading to ST3 expression. The use of selective signaling pathway inhibitors showed that conventional and novel protein kinase Cs (PKC) were required for ST3 induction, whereas Src kinases exerted a negative control. We observed by both conventional and real time confocal microscopy that green fluorescent protein-tagged PKCalpha and PKCepsilon, but not PKCdelta, transfected in fibroblasts, accumulate selectively at the cell-cell contacts between fibroblasts and tumor cells. In agreement, RNAi-mediated depletion of PKCalpha and PKCepsilon, but not PKCdelta significantly decreased co-culture-dependent ST3 production. Finally, a tetracycline-inducible expression model allowed us to confirm the central role of these PKC isoforms and the negative regulatory function of c-Src in the control of ST3 expression. Altogether, our data emphasize signaling changes occurring in the tumor microenvironment that may define new stromal targets for therapeutic intervention.

Beta-carotene inhibits UVA-induced matrix metalloprotease 1 and 10 expression in keratinocytes by a singlet oxygen-dependent mechanism

UVA exposure causes skin photoaging by singlet oxygen (1)O(2)-mediated induction of, e.g., matrix metalloproteases (MMPs). We assessed whether pretreatment with beta-carotene, a (1)O(2) quencher and retinoic acid (RA) precursor, interferes with UVA-induced gene regulation. HaCaT keratinocytes were precultured with beta-carotene at physiological concentrations (0.5, 1.5, and 3.0 microM) prior to exposure to UVA from a Hönle solar simulator (270 kJ/m(2)). HaCaT cells accumulated beta-carotene in a time- and dose-dependent manner. UVA irradiation massively reduced the cellular beta-carotene content. Beta-carotene suppressed UVA-induction of MMP-1, MMP-3, and MMP-10, three major matrix metalloproteases involved in photoaging. We show that regulation by not only MMP-1, but also MMP-10, involves (1)O(2)-dependent mechanisms. Beta-carotene dose-dependently quenched (1)O(2)-mediated induction of MMP-1 and MMP-10. Thus, as in chemical solvent systems, beta-carotene quenches (1)O(2) also in living cells. Vitamin E did not cooperate with beta-carotene to further inhibit MMP induction. HaCaT cells produced weak retinoid activity from beta-carotene, as demonstrated by mild upregulation of RAR beta and activation of an RARE-dependent reporter gene. Beta-carotene did not regulate the genes encoding other RARs, RXRs, or the two beta-carotene cleavage enzymes. These results demonstrate that beta-carotene acts photoprotectively, and that this effect is mediated by (1)O(2) quenching.

Stimulation of MMP-11 (stromelysin-3) expression in mouse fibroblasts by cytokines, collagen and co-culture with human breast cancer cell lines

Background

Matrix metalloproteinases (MMPs) are central to degradation of the extracellular matrix and basement membrane during both normal and carcinogenic tissue remodeling. MT1-MMP (MMP-14) and stromelysin-3 (MMP-11) are two members of the MMP family of proteolytic enzymes that have been specifically implicated in breast cancer progression. Expressed in stromal fibroblasts adjacent to epithelial tumour cells, the mechanism of MT1-MMP and MMP-11 induction remains unknown.

Methods

To investigate possible mechanisms of induction, we examined the effects of a number of plausible regulatory agents and treatments that may physiologically influence MMP expression during tumour progression. Thus NIH3T3 and primary mouse embryonic fibroblasts (MEFs) were: a) treated with the cytokines IL-1β, IL-2, IL-6, IL-8 and TGF-β for 3, 6, 12, 24, and 48 hours; b) grown on collagens I, IV and V; c) treated with fibronectin, con-A and matrigel; and d) co-cultured with a range of HBC (human breast cancer) cell lines of varied invasive and metastatic potential.

Results

Competitive quantitative RT-PCR indicated that MMP-11 expression was stimulated to a level greater than 100%, by 48 hour treatments of IL-1β, IL-2, TGF-β, fibronectin and collagen V. No other substantial changes in expression of MMP-11 or MT1-MMP in either tested fibroblast culture, under any treatment conditions, were observed.

Conclusion

We have demonstrated significant MMP-11 stimulation in mouse fibroblasts using cytokines, matrix constituents and HBC cell lines, and also some inhibition of MT1-MMP. Our data suggest that the regulation of these genes in the complex stromal-epithelial interactions that occur in human breast carcinoma, is influenced by several mechanisms.

Matrix metalloproteinases and tumor progression

The matrix metalloproteinases (MMPs) are a family of more than 20 distinct enzymes that are frequently overexpressed in human tumors. Functional studies have shown that MMPs play an important role in the proteolytic destruction of extracellular matrix and basement membranes, thereby facilitating tumor invasion and metastasis. In addition, these enzymes may also be important in other steps of tumor evolution including neoplastic cell proliferation and angiogenesis stimulation. On the basis of the relevance of MMPs in tumor progression, a number of different strategies aimed to block the unwanted activity of these enzymes in cancer have been developed. Unfortunately, most clinical trials with the first series of MMP inhibitors have failed to show clear benefit in patients with advanced cancer. Explanations for this lack of success include the failure to recognize the role of these enzymes in early stages of the disease as well as inadequacy of either the employed inhibitors or the proteases to be targeted. The introduction of novel concepts such as tumor degradome, and global approaches to protease analysis, may facilitate the identification of the relevant MMPs that must be targeted in each individual cancer patient. On the other hand, the finding that MMPs are enzymes whose effects on biologically active substrates can have profound consequences on cell behaviour, suggests that selective inhibition of a limited set of MMPs at early stages of tumor evolution might be much more effective than using wide-spectrum inhibitors active against most family members, and administered to patients at late stages of the disease. Further studies directed to elucidate these questions will be necessary to clarify whether any of the multiple strategies of MMP inhibition may be part of future therapeutic approaches to control tumor progression.

Differential regulation of protein expression, growth and apoptosis by natural and synthetic retinoids

All-trans retinoic acid (ATRA) can down regulate the anti-apoptotic protein Bcl-2 and the cell cycle proteins cyclin D1 and cdk2 in estrogen receptor-positive breast cancer cells. We show here that retinoids can also reduce expression of the inhibitor of apoptosis protein, survivin. Here we have compared the regulation of these proteins in MCF-7 and ZR-75 breast cancer cells by natural and synthetic retinoids selective for the RA receptors (RARs) alpha, beta, and gamma then correlated these with growth inhibition, induction of apoptosis and chemosensitization to Taxol. In both cell lines ATRA and 9-cis RA induced the most profound decreases in cyclin D1 and cdk2 expression and also mediated the largest growth inhibition. The RARalpha agonist, Ro 40-6055 also strongly downregulated these proteins although did not produce an equivalent decrease in S-phase cells. Only ATRA induced RARbeta expression. ATRA, 9-cis RA and 4-HPR initiated the highest level of apoptosis as determined by mitochondrial Bax translocation, while only ATRA and 9-cis RA strongly reduced Bcl-2 and survivin protein expression. Enumeration of dead cells over 96 h correlated well with downregulation of both survivin and Bcl-2. Simultaneous retinoid-mediated reduction of both these proteins also predicted optimal Taxol sensitization. 4-HPR was much weaker than the natural retinoids with respect to Taxol sensitization, consistent with the proposed requirement for reduced Bcl-2 in this synergy. Neither the extent of cell cycle protein regulation nor AP-1 inhibition fully predicted the antiproliferative effect of the synthetic retinoids suggesting that growth inhibition requires regulation of a spectrum of RAR-regulated gene products in addition even to pivotal cell cycle proteins.

Efficacy validation of synthesized retinol derivatives In vitro: stability, toxicity, and activity

Retinol (vitamin A) is used as an antiwrinkle agent in the cosmetics industry. However, its photo-instability makes it unsuitable for use in general cosmetic formulations. To improve the photo-stability of retinol, three derivatives (3, 4, and 5) were synthesized and their biological activities were analyzed. 1H NMR and HPLC analysis indicated that derivatives 3 and 5 were much more stable than retinol under our sunlight exposure conditions. When human adult fibroblasts were treated, the IC(50) of derivative 3 was 96 microM, which is similar to that of retinol, as determined by the MTT assay. Derivatives 4 and 5 were 2.5 and 8 times more toxic than retinol, respectively. At 1 microM treatment, like retinol, derivatives 3 and 4 were specifically active for RARalpha out of six retinoid receptors (RAR/RXRalpha, beta, gamma). Dose-dependent analysis confirmed that derivative 4 was as active as retinol and the other two derivatives were less active for RARalpha. The effect of our derivatives on the expression of collagenase, an indicator of wrinkle formation, was measured using the transient co-expression of c-Jun and RT-PCR in HaCaT cells. Collagenase promoter activity, which is increased by c-Jun expression, was reduced 42% by retinol treatment. The other derivatives inhibited collagenase promoter activity similarly. These results were further confirmed by RT-PCR analysis of the collagenase gene. Taken together, our results suggest that retinol derivative 3 is a promising antiwrinkle agent based on its higher photo-stability, lower RARalpha activity (possibly indicating reduced side effects), and similar effect on collagenase expression.

Maternal diabetes increases the risk of caudal regression caused by retinoic acid

Maternal diabetes increases the risk of congenital malformations in the offspring of affected pregnancies. This increase arises from the teratogenic effect of the maternal diabetic milieu on the developing embryo, although the mechanism of this action is poorly understood. In the present study, we examined whether the vitamin A metabolite retinoic acid (RA), a common drug with well-known teratogenic properties, may interact with maternal diabetes to alter the incidence of congenital malformations in mice. Our results show that when treated with RA, embryos of diabetic mice are significantly more prone than embryos of nondiabetic mice to develop caudal regression, a defect that is highly associated with diabetic pregnancy in humans. By studying the vestigial tail (Wnt-3a(vt)) mutant, we provide evidence that Wnt-3a, a gene that controls the development of the caudal region, is directly involved in the pathogenic pathway of RA-induced caudal regression. We further show that the molecular basis of the increased susceptibility of embryos of diabetic mice to RA involves enhanced downregulation of Wnt-3a expression. This positive interaction between RA and maternal diabetes may have implications for humans in suggesting increased susceptibility to environmental teratogens during diabetic pregnancy.

Retinoids and steroids regulate menstrual phase histological features in human endometrial organotypic cultures

OBJECTIVE

To determine whether organotypic cultures of human endometrium can be manipulated with hormones to exhibit histological features resembling different menstrual cycle phases.

DESIGN

Human menstrual cells were collected and cultured in monolayer and organotypic cultures.

SETTING

Healthy volunteer in an academic research environment.

PATIENT(S)

An individual premenopausal woman.

INTERVENTION(S)

Endometrial cultures were grown in collagen gels for 4 weeks, and exposed to various steroid and retinoid treatments.

MAIN OUTCOME MEASURE(S)

Histological features and expression of cytokeratins, vimentin, and reticulin.

RESULT(S)

Cultures developed multiple glands and surface epithelium that exhibited positive cytokeratin and negative vimentin staining. Single stromal cells inside the collagen exhibited negative cytokeratin and positive vimentin staining. Networks of reticulin fibers produced by the cells were increased by estrogen, decreased by progesterone, and unaffected by retinoids. Contraction of the collagen gels was inhibited by retinoids that activated retinoic acid receptors (RARs), but not by a retinoid specific for retinoid X receptors (RXRs). The combination and timing of retinoid and steroid hormone treatments were demonstrated to induce tissue architecture and histological features that resembled either proliferative or secretory phases.

CONCLUSION(S)

Growth of menstrual cells in collagen can be manipulated with retinoids and steroids to resemble histological features of the proliferative and secretory phases.

Alternative splicing and promoter usage generates an intracellular stromelysin 3 isoform directly translated as an active matrix metalloproteinase

Human stromelysin 3 (ST3) is a matrix metalloproteinase (MMP) that has been implicated in cancer progression and in various tissue remodeling processes. Unlike most MMPs, ST3 is characterized by a distinct substrate specificity and a specific regulation and is not directly involved in extracellular matrix degradation. In the present study, we have identified an additional ST3 gene promoter that is accessible to nuclear factors such as C/EBP and retinoic acid receptors. This human specific promoter is inducible and controls the expression of a novel ST3 transcript called the beta-ST3 that is expressed in cultured cells and in placenta. This transcript encodes a 40-kDa ST3 isoform that lacks both the signal peptide common to all secreted MMPs and the prodomain that normally maintains enzyme latency. Consistent with the lack of a signal peptide, the beta-ST3 was found to be intracellular. The relative amount of the extracellular alpha-ST3 isoform was about 20-fold higher than that of the intracellular ST3 isoforms, as estimated by Western blot analysis. Furthermore, recombinant beta-ST3 produced in Escherichia coli exhibits a proteolytic activity against alpha1-proteinase inhibitor, a substrate previously shown to be inactivated by the alpha-ST3. Therefore, although it was thought that all MMPs were synthesized as inactive zymogens and functioned extracellularly, this is the first MMP isoform reported that is generated by alternative promoter usage and directly translated as an active enzyme. Although the intracellular function of the beta-ST3 remains to be investigated, these data support the idea that the functions of MMPs are not restricted to the extracellular space.

Down-regulation of human papillomavirus E6/E7 oncogene by arsenic trioxide in cervical carcinoma cells

Arsenic trioxide (As2O3) has been implicated as a promising anticancer agent for treatment of many cancers including acute promylocytic leukemia. However, the molecular mechanisms are not yet fully defined in solid tumor cells, especially cervical cancer cells carrying human papillomavirus (HPV) genome. To analyze detailed mechanisms in vitro, we treated As2O3 to transformed HeLa cells, a well-studied cervical cancer cell line carrying HPV-18 sequence, and investigated its antiproliferative, antiviral and antimetastatic effects. As2O3 reduced survival and growth of HeLa cells in a dose- and time-dependent manner. Several indicatives of apoptosis were demonstrated by DNA fragmentation assay, DAPI nuclear staining and FACS analysis, respectively. Protein levels of p53 and cleavage of poly(ADP)-ribose polymerase were increased in a dose-dependent manner following treatment of As2O3. In parallel, semi-quantitative reverse transcription-polymerase chain reaction showed that the treatment inhibited HPV-18 E6/E7 viral gene expression in HeLa cells. Using transient transfection and CAT ELISA, we also found that AP-1 sites, located proximal to HPV-18 upstream regulatory region (URR) promoter, could be the major target sites for As2O3. Furthermore, As2O3-treated HeLa cells showed lesser capacity of invasion than those of untreated cells by in vitro invasion assay. Taken together, we proposed that antiviral effect, i.e. down-regulation of HPV E6/E7 oncogenes through targeting for AP-1 sites located in HPV URR might be associated with antiproliferative effect, i.e. induction of apoptosis as be resulted from the accumulation of p53, and that antimetastatic effect could be due to the targeted inactivation of AP-1, a transcription factor required for the expression of MMP-1 and -3. Therefore, our finding may provide a logical basis for the development of a new agent treating HPV-associated cervical neoplasia.

A regulatory cascade involving retinoic acid, Cbfa1, and matrix metalloproteinases is coupled to the development of a process of perichondrial invasion and osteogenic differentiation during bone formation

Tissue-remodeling processes are largely mediated by members of the matrix metalloproteinase (MMP) family of endopeptidases whose expression is strictly controlled both spatially and temporally. In this article, we have examined the molecular mechanisms that could contribute to modulate the expression of MMPs like collagenase-3 and MT1-MMP during bone formation. We have found that all-trans retinoic acid (RA), which usually downregulates MMPs, strongly induces collagenase-3 expression in cultures of embryonic metatarsal cartilage rudiments and in chondrocytic cells. This effect is dose and time dependent, requires the de novo synthesis of proteins, and is mediated by RAR-RXR heterodimers. Analysis of the signal transduction mechanisms underlying the upregulating effect of RA on collagenase-3 expression demonstrated that this factor acts through a signaling pathway involving p38 mitogen-activated protein kinase. RA treatment of chondrocytic cells also induces the production of MT1-MMP, a membrane-bound metalloproteinase essential for skeletal formation, which participates in a proteolytic cascade with collagenase-3. The production of these MMPs is concomitant with the development of an RA-induced differentiation program characterized by formation of a mineralized bone matrix, downregulation of chondrocyte markers like type II collagen, and upregulation of osteoblastic markers such as osteocalcin. These effects are attenuated in metatarsal rudiments in which RA induces the invasion of perichondrial osteogenic cells from the perichondrium into the cartilage rudiment. RA treatment also resulted in the upregulation of Cbfa1, a transcription factor responsible for collagenase-3 and osteocalcin induction in osteoblastic cells. The dynamics of Cbfa1, MMPs, and osteocalcin expression is consistent with the fact that these genes could be part of a regulatory cascade initiated by RA and leading to the induction of Cbfa1, which in turn would upregulate the expression of some of their target genes like collagenase-3 and osteocalcin.

Promoter characterization of the human and mouse epilysin (MMP-28) genes

Epilysin (MMP-28) is a recently cloned member of the matrix metalloproteinase family (Lohi et al., J. Biol. Chem. 276 (2001) 10134). It is expressed at highest levels in the skin by basal and suprabasal keratinocytes, and in testis by developing germ cells. To characterize the epilysin promoter, we isolated a 3.0 kb fragment of human genomic DNA containing 5'-flanking sequence of the epilysin gene, and a corresponding 660 bp fragment from the mouse. The 5'-flanking sequences contain no typical TATA-boxes or CCAAT sequences close to the translation initiation sites. RNase protection assay revealed that two transcription start sites are utilized in the human epilysin gene, situated 210 and 230 bp upstream from the translation start site. The promoter contains a GT-box, situated 300 bp upstream from the translation start site, with homology to the consensus binding site for transcription factors of the Sp family. This site is perfectly conserved between the human and mouse promoters. For reporter gene assays a series of constructs with fragments of increasing length of the epilysin promoter were coupled to the firefly luciferase gene. Reporter gene assays indicated that deletion or mutation of the GT-box dramatically reduces the transcriptional activity both in keratinocytes and in spermatogonia. Gel mobility shift assays showed that several nuclear proteins bind specifically to this sequence. Supershift assays with antibodies specific for members of the Sp family identified Sp1 and Sp3 as components of these protein/DNA complexes and hence as possible regulators of the epilysin gene. Our results indicate that the epilysin promoter has distinctive structural and functional features, which may control the unique expression and regulation patterns of the epilysin gene.

Placebo-Controlled Trial of Bexarotene, a Retinoid X Receptor Agonist, as Maintenance Therapy for Patients Treated with Chemotherapy for Advanced Non–Small-Cell Lung Cancer

This study was designed as a multicenter, randomized, double-blind, placebo-controlled trial. Patients were randomized by center to placebo (16 patients, 31%), oral bexarotene 300 mg/m2/day (21 patients, 40%), or oral bexarotene 600 mg/m2/day (15 patients, 29%) following demonstration of stable or responsive disease after first-line chemotherapy. The study was prematurely terminated because of slow accrual after 54 patients enrolled. Median time to progression (TTP) from the beginning of study drug treatment was 56 days for placebo, 82 days for moderate-dose bexarotene (300 mg/m2/day), and 128 days for high-dose bexarotene (600 mg/m2/day) (P = 0.56, log-rank test). For prior chemotherapy responders only, median TTP from the beginning of study drug treatment was 56 days for placebo, 146 days for moderate-dose bexarotene, and 177 days for high-dose bexarotene. Of note, there were more chemotherapy responders randomized to the placebo group (63%) than the bexarotene treatment arms (48% and 47%), further supporting a bexarotene-related improvement in TTP. Bexarotene-related toxicity was manageable and consisted primarily of elevated serum triglycerides and asthenia, skin toxicity (dryness, peeling, flaking), thyroid dysfunction, and headache. Because this study was closed prematurely, it does not have the statistical power to detect differences among the treatment groups. This study shows that patients can tolerate bexarotene at initial doses up to 600 mg/m2/day after platinum-based chemotherapy and that bexarotene may have the potential to delay disease progression in patients with advanced non-small-cell lung cancer with previously stable or responsive disease following platinum-based chemotherapy.

A synthetic triterpenoid selectively inhibits the induction of matrix metalloproteinases 1 and 13 by inflammatory cytokines

OBJECTIVE

To address the effects of a novel synthetic triterpenoid, 2-cyano-3,12-dioxoolean-1,9-dien-28-oic acid (CDDO), on the induction of matrix metalloproteinases 1 and 13 (MMP-1, MMP-13) by inflammatory cytokines.

METHODS

Human chondrosarcoma cells stimulated with inflammatory cytokines (interleukin-1beta [IL-1beta], tumor necrosis factor alpha) were used to study the effects of CDDO on the induction of MMPs and the invasion of cells through a collagen matrix.

RESULTS

CDDO selectively reduced the induction of MMP-1 and MMP-13 at the levels of messenger RNA and protein. Treatment with CDDO prior to cytokine stimulation enhanced this inhibition, and we demonstrated that CDDO functions at the level of transcription. Additionally, CDDO reduced IL-1beta-mediated invasion of cells through a collagen matrix.

CONCLUSION

This study demonstrates that CDDO is a novel inhibitor of MMP-1 and MMP-13 gene expression mediated by inflammatory cytokines. Thus, CDDO may have therapeutic potential for the inhibition of joint degradation in osteoarthritis.

Multiple regulatory elements in the murine stromelysin-3 promoter. Evidence for direct control by CCAAT/enhancer-binding protein beta and thyroid and retinoid receptors

Stromelysin-3 (ST3) belongs to the matrix metalloproteinase (MMPs) family, a protease family involved in tissue remodeling. Although this family of enzymes is regulated by nuclear receptors, few hormone-responsive elements have been demonstrated in MMP promoters. In order to identify regulatory elements and/or factors that control the expression of the mouse st3 gene, we have analyzed genomic sequences encompassing 5 kilobase pairs of the ST3 promoter. Analysis of these sequences revealed several CCAAT/enhancer-binding proteins (C/EBP) and retinoic acid-responsive elements (RAREs), as well as one thyroid-responsive element. However, in contrast to most MMP promoters, no AP-1-binding sites were identified. Specific binding activities were demonstrated for all elements. Consistent with previous reports, retinoid X receptor is required for maximal binding to the ST3 RAREs and the TRE. The ST3-C/EBP element was shown to mediate dose-dependent promoter activation by C/EBPbeta. Among the RAREs, the proximal DR1-RARE was shown to be sufficient for ST3 promoter activation by ligand-bound retinoid receptors, whereas the two distal DR2-RAREs appear to be involved more in the control of base-line promoter activity. Accordingly, ST3 expression was induced by retinoic acid and was reduced in cells where specific retinoic acid receptors had been inactivated. The involvement of these conserved regulatory elements is discussed in the context of physiological or pathological situations associated with st3 expression. Our findings therefore assign to C/EBP, retinoids, and thyroid hormone important roles in the regulation of ST3 gene expression.

Induced expression of dominant-negative c-jun downregulates NFkappaB and AP-1 target genes and suppresses tumor phenotype in human keratinocytes

Neoplastically transformed mouse and human keratinocytes elevate transactivation of both activator protein 1 (AP-1) and nuclear factor kappaB (NFkappaB) transcription factors. The present study addresses the question of whether elevated NFkappaB in addition to elevated AP-1-dependent gene expression is necessary for maintaining the tumor cell phenotype. When a tetracycline-regulatable dominant-negative c-jun (TAM67, having a truncated transactivation domain) was expressed in tumorigenic human keratinocytes, AP-1- and NFkappaB- but not p53-dependent reporter activity was inhibited by 40-60%. Tumor phenotype, as measured by anchorage-independent growth, was inhibited by 90%. Neither AP-1/NFkappaB activation nor expression of tumor phenotype was inhibited in TAM67-harboring keratinocytes under noninducing conditions. Electrophoretic mobility shift analysis showed that induction of TAM67 expression slightly increased AP-1- but reduced NFkappaB DNA-binding activity. Immunoprecipitation showed that TAM67 interacted in keratinocyte nuclei with NFkappaB p65, suggesting that inhibition of NFkappaB by TAM67 is mediated by direct protein-protein interactions, possibly producing decreased binding to DNA or inactivating p65. To analyze the putative effector genes that may be targeted by TAM67, expression of genes responsive to AP-1 or NFkappaB was measured by reverse transcriptase-polymerase chain reaction in TAM67 transfectants with or without TAM67 induction. Induction of TAM67 inhibited or reduced the expression of collagenase I, stromelysin I (AP-1 responsive), and interleukins 1 and 6 (NFkappaB responsive). These results indicate that genes controlled by NFkappaB and by AP-1 may be transformation-relevant targets of TAM67 and that TAM67 may inhibit NFkappaB activation through direct interaction with NFkappaB p65. Moreover, the findings provide proof for the principle of using inducible TAM67 as a gene therapy to suppress tumor phenotype in human carcinoma cells.

Differential influence of the E4 adenoviral genes on viral and cellular promoters

BACKGROUND

Strong and stable transgene expression is fundamental to the success of recombinant adenovirus vectors in human gene therapy. However, control of transgene expression is a complex process, involving both viral and cellular factors. In this study, the influence of the E4 adenoviral region on the activity of various promoters was investigated in vitro and in vivo.

METHODS

Pairs of isogenic E1o and E1oE4o vectors were generated and compared. Levels of transgene expression were determined by Northern blot, ELISA and FACS analysis. Initiation of transcription was studied by nuclear run-on assays.

RESULTS

Similar to the viral CMV and RSV promoters, the activity of the ubiquitous cellular PGK promoter required the presence of the E4 genes in vitro and in vivo. In contrast, transgene expression from selected liver- and tumor-specific promoters did not require E4 functions.

CONCLUSION

Together with the reported low liver toxicity of E1oE4o vectors, the independence of E4 of liver-specific promoters renders such vectors interesting alternatives to the use of gutless vectors.

All-trans-retinoic acid decreases vein graft intimal hyperplasia and matrix metalloproteinase activity in vivo

BACKGROUND

Development of vein graft intimal hyperplasia has been associated with increased activity of matrix metalloproteinases (MMPs). All-trans-retinoic acid (atRA) decreases expression and activity of MMPs in tissue culture and has decreased intimal hyperplasia following arterial balloon catheter injury. We examined the effect of oral administration of atRA on intimal hyperplasia and MMP expression in an animal model of vein bypass grafting.

MATERIALS AND METHODS

Interposition jugular vein bypass grafts were placed in the carotid artery of New Zealand white rabbits. Animals received either atRA (10 mg/kg/day) or vehicle (corn oil) for a period of 2 weeks. Retinoic acid serum levels were determined by HPLC. Intimal and medial areas were measured using morphometric analysis of perfusion-fixed vein graft specimens, and intimal thickness was calculated using circumferential measurements. Expression of MMP-2, MMP-9, and TIMP-1 in vein grafts and unoperated control veins was determined using Northern analysis, and proteolytic activity was determined using substrate gel zymography.

RESULTS

Animals treated with atRA had significantly elevated serum levels of this compound and its metabolites. A decrease in intimal to medial ratio was noted after 28 days in vein grafts from treated animals (0.63 vs 0.88, P < 0.01), and a decrease in calculated intimal thickness was noted at 7 and 28 days. Expression of MMP-2 was decreased in treated animals 7 days following surgery, and expression of both MMP-2 and MMP-9 was decreased at 28 days. A decrease in proteolytic activity was noted on zymography at 68 kDa, 7 and 28 days following surgery in vein grafts from animals treated with atRA, corresponding with a decrease in the active form of MMP-2. Increased expression of TIMP-1 was noted in vein grafts from both the treated and the control groups, 7 and 28 days following graft placement.

CONCLUSIONS

Oral administration of all-trans-retinoic acid resulted in decreased intimal hyperplasia in an animal model of vein bypass grafting. This was associated with decreased expression and activity of MMP-2 in treated animals.

Demonstration in vivo that stromelysin-3 functions through its proteolytic activity

Stromelysin-3 (ST3), a matrix metalloproteinase (MMP) expressed in aggressive carcinomas, has been shown to promote tumor development in different in vivo experimental models. However, the inability of its mature form to degrade extracellular matrix components casts doubt on whether ST3 functions in vivo as a protease. In this study, we evaluated whether the ST3 tumor-promoting effect could be ascribed to its proteolytic activity and whether this putative protease could be targeted with MMP inhibitors. Catalytically inactive mutant cDNA of human (h) ST3 or mouse (m) ST3 were generated and transfected into MCF7 cells. When injected into nude mice in the presence of matrigel, the mutant-bearing cells did not exhibit the enhanced tumorigenicity elicited by MCF7 cells transfected with wild-type ST3 cDNA. In a second approach, TIMP2 overproduction in MCF7 cells expressing hST3 was induced by retroviral infection. The co-expression of ST3 and TIMP2 failed to enhance the tumorigenicity of MCF7 cells. Notably, matrigel depleted of low-molecular-weight proteins and growth factors failed to promote the tumorigenicity of ST3-expressing MCF7 cells. These findings provide the first in vivo evidence that ST3 is indeed a protease that can modulate cancer progression by remodeling extracellular matrix and probably by inducing it to release the necessary microenvironmental factors. Thus, ST3 represents an interesting target for specific MMP inhibition.

Transcriptional induction of stromelysin-3 in mesodermal cells is mediated by an upstream CCAAT/enhancer-binding protein element associated with a DNase I-hypersensitive site

Stromelysin-3 (ST3) is a matrix metalloproteinase whose synthesis is markedly increased in stromal fibroblasts of most invasive human carcinomas. In the present study, we have investigated the molecular mechanisms by which high levels of ST3 expression can be induced. In contrast to the early and transient induction of interstitial collagenase by 12-O-tetradecanoylphorbol-13-acetate (TPA), the fibroblastic induction of ST3 was found to be delayed and to require protein neosynthesis. We demonstrated that this induction is transcriptional and does not result from changes in RNA stability. By looking next to promoter regions accessible to DNase I upon gene induction, we have identified two distal elements and have characterized their role in the transcriptional regulation of ST3. The first one is a TPA-responsive element that controls the base-line ST3 promoter activity but is not required for its activation. We demonstrate that ST3 gene induction is actually mediated by the second element, a C/EBP-binding site, by showing: (i) that this element becomes accessible in cells induced to express ST3, (ii) that endogenous C/EBPbeta binds to the ST3 promoter, and (iii) that this binding leads to ST3 transcriptional activation. Our study provides new insights into the regulation of ST3 and suggests an additional role for C/EBP transcription factors in tissue remodeling processes associated with this MMP.

Tocoretinate inhibited the contraction of collagen gel matrices by human dermal fibroblasts with tenascin-C expression

Retinoids are strong tissue modifiers and have been used to treat severe acne, keloids and photo-aged skin. Tocoretinate (TR), ester bound retinoic acid and tocopherol, has been topically applied for skin ulcers and, more recently, for sclerotic skin diseases. To clarify the mechanism of tissue softening by retinoids and TR, we investigated their effects on the contraction of hydrated type-1 collagen gel matrices by human dermal fibroblasts and on tenascin-C expression. TR, 13-cis-retinoic acid/isotretinoin and all trans-retinoic acid significantly inhibited collagen gel matrices contraction at concentrations from 10(-4) to 10(-8) M without significant changes of the fibroblast growth. TR and the other two retinoids dose-dependently induced tenascin-C expression in the fibroblasts. Since tenascin-C is involved in cellular detachment and tissue remodeling, these results suggest that TR and other retinoids down-regulated the tensile tension of fibroblasts in collagen gel matrices by the induction of tenascin-C.

Regulation of adenovirus-mediated transgene expression by the viral E4 gene products: requirement for E4 ORF3

In a previous study we showed that multiple deletions of the adenoviral regulatory E1/E3/E4 or E1/E3/E2A genes did not influence the in vivo persistence of the viral genome or affect the antiviral host immune response (Lusky et al., J. Virol. 72:2022-2032, 1998). In this study, the influence of the adenoviral E4 region on the strength and persistence of transgene expression was evaluated by using as a model system the human cystic fibrosis transmembrane conductance regulator (CFTR) cDNA transcribed from the cytomegalovirus (CMV) promoter. We show that the viral E4 region is indispensable for persistent expression from the CMV promoter in vitro and in vivo, with, however, a tissue-specific modulation of E4 function(s). In the liver, E4 open reading frame 3 (ORF3) was necessary and sufficient to establish and maintain CFTR expression. In addition, the E4 ORF3-dependent activation of transgene expression was enhanced in the presence of either E4 ORF4 or E4 ORF6 and ORF6/7. In the lung, establishment of transgene expression was independent of the E4 gene products but maintenance of stable transgene expression required E4 ORF3 together with either E4 ORF4 or E4 ORF6 and ORF6/7. Nuclear run-on experiments showed that initiation of transcription from the CMV promoter was severely reduced in the absence of E4 functions but could be partially restored in the presence of either ORF3 and ORF4 or ORFs 1 through 4. These results imply a direct involvement of some of the E4-encoded proteins in the transcriptional regulation of heterologous transgenes. We also report that C57BL/6 mice are immunologically weakly responsive to the human CFTR protein. This observation implies that such mice may constitute attractive hosts for the in vivo evaluation of vectors for cystic fibrosis gene therapy.

Retinoid-mediated suppression of tumor invasion and matrix metalloproteinase synthesis

Cancer mortality usually results from the tumor invading the local environment and metastasizing to vital organs, e.g. liver, lung, and brain. Degradation of the extracellular matrix is, therefore, the sine qua non of tumor cell invasion. this degradation is mediated mainly by MMPs, and thus, inhibition of MMP synthesis is a target for anticancer agents. Tumor cells must traverse both the basement membrane (type IV collagen) and the interstitial stroma (type I collagen). Therefore, we used scanning electron microscopy to examine the invasive behavior of several aggressive tumor cell lines, A2058 melanoma cells, and SCC and FaDu squamous cell carcinomas through these matrices; and we monitored the ability of all-trans retinoic acid and several RAR-specific ligands to block invasion. We demonstrate that several retinoids, which are specific RAR alpha, beta, or gamma agonists/antagonists, selectively inhibited MMP synthesis in the three tumor cell lines. However, there was not a common pattern of MMP inhibition by a particular retinoid. For instance, a RAR alpha antagonist suppressed MMP-1 and MMP-2 synthesis in the melanoma cell line, but not in the FaDu or SCC-25 cells. On the other hand, synthesis of MMP-1 and MMP-9 by the FaDu cells was affected hardly at all, while a RAR gamma antagonist reduced the levels of MMP-2. Only all-trans retinoic acid reduced MMP-1 synthesis in these cells. We postulate that the differences may be related to a differential pattern of RAR expression in each of these cells, and that the RARs expressed by each cell line may not be targets of these RAR specific compounds. All-trans retinoic acid is a pan ligand, binding to all three RARs and, therefore, may modulate gene expression more generally. We conclude that the power of these new ligands lies in their specificity, which can be directed towards modulating expression of certain RARs and, thus, of certain MMPs. By blocking MMP synthesis, retinoids may be effective in cancer therapy by decreasing tumor invasiveness.

Expression of retinoid receptor genes and proteins in non-small-cell lung cancer

BACKGROUND

Retinoids can suppress carcinogenesis in high-risk non-neoplastic bronchial lesions and can reduce the risk of second primary non-small-cell lung cancer (NSCLC). The effects of retinoids are mediated by nuclear receptors, i.e., the retinoic acid receptors (RARalpha, RARbeta, and RARgamma) and the retinoid X receptors (RXRalpha, RXRbeta, and RXRgamma). We investigated whether abnormalities in the in vivo expression of retinoid receptors are observed in NSCLC.

METHODS

Expression of retinoid receptors in paired specimens of normal and cancerous tissues from the lungs of 76 patients with NSCLC was studied by use of antiretinoid receptor antibodies (except those against RXRgamma) and immunohistochemistry. RAR messenger RNAs were analyzed by use of in situ hybridization and by reverse transcription-polymerase chain reaction (RT-PCR). Samples were also studied for loss of heterozygosity (LOH) at chromosome 3p24. All P values are two-sided.

RESULTS

All studied receptors were expressed in normal lung cells and in high- risk non-neoplastic lesions. In tumor cells, overexpression of RXRalpha and RARalpha was frequently observed. In contrast, RXRbeta expression decreased in 18% of the tumor specimens. Furthermore, there was a marked decrease in the expression of RARbeta in 63% of the tumors (P<.0001). Decreased expression of RARgamma was observed by RT-PCR in 41% of the tumors (P<.0001). LOH at 3p24 was observed in 41% of the tumor specimens from informative patients and in 20% of the non-neoplastic lesions.

CONCLUSIONS

Expression of RARalpha and RXRalpha is either normal or elevated in NSCLC. In contrast, a large percentage of tumors show a marked decrease in the expression of RARbeta, RARgamma, and RXRbeta as well as a high frequency of LOH at 3p24, which was also observed in non-neoplastic lesions. These data suggest that altered retinoid receptor expression may play a role in lung carcinogenesis.

Expression of stromelysin-3 in atherosclerotic lesions: regulation via CD40-CD40 ligand signaling in vitro and in vivo

Stromelysin-3 is an unusual matrix metalloproteinase, being released in the active rather than zymogen form and having a distinct substrate specificity, targeting serine proteinase inhibitors (serpins), which regulate cellular functions involved in atherosclerosis. We report here that human atherosclerotic plaques (n = 7) express stromelysin-3 in situ, whereas fatty streaks (n = 5) and normal arterial specimens (n = 5) contain little or no stromelysin-3. Stromelysin-3 mRNA and protein colocalized with endothelial cells, smooth muscle cells, and macrophages within the lesion. In vitro, usual inducers of matrix metalloproteinases such as interleukin-1, interferon-gamma, or tumor necrosis factor alpha did not augment stromelysin-3 in vascular wall cells. However, T cell-derived as well as recombinant CD40 ligand (CD40L, CD154), an inflammatory mediator recently localized in atheroma, induced de novo synthesis of stromelysin-3. In addition, stromelysin-3 mRNA and protein colocalized with CD40L and CD40 within atheroma. In accordance with the in situ and in vitro data obtained with human material, interruption of the CD40-CD40L signaling pathway in low density lipoprotein receptor-deficient hyperlipidemic mice substantially decreased expression of the enzyme within atherosclerotic plaques. These observations establish the expression of the unusual matrix metalloproteinase stromelysin-3 in human atherosclerotic lesions and implicate CD40-CD40L signaling in its regulation, thus providing a possible new pathway that triggers complications within atherosclerotic lesions.

Dual regulation of stromelysin-3 by fibroblast growth factor-2 in murine osteoblasts

Osteoblasts express stromelysin-3, a matrix metalloproteinase associated with normal remodeling processes and with stromal fibroblasts surrounding many invasive carcinomas. Fibroblast growth factors (FGFs) play an important role in skeletal development, fracture repair, and osteoblast function. The osteoblastic cell line MC3T3 was used to study the regulation of stromelysin-3 by FGF-2. Acutely, FGF-2 decreased stromelysin-3 mRNA levels, whereas prolonged treatment caused an induction of stromelysin-3 mRNA. RNA stability studies and nuclear run-off assays indicated that acute treatment with FGF-2 decreased stromelysin-3 mRNA stability but did not alter gene transcription. However, the induction of stromelysin-3 after prolonged treatment with FGF-2 resulted from increased gene transcription, with no effect on RNA stability. The stimulatory effect was protein synthesis-dependent, whereas the inhibitory effect was not. This study demonstrates dual regulation of stromelysin-3 by FGF-2: acute destabilization of stromelysin-3 mRNA, followed by induction of gene transcription. This complex regulation may be important in the function of stromelysin-3 in bone and in remodeling processes, such as wound and fracture repair.

Transdifferentiation of rat hepatic stellate cells results in leptin expression

Leptin is a peptide hormone that appears critical in regulating Fat metabolism. Recently, circulating leptin levels were reported higher in patients with alcoholic cirrhosis. In health, hepatic stellate cells store retinoids, but following liver injury they transdifferentiate into myofibroblast-like cells with loss of the retinoid stores. Leptin expression was demonstrated by detection of leptin mRNA by RT-PCR analysis and by immunohistochemistry viewed with confocal microscopy in transdifferentiated stellate cells after 14 days, or more, of culture. Leptin expression was not found in freshly isolated quiescent stellate cells. Leptin expression was not demonstrated in freshly isolated or cultured Kupffer cells. Treatment of activated stellate cells with either 1 microM retionic acid or 10 microM retinol acetate resulted in the inhibition of leptin mRNA expression. The observation that activated stellate cells in culture can express leptin has implications for understanding adipocyte biology in liver disease and treatment of malnutrition in cirrhotics.

Membrane type-1 matrix metalloprotease and stromelysin-3 cleave more efficiently synthetic substrates containing unusual amino acids in their P1' positions

The influence of the substrate P1' position on the specificity of two zinc matrix metalloproteases, membrane type-1 matrix metalloprotease (MT1-MMP) and stromelysin-3 (ST3), was evaluated by synthesizing a series of fluorogenic substrates of general formula dansyl-Pro-Leu-Ala-Xaa-Trp-Ala-Arg-NH2, where Xaa in the P1' position represents unusual amino acids containing either long arylalkyl or alkyl side chains. Our data demonstrate that both MT1-MMP and ST3 cleave substrates containing in their P1' position unusual amino acids with extremely long side chains more efficiently than the corresponding substrates with natural phenylalanine or leucine amino acids. In this series of substrates, the replacement of leucine by S-para-methoxybenzyl cysteine increased the kcat/Km ratio by a factor of 37 for MT1-MMP and 9 for ST3. The substrate with a S-para-methoxybenzyl cysteine residue in the P1' position displayed a kcat/Km value of 1.59 10(6) M-1 s-1 and 1.67 10(4) M-1 s-1, when assayed with MT1-MMP and ST3, respectively. This substrate is thus one of the most rapidly hydrolyzed substrates so far reported for matrixins, and is the first synthetic peptide efficiently cleaved by ST3. These unexpected results for these two matrixins suggest that extracellular proteins may be cleaved by matrixins at sites containing amino acids with unusual long side chains, like those generated in vivo by some post-translational modifications.