Tissue inhibitor of metalloproteinases-3 is a component of Bruch's membrane of the eye

Mutations in tissue inhibitor of metalloproteinases (TIMP)-3 are found in some patients with Sorsby's fundus dystrophy, a retinal degeneration characterized by abnormal deposits in Bruch's membrane and choroidal neovascularization. The purpose of this study was to localize TIMP-3 in the retina/choroid of normal human and animal eyes. Immunolabeling was performed on unfixed and fixed sections of human eyes aged 24 to 85 years and unfixed sections of baboon, chicken, cow, pig, and rat eyes using a monoclonal antibody against a human TIMP-3 synthetic peptide. The antibody produced strong immunolabeling of Bruch's membrane and drusen and weak labeling of retina blood vessels in unfixed human and baboon eyes. Unfixed chicken, cow, pig, and rat tissues showed no reactivity. After antigen retrieval, all fixed human eyes showed specific labeling of Bruch's membrane and drusen, which was strongest in eyes from elderly donors. The results indicate that TIMP-3 is an extracellular matrix component of Bruch's membrane. Thus, abnormal local function of TIMP-3 may lead to the characteristic Bruch's membrane deposits and choroidal neovascularization found in Sorsby's fundus dystrophy. Specific labeling of drusen raises the possibility that altered TIMP-3-mediated matrix remodeling may contribute to age-related degenerative changes in Bruch's membrane.

Tissue inhibitor of metalloproteinases-3 is the major metalloproteinase inhibitor in the decidualizing murine uterus

Embryo implantation in the mouse is a highly orchestrated process, a key aspect of which is the invasion of trophoblast cells of the blastocyst into the maternal uterine endometrium. Invasion is facilitated via proteinases expressed by trophoblast cells and balanced by expression of inhibitors of proteinases in the maternal decidua. The predominant proteinase expressed by trophectodermal derivatives of the implanting mouse embryo is matrix metalloproteinase-9 (MMP-9; gelatinase B). Using in situ hybridization, transcripts for MMP-9 were detected in trophoblast cells of the embryo from the earliest stage of decidual formation (day 6.0) examined. MMP-9 transcripts were localized to trophoblast giant cells at the periphery of the embryo at the egg cylinder stage (day 7.0). By the neural-fold stage (day 8.5), expression was restricted to giant cells adjacent to the maternal side of the developing placenta, and by day 9.5 few MMP-9-positive cells remained. The major tissue inhibitor of metalloproteinases (TIMP) produced during this period was TIMP-3. Transcripts encoding TIMP-3 were detected from day 6.0-7.0 in the maternal decidua immediately adjacent to embryonic cells expressing MMP-9. The intensity of TIMP-3 expression in later-stage embryos declined in parallel with MMP-9 expression. Maternal TIMP-3 expression also occurred in the absence of embryonic MMP-9 expression in decidual reactions induced by parthenogenetic embryos (where MMP-9 positive cells were not detected) or in oil-induced deciduomas. These results support the hypothesis that MMP-9 is an important mediator of cellular invasiveness during embryo implantation, and that TIMP-3 serves as a regulator within the uterus to restrict invasion to the site of implantation.

Characterization of a putative p53 binding site in the promoter of the mouse tissue inhibitor of metalloproteinases-3 (TIMP-3) gene: TIMP-3 is not a p53 target gene

We have recently cloned the promoter of the mouse tissue inhibitor of metalloproteinases-3 (TIMP-3) gene and have identified a putative p53 binding site (5'-GGGCTTGCTT GACGTCCA GAACAGGGTC-3'), which contains two p53 consensus binding motifs (bold) with two nucleotide mismatches (underlined) in the second motif and an 8 bp spacer in between. Since both p53 and TIMP-3 are involved in cell cycle progression, we tested the hypothesis that TIMP-3 is a p53 downstream effector gene, mediating p53 activity. A good correlation between p53 protein levels and TIMP-3 expression was found among mouse liver cell lines. However, when TIMP-3 promoter driven luciferase constructs were tested for p53 responsiveness in these cells, the construct containing the putative p53 binding site did not show significant difference from the one having the p53 site deleted. The gel retardation assay showed that the oligo (T3) made from the putative p53 binding site in the mouse TIMP-3 promoter did not bind to p53 protein, nor did an oligo (T3W) with a correction for the two mismatched nucleotides in the second motif. When the 8 bp spacer was removed, however, the oligo T3WSF (same as the T3W with spacer free) but not T3SF (T3 without spacer) binds to p53, indicating that both the spacer between two motifs and consensus binding sites determined the p53 binding. It is worth noting that under a less stringent assay condition (0.2 microg instead of 1.0 microg of dI/dC), T3SF did weakly bind to p53. Lastly, the compounds that induce p53 transactivation activity did not induce TIMP-3 expression. We concluded from this study that TIMP-3 is not a p53 downstream effector gene.

Regulation of tissue inhibitor of metalloproteinases-3 gene expression by transforming growth factor-beta and dexamethasone in bovine and human articular chondrocytes

Physiological and pathological degradation of cartilage extracellular matrix (ECM) is regulated by the balance between tissue inhibitors of metalloproteinases (TIMPs) and matrix metalloproteinases (MMPs). We examined the potential of chondrocytes from normal bovine or human osteoarthritic (OA) cartilage to express RNA for the new inhibitor TIMP-3 and studied its regulation by an inducer of matrix synthesis, transforming growth factor-beta (TGF-beta). Freshly released chondrocytes constitutively expressed three transcripts of TIMP-3 that are induced by serum factors. In primary cultures of chondrocytes, one of these factors, TGF-beta, increased TIMP-3 mRNA in a dose-dependent fashion that required de novo protein synthesis and transcription. TGF-beta did not alter stability of the TIMP-3 transcripts in RNA decay time-courses, suggesting a transcriptional control. Nuclear run-on assays confirmed increased rate of TIMP-3 gene transcription by TGF-beta. An antiinflammatory glucocorticoid, dexamethasone, inhibited the basal, and suppressed partially the TGF-beta-inducible, TIMP-3 expression in primary bovine and human chondrocytes. DNA sequencing of bovine TIMP-3 cDNA revealed an open reading frame of a 211-amino-acid protein containing signal peptide and 12 conserved cysteines. The encoded protein differed from human TIMP-3 at four positions. The constitutive expression and evolutionary conservation of TIMP-3 imply its important function. TIMP-3 induction by TGF-beta suggests the role of this factor and TIMP-3 in cartilage remodeling with important implications for arthritis.

Oncostatin M differentially regulates tissue inhibitors of metalloproteinases TIMP-1 and TIMP-3 gene expression in human synovial lining cells

Tissue inhibitor of metalloproteinases (TIMP) 1, 2 and 3 are related proteins that can form complexes with all known matrix metalloproteinases (MMPs). They inhibit the action of MMPs on extracellular matrix components. The balance of MMPs and TIMPs is important for tissue remodeling and its disturbance is believed to play a crucial role in pathophysiological processes such as tumor metastasis, destruction of cartilage and fibrosis. Cytokines and growth factors were found to regulate TIMPs and MMPs in a complex manner. In order to better understand the role of TIMPs in inflammatory joint diseases we have studied in vitro the regulation of TIMP-1 and TIMP-3 by inflammatory cytokines in cultured human synovial lining cells. We found that transforming growth factor beta 1 as well as interleukin-1 beta induce gene expression of both TIMP-1 and TIMP-3. In contrast, oncostatin M, an interleukin-6-type cytokine produced by activated T-lymphocytes and monocytes, had a differential effect on TIMP mRNA levels. After oncostatin M treatment, TIMP-1 expression was up-regulated but basal, as well as interleukin-1 beta-induced, TIMP-3 expression was inhibited. Interleukin-6 itself had no effect on synovial lining cells but a complex of interleukin-6 and the soluble interleukin-6 receptor induced activation of signal transducer and activator of transcription (STAT) factors in these cells and regulated TIMP-1 and TIMP-3 expression in a similar fashion as oncostatin M. Since TIMP-3 is matrix-associated whereas TIMP-1 is found in many body fluids, the role of oncostatin M during inflammatory processes might be to promote ECM degradation in the local environment but to prevent it systemically.

TIMP-3 is expressed in the human retinal pigment epithelium

TIMP-3 is the most recent member of the tissue inhibitor of metalloproteinases (TIMP) family. In the present study, we describe the expression of TIMP-3 messenger RNA (mRNA) by the retinal pigment epithelium of the normal human eye (hRPE). In addition to the three predominant transcripts of approximately 5.1, 2.8, and 2.4 Kbp found in several other human tissues at adult and fetal stages. The hRPE also expresses two RNA species of 1.2 and 1.0 Kbp. Based on the sequence analysis of cDNA clones isolated from a hRPE cDNA library, the use of alternate polyadenylation signals could account for the expression of these smaller transcripts. The possibility of an alternative mechanism of regulation of the expression of TIMP-3 by the RPE is not discarded. The number of RNA transcripts specific for TIMP-3 per nanogram of poly A+ RNA was quantified by RT-PCR. 9.6 x 10(5) transcripts per nanogram of polyA +RNA were found at the adult stage and 1.2 x 10(6) transcripts per nanogram of polyA +RNA were detected at the fetal stage. These findings were supported by the predominant labeling in the RPE layer of retinal tissue sections in in situ hybridization experiments. All of these data support the hypothesis that the production of TIMP-3 by the RPE may be crucial for the maintenance of Bruch's membrane, the complex layer of extracellular matrix that provides a structural substrate for the RPE in the healthy retina and is perturbed during the ageing process and in Sorby's Fundus Dystrophy a inherited disease.

Temporal and spatial expression of tissue inhibitors of metalloproteinases during the natural ovulatory cycle of the mouse

The role of tissue inhibitors of metalloproteinases (TIMPs) in ovarian function has primarily been documented by studies that utilize hormone-primed animals. In this study, our objectives were to elucidate the spatiotemporal expression of individual TIMP genes during the natural ovulatory cycle, and to correlate these with specific biological events. Two models of spontaneous ovulation used were the murine estrous cycle and the first ovulation postpartum. Ovaries were collected from mice at diestrus, estrus, and metestrus, or at early and late proestrus, and from pregnant females on Days 17 and 18 of gestation (D17, D18) and within 24 or 48 h postpartum (PP1, PP2). We observed that TIMP-1 mRNA was elevated at early proestrus and D18 and was maximal at late proestrus and PP1. The TIMP-3 pattern was distinct from that of TIMP-1, maximal expression occurring at early proestrus and D17 and D18. In both models, TIMP-2 mRNA remained constant and at very low levels throughout ovulation. In situ hybridization localized TIMP-1 mRNA to the corpus luteum at D18 and PP1, and to oocytes at specific stages of follicular development. Expression of TIMP-1 in granulosa and thecal cells was not observed at any stage. Demonstrating a distinct distribution, TIMP-3 mRNA was localized to oocytes, thecal and granulosa cells of small and large follicles, and corpora lutea only at D17. These data suggest specific hormonal regulation of individual TIMP gene expression in the ovary associated with distinct physiological functions. We propose that in the natural ovulatory process, TIMP-1 is probably a factor that regulates corpus luteum regression while TIMP-3 is important in maintaining the structural integrity of the corpus luteum.

Suppression of in vivo tumor growth and induction of suspension cell death by tissue inhibitor of metalloproteinases (TIMP)-3

Tissue inhibitor of metalloproteinases-3(TIMP-3), a novel member of TIMP family genes, has been recently cloned and shown to be expressed in preneoplastic but not in neoplastic mouse JB6 epidermal cells (Sun et al. 1994 Cancer Res., 54, 11139). This down regulation of the gene appears to be attributable at least in part to alteration of gene methylation (Sun et al. 1995 J. Biol. Chem., 270, 19312). Little is known, however, about the role of TIMP-3 in human cancers. We screened several human tumor cell lines for TIMP-3 expression and found that a colon carcinoma line, DLD-1, did not express TIMP-3. If down regulation of TIMP-3 is causally related to carcinogenesis, re-expression by transfection may reverse the tumor cell phenotype. We therefore overexpressed human TIMP-3 in DLD-1 cells. TIMP-3 transfectants showed a serum-dependent growth inhibition in monolayer culture and a decreased growth potential in nude mice in a manner dependent on the level of TIMP-3 expression. A transfectant expressing a high level of active hTIMP-3 completely lost the ability to form tumors following s.c. injection into nude mice. We also tested TIMP-3 expressing cells and neocontrol TIMP-3 negative cells for their ability to grow in liquid suspension culture, since both cells grew in semi-solid soft agar. As compared to neocontrol cells, TIMP-3 overexpressors formed large aggregates, followed by cell death. This effect was not mimicked by BB94, a broad MMP inhibitor. We conclude from this study that (i) TIMP-3 overexpression in human colon carcinoma cells induces growth arrest in low serum conditions and inhibits in vivo tumor growth and (ii) the TIMP-3-induced large aggregate formation and subsequent cell death under suspension growth cannot be explained by its MMP inhibitory activity.

Localization of TIMP-3 mRNA expression to the retinal pigment epithelium

PURPOSE

To evaluate ocular sites of expression of the tissue inhibitor of metalloproteinases-3 gene (TIMP-3).

METHODS

In situ hybridization was performed on frozen sections of albino mouse eyes using riboprobes generated to the 3' untranslated region of TIMP-3.

RESULTS

TIMP-3 mRNA expression was detected strongly in the retinal pigment epithelium (RPE) and to a minor extent in the ciliary epithelium, but not at any other site within the eye.

CONCLUSIONS

Expression of TIMP-3 in the RPE is consistent with the recent demonstration of TIMP-3 mutations in patients with Sorsby's fundus dystrophy, a condition marked by the early onset of choroidal neovascularization in the macula. Unlike many of the recently described genes that cause human retinal disease, TIMP-3 is preferentially expressed in the RPE of the normal eye, as opposed to the photoreceptors.

Molecular genetics of central retinal dystrophies

A range of chorioretinal dystrophies that principally affect the central retina have recently been associated with either specific genetic mutations or mapped to refined genomic loci. Mutations of two genes, peripherin/RDS (chromosome 6p) and TIMP3 (chromosome 22q) have been shown to be of particular importance to this group of disorders. Other conditions such as Stargardt's disease, Best's disease, pattern dystrophy, cone dystrophy and cone-rod dystrophy have been mapped to different regions of the genome, however the underlying genetic mutations await identification. Molecular genetic diagnostic techniques are now available for a number of central choroidoretinal dystrophies allowing for earlier, accurate diagnosis and laying the groundwork for future studies of potential therapeutic protocols.

The soluble catalytic domain of membrane type 1 matrix metalloproteinase cleaves the propeptide of progelatinase A and initiates autoproteolytic activation. Regulation by TIMP-2 and TIMP-3

It has been proposed that the cell-mediated activation of progelatinase A requires binding of the C-terminal domain of the proenzyme to a membrane-associated complex of the membrane type matrix metalloproteinase MT1-MMP and TIMP-2. Subsequent sequential proteolysis of the propeptide by MT1-MMP and gelatinase A is thought to generate the active form of gelatinase A. We have prepared the proform of the catalytic domain of the MT1-MMP and demonstrated that this may be activated in vitro by trypsin proteolysis to yield a functional proteinase capable of cleaving typical metalloproteinase peptide substrates, gelatin and casein. The active catalytic domain of MT1-MMP was also shown to activate progelatinase A to a fully active form. Using the inactive mutant pro-E375A gelatinase A, we dissected the propeptide processing events that occur. MT1-MMP cleaves the propeptide at the sequence Asn37-Leu38 only. Further cleavage of the mutant enzyme propeptide at Asn80-Tyr81, equivalent to that of the active wild type gelatinase A, could only be effected by addition of gelatinase A to the system. TIMP-1 was essentially unable to prevent MT1-MMP processing of wild type or E375A progelatinase A, whereas TIMP-2 and TIMP-3 were good inhibitors of these events. Analysis of the rate of binding of TIMPs to the catalytic domain of MT1-MMP using kinetic methods showed that TIMP-1 is an extremely poor inhibitor of MT1-MMP. In comparison, TIMP-2 and TIMP-3 are excellent inhibitors, binding more rapidly to the catalytic domain of MT1-MMP than to the catalytic domain of gelatinase A. These data demonstrate the basic mechanism of MT1-MMP action on progelatinase A and the reason for the lack of inhibition by TIMP-1 previously demonstrated in cell-based activation studies.

Sorsby fundus dystrophy. A family with the Ser181Cys mutation of the tissue inhibitor of metalloproteinases 3

Sorbsy fundus dystrophy (SFD) is an autosomal dominant disorder that is characterized by bilateral loss of central vision secondary to choroidal neovascularization and/or pigment epithelial atrophy in the macula, with onset of visual symptoms usually in the fourth or fifth decade. Drusenlike changes may occur, with impaired dark adaptation and abnormal electroretinographic results.

Expression and function of matrix metalloproteinases and their inhibitors at the maternal-embryonic boundary during mouse embryo implantation

Gelatinase B, a matrix metalloproteinase (MMP) of high specific activity, is highly expressed and activated by mouse blastocysts in culture, and inhibition of this enzyme activity inhibits lysis of extracellular matrix (Behrendtsen, O., Alexander, C. M. and Werb, Z. (1992) Development 114, 447–456). Because gelatinase B expression is linked to invasive potential, we studied the expression of gelatinase B mRNA and protein in vivo, in implanting trophoblast giant cells, and found that it was expressed and activated during colonization of the maternal decidua. mRNAs for several other MMPs (stromelysin-1, stromelysin-3 and gelatinase A) and MMP inhibitors (TIMP-1 and TIMP-2) were expressed in the undifferentiated stroma toward the outside of the decidua, and TIMP-3 mRNA was expressed in primary and some mature decidual cells during their differentiation. Both mRNA and TIMP-3 protein were present at high concentrations transiently, and declined from 6.5 days post coitum onward, as the cells underwent apoptosis during the main period of gelatinase B expression and ectoplacental growth and expansion. To assess the function of MMPs during implantation and decidual development, we either injected a peptide hydroxamate MMP inhibitor into normal mice or studied transgenic mice overexpressing TIMP-1. In both cases, decidual length and overall size were reduced, and the embryo was displaced mesometrially. Embryo orientation was less strictly regulated in inhibitor-treated deciduae than in control deciduae. Morphogenesis and development of oil-induced deciduomas were also slowed in the presence of the inhibitor. We conclude that administration of MMP inhibitors retards decidual remodeling and growth, and we suggest that the MMPs expressed in precursor stromal cells promote their differentiation and expansion.

Cloning and partial structure of the gene encoding human tissue inhibitor of metalloproteinases-3

Using a cDNA probe, two genomic clones were obtained encoding the human tissue inhibitor of metalloproteinases-3 (TIMP-3). Analysis of these clones showed that they contained four distal exons and three introns of the gene. Although the intron-exon structure is similar to that of the timp1 gene, the first intron of the timp3 gene is much longer, being at least 17.5 kb in size.

Regulation of granulosa cell-derived ovarian metalloproteinase inhibitor(s) by prolactin

Increased prolactin concentrations are known to inhibit the ovarian proteolytic enzyme cascade associated with follicular rupture. It is not known whether there is also an effect of prolactin on endogenous proteinase inhibitors such as the tissue inhibitors of metalloproteinases (TIMPs). We sought to study the effect of prolactin on ovarian metalloproteinase inhibitors in cultured rat granulosa cells. Granulosa cells were cultured for 24 h with prolactin (0-1000 ng ml-1) in the absence or presence of LH. Metalloproteinase inhibitor activity in the conditioned culture media was measured by a colorimetric assay. Prolactin at 1000 ng ml-1 increased inhibitor activity by 2.86 +/- 0.63 times. Expression of mRNA encoding TIMP-1 measured by Northern analysis increased by 2.34 +/- 0.34 times with 100 ng prolactin ml-1 and by 2.43 +/- 0.42 times with 1000 ng prolactin ml-1 compared with control cultures (no LH, no prolactin). In the presence of LH, expression of mRNA encoding TIMP-1 and inhibitor activity increased by 2.60 +/- 0.6 and 4.60 +/- 0.54 times, respectively. However, no further change in mRNA expression or inhibitor activity was apparent with the addition of prolactin to LH-treated cultures. Prolactin had no effect on expression of mRNA encoding TIMP-3 in the absence or presence of LH, although LH stimulated a 1.7-fold increase in mRNA encoding TIMP-3 compared with controls. Addition of prolactin had no effect on media concentrations of oestradiol or progesterone. These data demonstrate that metalloproteinase inhibitor activity increases with increasing doses of prolactin; however, when LH was added, this effect was no longer seen. With an increase in metalloproteinase inhibitor activity, tissue metalloproteinase action could be decreased, providing a possible explanation for the local inhibition on pre- and peri-ovulatory pathways by hyperprolactinaemia.

Divergent regulation by growth factors and cytokines of 95 kDa and 72 kDa gelatinases and tissue inhibitors or metalloproteinases-1, -2, and -3 in rabbit aortic smooth muscle cells

The migration and proliferation of vascular smooth muscle cells (SMCs) during neointima formation in atherosclerosis and angioplasty restenosis is mediated by certain growth factors and cytokines, one action of which may be to promote basement-membrane degradation. To test this hypothesis further, the effects of such growth factors and cytokines on the synthesis of two basement-membrane-degrading metalloproteinases, namely the 72 kDa gelatinase (MMP-2, gelatinase A) and the 95 kDa gelatinase (MMP-9, gelatinase B) and three tissue inhibitors of metalloproteinases (TIMPs) was studied in primary cultured rabbit aortic SMCs. Expression of the 95 kDa gelatinase was increased by phorbol myristate acetate, foetal calf serum, thrombin and interleukin-1alpha (IL-1alpha); platelet-derived growth factor (PDGF) BB alone had no effect but acted synergistically with IL-1alpha. A selective protein kinase C inhibitor, Ro 31-8220, abolished induction of the 95 kDa gelatinase. In contrast, none of the agents tested modulated the synthesis of the 72 kDa gelatinase. We conclude that maximal up-regulation of 95 kDa gelatinase expression requires the concerted action of growth factors and inflammatory cytokines mediated, in part, by a protein kinase C-dependent pathway. TIMP-1 and TIMP-2 were highly expressed, and their synthesis was not affected by growth factors or cytokines. Expression of TIMP-3 mRNAs was, however, increased by PDGF and transforming growth factor beta, especially in combination. Divergent regulation of gelatinase and TIMP expression implies that either net synthesis or net degradation of basement membrane can be mediated by appropriate combinations of growth factors and cytokines.

A second independent Tyr168Cys mutation in the tissue inhibitor of metalloproteinases-3 (TIMP3) in Sorsby's fundus dystrophy

Sorsby's fundus dystrophy (SFD) is a rare autosomal dominant macular disorder with age of onset usually in the fourth decade. It is characterised by loss of central vision owing to subretinal neovascularisation and disciform macular degeneration. In an effort to identify the SFD gene, the disease locus was first mapped to chromosome 22q13-qter by genetic linkage analysis, the same chromosomal region as the gene encoding the tissue inhibitor of metalloproteinases-3 (TIMP3). Subsequently, two separate mutations in TIMP3 were found in affected members of two unrelated SFD pedigrees (Tyr168Cys and Ser181Cys). More recently, two additional SFD related mutations, Ser156Cys and Gly167Cys, have provided further confirmation that heterozygous mutations in TIMP3 are causally responsible for the SFD phenotype. We now report the occurrence of the Tyr168Cys mutation in an SFD patient of Austrian descent and show that this mutation found earlier in an American SFD family arose independently. The new findings add to an emerging pattern of SFD mutations which all seem to affect the C-terminal region of the mature TIMP3 protein. In addition, all known mutations cause a change of an amino acid to a cysteine residue. This suggests a critical role for the additional C-terminal free thiol group in SFD pathogenesis.

Sorsby's fundus dystrophy in the British Isles: demonstration of a striking founder effect by microsatellite-generated haplotypes

Sorsby's fundus dystrophy (SFD) has been mapped to a genetic interval of 8 cM between loci D22S275 and D22S278. A total of 15 families, unrelated on the basis of genealogy and expressing the SFD phenotype were identified from a large data base of genetic eye disease families originating from diverse parts of the British Isles. The identification of the same Ser181Cys mutation cosegregating with disease in each family led us to consider the hypothesis of a founder effect being present. In all families studied, the same relatively infrequent allele (occurring in just 11% of the control group) was associated with disease at marker locus D22S280. A highly significant disease-associated haplotype, spanning across 3 cM of the SFD locus, was conserved in 11 of the 15 families (68% of all affected chromosomes); a further extended haplotype spanning up to 7 cM, was identified in 5 families (27% of SFD-associated chromosomes) and possibly represents the ancestral haplotype. This haplotype analysis has refined the TIMP3 gene localization to a 1- to 3-cM interval between marker loci D22S273 and D22S281 and provides strong evidence for a single mutational event being responsible for the majority of SFD identified in the British Isles.

Lack of suppression of tumor cell phenotype by overexpression of TIMP-3 in mouse JB6 tumor cells identification of a transfectant with increased tumorigenicity and invasiveness

BACKGROUND

We have recently cloned mouse tissue inhibitor of metalloproteinases-3 (mTIMP-3) by the differential display technique and found that mTIMP-3 was expressed in preneoplastic but not in neoplastic mouse JB6 epidermal cells (Sun et at. Cancer Res. 54:11139, 1994). This down regulation of the gene is attributable at least in part to alteration in gene methylation (Sun et al., J. Biol. Chem., 270:19312, 1995).

METHODS

To examine the potential role of TIMP-3 in two JB6 tumor cell model, we overexpressed mouse TIMP-3 in two JB6 tumor cell lines lacking endogenous mTIMP-3 expression. Stable transfectants from each line were selected and assayed for possible changes in tumor cell phenotype.

RESULTS

Our results showed overexpression of mTIMP-3 in these two tumor lines did not change their ability to grow in soft agar, an assay for anchorage-independent growth, nor in nude mice, an in vivo tumorigenicity assay, nor to penetrate matrigel, an assay for invasiveness We, however, isolated a clone which is highly malignant was demonstrated by a) very short latent period for tumor formation; b) very fast tumor growth; and c) highly invasive in the matrigel assay.

CONCLUSION

We conclude from this study that although TIMP-3 is not expressed in mouse JB6 tumor cells, overexpression by DNA transfection did not reverse tumor cell phenotype, suggesting a complex role for TIMP-3 in tumorigenesis. The highly malignant transfectant isolated by this study can be used as a tool for the cloning of dominant oncogenes as well as tumor suppressor genes.

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.

A review of tissue inhibitor of metalloproteinases-3 (TIMP-3) and experimental analysis of its effect on primary tumor growth

The family of tissue inhibitors of metalloproteinases (TIMPs) presently numbers four distinct gene products that are specific inhibitors of the matrix metalloproteinases (MMPs). The local balance between MMPs and TIMPs is believed to play a major role in extracellular matrix (ECM) remodeling during development and in diseases such as cancer and arthritis. Unlike the other TIMPs, which are soluble. TIMP-3 is unique in being a component of ECM. Mutations in the human TIMP-3 gene cause a dominantly inherited, adult-onset blindness (Sorsby's fundus dystrophy or SFD). In this article, we summarize what is currently known about TIMP-3, discuss possible mechanisms leading up to SFD, and investigate the effect of TIMP-3 on tumor growth. Breast carcinoma and malignant melanoma cell lines were transfected with TIMP-3 expression plasmids and injected subcutaneously into nude mice. Growth curves of the resulting tumors over a period of 6 to 8 weeks demonstrated that increased expression of TIMP-3 resulted in a statistically significant suppression of tumor growth. Deposition of TIMP-3 in the surrounding ECM by tumor cells may inhibit tumor growth by preventing local expansion of tumor, retarding the release of growth factors sequestered in ECM, or inhibiting angiogenesis. TIMP-3 over-expression had no effect on the growth of the two tumor cell lines in vitro. Because recombinant TIMP-3 inhibits endothelial cell migration and tube formation in response to angiogenic factors, we believe that the effect of TIMP-3 on tumor growth seen in this study may be a consequence of its angiostatic action.

Sorsby's fundus dystrophy in a family with a Ser-181-CVS mutation in the TIMP-3 gene: poor outcome after laser photocoagulation

PURPOSE

Mutations in the TIMP-3 (tissue inhibitor of metalloproteinase-3) gene can cause Sorsby's fundus dystrophy (SFD) and lead to choroidal neovascular membrane (CNV) formation. We studied a large American family of Irish Protestant descent with CNV inherited as an autosomal dominant trait, to determine the phenoptype and to learn whether a mutation was present in TIMP-3.

METHODS

Twelve members of 5 generations were evaluated clinically, with psychophysical and electroretinographic testing, and by fluorescein angiography. Blood samples for DNA extraction were obtained from 21 affected and unaffected family members and from 1 unrelated spouse. DNA sequence was determined, and affected individuals showed a Ser-181-Cys mutation in TIMP-3 exon 5.

RESULTS

Observable pathology involved primarily the macula, and both the full-field ERG and visual fields were normal. Acute CNV occurred during the third through fifth decades, with second eyes typically also affected during the subsequent year. Three affected members complained of nyctalopia prior to developing CNV. A Ser-181-Cys mutation in the TIMP-3 gene cosegregated with CNV in 10 affected subjects but was absent in 3 relatives at risk and sufficiently old to trust the clinical designation of normalcy. Nine eyes of 6 family members were treated by laser photocoagulation by 5 different ophthalmologists for foveal and juxtafoveal CNV. All eyes had recurrent CNV and lost acuity to 20/300 or less within several months.

CONCLUSIONS

Laser photocoagulation of CNV did not stem vision loss in this SFD family. Although possible benefits of laser treatment were not put to formal clinical trial owing to the limited number of Sorsby's cases, it appears that photocoagulation is not of long-term benefit for preserving vision loss from the TIMP-3 Ser-181-Cys mutation. Several younger family members with the mutation are thus far not clinically affected and are being followed up.

Identification of melanoma inhibitory activity and other differentially expressed messenger RNAs in human melanoma cell lines with different metastatic capacity by messenger RNA differential display

The differential display technique was used to identify mRNAs differentially expressed in human melanoma cell lines with different metastatic capacity. We report the isolation of nine different clones, of which four were uniquely expressed in the highly metastatic human melanoma cell line MV3, whereas the other five clones were uniquely expressed in the poorly metastatic human melanoma cell line 530. The differences in expression identified by differential mRNA display were confirmed by Northern blot analyses. DNA sequencing followed by computer search analyses indicated that of the nine differentially expressed clones, five represented novel gene products. The other four were histocompatibility antigen HLA-DR, laminin B2, melanoma inhibitory activity (MIA), and tissue inhibitor of metalloproteinases 3. MIA was also identified in RNA from human melanoma metastasis lesions in a comparison by differential display with pooled human nevi. Northern blot analysis confirmed MIA mRNA expression in nonmetastasizing melanoma cell lines and in melanoma metastasis lesions, while expression was absent in highly metastasizing cell lines and pretumor stages. In the 11 metastasis lesions examined, MIA mRNA expression was apparently inversely correlated with pigmentation.