The tissue inhibitors of metalloproteinases (TIMPs) constitute a family of proteins, of which three members have so far been described. Using the expressed sequence tag sequencing approach, we have identified a novel TIMP-related cDNA fragment and subsequently cloned a fourth human TIMP (TIMP-4) from a human heart cDNA library. The open reading frame encodes a 224-amino acid precursor including a 29-residue secretion signal. The predicted structure of the new protein shares 37% sequence identity with TIMP-1 and 51% identity with TIMP-2 and -3. The protein has a predicted isoelectric point of 7.34. The open reading frame-directed expression of TIMP-4 protein in MDA-MB-435 human breast cancer cells showed metalloproteinase inhibitory activity on reverse zymography. By Northern analysis, only the adult heart showed abundant TIMP-4 transcripts with a 1.4-kilobase predominant transcript band; very low levels of the transcripts were detected in the kidney, placenta, colon, and testes, and no transcripts were detected in the liver, brain, lung, thymus, and spleen. This unique expression pattern suggests that TIMP-4 may function in a tissue-specific fashion in extracellular matrix homeostasis. Matrix metalloproteinases (MMPs)1 play a critical role in ECM homeostasis. Controlled remodeling of the ECM is an essential aspect in the process of normal development, and deregulated remodeling has been indicated to have a role in the etiology of diseases such as arthritis, periodontal disease, and cancer metastasis (1-5). The overproduction and unrestrained activity of MMPs has been linked to malignant conversion of tumor cells (4 -12). The down-regulation of MMPs may occur at the levels of transcriptional regulation of the genes and activation of secreted proenzymes and through interaction with specific inhibitor proteins such as TIMPs. TIMPs are secreted multifunctional proteins that play pivotal roles in the regulation of ECM metabolism. Their most widely recognized action is as inhibitors of matrix MMPs. Thus, the net MMP activity in the ECM is the result of the balance between activated enzyme levels and TIMPs levels. Augmented MMP activity is associated with the metastatic phenotype of carcinomas, especially breast cancer (7-9, 13-16); the decreased production of TIMP could also result in greater effective enzyme activity and invasive potentials (17-19). These results suggest that an increase in the amount of TIMPs relative to MMPs could function to block tumor cell invasion and metastasis. In fact, tumor cell invasion and metastasis can be inhibited by up-regulation of TIMP expression or by an exogenous supply of TIMPs (17, 40 -44).Three mammalian TIMPs have been characterized at the sequence level: TIMP-1 (20), TIMP-2 (21), and 36). The proteins are classified based on structural similarity to each other as well as their ability to inhibit matrix metalloproteinases. There have been other reports of inhibitors of metalloproteases (IMPs) with characteristics different from these known TIMPs. In some cases these activitie...

The binding properties of the newly described tissue inhibitor of metalloproteinases-4 (TIMP-4) to progelatinase A and to the COOH-terminal hemopexin-like domain (C domain) of the enzyme were examined. We present evidence for the first time of a specific, high affinity interaction between TIMP-4 and the C domain of human gelatinase A and show that TIMP-4 binds both progelatinase A and the C domain in a similar manner to that of TIMP-2. Saturable binding of recombinant C domain to TIMP-4 and to TIMP-2 but not to TIMP-1 was demonstrated using a microwell protein binding assay.

MMPs 1 and their inhibitors TIMPs play a critical role in ECM homeostasis. Controlled remodeling of the ECM is an essential aspect of normal development, and deregulated remodeling has been indicated to have a role in the etiology of diseases such as arthritis, periodontal disease, and cancer metastasis (1-5). Four mammalian TIMPs have been identified so far: TIMP-1 (6), TIMP-2 (7), TIMP-3 (8 -11), and the recently cloned TIMP-4 (12, 41). The proteins are classified based on structural similarity to each other, as well as their ability to inhibit metalloproteinases.TIMPs are secreted multifunctional proteins that have anti-MMP activity as well as erythroid-potentiating and cell growth-promoting activities. The stimulating effect on cell growth was initially recognized when TIMP-1 and TIMP-2 were identified as having erythroid-potentiating activities (14,15). It is now clear through several recent reports that TIMP-1 and TIMP-2 are mitogenic for non-erythroid cells, including normal keratinocytes (16), fibroblasts (17), lung adenocarcinoma cells (18), and melanoma cells (18). The involvement of TIMPs in the activation of pro-MMP has also been demonstrated (19). In addition, the recent evidence indicates that the TIMP family may be involved in steroidogenesis of rat testis and ovary indicating the potential role of TIMP in the reproduction (20).The most widely appreciated biological function of the TIMPs is their role in the inhibition of cell invasions in vitro (21-24) and tumorigenesis (25-29) and metastasis in vivo (25-31). Since the net MMP activity is the result of the balance between activated enzyme levels and TIMP levels, an increase in the amount of TIMPs relative to MMPs could function to block tumor cell invasion and metastasis. The tumor-suppressing activity of TIMP on primary tumor growth may be in part due to its anti-angiogenic activity. In fact, both TIMP-1 (32) and TIMP-2 (33, 34) have been demonstrated to have an antiangiogenic activity, and such inhibition of angiogenesis is mediated by inhibition of both endothelial cell proliferation (34) and migration (32). The underlying molecular mechanism for the tumor suppressing activities of TIMPs, nevertheless, is thought to depend on their anti-MMP activities.We had recently cloned and characterized a human TIMP-4 (12). Transfection of TIMP-4 into human breast cancer cells inhibited the invasion potential of the cells in the in vitro invasion assay (13). When injected orthotopically into nude mice, TIMP-4 transfectants were significantly inhibited in their tumor growth and axillary lymph node and lung metastasis as compared with controls (13). These results suggest the therapeutic potential of TIMP-4 in treating cancer malignant progression. These results suggest an important role of TIMP-4 in inhibiting primary tumor growth and progression leading to invasion and metastasis. In the present study, we have produced and purified rTIMP4p from baculovirus infected cells. rTIMP4p was shown to inhibit MMP activity and tumor cell invasion across reconstitute...

Previously, we have shown that synuclein gamma (SNCG), a member of the brain protein synuclein family, is highly expressed in human infiltrating breast carcinomas but not expressed in normal or benign breast tissues. The SNCG mRNA was also detected in several human breast cancer cell lines with the highest expression found in H3922, a cell line derived from an infiltrating ductal carcinoma. In this study, we show that expression of SNCG mRNA in H3922 cells is significantly decreased by treating cells with the cytokine oncostatin M (OM) who has a growth-inhibitory effect on these cells. A decrease in SNCG mRNA level can be detected as early as 30 min after OM addition. By 4 h OM treatment, the level of SNCG mRNA was decreased to 70% of control, and by 24 h the mRNA was below detectable level. Western blot analysis further demonstrated the suppression of SNCG protein expression by OM. The level of SNCG protein in H3922 cells was reduced more than 90% by OM after 2 days. Since OM-induced growth inhibition occurs after 3-4 days, the down-regulation of SNCG expression appears to proceed the effect of OM on cell growth. Additional experiments to measure the transcriptional rates of SNCG indicate that the observed OM-induced down-regulation of SNCG mRNA occurs mainly at the transcriptional level. In an attempt to examine the role of SNCG gene in the proliferation of breast cancer cells, SNCG cDNA was stably transfected into MCF-7 cells that do not express endogenous SNCG gene. Examination of cell growth under anchorage-dependent and anchorage-independent conditions demonstrates that over expression of SNCG gene significantly stimulated the growth of MCF-7 cells both in monolayer culture and in soft agar. These data together suggest that SNCG may play a role in cell proliferation.

—The role of basement membrane–degrading matrix metalloproteinases (MMPs) in enabling vascular smooth muscle cell migration after vascular injury has been established in several animal models. In contrast, the role of their native inhibitors, the tissue inhibitors of matrix metalloproteinases (TIMPs), has remained unproven despite frequent coregulation of MMPs and TIMPs in other disease states. We have investigated the time course of expression and localization of TIMP-4 in rat carotid arteries 6 hours, 24 hours, 3 days, 7 days, and 14 days after balloon injury by in situ hybridization, immunohistochemistry, and Western blot analysis. TIMP-4 protein was present in the adventitia of injured carotid arteries from 24 hours after injury. At 7 and 14 days after injury, widespread immunostaining for TIMP-4 was observed throughout the neointima, media, and adventitia of injured arteries. Western blot analysis confirmed the quantitative increase in TIMP-4 protein at 7 and 14 days. In situ hybridization detected increased expression of TIMP-4 as early as 24 hours after injury and a marked induction in neointimal cells 7 days after injury. We then studied the effect of TIMP-4 protein on the migration of smooth muscle cells through a matrix-coated membrane in vitro and demonstrated a 53% reduction in invasion of rat vascular smooth muscle cells. These data and the temporal relationship between the upregulation of TIMP-4, its accumulation, and the onset of collagen deposition suggest an important role for TIMP-4 in the proteolytic balance of the vasculature controlling both smooth muscle migration and collagen accumulation in the injured arterial wall.

Abstract-The role of basement membrane-degrading matrix metalloproteinases (MMPs) in enabling vascular smooth muscle cell migration after vascular injury has been established in several animal models. In contrast, the role of their native inhibitors, the tissue inhibitors of matrix metalloproteinases (TIMPs), has remained unproven despite frequent coregulation of MMPs and TIMPs in other disease states. We have investigated the time course of expression and localization of TIMP-4 in rat carotid arteries 6 hours, 24 hours, 3 days, 7 days, and 14 days after balloon injury by in situ hybridization, immunohistochemistry, and Western blot analysis. TIMP-4 protein was present in the adventitia of injured carotid arteries from 24 hours after injury. At 7 and 14 days after injury, widespread immunostaining for TIMP-4 was observed throughout the neointima, media, and adventitia of injured arteries. Western blot analysis confirmed the quantitative increase in TIMP-4 protein at 7 and 14 days. In situ hybridization detected increased expression of TIMP-4 as early as 24 hours after injury and a marked induction in neointimal cells 7 days after injury. We then studied the effect of TIMP-4 protein on the migration of smooth muscle cells through a matrix-coated membrane in vitro and demonstrated a 53% reduction in invasion of rat vascular smooth muscle cells. These data and the temporal relationship between the upregulation of TIMP-4, its accumulation, and the onset of collagen deposition suggest an important role for TIMP-4 in the proteolytic balance of the vasculature controlling both smooth muscle migration and collagen accumulation in the injured arterial wall. (Circ Res. 1999;84:498-504.)

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A mammary-derived growth inhibitor-related gene (MRG) was previously identified and characterized. MRG induces differentiation of mammary epithelial cells in vitro and its expression is associated with mammary differentiation. To further define the role of MRG on mammary gland differentiation, a MRG transgenic mice model under the control of mouse mammary tumor virus promoter was established and the effect of MRG on mammary gland differentiation was investigated at histological and molecular levels. Expression of endogenous mouse MRG gene was significantly increased from the non-differentiated gland of control virgin mice to the functionally differentiated gland of pregnant control mice. Whole mount analyses demonstrated that ductal development was not affected by MRG transgene expression. While there was no lobuloalveolar structure in control virgin mice, expression of MRG transgene in the mammary gland resulted in the development of lobuloalveolar-like structure, which mimics the gland from early pregnancy. Consistent with the morphological change, expression of MRG also increased milk protein ␤-casein expression in the gland. To study the mechanism of MRG-induced mammary differentiation, we investigated the Stat5 activation in the glands from the transgenic mouse versus virgin control mouse. While activated Stat5 was expressed at the minimal level in the non-differentiated control virgin gland, a significant Stat5 phosphorylation was observed in the virgin transgenic gland. Our data indicate that MRG is a mediator of the differentiating effects of pregnancy on breast epithelium, and overexpression of MRG in young nulliparous mice can induce differentiation.In an effort to search for growth regulators in the human mammary gland development, we generated cDNA libraries from a breast cancer biopsy specimen and a normal breast and analyzed these libraries by differential cDNA sequencing (1, 2). We identified, cloned, and characterized a novel tumor growth inhibitor and named it as a mammary-derived growth inhibitor-related gene MRG 1 (3). The predicted amino acid sequence of MRG has a significant sequence homology to previously identified mammary derived growth inhibitor MDGI (4). Interestingly, MRG and MDGI revealed no homology to any other known growth inhibitors; rather, they revealed extensive sequence homology to fatty acid binding protein (FABP) (5, 6). A striking homology was evident between MDGI and heart type (H-) FABP, which differ only in seven positions of the amino acid sequence (5). In fact, it turned out that the originally described MDGI is the same protein of H-FABP, which is also expressed in mammary gland (7,8). H-FABP fully replaced the MDGI effect and inhibited the growth of mammary epithelial cells (7). Thus, MDGI was also named as H-FABP. Interestingly, similar to the story of MDGI and H-FABP, subsequent to our isolation of MRG, human brain type (B-) FABP was independently cloned from human fetal whole-brain cDNA library (9). In fact, the sequence of MRG was found to be exactly identical to...