Differential expression patterns of MMPs and their role in the invasion of epithelial premalignant tumors and invasive cutaneous squamous cell carcinoma

Co-expression of several members of the matrix metalloproteinase (MMP) family is characteristic of human malignant tumors. MMP-2, MMP-9, TIMP-2, and MT1-MMP are thought to be involved in the process of destruction of basement membranes and stromal invasion by neoplastic epithelial cells. In this study, we investigated the expression and role of MMPs in cutaneous oncogenesis. Tissue microarray consisting of 62 squamous cell carcinomas (SCC), 32 Bowen's disease (BD) samples, 25 normal epidermis samples were obtained for the study. MMP-2,-9, MT1-MMP and TIMP-2 proteins were examined by immunohistochemical staining and mRNA level was detected by quantitative RT-PCR in fresh tissues consisting of 5 cutaneous SCCs and paired normal epidermis samples. Gelatinase activity of MMP-2 and MMP-9 was investigated by gelatin zymography and protein levels of MT1-MMP and TIMP-2 were measured by western blot in 2 human SCC cell lines. The invasive property was evaluated with invasion assays using Transwell filters. SCC exhibited significantly increased MMP-2, MT1-MMP and decreased TIMP-2 mRNA and protein expression compared to that of the normal epithelium. Immunohistochemical staining revealed that MT1-MMP was strongly expressed on the invasive front of SCCs, whereas BD exhibited higher expression around the dyskeratotic cells in the epithelium. In comparison with the expression observed in BD, SCC exhibited significantly increased MMP-2 expression. In addition, high MMP-2 and MT1-MMP expression and low TIMP-2 expression had a significant positive correlation with the invasiveness of SCC cell lines in vitro. Our results revealed significantly increased MT1-MMP and MMP-2 expression and decreased TIMP-2 expression in cutaneous SCC, and the expression correlated with the invasiveness of SCC cell lines. Therefore, the expression of these factors in cutaneous tumors may serve as an indicator of tumor aggressiveness and invasion.     

Up-regulation of angiopoietin-2, matrix metalloprotease-2, membrane type 1 metalloprotease, and laminin 5 gamma 2 correlates with the invasiveness of human glioma

Diffuse infiltration of malignant human glioma cells into surrounding brain structures occurs through the activation of multigenic programs. We recently showed that angiopoietin-2 (Ang2) induces glioma invasion through the activation of matrix metalloprotease-2 (MMP-2). Here, we report that up-regulation of Ang2, MMP-2, membrane type 1-MMP (MT1-MMP), and laminin 5 gamma 2 (LN 5 gamma 2) in tumor cells correlates with glioma invasion. Analyses of 57 clinical human glioma biopsies of World Health Organization grade I to IV tumors displaying a distinct invasive edge and 39 glioma specimens that only contain the central region of the tumor showed that Ang2, MMP-2, MT1-MMP, and LN 5 gamma 2 were co-overexpressed in invasive areas but not in the central regions of the glioma tissues. Statistical analyses revealed a significant link between the preferential expression of these molecules and invasiveness. Protein analyses of microdissected primary glioma tissue showed up-regulation and activation of MT1-MMP and LN 5 gamma 2 at the invasive edge of the tumors, supporting this observation. Concordantly, in human U87MG glioma xenografts engineered to express Ang2, increased expression of MT1-MMP and LN 5 gamma 2, along with MMP-2 up-regulation, in actively invading glioma cells was also evident. In cell culture, stimulation of glioma cells by overexpressing Ang2 or exposure to exogenous Ang2 promoted the expression and activation of MMP-2, MT1-MMP, and LN 5 gamma 2. These results suggest that up-regulation of Ang2, MMP-2, MT1-MMP, and LN 5 gamma 2 is associated with the invasiveness displayed by human gliomas and that induction of these molecules by Ang2 may be essential for glioma invasion.     

Clinical significance of expression of membrane type 1 matrix metalloproteinase and matrix metalloproteinase-2 in human head and neck squamous cell carcinoma

Three different membrane-type matrix metalloproteinases (MT-MMPs) activate in vitro the latent form of matrix metalloproteinase-2 (MMP-2), which is one of the key proteinases in invasion and metastasis of various cancers. We examined the mRNA expression of MT1, 2, and 3-MMPs and MMP-2 in cell lines of head and neck squamous cell carcinoma (HNSCC) and quantitated the relative expression levels in human HNSCC tissues by Northern blotting. The tissue localization of MT1-MMP and MMP-2 was determined by immunohistochemistry and in situ hybridization. Their implications in clinicopathologic factors were statistically evaluated. All cell lines examined consistently expressed MT1-MMP and MMP-2, but not MT2, 3-MMP. In the clinical specimens, there was a significant correlation in coexpression of messenger of RNA (P = .0005) and colocalization by immunohistochemistry (P < .0001) for MT1-MMP and MMP-2. Relative mRNA expression levels of MT1-MMP and MMP-2 in the carcinoma tissues were significantly higher than those of the control tissues (P = .0045 and P = .0122, respectively). Both mRNA expression level and immunopositivity of MT1-MMP significantly correlated with lymph node metastasis (P = .0081 and P = .0193, respectively), which was confirmed by multivariate logistic regression analysis. Immunoreaction of MT1-MMP and its mRNA expression were observed in both carcinoma cells and stromal cells. The localization of MMP-2 closely corresponded to that of MT1-MMP. These observations suggest that MT1-MMP possesses a role as a determinant of lymph node metastasis in HNSCC, and that concurrent expression of MT1-MMP and MMP-2 are involved in progression of HNSCC.     

Curcumin, a potential inhibitor of MMP-2 in human laryngeal squamous carcinoma cells HEp2.

Curcumin (diferuloylmethane) has been widely studied for its tumor inhibiting and anticarcino-genic properties. In the present communication, we studied the effect of curcumin on matrix-metalloproteinase-2 (MMP-2), integrin receptors, and focal adhesion kinase (FAK) in human laryngeal cancer cells, HEp2. METHODS: HEp2 cells were treated with curcumin (5 microM) for 30 days and then grown without curcumin for 28 days. Effect of curcumin on MMP-2 expression and activity and on membrane type matrixmetalloproteinase-1 (MT1-MMP), FAK, and integrin receptors was studied by zymography, Western blot, ELISA, RT-PCR, and cell adhesion assay. RESULTS: Treatment of HEp2 cells with curcumin downregulated MMP-2 expression and activity and expression of integrin receptors, FAK, and MT1-MMP to almost background levels. MMP-2 (but not MMP-9) mRNA expression was abolished on curcumin treatment, indicating specific inhibition of MMP-2. Invasive potential of HEp2 cells was also significantly reduced. After drug withdrawal, expression of MMP-2, integrin receptors, MT1-MMP, and FAK returned to control levels. However, MMP-2 activity in serum free medium remained low. CONCLUSIONS: Downregulation of integrin receptors and low levels of FAK may hinder integrin-mediated signal transduction, preventing upregulation of MMP-2 activity. Reduction of MMP-2 activity and inhibition of HEp2 cell invasion by curcumin strongly indicate the potential of curcumin as an inhibitor of tumor cell invasion and metastasis.     

Differential Expression and Origin of Membrane-Type 1 and 2 Matrix Metalloproteinases (MT-MMPs) in Association with MMP2 Activation in Injured Human Livers

Matrix metalloproteinase-2 (MMP2) activation is associated with basement membrane remodeling that occurs in injured tissues and during tumor invasion. The newly described membrane-type MMPs (MT-MMPs) form a family of potential MMP2 activators. We investigated the localization and steady-state levels of MT1-MMP and MT2-MMP mRNA, compared with those of MMP2 and tissue inhibitor of MMP-2 in 22 hepatocellular carcinomas, 12 liver metastases from colonic adenocarcinomas, 13 nontumoral samples from livers with metastases, 10 benign tumors, and 6 normal livers. MMP2 activation was analyzed by zymography in the same series. The expression of MT1-MMP mRNA and the activation of MMP-2 were increased in hepatocellular carcinomas, metastases, and cholestatic nontumoral samples. MT2-MMP mRNA was rather stable in the different groups. MT1-MMP mRNA levels, but not MT2-MMP mRNA, correlated with MMP-2 and tissue inhibitor of MMP-2 mRNA levels and with MMP2 activation. In situ hybridization showed that MT1-MMP mRNA was expressed in stromal cells, and MT2-MMP mRNA was principally located in both hepatocytes and biliary epithelial cells. Consistently, freshly isolated hepatocytes expressed only MT2-MMP mRNA, and culture-activated hepatic stellate cells showed high levels of MT1-MMP mRNA. These results indicate that in injured livers, MMP2 activation is related to a coordinated high expression of MMP2, tissue inhibitor of MMP-2, and MT1-MMP. Furthermore, the finding of a preferential expression of MT2-MMP in hepatocytes, together with our previous demonstration that the activation of stellate cell-derived MMP2 in co-culture requires interactions with hepatocytes (Am J Pathol 1997, 150:51–58), suggests that parenchymal cells might play a pivotal role in the MMP2 activation process.     

Protein kinase C-mediated in vitro invasion of human glioma cells through extracellular-signal-regulated kinase and ornithine decarboxylase.

We investigated the involvement of protein kinase C (PKC) in the in vitro invasiveness of the A-172, U-87 and U-373 human glioma cell lines, as well as the role of ornithine decarboxylase (ODC) and/or extracellular-signal-regulated kinase (ERK) in the actions of PKC. Thus, cells were treated under serum-free conditions with the PKC activator phorbol 12-myristate 13-acetate (PMA), or with the PKC inhibitors bisindolylmaleimide I (GF 109203X) or calphostin C in the absence or presence of the ODC inhibitor D,L-alpha-difluoromethylornithine (DFMO), and/or the mitogen-activated protein kinase/extracellular-signal-regulated kinase inhibitor 2'-amino-3'-methoxyflavone (PD 098059). Subsequently, cells were assessed for membrane-type 1 matrix metalloproteinase (MT1-MMP) mRNA contents, 72-kD latent, and 59/62-kD activated matrix metalloproteinase 2 (MMP-2) in conditioned media, as well as invasiveness. For these purposes, we used Northern blot analysis, gelatine zymography, and an in vitro filter invasion assay, respectively. Data were related to those found with untreated cells. PKC activity was 2- to 3-fold stimulated by PMA (100 nM for 30 min), and about 2-fold inhibited by calphostin C (40 nM for 2 h) or GF 109203X (5 microM for 20 min). This was accompanied by a similar increase or decrease, respectively, in MT1-MMP mRNA expression, 59/62-kD MMP-2 activity, and in vitro invasion. Inhibition of ODC activity (about 2-fold by 24 h DFMO 5 mM), ERK activation (almost completely by 20 min PD 098059 50 microM), or both these enzymes simultaneously led to a reduction by about half in levels of MT1-MMP mRNA, 59/62-kD MMP-2 activity, and invasion in untreated as well as PMA-stimulated cells. The use of these compounds did not significantly alter the inhibitory effects of GF 109203X or calphostin C. Modulation of PKC and/or ERK activity resulted in corresponding changes in ERK and/or ODC activities, but interference with ODC affected neither ERK nor PKC. Our data suggest a regulatory role for PKC, in co-operation with ERK and ODC, in glioma cell invasion, by modulation of MT1-MMP mRNA expression and MMP-2 activation.     

Expression and tissue localization of membrane-types 1, 2, and 3 matrix metalloproteinases in rheumatoid synovium

In vitro, membrane-type matrix metalloproteinases (MT-MMP) are known to activate the zymogen of MMP-2 (proMMP-2, progelatinase A), which is one of the key MMP in joint destruction in rheumatoid arthritis. In the present study, we examined the production and activation of proMMP-2, and the expression of MT1-MMP, MT2-MMP, and MT3-MMP, their correlation with proMMP-2 activation, and their localization in rheumatoid synovial tissue. Using sandwich enzyme immunoassay and gelatin zymography techniques, proMMP-2 production levels and activation ratios were found to be significantly higher in rheumatoid synovium compared with normal synovium (p < 0.01). Quantitative RT-PCR analyses demonstrated that MT1-MMP and MT3-MMP were expressed in all rheumatoid synovial tissue (30 of 30 cases), but that the mean expression level of MT1-MMP was approximately 11-fold higher than MT3-MMP. Significant correlation was found between the mRNA expression level of MT1-MMP and the activation ratio of proMMP-2 (p < 0.01). In situ hybridization indicated that the hyperplastic lining cells of rheumatoid synovium expressed MT1-MMP. Immunohistochemistry demonstrated that MT1-MMP was co-localized with MMP-2 and with a tissue inhibitor of metalloproteinase-2, and was mainly located in the rheumatoid synovial lining cells. In situ zymography of rheumatoid synovium showed gelatinolytic activity, predominantly in the lining cell layer. This activity was blocked when incubated with BB94, a specific MMP inhibitor. These results demonstrate that MT1-MMP plays an important role in the activation of proMMP-2 in the rheumatoid synovial lining cell layer, and suggest that its activity may be involved in the cartilage destruction of rheumatoid arthritis.     

Matrix metalloproteinase-2 from bronchial epithelial cells induces the proliferation of subepithelial fibroblasts

BACKGROUND: In bronchial asthma, subepithelial fibrosis in the conducting airways is associated with increased numbers of subepithelial fibroblasts. OBJECTIVE: This study examined the hypothesis that MMP-2 from airway epithelial cells induces the proliferation of subepithelial fibroblasts. METHODS: Using primary bronchial epithelial cells MMP-2, MT1-MMP and TIMP-2 mRNA expression were assessed by Northern blotting and RT-PCR. Primary bronchial epithelial cells transfected with constructs encoding pro-MMP-2 and MT1-MMP (MMP-14). RESULTS: Transfected cells showed enhanced expression of the appropriate mRNA species by RT-PCR and enhanced MMP-2 or MT1-MMP activity by zymography. Active MMP-2 levels in epithelial supernatants were increased most by cotransfection with pro-MMP-2 and MT1-MMP encoding constructs. By measuring tritiated thymidine incorporation, supernatants from transfected cells were found to enhance DNA synthesis of primary airway fibroblast cultures compared with controls. There was a strong correlation (r = 0.9, P < 0.01) between MMP-2 levels in epithelial cell conditioned media and fibroblast proliferation as indicated by DNA synthesis. The MMP inhibitor 1,10-phenanthroline attenuated the increased proliferation, while the addition of exogenous purified MMP-2 alone also increased fibroblast proliferation. CONCLUSIONS: Our results support a role for MMP-2 in mediating cross-talk between epithelial cells and myofibroblasts.     

Expression of matrix metalloproteinase-2 (MMP-2) and of membrane-type-1-matrix metalloproteinase (MT1-MMP) in transitional cell carcinoma of the upper urinary tract

Tumor cell invasion and metastasis are biologically dependent on the proteolytic destruction of surrounding matrix components. Matrix metalloproteinase-2 (MMP-2) is able to cleave type IV collagen, and membrane-type-1-matrix metalloproteinase (MT1-MMP) induces activation of proMMP-2. We investigated the expression of MMP-2 and MT1-MMP using in situ hybridization and immunohistochemistry in 102 cases of transitional cell carcinoma of the upper urinary tract (TCC-UUT). A positive expression of each metalloproteinase was recognized in all samples and was apparent within the cytoplasm of tumor epithelial cells and/or stromal cells situated at the interface between tumor and stroma. Our analysis of clinicopathologic findings showed a relationship between MMP-2 and MT1-MMP expression and stage. The correlation between the MMP-2 protein staining score for tumor epithelial cells and overall survival rate reached significance in the univariate analysis. However, only stage was associated with disease-free and overall survivals in the multivariate analysis. In conclusion, the detection of MMP-2 and MT1-MMP would appear to be of limited value in informing the prognosis of TCC-UUT.     

Role of MMP-2 in alveolar epithelial cell repair after bleomycin administration in rabbits

Matrix metalloproteinases (MMPs) have been implicated in the pathological processes of interstitial lung diseases. However, underlying mechanisms, particularly for activity levels and distribution of activated MMP-2 in the disease process, are yet to be elucidated. The present study investigated the immunolocalization of MMP-2, membrane type 1-matrix metalloproteinase (MT1-MMP), tissue inhibitor of metalloproteinase (TIMP)-2, p53, and Ki-67 in a rabbit model of bleomycin-induced pulmonary fibrosis. Gelatin zymography and in situ zymography were used to examine the activity and the localization of MMP-2. Furthermore, we performed Western blot and in situ hybridization for MT1-MMP, an activator for MMP-2. The total MMP-2 level estimated by gelatin zymography increased significantly at 3, 7, and 14 days after bleomycin administration, compared with controls. In the immunohistochemical study, immunoreaction for MMP-2 was strongest in alveolar epithelial cells among the cell populations. Swollen and/or elongated type II alveolar epithelial cells showed strong immunoreactions for MMP-2, MT1-MMP, and TIMP-2. After bleomycin administration, immunoreaction for p53 was observed in bronchiolar and alveolar epithelial cells. The proportion of p53-positive cells was high in epithelial cells from 1 to 14 days as MMP-2 levels were increased, suggesting that p53 may be responsible, at least in part, for the increase of MMP-2. The ratio of activated MMP-2 to total MMP-2 estimated by gelatin zymography increased significantly at 3, 7, 14, and 28 days after bleomycin treatment. In situ zymography revealed that type II alveolar epithelial cells degraded gelatin. An increased expression of MT1-MMP protein was observed by Western blot following administration of bleomycin. In situ hybridization demonstrated that type II alveolar epithelial cells gave intense signal for MT1-MMP mRNA. These results suggest that type II alveolar epithelial cells express MT1-MMP and activate MMP-2 on their cell surfaces, which may lead to the elongation and migration of alveolar epithelial cells in the repair process of bleomycin-induced pulmonary fibrosis.     

Survivin, MMP-2, MT1-MMP, and TIMP-2: their impact on survival, implantation, and proliferation of endometriotic tissues

In order to study survivin, matrix metalloproteinases (MMP-2), membranous type 1 matrix metalloproteinase (MT1-MMP), and tissue inhibitor metalloproteinase-2 (TIMP-2) expression immunohistochemically in endometriotic tissues and normal endometrium, our retrospective study considered 194 patients affected by endometriosis and 71 patients with normal endometrium. Tissue microarrays were created from paraffin-embedded blocks; immunohistochemistry was used to assess protein expression. In endometriotic tissues, survivin was expressed at a higher level than in normal endometrium; its glandular expression level was higher in non-ovarian than in ovarian endometriotic tissues and lower in stromal components. Endometrial tissues from women without endometriosis and endometriotic tissues had different matrix metalloproteinase expression profiles. MMP-2 and MT1-MMP correlated with TIMP-2 in endometriotic tissues. Furthermore, in endometriotic tissues, expression of survivin, aurora B kinase, and Ki-67 showed a significant positive correlation, which indicates a role in cellular proliferation that could be closely linked to its anti-apoptotic activity in endometriosis development. Our results imply a role for matrix metalloproteinases in endometriosis invasiveness; correlation of their expression with that of TIMP-2 underscores its possible key regulatory role.     

胸腺上皮肿瘤组织中基质金属蛋白酶-2活性与Ⅰ型膜型基质金属蛋白酶 mRNA表达的相关性

目的探讨胸腺瘤和胸腺癌中基质金属蛋白酶（MMP）-2、Ⅰ型膜型（MT1）-MMP、金属蛋白酶组织抑制剂（TIMP）-2mRNA的表达和MMP-2蛋白活性的关系。方法分别用real-time逆转录．聚合酶链反应（RT-PCR,Taqman法）、明胶酶谱法和Filmin situ gelatin-Zymography（FIZ）对正常的胸腺组织（2例）、胸腺瘤（12例）和胸腺癌（2例）患者的新鲜肿瘤组织中MMP-2、MT1-MMP、TIMP-2mRNA的表达,pro-MMP-2的活性率及活性蛋白的定位进行测定。结果MMP-2、MT1-MMP及TIMP-2mRNA在Ⅰ期与Ⅱ期和Ⅲ期与Ⅳ期中的表达差异均无统计学意义（P〉0．05）,在Ⅰ～Ⅱ期与Ⅲ～Ⅳ期和胸腺癌3组中差异均有统计学意义（P〈0．01）。在AB、B1型（混合型和淋巴细胞为主型）与B2、B3型（皮质型和多角细胞为主型）以及胸腺癌3组中差异均有统计学意义（P〈0．05）。MMP-2的蛋白活性率（MMP-2／pro—MMP-2＋MMP-2）在Ⅰ～Ⅱ期、Ⅲ～Ⅳ期和胸腺癌各组中差异有统计学意义（P〈0．05）,在AB、B1型与B2、B3型以及胸腺癌各组中的差异均具有统计学意义（P〈0．05）。胸腺瘤各期及各型中MT1-MMP、TIMP-2mRNA与MMP-2蛋白活性表达均呈正相关,且相关程度相似（r=0．7235、r=0．7647、P〈0．005）。MMP-9的蛋白表达在各组间差异均无统计学意义。结论MMP-2、MT1-MMP及TIMP-2的mRNA表达与胸腺瘤临床分期、病理分型相关,MMP-2的活性与MT1-MMP和TIMP-2的表达升高正相关。推测MT1-MMP通过TIMP-2对MMP-2的激活起促进作用。     

(-)Epigallocatechin-3-gallate directly inhibits MT1-MMP activity,leading to accumulation of nonactivated MMP-2 at the cell surface

Consumption of green tea has been associated with prevention of cancer development, metastasis, and angiogenesis. Given the crucial role of the matrix metallo-proteinase-2 (MMP-2) on the degradation of the extracellular matrix instrumental to invasion, we examined the effect of the main flavanol present, (-)epigallocatechin-3-gallate (EGCG), on membrane-type 1 MMP (MT1-MMP), the receptor/activator of MMP-2. In-solution fluorimetric assay with activated MT1-MMP and gelatin-zymography with MT1-MMP catalytic domain alone and pro-MMP-2 activation by the same domain revealed dose-dependent inhibition of MT1-MMP at EGCG concentrations slightly lower than that reported to inhibit MMP-2 and MMP-9. Cytofluorimetry and immunolocalization revealed that EGCG does not impair MT1-MMP/TIMP-2/MMP-2 presence on the cell membrane. In the membrane extract of HT-1080 human fibrosarcoma cells, 10 micro M EGCG caused a strong increase in MT1-MMP level and accumulation of pro-MMP-2 while leaving activated MMP-2 unchanged. EGCG thus exerts inhibition of MT1-MMP, which restrains activation of MMP-2; this may confer the antiangiogenic and antimetastatic activity associated with green tea.     

Upregulation of tissue inhibitor of metalloproteinases (TIMP)-2 promotes matrix metalloproteinase (MMP)-2 activation and cell invasion in a human glioblastoma cell line

Local invasiveness is a characteristic feature of glioblastoma that makes surgical resection nearly impossible and accounts in large part for its poor prognosis. To identify mechanisms underlying glioblastoma invasion and motility, we used Transwell invasion chambers to select for a more potently invasive subpopulation of U87MG human glioblastoma cells. The stable population of tumor cells (U87-C1) obtained through this in vitro selection process were three times more invasive than parental U87MG cells and demonstrated faster monolayer wound healing and enhanced radial motility from cell spheroids. This enhanced invasiveness was associated with an 80% increase in matrix metalloproteinase 2 (MMP-2) activation. No differences in expression levels of pro-MMP-2, membrane-type matrix metalloproteinase I (MT1-MMP), or integrin alphavbeta3 (mediators of MMP-2 activation) were detected. However, U87-C1 cells exhibited two-fold elevation of tissue inhibitor of metalloproteinases (TIMP)-2 mRNA and protein relative to parental cells. Exogenous addition of comparable levels of purified TIMP-2 to parental U87MG cells increased MMP-2 activation and invasion. Similarly, U87MG cells engineered to overexpress TIMP-2 at the same levels as U87-C1 cells also demonstrated increased MMP-2 activation, indicating that an increase in physiological levels of TIMP-2 can promote MMP-2 activation and invasion in glioblastoma cells. However, exogenous administration or recombinant overexpression of higher amounts of TIMP-2 in U87MG cells resulted in inhibition of MMP-2 activation. These results demonstrate that the complex balance between TIMP-2 and MMP-2 is a critical determinant of glioblastoma invasion, and indicate that increasing TIMP-2 in glioblastoma patients may potentially cause adverse effects, particularly in tumors containing high levels of MT1-MMP and MMP-2.     

Co-ordinated expression of MMP-2 and its putative activator, MT1-MMP, in human placentation

The spatial expression of mRNA for matrix metalloproteinase 2 (MMP-2), its putative activator, the membrane-type 1 matrix metalloproteinase (MT1-MMP), and the MMP-2 substrate type IV collagen was investigated in human placentas of both normal and tubal ectopic pregnancies and in cyclic endometrium using in-situ hybridization. Cytokeratin staining applied to adjacent sections was used to identify epithelial and trophoblast cells. In both normal and tubal pregnancies MT1-MMP, MMP-2 and type IV collagen mRNA were highly expressed and co-localized in the extravillous cytotrophoblasts of anchoring villi, in cytotrophoblasts that had penatrated into the placental bed and in cytotrophoblastic cell islands. In addition, the decidual cells of normal pregnancies in some areas co-expressed MT1-MMP and MMP-2 mRNA, with moderate signals for both components. Fibroblast-like stromal cells in tubal pregnancies were positive for MMP-2 mRNA but generally negative for MT1-MMP mRNA. The consistent co-localization of MT1-MMP with MMP-2 and type IV collagen in the same subset of cytotrophoblasts strongly suggests that all three components co-operate in the tightly regulated fetal invasion process. The co-expression of MT1-MMP and MMP-2 mRNA in some of the decidual cells indicates that these cells are also actively involved in the placentation process.