Regulation of MMP-9 (92 kDa type IV collagenase/gelatinase B) expression in stromal cells of human giant cell tumor of bone

Matrix metalloproteinases (MMPs) play an important regulatory role in tissue morphogenesis, cell differentiation, tumor invasion and metastasis. Several authors have reported a direct correlation between the production of 72 kDa (MMP-2) and 92 kDa (MMP-9) type IV collagenases/gelatinases and the metastatic potential of cancer cells. Recently, we have identified the expression of both MMP-2 and MMP-9 in primary cultures of human giant cell tumor (GCT) of bone in vitro, and in tissue extracts in vivo. Interestingly, MMP-9 is not secreted by late-passaged GCT cells. It is possible that the production of MMP-9 is regulated by certain factor(s) secreted by the multinucleated giant cells in the primary culture. In order to test this hypothesis, the effect of primary-culture-conditioned medium on the expression of MMP-9 by late-passaged mononuclear stromal cells was examined. Adding conditioned medium from the primary GCT culture to the late-passaged stromal cells induced MMP-9, as evidenced by the presence of lytic bands at Mr 92000 and 72000 on a gelatin zymogram. These enzyme activities were inhibited by EDTA, a well-known inhibitor of the MMPs. We confirmed these results by Western blotting using specific antibodies and RT-PCR for MMP-2 and MMP-9. Immunofluorescence studies with specific antibodies to MMP-9 further confirmed its expression by the passaged stromal cells cultured in the primary-culture-conditioned medium. The data indicate that MMP-2 and MMP-9 are produced by the mononuclear stromal cells when cultured in GCT primary-culture-conditioned medium. This suggests that multinucleated giant cells in primary cultures secrete a factor(s) that stimulates stromal cells to produce MMP-9, which, in turn, may contribute to the aggressive behavior of GCT.     

Induction of MMP-9 mediated gelatinolytic activity in human monocytic cells by cell wall components of Mycobacterium tuberculosis

Mycobacterium tuberculosis (Mtb) infection induces the expression of host matrix metalloIproteinases (MMPs) capable of tissue degradation. We show that infection of mice with Mtb results in differential expression of MMPs in the lung. MMP-9 activity increased by week 1 post-infection, while MMP-2 activity increased after week 2. RT-PCR analysis for gene expression of gelatinases and their respective inhibitors showed: a small increase in MMP-9 by week 1, no change in TIMP-1 and MMP-2, and a significant decrease in TIMP-2 by week 4. The increase in MMP-2 could be due to a decrease in TIMP-2 expression. Addition of 4-aminophenylmercuric acid to lung extracts increased MMP-9 activity, suggesting that its regulation could be due to endogenous activation by proteases. In vitro, attenuated and virulent Mtb strains equally induced MMP-9 expression in U937 monocytes. The inducer of MMP-9 in Mtb was present in culture filtrates, and was active after paraformaldehyde fixation. LAM stimulated MMP-9 expression in THP-1 cells, but not U937 cells. However, LAM-free extracts also induced MMP-9 activity in THP-1 cells. Fractionation of Mtb extracts by chromatography revealed fractions of 17 and 156 kDa with MMP-9 inducing activity. In conclusion, LAM and other components of Mtb induce the expression of MMP-9.     

PRL-2基因转染对肝细胞基质金属蛋白酶及其抑制剂表达的影响

目的:研究PRL-2基因增强肿瘤细胞侵袭及转移能力的机制。 方法:采用脂质体转染的方法将PRL-2基因表达质粒转染至正常永生化肝细胞系CL1中，G418筛选阳性克隆。应用明胶酶谱法检测转染肝细胞分泌MMPs 酶谱变化，Western blotting 及RT-PCR检测转染肝细胞MMP-2、MMP-9、TIMP-1和TIMP-2的变化。以PRL-2磷酸酯酶特异性抑制剂处理转染细胞，观察抑制PRL-2活性对上述指标的影响。 结果:经过 8周G418筛选及RT-PCR和Western blotting鉴定,获得稳定表达PRL-2的细胞亚系PRL-2-CL1。转染后的CL1细胞分泌MMP－9 、活性型MMP－9 和MMP－2 ,均显著高于转染前CL1细胞的MMPs 分泌(P<0.01);使用特异性抑制剂后， MMP－9 、活性型MMP－9 和MMP－2活性显著降低(P<0.01)。Western blotting及RT-PCR检测显示PRL-2-CL1细胞MMP2、MMP9蛋白及mRNA含量均较转染前显著升高(P<0.05)，TIMP-2则显著降低(P<0.05)；使用抑制剂后，可以逆转上述变化。 结论:PRL-2在永生化肝细胞中获得稳定、高效表达，PRL-2基因增强肝细胞侵袭及转移能力与其提高细胞MMP2、MMP9表达，降低TIMP-2有关。     

Ras-transfection up-regulated HaCaT cell migration: Inhibition by Marimastat

Cell migration is an essential process in physiological and pathological conditions such as wound healing and tumor invasion. This phenomenon involves cell adhesion on the extracellular matrix mediated by integrins, and cell detachment promoted in part by metalloproteinases (MMPs). In the present study, the migration of two HaCaT-ras clones (metastatic or not), was compared with HaCaT cells, and normal human primary cultured keratinocytes. Using colloidal gold migration assay, the migration index on type I and type IV collagen was similar for primary cultured keratinocytes and HaCaT, whereas it was markedly higher for the HaCaT-ras clones. High motility of ras-transfected cells was confirmed from an in vitro wound healing assay. It was not correlated with changes in integrin expression or related to a different adhesion on extracellular matrix. The Marismastat (BB-2516), a MMP inhibitor, inhibited in a dose-dependent effect the migration in both assays, demonstrating the important role of MMPs in the migration process. Under our experimental conditions, MMP-1 activity was not detected in HaCaT and MMP-9 activity was secreted by these cells only after their stimulation by EGF. Here, MMP-2 was the major gelatinolytic activity secreted by all the cells and its secretion was markedly higher for HaCaT-ras clones compared with HaCaT. In addition, Western blotting results confirmed a higher expression of MMP-2 associated with a lower expression of TIMP-2 in HaCaT-ras compared with HaCaT. These results suggest that Ha-ras oncogene could be a stimulating factor of migration and might modified the balance between MMP-2 and TIMP-2 in keratinocyte cell lines. This revised version was published online in July 2006 with corrections to the Cover Date.     

Matrix metalloproteinases and their inhibitors in the foreign body reaction on biomaterials

Matrix metalloproteinases (MMPs) can degrade structural components within the extracellular matrix and at the cellular surface producing changes in cellular behavior (i.e., adhesion and migration) and subsequent pathological responses (i.e., the foreign body reaction and wound healing). We continue to study the foreign body reaction that occurs following biomaterial implantation by investigating secretory responses of biomaterial-adherent macrophages and foreign body giant cells (FBGCs) as directed by material surface chemistry and further this research by determining whether secreted MMPs play a role in macrophage adhesion and fusion. We have identified numerous MMPs and their tissue inhibitors (TIMPs) in in vitro cell-culture supernatants using antibody arrays and quantified select MMP/TIMPs with ELISAs. MMP-9 concentrations were significantly greater than both TIMP-1 and TIMP-2 on all materials. The ratios of MMP-9/TIMP-1 and MMP-9/TIMP-2 increased with time because of an increase in MMP-9 concentrations over time, while the TIMP concentrations remained constant. Total MMP-9 concentrations in the supernatants were comparable on all materials at each timepoint, while TIMP-1 and TIMP-2 concentrations tended to be greater on hydrophilic/anionic surfaces. Analysis of the MMP/TIMP quantities produced per cell revealed that the hydrophilic/neutral surfaces, which inhibited macrophage adhesion, activated the adherent macrophages/FBGCs to produce a greater quantity of MMP-9, TIMP-1, and TIMP-2 per cell. Pharmacological inhibition of MMP-1,-8,-13, and -18 reduced macrophage fusion without affecting adhesion, while inhibitors of MMP-2,-3,-9, and -12 did not affect adhesion or fusion. These findings demonstrate that material surface chemistry does modulate macrophage/FBGC-derived MMP/TIMP secretion and implicates MMP involvement in macrophage fusion.     

Platelet-derived growth factor and transforming growth factor-β modulate the expression of matrix metalloproteinases and migratory function of human airway smooth muscle cells

Background Matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinase (TIMPs) have been suggested to be involved in the pathogenesis of asthma. Their expression in airway smooth muscle (ASM) cells could be involved in collagen turnover and migration of these cells and thus may contribute to airway remodelling.
Objective To examine the effect of pro-fibrotic growth factors TGF-β and platelet-derived growth factor (PDGF) on the expression of MMPs/TIMPs in cultured human ASM cells and to examine the role of MMP in the migration of ASM cells.
Methods ASM cells were stimulated with TGF-β and/or PDGF. Expression and activity of MMP-1, MMP-2, MMP-3, TIMP-1 and TIMP-2 were evaluated by quantitative RT-PCR, Western blot and zymography. Modified Boyden-chamber migration assay was performed to investigate the effect of secreted MMP-3 and TIMP-1 on ASM-cell migration.
Results PDGF strongly up-regulated the expression of MMP-1 at mRNA and protein levels. PDGF, when combined with TGF-β, caused synergistic up-regulation of MMP-3. TIMP-1 was additively up-regulated by TGF-β and PDGF. These growth factors had no effect on the expression of MMP-2 and TIMP-2. U0126, an extracellular signal-regulated kinase (ERK) pathway inhibitor, inhibited the up-regulation of MMP-1 by PDGF. The synergistic/additive up-regulation of MMP-3 and TIMP-1 was inhibited by U0126 and SB431542, a Smad pathway inhibitor. Supernatant from ASM cells in which MMP-3 production was knocked down by RNA interference showed a decreased migratory effect on ASM cells, whereas supernatant from cells with suppressed TIMP-1 expression resulted in increased migration.
Conclusion Our results suggest that PDGF with/without TGF-β could facilitate migration of ASM cells by modification of MMP–TIMP balance through the ERK pathway.     

Protein expression of matrix metalloproteinases 2 and 9 and tissue inhibitors of metalloproteinase 1 and 2 in papillary thyroid carcinomas

Matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) play an important role in tumor invasion and metastasis. There have been only a few studies on the protein expression of MMPs and TIMPs in thyroid carcinomas. Therefore, we investigated the protein expression of MMP-2, MMP-9, TIMP-1 and TIMP-2 in 86 papillary thyroid carcinomas using immunohistochemistry, semiquantitative scoring morphometry of immunohistochemistry, gelatin zymography, and western blotting. We also examined the correlations between the immunohistochemical scores and several clinicopathological parameters. The immunoreactivities of MMP-2, MMP-9, TIMP-1, and TIMP-2 were largely located in the tumor cells or non-tumor follicular cells and to a much lesser extent in the fibroblasts and endothelial cells in the tumor and non-tumor regions. Compared with non-tumor regions, these four proteins tended to be overexpressed in the tumor cells; the overexpression was found in 64 of 86 (74%), 80 of 86 (93%), 79 of 86 (92%), and 64 of 86 (74%) cases for MMP-2, MMP-9, TIMP-1, and TIMP-2, respectively. Gelatin zymography showed distinct bands of MMP-2 and MMP-9 in tumor extracts but vague bands in non-tumor extracts. Western blotting revealed the specific bands of MMP-2 and MMP-9 in both tumor and non-tumor extracts. Morphometric scoring revealed that high expression of these proteins significantly correlated with large tumor size, presence of lymph node metastasis, high clinical stage, high intrathyroidal invasion, and high vascular invasion. These data suggest that MMP-2, MMP-9, TIMP-1, and TIMP-2 proteins and activities are increased in tumors cells of papillary thyroid carcinomas and that they play an important role in the invasion and metastasis of papillary thyroid carcinomas.     

基质金属蛋白酶及其组织抑制因子在人前列腺组织及各种类型前列腺细胞中的表达

目的：研究基质金属蛋白酶（MMPs）及其组织抑制因子（TIMPs）在人前列腺组织及各种类型细胞中的表达。方法： 用半定量RT－PCR的方法，对癌变和非癌变部分的前列腺组织、原代培养的平滑肌细胞、成纤维细胞、上皮细胞以及4种前列腺上皮细胞系（BPH－1、LNCaP、DU－145和PC－3）中MMP2、MMP7和MMP9、膜型基质金属蛋白酶1和3（MT1－MMP和MT3－MMP）及其组织抑制因子1和2（TIMP－1和TIMP－2）的mRNA 水平进行了测定。结果：MMP-2主要在前列腺基质细胞中表达；MMP-7和MMP-9则在前列腺上皮细胞中有较高的表达；MT1-MMP、MT3-MMP、TIMP-1和TIMP-2在前列腺基质细胞和上皮细胞中均有表达，但MT1-MMP和MT3-MMP在成纤维细胞中的表达量较高；另外，各种基质金属蛋白酶及其组织抑制因子在各种前列腺细胞系中也存在差异表达。结论： MMPs和TIMPs在前列腺组织及其各种类型细胞中的差异表达提示：它们可能在前列腺癌的转移中起着不同的作用。     

Invasion-associated MMP-2 and MMP-9 are Up-regulated Intracellularly in Concert with Apoptosis Linked to Melanoma Cell Detachment

Matrix metalloproteinases, like MMP-2 and MMP-9 gelatinases, show multiple functions as extracellular/cell-surface enzymes, and are broadly recognised for their matrix-degrading ability and involvement in cell motility. Given that adherent cells have reduced attachment during migration and also detach from their substratum during apoptosis, we now investigated whether extracellular matrix-bound gelatinases and intracellular MMP-2 and MMP-9 are modified with progression of death-inducing stimuli. This report shows that melanoma cells undergoing death in response to 2-acetyl furanonaphtoquinone (FNQ) as evidenced by greater Annexin V binding, increased cytosolic expression of pro-MMP-2 and intracellular activation of particulate MMP-9. These changes were associated with early activation of a substrate-attached 40 kDa gelatinase reciprocal with changes in extracellular matrix-bound activated MMP-2. A subsequent activation of secreted MMP-9 and induction of apoptosis-associated fragmentation of poly ADP-Ribose polymerase (PARP) correlated with cell detachment. Our data suggests that intracellularly activated gelatinases may cleave survival-associated substrates other than gelatin that share the Gly-Leu/Iso-Pro like collagen-binding acetylcholinesterase, thereby linking them to apoptosis associated with cell detachment.     

Secretion of matrix metalloproteinase-2, matrix metalloproteinase-9 and tissue inhibitor of metalloproteinases into the intrauterine compartments during early pregnancy.

Matrix metalloproteinases (MMPs) are important enzymes in tissue remodelling, a key event for the development of the fetal membranes and placenta and establishing the feto-maternal interface during early pregnancy. This study has examined the secretion of the gelatinases, MMP-2 (72 kDa) and MMP-9 (92 kDa), and the endogenous tissue inhibitors of metalloproteinases (TIMPs) into extra-embryonic coelomic and amniotic fluids, the two principal intra-uterine compartments of the first trimester, and compared them to amniotic fluid collected later in gestation. In extra-embryonic coelomic fluid, gelatin zymography demonstrated that MMP-2 (72 kDa) was the predominant gelatinase, with some MMP-9 present. A broad range of TIMPs corresponding to TIMP-1 and TIMP-2, glycosylated and unglycosylated TIMP-3 and TIMP-4 was detected in this compartment by reverse zymography and immunoblot analyses. There was little gelatinase or TIMP activity in amniotic fluid in the first trimester. In amniotic fluid from the second trimester after fusion of the membranes obliterating the extra-embryonic coelom, and at term elective caesarean section, MMP-2 is the predominant gelatinase present, with a broad spectrum of TIMPs. These findings demonstrate that predominantly MMP-2 and also MMP-9, regulated by a range of TIMPs, are involved in intra-uterine tissue remodelling during the establishment of pregnancy.     

Expression and Roles of MMP-2, MMP-9, MMP-13, TIMP-1, and TIMP-2 in Allergic Nasal Mucosa

Purpose

Allergic rhinitis (AR) and asthma share many characteristics, but structural changes are observed far less often in AR. Matrix metalloproteinases (MMPs) constitute a family of Zn-dependent endopeptidases that can decompose the extracellular matrix and basement membrane, and regulate cell infiltration. We analyzed the expression of MMPs and their inhibitors, tissue inhibitors of metalloproteinases (TIMPs), in allergic nasal mucosa after nasal allergen challenge (NAC) and determined their relationship to inflammatory cells.

Methods

Nasal mucosa specimens were obtained at surgery performed for hypertrophied turbinates. We performed NAC with house dust mite (HDM) allergen disks and control disks, and took biopsies at 30 minutes, 6 hours, and 12 hours after NAC. Cells expressing MMP-2, MMP-9, MMP-13, TIMP-1, and TIMP-2, as well as eosinophils and mast cells, were analyzed immunohistochemically. The MMPs and TIMPs in allergic nasal mucosa were quantified using enzyme-linked immunosorbent assays.

Results

At 30 minutes post-NAC, HDM-exposed nasal mucosa exhibited significantly more MMP-2+, MMP-9+, MMP-13+, TIMP-1+, and TIMP-2+ cells compared with control mucosa, and the numbers of MMP-9+ and TIMP-1+ cells correlated strongly with the number of mast cells. At 6 hours post-NAC, the numbers of MMP+ and TIMP+ cells did not differ significantly between HDM-exposed mucosa and control mucosa, but the ratios of MMP+ cells to TIMP+ cells were higher in HDM-exposed mucosa. At 12 hours post-NAC, the number of MMP-13+ cells tended to be higher in HDM-exposed mucosa and was strongly correlated with the number of eosinophils. Quantitatively, the levels of MMP-2 and MMP-13 were significantly higher than the MMP-9 level, and the TIMP-2 level was significantly higher than the TIMP-1 level in allergic nasal mucosa.

Conclusions

We demonstrated increased expression of MMP-2, MMP-9, and MMP-13 in allergic nasal mucosa, high MMPs-to-TIMP-1 ratios, and a strong correlation between MMP-9 and mast cells and between MMP-13 and eosinophils. The imbalance between MMPs and TIMPs may contribute to the migration of inflammatory cells such as eosinophils and mast cells to the nasal mucosa of AR patients, suggesting a possible active role of MMPs in AR.     

Modulation of endothelial cell morphogenesis in vitro by MMP-9 during glial-endothelial cell interactions*

The purpose of this study was to investigate the roles of matrix metalloproteinase-9 (MMP-9) and tissue inhibitor of metalloproteinase-1 (TIMP-1) in the formation of capillary structures by human brain microvascular endothelial cells cocultured with SNB19 glioblastoma cells. Unstimulated cocultures did not form capillaries and produce MMP-9 but stimulation with the protein kinase C (PKC) activator 4-phorbol-12-myristate 13-acetate (PMA) produced MMP-9 and capillary networks. Addition of recombinant MMP-9 increased capillary formation. Anti-MMP-9 antibodies, TIMP-1, the synthetic MMPs inhibitor Batimastat (BB-94), and the PKC inhibitor calphostin-C all reduced MMP-9 activity and capillary network formation in these cocultures. Cytochalasin-D in the presence of PMA suppressed MMP-9 expression and capillary formation, but colchicine-B had no such effect. Finally, PMA-induced MMP-9 expression and capillary formation were inhibited by the MEKK-specific inhibitor PD98059. These results suggest that MMP-9 is important in endothelial cell morphogenesis and the formation of capillaries in glial/endothelial cocultures in vitro. This revised version was published online in July 2006 with corrections to the Cover Date.     

Increased expression of matrix metalloproteinase-2, matrix metalloproteinase-9 and matrix metalloproteinase-13 in lesional skin of bullous pemphigoid

BACKGROUND: Matrix metalloproteinase (MMP)-2, MMP-9 and MMP-13 can degrade type IV collagen which is the major component of the basement membrane zone (BMZ). In bullous pemphigoid (BP), the separation occurs within the BMZ. OBJECTIVE: To evaluate the involvement of MMPs in the pathogenesis of BP, we examined the expression of MMP-2, MMP-9 and MMP-13 in the lesional skin of BP patients. METHODS: The expression of MMP-2, MMP-9, MMP-13, tissue inhibitors of metalloproteinase (TIMP)-1 and TIMP-2 was analyzed by immunohistochemistry in the lesional skin of BP patients in comparison with that in normal human skin. Next, the cellular sources of MMP-2, MMP-9 and MMP-13 were analyzed by double immunohistochemistry. Finally, the levels of these MMPs in the serum and blister fluid of BP patients were measured by ELISA. RESULTS: The number of cells expressing MMP-2, MMP-9 and MMP-13 were significantly increased in the lesional skin of BP patients as compared to that in normal skin. Although the number of cells expressing TIMP-1 and TIMP-2 were also increased in the lesional skin of BP patients as compared to that in normal skin, the ratio of MMPs to TIMPs in the lesional skin of BP patients was high (2.4:1). T cells comprised the major source of MMP-2, MMP-9 and MMP-13, while a proportion of mast cells and eosinophils also expressed these MMPs. Furthermore, marked expression of MMP-2 was detected in the epidermal keratinocytes. The levels of these MMPs in the blister fluid were significantly greater than those in the serum. CONCLUSION: These results suggest that MMP-2, MMP-9 and MMP-13 may be involved in the mechanism of blister formation in BP and that besides infiltrating inflammatory cells, structural cells like epidermal keratinocytes may also participate in the induction of blister formation in BP.     

Differential expression of stromal MMP-1, MMP-9 and TIMP-1 in basal cell carcinomas of immunosuppressed patients and controls

Matrix metalloproteinases (MMPs) have an important role in the initiation, growth, and invasion of malignant tumors. Basal cell cancer (BCC) is the most common human malignancy. The risk of BCC is 10–16 times higher among organ transplant recipients compared with the nontransplanted population. The aim of this study was to compare the expression of several MMPs and their tissue inhibitors (TIMPs) in BCCs from kidney transplant recipients and controls. Expression of MMPs-1, -7, -8, -9, -10, -13, -26, and TIMPs-1 and -3 was evaluated by immunohistochemistry in 25 samples of BCC of kidney transplant recipients and 25 matched controls representing superficial and nodular subtypes. No significant differences were detected in MMP expression of BCC tumor cells between immunocompetent and immunodeficient patients. However, MMPs-1 and -9 and TIMP-1 were expressed more frequently in stromal macrophages in the BCCs of immunocompetent patients. When tumor subtypes were compared irrespective of the patient group, more MMP-1-positive fibroblasts and MMP-9-positive neutrophils were detected in the superficial subtype, while stromal MMP-10 expression was more abundant in nodular tumors. Our results suggest that abundant peritumoral expression of TIMP-1 in non-immunocompromised patients limits ECM degradation permissive for cancer cell migration.     

Matrix metalloproteinase 9 (gelatinase B) is expressed in multinucleated giant cells of human giant cell tumor of bone and is associated with vascular invasion.

Human giant cell tumor (GCT) consists of multinucleated giant cells and mononuclear stromal cells, and is characterized by frequent vascular invasion without distant metastases. To study the role of matrix metalloproteinases (MMPs) in the vascular invasion, we examined production of MMP-1 (tissue collagenase), -2 (gelatinase A), -3 (stromelysin-1), -9 (gelatinase B), and tissue inhibitors of metalloproteinases (TIMP-1 and -2) in GCT. MMP-9 was highly and predominantly expressed in giant cells by both immunohistochemistry and in situ hybridization. Expression of other MMPs was also observed in some cases but was inconstant. Sandwich enzyme immunoassays demonstrated that MMP-9 is the predominant MMP secreted by GCT. There was a definite imbalance between the amounts of MMP-9 and those of TIMPs in the culture media of GCT, leading to detectable gelatinolytic activity in an assay using 14C-gelatin. Gelatin zymography demonstrated the main activity at about 90 kd, which was identified as the zymogen of MMP-9 by immunoblotting. Immunohistochemistry for type IV collagen and laminin, major basement membrane components, showed that disappearance of the proteins is closely associated with MMP-9-positive giant cells. These results indicate the production of MMP-9 by multinucleated giant cells and suggest that the metalloproteinase may contribute to proteolysis associated with vascular invasion and local bone resorption in human GCT.     

Differences in proliferation and invasion by normal,transformed and NF1 Schwann cell cultures are influenced by matrix metalloproteinase expression

Loss of negative growth regulation and high invasive potential are neoplastic traits often associated with abnormal expression of matrix metalloproteinases (MMPs). We previously found MMP-3 (stromelysin/transin) was secreted by quiescent rat Schwann cell cultures and expressed potent antiproliferative activity. In the present study we observed that human Schwann cells and cutaneous neurofibroma Schwann cell cultures secreted abundant MMP-3 and their proliferation was inhibited by autologous and rat Schwann cell conditioned media. Antiproliferative activities were depleted by immunoadsorption with anti-stromelysin antibodies. In contrast, plexiform neurofibroma cultures did not secrete MMP-3 and failed to respond to Schwann cell antiproliferative activities associated with MMP-3. Quiescent Schwann cells constitutively secreted low levels of MMP-2 (gelatinase A) and showed a low invasion potential in filter-based assays of basement membrane invasion. Cyclic AMP elevation, which profoundly influences cell differentiation, increased the invasion potential of rat Schwann cells and caused a corresponding increase in secretion of MMP-2. Schwann cells immortalized by protracted elevation of CAMP, as well as a schwannoma cell line (D6P2T), also rapidly invaded a reconstituted basement membrane and over-expressed MMP-2. Similarly, neurofibroma Schwann cells were highly invasive and secreted up to 10-fold more MMP-2 than normal human Schwann cells. Additionally, only cutaneous neurofibroma Schwann cell cultures secreted MMP-9 (gelatinase B) and MMP-1 (interstitial collagenase) and also invaded native type I collagen barriers. Cultures of normal Schwann cells and plexiform neurofibroma tumor expressed little or no MMP-1 and did not invade type I collagen barriers. These results suggest a role for MMPs in the control of proliferation and invasion by Schwann cells and in the formation of peripheral nerve sheath tumors.