Coordinate enhancement of gelatinase A mRNA and activity levels in human fibroblasts in response to breast-adenocarcinoma cells

High threshold of β1 integrin inhibition required to block collagen I-induced membrane type-1 matrix metalloproteinase (MT1-MMP) activation of matrix metalloproteinase 2 (MMP-2)

Background

Matrix metalloproteinase-2 (MMP-2) is an endopeptidase that facilitates extracellular matrix remodeling and molecular regulation, and is implicated in tumor metastasis. Type I collagen (Col I) regulates the activation of MMP-2 through both transcriptional and post-transcriptional means; however gaps remain in our understanding of the involvement of collagen-binding β1 integrins in collagen-stimulated MMP-2 activation.

Methods

Three β1 integrin siRNAs were used to elucidate the involvement of β1 integrins in the Col I-induced MMP-2 activation mechanism. β1 integrin knockdown was analyzed by quantitative RT-PCR, Western Blot and FACS analysis. Adhesion assay and collagen gel contraction were used to test the biological effects of β1 integrin abrogation. MMP-2 activation levels were monitored by gelatin zymography.

Results

All three β1 integrin siRNAs were efficient at β1 integrin knockdown and FACS analysis revealed commensurate reductions of integrins α2 and α3, which are heterodimeric partners of β1, but not αV, which is not. All three β1 integrin siRNAs inhibited adhesion and collagen gel contraction, however only the siRNA showing the greatest magnitude of β1 knockdown inhibited Col I-induced MMP-2 activation and reduced the accompanying upregulation of MT1-MMP, suggesting a dose response threshold effect. Re-transfection with codon-swapped β1 integrin overcame the reduction in MMP-2 activation induced by Col-1, confirming the β1 integrin target specificity. MMP-2 activation induced by TPA or Concanavalin A (Con A) was not inhibited by β1 integrin siRNA knockdown.

Conclusion

Together, the data reveals that strong abrogation of β1 integrin is required to block MMP-2 activation induced by Col I, which may have implications for the therapeutic targeting of β1 integrin.

L-cysteine as a regulator for arsenic-mediated cancer-promoting and anti-cancer effects

Previous studies have shown that activities of tyrosine kinases and secretion of the active form of matrix metalloproteinase-2 (MMP-2) are correlated with promotion of tumor growth, while apoptotic cell death in cancer cells is correlated with anti-cancer effects. Although arsenic has been reported to have both cancer-promoting and anti-cancer effects, the mechanisms of the arsenic-mediated bidirectional effects remain unknown. We examined the effects of arsenic on both proto-oncogene c-RET-transfected NIH3T3 cells with benign characters and oncogenic RET-MEN2A-transfected NIH3T3 cells with malignant characters. Arsenic promoted not only c-RET tyrosine kinase activity but also genetically activated RET-MEN2A kinase activity with promotion of dimer formation of RET proteins. Arsenic also increased secretion of the active form of MMP-2 in both RET-MEN2A-transfectants and c-RET-transfectants. On the other hand, arsenic promoted poly-(ADP-ribose) polymerase (PARP) degradation and cell death in both malignant and non-malignant cells. Interestingly, l-cysteine inhibited the arsenic-mediated tumor-promoting effects (activation of kinases and MMP-2 secretion) but not arsenic-mediated anti-cancer effects (PARP degradation and cell death). Our results suggest redox-linked regulation of arsenic-mediated activities of kinases and MMP-2 secretion but not arsenic-mediated cell death. Our results also suggest that l-cysteine is an ideal supplement that inhibits arsenic-mediated tumor-promoting effects without affecting arsenic-mediated anti-cancer effects.

Arsenic enhances matrix metalloproteinase-14 expression in fibroblasts

This study focused on the effects of arsenic (As) on fibroblast-derived matrix metalloproteinase (MMP)-2 and -14 levels, as these proteins were reported to be associated with tumor progression. Arsenic was found to promote production of the fibroblast-derived active form of MMP-2. Further, As at 100 or 1000 microM increased MMP-14 expression levels in fibroblasts. In addition, 1000 microM mercury (Hg) but not As increased pro-MMP-2 protein, which is involved in the conversion of the proenzyme into its active form. Since MMP-14 is an activator of pro-MMP-2, data suggest that As promotes production of fibroblast-derived active form of MMP-2 through increased expression of MMP-14. Evidence indicates that As appeared to be less effective than Hg in the conversion of pro-MMP-2 into its active form.

CD147 immunoglobulin superfamily receptor function and role in pathology

The immunoglobulin superfamily member CD147 plays an important role in fetal, neuronal, lymphocyte and extracellular matrix development. Here we review the current understanding of CD147 expression and protein interactions with regard to CD147 function and its role in pathologic conditions including heart disease, Alzheimer's disease, stroke and cancer. A model linking hypoxic conditions found within the tumor microenvironment to upregulation of CD147 expression and tumor progression is introduced.

Pancreatic stellate cells are an important source of MMP-2 in human pancreatic cancer and accelerate tumor progression in a murine xenograft model and CAM assay

The effect of the characteristic desmoplastic reaction of pancreatic cancer on tumor progression is largely unknown. We investigated whether pancreatic stellate cells, which are responsible for the desmoplastic reaction, support tumor progression. Immunohistology revealed that matrix metalloproteinase-2 (MMP-2), which is suggested to promote pancreatic cancer progression, is present in stellate cells adjacent to cancer cells. In vitro, stellate cells exhibited a much higher basal expression of MMP-2 compared with cancer cells. Panc1-, MiaPaCa2- and SW850-conditioned media stimulated MMP-2 release of stellate cells as detected by zymography. Cancer cells expressed and released basigin [BSG, extracellular matrix metalloproteinase inducer (EMMPRIN), CD147], a glycoprotein that is known to stimulate MMP-2 in mesenchymal cells, as detected by immunostaining, western blot and reverse transcription-polymerase chain reaction. Tumor cell-conditioned medium and BSG purified by affinity chromatography from supernatants of cancer cells, but not supernatants depleted from BSG, stimulated expression of MMP-1 and MMP-2 of stellate cells as demonstrated by western blot and zymography. Moreover, the interaction of stellate cells and cancer cells promoted the invasiveness of Panc-1 cells in the chorioallantoic membrane assay and increased the weight of tumors induced by all carcinoma cell lines in nude mice by 2.1-3.7-fold. Our findings support the assumption that the interaction of stellate cells and cancer cells promotes progression of pancreatic cancer.

MMP-2 mediates ethanol-induced invasion of mammary epithelial cells over-expressing ErbB2

Ethanol is a tumor promoter and may enhance the metastasis of breast cancer. We have previously demonstrated that over-expression of ErbB2 promoted ethanol-mediated invasion of mammary epithelial cells and breast cancer cells. However, the underlying cellular/molecular mechanisms remain unknown. By gelatin zymography, we showed that over-expression of ErbB2 increased the production of matrix metalloproteinase-2 (MMP-2) and MMP-9 in human mammary epithelial cells (HB2). Transient or stable transfection of ErbB2 cDNA to HB2 cells upregulated the transcripts and the activity of the MMP-2/-9 gene promoter; the upregulation of MMP-2/-9 expression was mediated by p38 mitogen-activated protein kinase (p38 MAPK) and phosphatidylinositol 3-kinase (PI3K). Although ethanol, at physiologically relevant concentrations (100-400 mg/dl), did not affect the production of MMP-2/-9, it activated MMP-2 in HB2 cells over-expressing ErbB2 (HB2(ErbB2)), but not HB2 cells; it enhanced the cleavage of proform MMP-2 (72 kDa) to an active form (62 kDa). The activation was dependent on c-jun N-terminal kinases (JNKs) and reactive oxygen species (ROS). On the other hand, ethanol affected neither the expression nor the activation of MMP-9. Selective inhibitors of MMP-2 (SB-3CT and OA-Hy) and antioxidants significantly inhibited ethanol-stimulated invasion of HB2(ErbB2) cells. Furthermore, knocking down MMP-2 by small interference RNA also induced a partial blockage on ethanol-promoted invasion of HB2(ErbB2) cells. Thus, ethanol-stimulated invasion of cells over-expressing ErbB2 was mediated, at least partially, by MMP-2 activation.

Type I collagen abrogates the clathrin-mediated internalization of membrane type 1 matrix metalloproteinase (MT1-MMP) via the MT1-MMP hemopexin domain

Type I collagen (Col I)-stimulated matrix metalloproteinase-2 (MMP-2) activation via membrane type 1 MMP (MT1-MMP) involves both a transcriptional increase in MT1-MMP expression and a nontranscriptional response mediated by preexisting MT1-MMP. In order to identify which MT1-MMP domains were required for the nontranscriptional response, MCF-7 cells that lack endogenous MT1-MMP were transfected with either wild type or domain mutant MT1-MMP constructs. We observed that mutant constructs lacking the MT1-MMP cytoplasmic tail were able to activate MMP-2 in response to Col I but not a construct lacking the MT1-MMP hemopexin domain. Col I did not alter total MT1-MMP protein levels; nor did it appear to directly induce MT1-MMP oligomerization. Col I did, however, redistribute preexisting MT1-MMP to the cell periphery compared with unstimulated cells that displayed a more diffuse staining pattern. In addition, Col I blocked the internalization of MT1-MMP in a dynamin-dependent manner via clathrin-coated pit-mediated endocytosis. This mechanism of impaired internalization is different from that reported for concanavalin A, since it is not mediated by the cytoplasmic tail of MT1-MMP but rather by the hemopexin domain. In summary, upon Col I binding to its cell surface receptor, MT1-MMP internalization via clathrin-coated pit-mediated endocytosis is impaired through interactions with the hemopexin domain, thereby regulating its function and ability to activate MMP-2.

Abrogation of fibroblast activation protein enzymatic activity attenuates tumor growth

Tumor-associated fibroblasts are functionally and phenotypically distinct from normal fibroblasts that are not in the tumor microenvironment. Fibroblast activation protein is a 95 kDa cell surface glycoprotein expressed by tumor stromal fibroblasts, and has been shown to have dipeptidyl peptidase and collagenase activity. Site-directed mutagenesis at the catalytic site of fibroblast activation protein, Ser624 --> Ala624, resulted in an approximately 100,000-fold loss of fibroblast activation protein dipeptidyl peptidase (DPP) activity. HEK293 cells transfected with wild-type fibroblast activation protein, enzymatic mutant (S624A) fibroblast activation protein, or vector alone, were inoculated subcutaneously into immunodeficient mouse to assess the contribution of fibroblast activation protein enzymatic activity to tumor growth. Overexpression of wild-type fibroblast activation protein showed growth potentiation and enhanced tumorigenicity compared with both fibroblast activation protein S624A and vector-transfected HEK293 xenografts. HEK293 cells transfected with fibroblast activation protein S624A showed tumor growth rates and tumorigenicity potential similar only to vector-transfected HEK293. In vivo assessment of fibroblast activation protein DPP activity of these tumors showed enhanced enzymatic activity of wild-type fibroblast activation protein, with only baseline levels of fibroblast activation protein DPP activity in either fibroblast activation protein S624A or vector-only xenografts. These results indicate that the enzymatic activity of fibroblast activation protein is necessary for fibroblast activation protein-driven tumor growth in the HEK293 xenograft model system. This establishes the proof-of-principle that the enzymatic activity of fibroblast activation protein plays an important role in the promotion of tumor growth, and provides an attractive target for therapeutics designed to alter fibroblast activation protein-induced tumor growth by targeting its enzymatic activity.

Modulation of monocyte matrix metalloproteinase-2 by breast adenocarcinoma cells

Introduction

The presence of monocyte and macrophage cells in growing breast tumors, and the positive relationship between the degree of immune cell infiltration and tumor growth, suggest a possible paracrine growth regulatory function of immune cells in breast cancer.

Method

To better understand the interaction between monocytes and breast cancer cells, in vitro matrix metalloproteinase and tissue inhibitor of metalloproteinase activity was assessed from the THP-1 myeloid cell line in response to conditioned media from two breast cancer cell lines, MCF-7 and MDA-MB-231.

Results

Enzymography and immunoblotting revealed increased MMP-2 as well as increased levels of TIMP-1 and TIMP-2. Furthermore, a significant increase in the invasive potential of MCF-7 and MDA-MB-231 cells was noted in response to THP-1 cell-conditioned media.

Conclusion

These data demonstrate that monocyte cells in the breast tumor microenvironment play an important role in the modulation of MMPs, which may have a significant effect on the control of tumor growth and metastatic spread.

Predictive value of lymph node and tumor matrix metalloproteinase expression in the analysis of metastatic periampullary tumors

BACKGROUND AND OBJECTIVES

Matrix metalloproteinases (MMP) are endogenous peptidases capable of degrading various components of the basement membrane. The ability of malignant epithelial cells to degrade extracellular matrix and basement membrane is an important step in the process of metastatic invasion. In this study, we prospectively compared the outcome of patients undergoing laparotomy for resection of periampullary malignancies with lymph node and tumor MMP expression to determine if there was a correlation between metalloproteinase expression and patient outcome.

METHODS

Sixteen patients undergoing operation were followed prospectively. Expression of MMP-2 and -9 and their inhibitors TIMP (tissue inhibitor of matrix metalloproteinase) -1 and -2 were measured in lymph node and tumor samples by semiquantitative PCR analysis.

RESULTS

All patients who died from their disease process had significantly greater MMP-2 expression in their lymph nodes relative to TIMP-2 expression. In contrast, patients with prolonged disease-free survival had decreased nodal MMP-2/TIMP-2 expression (P = 0.001). Patients with relatively higher MMP-2/TIMP-2 expression in their tumors also had a worse prognosis (P = 0.06).

CONCLUSION

The data demonstrate that the mRNA expression of MMPs and TIMPs in the draining lymph node of patients with periampullary adenocarcinomas may hold prognostic significance for patient survival. This prognostic information may be of use in patients when planning future adjuvant therapies.

Ethanol-induced in vitro invasion of breast cancer cells: the contribution of MMP-2 by fibroblasts

Ethanol is a tumor promoter and may promote metastasis of breast cancer. However, the underlying cellular/molecular mechanisms remain unknown. Overexpression and high activity of matrix metalloproteinase-2 (MMP-2) are frequently associated with metastatic breast cancers and serve as a prognostic indicator of clinical outcome. MMP-2 is predominantly expressed in stromal fibroblasts and plays a pivotal role in regulating the invasive behavior of breast tumor cells. We hypothesized that ethanol may enhance the invasion of breast tumor cells by modulating the activity of fibroblastic MMP-2. With in vitro models (HS68 and CCD1056SK human fibroblasts), we showed that ethanol at physiologically relevant concentrations (50-200 mg/dl) activated MMP-2; conversely, at a higher concentration (400 mg/dl), it inhibited the MMP-2 activity. Consistently, conditioned medium collected from ethanol (50-200 mg/dl)-exposed fibroblasts markedly enhanced the invasive potential of breast cancer cells and mammary epithelial cells overexpressing ErbB2/HER2 (BT474, SKBR-3 and HB2(ErbB2) cells) but had little effect on cells with low ErbB2 levels (BT20 and HB2 cells). In contrast, conditioned medium obtained from ethanol (400 mg/dl)-treated fibroblasts inhibited cell invasion. Selective inhibitors of MMP-2 (SB-3CT and OA-Hy) eliminated ethanol-stimulated invasion, indicating that the effect of ethanol was mediated by MMP-2. Ethanol activated conventional PKCs and JNKs in fibroblasts; inhibitors of PKC (Go6850 and Go6976) and JNKs (SP600125) significantly inhibited ethanol-mediated MMP-2 activation as well as cell invasion, indicating that PKCs and JNKs play a role in ethanol-induced MMP-2 activation and cell invasion in vitro. Thus, ethanol-promoted breast cancer cell invasion may be mediated by the modulation of fibroblastic MMP-2.

Gene expression profiling of normal human pulmonary fibroblasts following coculture with non-small-cell lung cancer cells reveals alterations related to matrix degradation, angiogenesis, cell growth and survival

Increasing evidence supports a major role for the microenvironment in carcinoma formation and progression. The influence of the stroma is partly mediated by signalling between epithelial tumor cells and neighboring fibroblasts. However, the molecular mechanisms underlying these interactions are largely unknown. To mimic the initial steps of invasive carcinoma in which tumor cells come in contact with normal stromal cells, we used a coculture model of non-small-cell lung cancer tumor cells and normal pulmonary fibroblasts. Using DNA filter arrays, we first analysed the overall modification of gene expression profile after a 24 h period of coculture. Next, we focused our interest on the transcriptome of the purified fibroblastic fraction of coculture using both DNA filter arrays and a laboratory-made DNA microarray. These experiments allowed the identification of a set of modulated genes coding for growth and survival factors, angiogenic factors, proteases and protease inhibitors, transmembrane receptors, kinases and transcription regulators that can potentially affect the regulation of matrix degradation, angiogenesis, invasion, cell growth and survival. This study represents to our knowledge the first attempt to dissect early global gene transcription occurring in a tumor-stroma coculture model and should help to understand better some of the molecular mechanisms involved in heterotypic signalling between epithelial tumor cells and fibroblasts.

Membrane type-1 matrix metalloproteinase and TIMP-2 in tumor angiogenesis

The matrix metalloproteinases (MMPs) constitute a multigene family of over 23 secreted and cell-surface associated enzymes that cleave or degrade various pericellular substrates. In addition to virtually all extracellular matrix (ECM) compounds, their targets include other proteinases, chemotactic molecules, latent growth factors, growth factor-binding proteins and cell surface molecules. The MMP activity is controlled by the physiological tissue inhibitors of MMPs (TIMPs). There is much evidence that MMPs and their inhibitors play a key role during extracellular remodeling in physiological situations and in cancer progression. They have other functions that promoting tumor invasion. Indeed, they regulate early stages of tumor progression such as tumor growth and angiogenesis. Membrane type MMPs (MT-MMPs) constitute a new subset of cell surface-associated MMPs. The present review will focus on MT1-MMP which plays a major role at least, in the ECM remodeling, directly by degrading several of its components, and indirectly by activating pro-MMP2. As our knowledge on the field of MT1-MMP biology has grown, the unforeseen complexities of this enzyme and its interaction with its inhibitor TIMP-2 have emerged, often revealing unexpected mechanisms of action.

Role of endocrine status and cell type in adhesion of human endometrial cells to the peritoneum in nude mice

OBJECTIVE

To investigate the role of different cellular types (epithelial and stromal endometrial cells and peritoneal cells) in the ectopic implantation of endometrium and to evaluate the importance of endocrine environment on the adhesion of endometrial cells to the peritoneum.

DESIGN

Experimental prospective study.

SETTING

University hospital, department of cell biology.

ANIMAL(S)

One hundred one nude mice.

INTERVENTION(S)

Monolayer culture of human epithelial and stromal endometrial cells obtained from patients undergoing hysterectomy or laparoscopy for benign disease. Intraperitoneal injection of cells into nude mice.

MAIN OUTCOME MEASURE(S)

Two weeks after cell injection, adhesion of endometrial cells was evaluated by histological and immunohistochemical examination.

RESULT(S)

Mixed cultures of stromal and epithelial cells, but not purified epithelial or stromal cells alone, adhered to the mouse peritoneum and led to endometriotic-like nodules. Pretreatment of cells with estrogen alone or with estrogen and progestin resulted in a higher percentage of animals developing endometriotic-like nodules, whereas treatment with progestin alone did not affect endometriotic implantation.

CONCLUSION(S)

Our data indicate that the success of endometrial cell implantation is dependent on the cooperativeness between stromal and epithelial endometrial cells, as well as on the endocrine environment of endometrial cells, but not that of recipient animals. The results emphasize the role of both endometrial cell types for ectopic implantation.

A role for matrix metalloproteinases and tumor host interaction in hepatocellular carcinomas

BACKGROUND

Hepatocellular carcinoma (HCC) occur in livers with injury-remodeling, accomplished by enzymes called matrix metalloproteinases (MMP). Metastasis involves basement membrane invasion also caused by MMP activity. Alterations in MMP expression and their endogenous inhibitor (TIMP) may factor in HCC metastasis.

METHODS

HCC specimens and lymph nodes (n = 7), and normal lymph tissue from organ donors (n = 8), were snap-frozen in liquid nitrogen and the mRNA precipitated. A series of reverse transcription-polymerase chain reactions (RT-PCR) were performed using MMP (MMP2, MMP7, MMP9) primers and TIMP (TIMP1, TIMP2) primers. These were semiquantitatively analyzed by comparing concentration with constitutive GADPH expression.

RESULTS

There is an increase in MMP2:TIMP2 mRNA expression ratio in the normal and tumor margin tissue compared to the tumor. There are increases in all MMP and TIMP mRNA expression (except TIMP1) and alterations in all of the MMP:TIMP expression ratios in the draining lymph node.

CONCLUSIONS

Alterations exist in MMP2:TIMP2: expression at the margin, and all of the MMPs in the draining lymph nodes. This likely reflects a host-tumor interaction that regulates tumor metastasis.

MMP-2 and MMP-9 expression in breast cancer-derived human fibroblasts is differentially regulated by stromal-epithelial interactions

Tissue remodeling is a key element in the local invasion and metastasis of malignant breast tumors. The degradation of extracellular matrix that is associated with this process is thought to be mediated by a number of Zn2+-dependent matrix metalloproteinases (MMPs). In most cases these enzymes are not produced by the malignant epithelium itself but by adjacent breast stroma, suggesting an important role for cell-cell interactions. We have analyzed Gelatinase A (MMP-2) and Gelatinase B (MMP-9) gene expression in a panel of six breast cancer cell lines and six primary cultures of stromal cells deriving from breast cancer biopsies. With one exception we did not detect MMP-2 or MMP-9 gene expression in any of the established tumor cell lines. Conversely, tumor stroma-derived fibroblasts expressed MMP-2 mRNA. although no MMP-9 mRNA was seen in RNase protection assays. When fibroblasts were cultured in the presence of media conditioned by MCF-7 tumor cells, MMP-2 enzyme production increased but MMP-9 activity remained undetectable. However, when fibroblasts and MCF-7 tumor cells were co-cultured together, MMP-9 was induced. These observations were confirmed by immunocytochemical analysis of co-cultures of MCF-7 and tumor-derived fibroblasts in which MMP-2 and MMP-9 protein expression was confined to stromal cells adjacent to MCF-7 tumor cells. No MMP-2 or MMP-9 staining was detected in monocultures of the two respective cell types. We conclude that MMP-2 expression is present in the stroma of malignant tumors and is increased by paracrine stimulation mediated by soluble factors. In contrast, MMP-9 expression tumor-derived fibroblasts requires direct contact with malignant tumor epithelium.

Role of myofibroblasts at the invasion front

Tumor progression occurs within a microecosystem, where cancer cells and myofibroblasts exchange proteinases and cytokines that promote growth directly through stimulation of proliferation and survival, as well as invasion through local proteolysis of the extracellular matrix and stimulation of motility. Myofibroblasts maintain the capacity of fibroblasts to induce differentiation. Fibroblasts are the main source of tumor-associated myofibroblasts. The transition to myofibroblasts also occurs in noncancerous situations. This transition is modulated by mechanical stress and cytokines, amongst which transforming growth factor-beta. The cross-talk between cancer cells and myofibroblasts illustrates the microecosystem of tumor invasion. In order to consider myofibroblasts as a possibly new target for cancer therapy, further characterization of the molecular cross-talk between myofibroblasts and cancer cells is required.

Matrix metalloproteinase inhibitors: past lessons and future prospects in breast cancer

The matrix metalloproteinases (MMPs) play a central role in invasion and metastasis. However, despite striking activity in preclinical models, the clinical development of the matrix metalloproteinase inhibitors (MMPIs) has been difficult. The results of important phase III trials are now emerging and it is therefore opportune to review the current state of the MMPIs. In this article the evidence for the role of MMPs in the progression of breast cancer, the development of the MMPIs and the recent phase III results are discussed. Despite the problems encountered it is hoped that the MMPIs may yet provide another mechanism for the long-term control of micrometastatic disease. Furthermore, important lessons can be learnt from their development that are relevant to the development of other biological agents.

Production of bioengineered cancer tissue constructs in vitro: epithelium-mesenchyme heterotypic interactions

A few models have been established to study cancer cells in vitro. However, the cellular interactions have rarely been studied specifically using bioengineered cancer constructs combining human carcinoma cells and tumor-associated fibroblasts. We developed an in vitro model of tridimensional bioengineered cancer tissue constructs (bCTC) by seeding mammary epithelial cancer cells or normal keratinocytes over a mesenchymal layer containing tumor-derived fibroblastic cells or normal skin fibroblasts. After the introduction of epithelial cells, each construct was cultured for another 10 d. Histologic analyses showed that carcinoma cell lines could invade the subjacent mesenchymal layer and that the capacity to migrate was related to the invasive potential of cancer cells and the type of fibroblasts used, while noninvasive populations did not. Of the tested epithelial cells, MDA-MB-231 and, to a lesser degree, HDQ-P1 cell lines were invasive, and the invasion was deeper into the mesenchymal component containing tumor-derived fibroblasts. However, with normal skin fibroblasts, the mesenchymal layer was degraded twice faster than with tumor-derived fibroblastic cells. MDA-MB-231 cells and normal keratinocytes induced the highest level of gelatinase B, and the level was lowest with the MCF-7 cell line. The activated form of gelatinase B was, however, induced to the highest levels in the keratinocyte-seeded bCTC containing tumor-derived but not normal fibroblasts. MDA-MB-231 was the only epithelial cancer cell line whose activity of gelatinase A was reduced when cocultured with tumor-derived fibroblasts but not under normal fibroblast stimulation. Finally, a 50/48-kDa gelatinase band has been observed in bCTCs with noninvasive epithelial cells only. Our study demonstrates the selective secretion of gelatinases according to the phenotype of the cells seeded in the various bCTCs.

Spectrum of matrix metalloproteinase expression in primary and metastatic colon cancer: relationship to the tissue inhibitors of metalloproteinases and membrane type-1-matrix metalloproteinase

The matrix metalloproteinases, MMP-2 and MMP-9, are capable of degrading components of the basement membrane, a vital barrier breached during the progression of colorectal cancer. The regulation of MMP-2 activation and subsequent targets is vital to understanding the metastatic process. MMP-2 was not expressed by colorectal cancer cells (C170 and C170HM(2)) in vitro but by stromal fibroblasts (46BR.1GI). There was induction of this MMP upon transwell co-cultivation of the colon cancer cells with the fibroblasts but in vivo growth did not lead to a similar increase in the metastatic tumour cells (C170HM(2)), MMP-2 again being attributed to the stromal cells. MMP-2 mRNA was overexpressed in human colorectal tumours compared to normal colorectal tissue, which correlated with Dukes' stage and immunolocalized to the stromal compartment of the tumour tissue. The active form of the MMP-2 enzyme was also present in the colorectal tumour tissue (7/8) but essentially absent in all normal colon samples examined (1/8). MMP-2 activation was not related to an increase in MT-1-MMP mRNA or a decrease in the specific inhibitor TIMP-2 in human tissue. There was however an increase in MMP-2/TIMP-2 ratio in tumour compared to normal. MMP-9, a target of active MMP-2, was present in the metastatic cell line but expression was down-regulated in the tumour cells in vivo, gelatin analysis revealed that MMP-9 was almost entirely attributable to the murine host, confirmed by PCR. There was no increase in mRNA for MMP-9 or its specific inhibitor TIMP-1 in colorectal tumour tissue compared to normal, MMP-9 protein localized to the inflammatory infiltrate. Fibroblast cells may provide malignant epithelial cells with a ready source of enzyme which is crucial to the metastatic process.

Expression of emmprin (CD147), a cell surface inducer of matrix metalloproteinases, in normal human brain and gliomas

EMMPRIN (extracellular matrix metalloproteinase inducer), also called CD147, basigin or M6 in the human, is a member of the immunoglobulin superfamily that is present on the surface of tumor cells and stimulates adjacent fibroblasts to produce matrix metalloproteinases (MMPs). In our study, we investigated expression of EMMPRIN in human normal brain and gliomas, since mouse basigin and chicken HT7, the species homologues of human EMMPRIN, are associated with neuronal interactions and normal blood-brain barrier function, respectively. EMMPRIN expression was detected in all samples of non-neoplastic brain and glioma tissues examined. However, expression levels of EMMPRIN mRNA and protein were significantly higher in gliomas than in non-neoplastic brain. Moreover, levels of mRNA expression and immunohistochemical staining correlated with tumor progression in gliomas: They were highest in the most malignant form of glioma, glioblastoma multiforme, followed by anaplastic astrocytoma and then low-grade astrocytoma. Also, immunolocalization revealed quite different distributions in non-neoplastic brain and glioma: EMMPRIN was demonstrated only in vascular endothelium in non-neoplastic regions of the brain, whereas it was present in tumor cells but not in proliferating blood vessels in malignant gliomas. These data indicate that an MMP inducer molecule EMMPRIN is differently expressed in human normal brain and gliomas and could be associated with astrocytoma progression. Possible mechanisms whereby glioma cell EMMPRIN could influence tumor progression will be discussed.

Analysis of the ex vivo specificity of human gelatinases A and B towards skin collagen and elastic fibers by computerized morphometry

Cutaneous aging and chronic exposure to UV irradiation leads to alterations in the appearance and biochemical composition of the skin. Members of the MMP family have been involved in the destruction of the extracellular matrix. Among them, gelatinases A and B were found to display elastolytic activity, in vitro. In this study, we first determined the ex vivo elastolytic potential of both endopeptidases, using human skin tissue sections and computerized morphometric analyses, and compared it with those of neutrophil elastase. In such conditions, gelatinase B (50 nM) induced 50% elastolysis. The percentage of elastic fibers degraded by gelatinase A (10-100 nM) never exceeded 10%. Elastolysis by gelatinase B and leukocyte elastase was characterized by a decrease in fiber length and an increase in the average diameter of the fibers. In addition, gelatinase B exhibited fibrillin-degrading activities. On the contrary, gelatinase A (50 nM) elicited up to 50% hydrolysis of collagen fibers, preferentially degrading type III collagen fibers. Gelatinase B did not promote any collagen degrading activity. Our data suggested that in vivo gelatinases could disrupt most extracellular matrix structures of human skin. Gelatinase B and to a much lesser extent, gelatinase A would degrade components of the elastic fibers network while gelatinase A, but not gelatinase B, would alter mostly collagen fibers and also degrade constituents of the dermo-epidermal junction.

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

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

Unraveling the role of proteases in cancer

Investigators have been studying the expression and activity of proteases in the final steps of tumor progression, invasion and metastasis, for the past 30 years. Recent studies, however, indicate that proteases are involved earlier in progression, e.g., in tumor growth both at the primary and metastatic sites. Extracellular proteases may co-operatively influence matrix degradation and tumor cell invasion through proteolytic cascades, with individual proteases having distinct roles in tumor growth, invasion, migration and angiogenesis. In this review, we use cathepsin B as an example to examine the involvement of proteases in tumor progression and metastasis. We discuss the effect of interactions among tumor cells, stromal cells, and the extracellular matrix on the regulation of protease expression. Further elucidation of the role of proteases in cancer will allow us to design more effective inhibitors and novel protease-based drugs for clinical use.

Metastatic and non-metastatic colorectal cancer (CRC) cells induce host metalloproteinase production in vivo

Numerous studies have demonstrated the persistent localization of matrix metalloproteinase (MMP) expression to the interface between invading human colorectal cancer (CRC) cells and surrounding stroma supporting a role for MMPs in CRC invasion and metastasis. The present study sought to determine whether CRC cells of varying metastatic potential would have differential effects on host MMP release. Subcutaneous CRC tumors were generated in BALB/c nude mice using three CRC cell lines: SW480, SW620, and the highly metastatic SW620S5 clone. Representative samples from the subcutaneous CRC were then orthotopically implanted on the cecum of recipient nude mice. Subcutaneous and cecal tumors were analyzed for MMP expression via zymography, western blot, and RT-PCR. In vitro, none of the three cell lines expressed MMP-2 nor MMP-9. In contradistinction, the subcutaneous tumors expressed limited amounts of MMP-2 and MMP-9 while the cecal tumors expressed significant amounts of MMP-2 and MMP-9 as well as other smaller members of the MMP family. MMP-9 mRNA and protein was confirmed as host in origin by RT-PCR with mouse specific primers and a mouse MMP-9 molecular weight of 105 kDa as determined by zymography and western blot analysis. In situ hybridization also localized the mRNA for MMP-9 to the host stromal cells. In conclusion, CRC cells appear incapable of producing MMP-2 and MMP-9 in vitro but are capable of up-regulating host MMP production in vivo. Enhanced host MMP-9 production in metastatic CRC cell-derived subcutaneous and cecal tumors suggests that metastatic colon cells may acquire the expression of important MMP regulating factor(s) in vivo.

Cathepsin D expression by cancer and stromal cells in breast cancer: an immunohistochemical study of 1348 cases

This study was aimed at investigating the influence of cathepsin D (CD) expression by cancer cells and stromal cells on breast cancer prognosis. This is a study of 1348 node-positive (NPBC) and node-negative (NNBC) breast cancers diagnosed between 1980 and 1986 and with a minimum follow-up of 5.2 years. CD expression was assessed by immunohistochemistry on archival material using a polyclonal antibody. The expression by cancer and stromal cells was assessed separately and correlated with distant metastasis free (DMFS) and overall survival (OS). Cancer cells expressed CD (more than 10% cells expressing CD) in 38.9% of cases and reactive stromal cells in 43.6%. CD expression by reactive stromal cells, and not cancer cells, correlated with several factors of poor prognosis by cancer cells. A strong association was also found with expression of other proteases (stromelysin-3, gelatinase A, and urokinase Plasminogen Activator) by these same reactive stromal cells. CD expression by cancer cells did not predict DMFS or OS but, by univariate analysis, CD expression by reactive stromal cells was associated with earlier recurrence and shorter survival in NNBC (p = 0.0425) and NPBC patients submitted to adjuvant chemotherapy (p = 0.0234). However, CD expression by reactive stromal cells remained a significant predictor of recurrence by multivariate analyses only in a subgroup of NPBC submitted to adjuvant chemotherapy. Overall, those data support the concept that proteases produced by reactive stromal cells are under cancer cell stimulation and that CD by stromal cells, and not cancer cells, influences the prognosis, but only in a subgroup of patients with breast cancer.

MMP-2 release and activation in ovarian carcinoma: the role of fibroblasts

The matrix metalloproteinase MMP-2 is up-regulated in epithelial cancers and its mRNA localizes to stromal fibroblasts. In this paper we show that co-culture of ovarian carcinoma cells with fibroblasts resulted in an enhanced release of proMMP-2 and TIMP-2 into the culture medium. Cell-cell interaction was a major factor in this response and carcinoma cells stimulated proMMP-2 release from fibroblasts but not vice versa. Collagen 1, in a dose-dependent fashion, induced activation of proMMP-2 by tumour-derived, but not normal, fibroblasts. Antibody to beta1 integrin also induced proMMP-2 activation by tumour-derived fibroblasts. The activation involved the processing of proMMP-2 by a membrane-bound metalloproteinase. We propose that, in the ovarian tumour microenvironment, interaction between tumour cells and fibroblasts may enhance fibroblast production of the proMMP-2 and TIMP-2. Collagen I, also present in the ovarian tumours, then induces these fibroblasts to activate proMMP-2 even in the presence of TIMP-2. This active MMP-2 can associate with the cell surface of tumour cells and fibroblasts and is used in the processes of tissue remodelling and invasion.

Involvement of focal adhesion kinase in inhibition of motility of human breast cancer cells by sphingosine 1-phosphate

Sphingosine 1-phosphate (SPP), a bioactive sphingolipid metabolite, inhibits chemoinvasiveness of the aggressive, estrogen-independent MDA-MB-231 human breast cancer cell line. As in many other cell types, SPP stimulated proliferation of MDA-MB-231 cells, albeit to a lesser extent. Treatment of MDA-MB-231 cells with SPP had no significant effect on their adhesiveness to Matrigel, and only high concentrations of SPP partially inhibited matrix metalloproteinase-2 activation induced by Con A. However, SPP at a concentration that strongly inhibited invasiveness also markedly reduced chemotactic motility. To investigate the molecular mechanisms by which SPP interferes with cell motility, we examined tyrosine phosphorylation of focal adhesion kinase (FAK) and paxillin, which are important for organization of focal adhesions and cell motility. SPP rapidly increased tyrosine phosphorylation of FAK and paxillin and of the paxillin-associated protein Crk. Overexpression of FAK and kinase-defective FAK in MDA-MB-231 cells resulted in a slight increase in motility without affecting the inhibitory effect of SPP, whereas expression of FAK with a mutation of the major autophosphorylation site (F397) abolished the inhibitory effect of SPP on cell motility. In contrast, the phosphoinositide 3'-kinase inhibitor, wortmannin, inhibited chemotactic motility in both vector and FAK-F397-transfected cells. Our results suggest that autophosphorylation of FAK on Y397 may play an important role in SPP signaling leading to decreased cell motility.

Prognostic significance of stromelysin 3, gelatinase A, and urokinase expression in breast cancer

This study was aimed at testing the hypothesis that the expression of proteases essentially produced by reactive stromal cells (stromelysin-3 [ST3], gelatinase A [GELA], and urokinase [uPA]) is predictive of prognosis in patients with breast cancer. This was a study of patients with node-positive and node-negative breast cancer diagnosed from 1980 to 1986 and with an average of 10 years follow-up. ST3 (665 cases), GELA, and uPA (575 cases each) expression was obtained by in situ hybridization on formalin-fixed, paraffin-embedded material using mRNA antisense probes. ST3 was expressed by 86.6% of the cases; GELA, 77.7%; and uPA, 64.7%. A significant correlation (P < .05) was found between high (more than 10%) ST3 expression and a younger age, lymph node involvement, poor nuclear grade, ductal histology, aneuploidy, and HSP-27 expression. High GELA expression was significantly associated with c-erbB2, ductal histology, and HSP-27 expression. High uPA expression correlated with poor nuclear grade, ductal histology, lack of estrogen and progesterone receptors, and p53 protein accumulation. High level of expression of all three proteases correlated significantly with each other and with cathepsin D expression by reactive stromal cells. By univariate analysis, both ST3 and uPA expression significantly predicted a shorter recurrence-free survival (ST3, P = .0199; uPA, P = .0269). By multivariate analyses, the prognostic significance was lost, most particularly at longer term. This study adds support to the concept that protease expression by reactive stromal cells is related to cancer cell characteristics but that their contribution to cancer progression is marginal.

Regulation of matrix metalloproteinase-2 (gelatinase A, MMP-2), membrane-type matrix metalloproteinase-1 (MT1-MMP) and tissue inhibitor of metalloproteinases-2 (TIMP-2) expression by elastin-derived peptides in human HT-1080 fibrosarcoma cell line

Soluble kappa-elastin peptides were shown to stimulate the expression of MMP-2 (but not MMP-9) by human fibrosarcoma HT-1080 cells, both at the protein and mRNA levels; maximal effect being observed at a concentration of 25 microg/ml of kappa-elastin. The stimulatory effect could be reproduced using Val-Gly-Val-Ala-Pro-Gly (VGVAPG) peptide, an elastin-derived hydrophobic hexapeptide which represented the elastin receptor binding sequence of tropoelastin. Furthermore, treatment of cells with lactose (30 mM), which dissociated 67-kDa elastin binding protein (EBP) from cell surfaces, completely abolished this effect, suggesting that the elastin receptor could mediate such a response. Using a specific monoclonal antibody, 67-kDa EBP was detected in HT-1080 membrane preparations by Western immunoblotting. Following treatment with 25 microg/ml kappa-elastin or 200 microg/ml VGVAPG, increased levels of the active 62-kDa form of MMP-2 were found in HT-1080 cell extracts. Stimulation of MT1-MMP mRNA expression by treatment with elastin-derived peptides (EDPs) was shown by competitive polymerase chain reaction (PCR). A reverse zymography analysis revealed that EDPs also stimulated TIMP-2 (but not TIMP-1) production by HT-1080 cells. Competitive PCR confirmed increased TIMP-2 mRNA expression by such treatment. These results suggest that occupancy of the 67-kDa elastin receptor by elastin-derived peptides enhanced both expression and activation of proMMP-2 and consequently, could promote the invasive/metastatic ability of tumor cells expressing this receptor.

Roles of the matrix metalloproteinases in mammary gland development and cancer

Tissue remodeling is a key process involved in normal development, wound healing, bone remodeling, and embryonic implantation, as well as pathological conditions such as tumor invasion and metastasis, and angiogenesis. The degradation of the extracellular matrix that is associated with those processes is mediated by a number of families of extracellular proteinases. These families include the serine proteinases, such as the plasminogen-urokinase plasminogen activator system and leukocyte elastases, the cysteine proteinases, like cathepsin D and L, and the zinc-dependent matrix metalloproteinases (MMPs) [1]. Accumulating evidence has highlighted the central role of MMP-driven extracellular matrix remodeling in mammary gland development and breast cancer.

NF-kappaB activation and interleukin 6 production in fibroblasts by estrogen receptor-negative breast cancer cell-derived interleukin 1alpha

Several angiogenic factors and extracellular matrix-degrading enzymes that promote invasion and metastasis of cancer are produced by stromal fibroblasts that surround cancer cells. The expression of genes that code for some of these proteins is regulated by the transcription factor NF-kappaB. In this report, we demonstrate that conditioned medium (CM) from estrogen receptor (ER)-negative but not ER-positive breast cancer cells induces NF-kappaB in fibroblasts. In contrast, CM from both ER-positive and ER-negative breast cancer cells induces NF-kappaB in macrophages and endothelial cells. NF-kappaB activation in fibroblasts was accompanied by induction of interleukin 6 (IL-6) and urokinase plasminogen activator (uPA), both of which promote angiogenesis and metastasis. A survey of cytokines known for their ability to induce NF-kappaB identified IL-1alpha as the factor responsible for NF-kappaB activation in fibroblasts. Analysis of primary breast carcinomas revealed the presence of IL-1alpha transcripts in majority of lymph node-positive breast cancers. These results along with the known role of IL-1alpha and IL-6 in osteoclast formation provide insight into the mechanism of metastasis and hypercalcemia in advanced breast cancers.

Inhibition of stromal matrix metalloproteases: effects on breast-tumor promotion by fibroblasts

Co-injection of fibroblasts with human epithelial breast-tumor MCF7 cells in the presence of Matrigel enhances tumor growth in nude mice. While most of the matrix metalloproteinases (MMPs) have been shown to be produced by stromal cells, tumor cells such as MCF7 cells are unable to produce MMPs. We therefore, hypothesized that the tumor-promoting effect of fibroblasts could be related to their production of MMPs. In order to inhibit stromal proteases, over-production of TIMP-2 was induced in MCF7 cells by in vitro retroviral-mediated gene transfer. TIMP-2-producing MCF7 cells were then co-injected with fibroblasts into nude mice. Alternatively, we evaluated the effect of Batimastat, a synthetic inhibitor of MMPs, on the tumorigenicity of MCF7 cells co-inoculated with fibroblasts into nude mice. Both physiological (TIMP-2) and synthetic (Batimastat) inhibitors of MMPs were able to abolish the tumor-promoting effect of fibroblasts. On the contrary, they failed to modulate the tumorigenicity of MCF7 cells injected alone. Interestingly, Matrigel from which low-molecular-weight proteins or growth factors had been removed failed to favor the tumorigenicity of MCF7 cells inoculated with fibroblasts. These findings emphasize the importance of fibroblasts in cancer progression, and suggest that their role could be related at least in part to production of proteases which can induce the release of factors from the extracellular matrix.

Assay of matrix metalloproteinases types 1, 2, 3 and 9 in breast cancer

Matrix metalloproteinases (MMPs) are zinc dependent endopeptidases implicated in cancer invasion and metastasis. Gelatin zymography was performed on 84 human breast carcinomas and seven normal breast tissues. The precursor form of MMP-2 (72 kDa) was found in 11 (12%) samples, while its two activated forms, i.e. 62 kDa and 59 kDa, were found in three (6%) and 34 (40%) samples respectively. In contrast to MMP-2, most of the samples (52%) contained MMP-9 in its precursor form. Using ELISA, MMP-1 levels were found in 12% of the samples while MMP-3 levels were found in only 2% of the samples. Levels of MMP-2, -3 and -9 correlated inversely with numbers of nodal metastases. Neither MMP-2 nor -9 levels were significantly related to patient outcome. However, patients with high levels of a 50-kDa gelatinase band after zymography had a significantly better survival than patients with low levels. This species was never observed in normal breast tissue.

Increased activity of cathepsin B in fibroblasts isolated from primary melanoma in comparison to fibroblasts from normal skin

We determined activity of cathepsin B in early-passage fibroblasts isolated from primary melanoma and in fibroblasts from normal skin. Our results show an up to 5-fold increase in activity of cathepsin B in the tumor-derived fibroblasts in comparison to the fibroblasts from normal skin. We conclude that fibroblasts isolated from melanoma tissue are altered with regard to their specific activity of cathepsin B and preserve this elevated activity in early-passage cell culture. The data support the idea that stromal cells are not passive elements of the peritumoral environment but actively participate in the production of proteolytic enzymes.

Fibroblast-directed expression and localization of 92-kDa type IV collagenase along the tumor-stroma interface in an in vitro three-dimensional model of human squamous cell carcinoma

The malignant dissemination of tumors has been shown to require expression of one or more members of the matrix metalloprotease (MMP) enzyme family, whose function is to catalyze degradation of extracellular matrix proteins. In human squamous cell carcinoma (SCC) of the skin, expression of the MMP 92-kDa type IV collagenase (MMP-9), was previously shown to localize to malignant keratinocytes residing along the tumor/stromal interface. The purpose of the study presented here was to determine whether this localized expression pattern is due to interactions between SCC cells and adjacent stromal fibroblasts. To examine this question, SCC cells were grown as organotypic skin cultures, an in vitro three-dimensional model of reconstructed human epidermis in which keratinocytes are grown on a type 1 collagen gel embedded with human dermal fibroblasts. In this study, MMP-9 expression was compared in organotypic cultures (constructed with SCC cells or the non-tumorigenic keratinocyte cell line HaCaT), in which human dermal fibroblasts were either included or excluded from the underlying stromal layer. In the absence of fibroblasts, expression of MMP-9 was slightly higher in SCC than HaCaT cultures. In cultures constructed with fibroblasts, however, induction of MMP-9 mRNA was observed in SCC but not HaCaT cultures. This induction of MMP-9 mRNA was accompanied by high levels of MMP-9 protein expression along the SCC/stromal interface. These data provide strong evidence that interactions between malignant keratinocytes and adjacent stromal fibroblasts are critical in directing expression of MMP-9 to the tumor-stroma interface in human SCC tumors.

Tumor collagenase stimulatory factor (TCSF) expression and localization in human lung and breast cancers

Tumor cell-derived collagenase stimulatory factor (TCSF) stimulates in vitro the biosynthesis of various matrix metalloproteinases involved in tumor invasion, such as interstitial collagenase, gelatinase A, and stromelysin 1. The expression of TCSF mRNAs was studied in vivo, using in situ hybridization and Northern blotting analysis, in seven normal tissues and in 22 squamous cell carcinomas of the lung, and in seven benign proliferations and in 22 ductal carcinomas of the mammary gland. By in situ hybridization, TCSF mRNAs were detected in 40 of 44 carcinomas, in pre-invasive and invasive cancer cells of both lung and breast cancers. TCSF mRNAs and gelatinase A mRNAs were both visualized in the same areas in serial sections in breast cancers, and were expressed by different cells, tumor cells, and fibroblasts. The histological results were confirmed by Northern blot analysis, which showed a higher expression of TCSF mRNAs in cancers than in benign and normal tissues. These observations support the hypothesis that TCSF is an important factor in lung and breast tumor progression.

Metastatic ability of MXT mouse mammary subpopulations correlates with clonal expression and/or membrane-association of gelatinase A

We have developed a novel murine mammary tumor system with variants representing different stages of tumor progression. The MXT-s parental cell line was established from a urethane-induced and hormone-sensitive mammary tumor. MXT-s parental cells are highly tumorigenic but poorly metastatic. MXT clones and variants were selected by either in vitro or in vivo procedures, and they differ in metastatic ability and 17 beta-estradiol dependency for tumor growth. The MXT-c1.1 and MXT-B2 cell lines produced lung metastasis after intravenous injection into 100% of syngenic mice, but only MXT-c1.1 cells were highly metastatic from intramammary tumors. The fingerprints obtained by arbitrarily primed-polymerase chain reaction demonstrated that the metastatic variants and clones had a common genetic background and resulted from clonal selection from the parental cell line. We studied whether the matrix metalloproteinase (MMP) profile is correlated with tumor progression and metastatic ability in the MXT tumor system. Gelatinases A and B were assayed in the cells, both by enzyme activity and mRNA expression. Gelatinase A was expressed in MXT-c1.1 cells, whereas MXT-B2 cells did not express either MMP. In contrast, the mammary fat pad tumors expressed both gelatinases. Membrane Type 1-MMP transcripts were also detected in MXT cells and tumors. Because the mRNA levels of gelatinase. A were low in MXT-B2 tumors, we suggested that exogenous gelatinase A bound the cell membranes of MXT-B2 cells in vivo. Indirect evidence was obtained in vitro by treatment of MXT-B2 cells with NIH/3T3 fibroblast-conditioned medium. After this treatment, we detected a gelatinolytic activity at M(r) 68,000 in the cell-membrane extract of MXT-B2 cells and an increase in migratory ability through type IV collagen matrices. On the other hand, Ha-ras gene dosage correlated positively with metastatic ability but not with either gelatinase A or gelatinase B expression. No significant differences were observed in the expression of stromelysin-1 and tissue inhibitors of MMP. Thus, in the MXT tumor system, the expression of gelatinase A or its cell association and Ha-ras gene dosage independently contribute to the metastatic phenotype.

Binding of 92 kDa and 72 kDa progelatinases to insoluble elastin modulates their proteolytic activation

92 kDa and 72 kDa gelatinases, two neutral proteinases exhibiting elastinolytic activity and secreted as zymogens by aortic smooth muscle cells, were shown to bind to insoluble elastin. The active form of each enzyme interacted with substrate more avidly than latent form. Once bound to insoluble elastin, 92 kDa progelatinase was totally unaffected by any potential activators tested (tissue kallikrein, neutrophil elastase, plasmin, and stromelysin-1), except aminophenylmercuric acetate (APMA). Binding of 72 kDa progelatinase to insoluble elastin induced a fast autoactivation of the proenzyme followed by its inactivation. This process can be partly inhibited by tissue inhibitor of matrix metalloproteinases-2 (TIMP-2), EDTA and a synthetic inhibitor of matrix metalloproteinases (BB-94). Such an autoactivation process was also partially observed following adsorption of 72 kDa gelatinase to elastin-derived peptides but not to gelatin. Therefore, elastin can act as a template to direct its own proteolysis by 72 kDa gelatinase; such a mechanism could be relevant to the focal elastolysis in the arterial wall during arteriosclerosis.

Induction of membrane-type matrix metalloproteinase 1 (MT1-MMP) expression in human fibroblasts by breast adenocarcinoma cells

Membrane-type matrix metalloproteinase 1 (MT1-MMP) has been recently described as an activator of proMMP-2 (MMP-2) which is involved in tumor invasion. We have shown by in situ hybridization that MT1-MMP is produced by stromal cells in close contact to preinvasive and invasive tumor cells of breast carcinomas. Of particular interest was the observation that some fibroblasts express this enzyme in focal areas in preinvasive lesions, suggesting that particular tumor cells may stimulate fibroblasts to produce MT1-MMP. We have therefore compared the ability of two different breast cancer cell lines, one non-invasive (MCF7) and one invasive (MDA-MB-231) to stimulate MT1-MMP production in human fibroblasts with consequent proMMP-2-activation. The MDA-MB-231 conditioned medium induced MT1-MMP mRNAs in human fibroblasts and a parallel activation of proMMP-2 whereas MCF7 conditioned medium did not have any effect. These results suggest the existence of soluble factor(s) secreted by invasive or some preinvasive breast tumor cells which stimulate fibroblasts to produce and activate MMPs, and emphasize the cooperation between cancer and stromal cells in tumor invasion.

Differential display of reticulocalbin in the highly invasive cell line, MDA-MB-435, versus the poorly invasive cell line, MCF-7

Matrigel invasion assays were used to characterize the invasive abilities of five breast cancer cell lines. Reverse Transcription Polymerase Chain Reaction (RT-PCR) was used to detect the differential gene expression of estrogen receptor (ER), E-cadherin, vimentin and cathepsin D in these cell lines. Using mRNA differential display, we identified novel cDNA clones representing the partial sequences of genes overexpressed in the invasive MDA-MB-435 cells as compared to that of the less invasive MCF-7 cells. One of the cDNAs was homologous to reticulocalbin. The studies were repeated in all of the cell lines and the overexpression of this cDNA was confirmed by RT-PRC and Northern hybridization analysis. Reticulocalbin was expressed in the highly invasive breast cancer cell lines but was not expressed in poorly invasive ones. Although its function is still unknown, reticulocalbin is implicated in tumor cell invasiveness because of its differential expression in breast tumor cell lines.

Induction of matrix metalloproteinase 9 expression in breast carcinoma cells by a soluble factor from fibroblasts

Tumor-stromal interactions appear to play an important role in the induction of metalloproteinase expression in malignant tumors. We describe a tissue culture system in which expression of MMP-9 (gelatinase B or the 92 kDa type IV collagenase/gelatinase) was induced by co-cultivation of fibroblasts with breast cancer cell lines. While neither the breast cancer cells nor the normal rat embryo fibroblasts made MMP-9 alone in culture, human MMP-9 was made in the co-cultures. The MMP-9 was secreted in a latent form. The induction occurred at least in part through increases in the MMP-9 mRNA levels in the breast cancer cells. These increases did not appear to require protein synthesis. Conditioned medium from the fibroblasts could duplicate the induction of MMP-9 in the breast cancer cell lines. The active factor in the medium was inactivated by heat or by trypsin suggesting that it was a protein. This protein was in the size range of 30-100 kDa. Thus, fibroblasts could secrete a factor which was able to regulate the expression of MMP-9 in breast cancer cells.

The distribution of matrix metalloproteinases and tissue inhibitor of metalloproteinases in colorectal cancer

Studies suggest that the interplay between matrix metalloproteinases (MMPs) and their inhibitors, tissue inhibitor of metalloproteinases (TIMPs), is an important mediator of tumour invasion and metastasis. Using immunohistochemistry, 40 specimens of colorectal cancer were examined for the presence of TIMP-1 and the MMPs, stromelysin, gelatinases A and B and interstitial collagenase. Neither enzyme nor TIMP-1 was detected in histologically normal mucosa. Within malignant tissue, stromelysin and gelatinase A were conspicuously absent in tumour cells but were immunolocalized to the extracellular matrix and for gelatinase A also to peritumoural fibroblast-like cells. Gelatinase B was confined to polymorphonuclear leucocytes. Interstitial collagenase was not identified. TIMP-1 was present in only three of the 40 tumours within the malignant stroma. These observations suggest that the mesenchymal elements of colorectal carcinomas, by acting as a source of MMPs and TIMPs, may modulate tumour invasion.

The distribution of matrix metalloproteinases and tissue inhibitor of metalloproteinases in colorectal cancer

Studies suggest that the interplay between matrix metalloproteinases (MMPs) and their inhibitors, tissue inhibitor of metalloproteinases (TIMPs) is an important mediator of tumour invasion and metastasis. Using immunohistochemistry, 40 specimens of colorectal cancer were examined for the presence of TIMP-1 and the MMPs, stromelysin, gelatinases A and B and interstitial collagenase. Neither enzyme nor TIMP-1 was detected in histologically normal mucosa. Within malignant tissue, stromelysin and gelatinase A were conspicuously absent in tumor cells but were immunolocalized to the extracellular matrix and for gelatinase A also to peritumoural fibroblast-like cells. Gelatinase B was confined to polymorphonuclear leucocytes. Interstitial collagenase was not identified. TIMP-1 was present in only three of the 40 tumours within the malignant stroma. These observations suggest that the mesenchymal elements of colorectal carcinomas, by acting as a source of MMPs and TIMPs, may modulate tumour invasion.

Tumor metastasis: current biologic concepts and their implications for control of residual disease

Metastatic disease presents an important obstacle to curative cancer therapy. This article reviews cancer biology concepts relevant to the pathogenesis of tumor metastasis and their implications for the surgical oncologist seeking to control or eradicate metastatic disease.