Modeling the extracellular matrix in cell migration and morphogenesis: a guide for the curious biologist

The extracellular matrix (ECM) is a highly complex structure through which biochemical and mechanical signals are transmitted. In processes of cell migration, the ECM also acts as a scaffold, providing structural support to cells as well as points of potential attachment. Although the ECM is a well-studied structure, its role in many biological processes remains difficult to investigate comprehensively due to its complexity and structural variation within an organism. In tandem with experiments, mathematical models are helpful in refining and testing hypotheses, generating predictions, and exploring conditions outside the scope of experiments. Such models can be combined and calibrated with in vivo and in vitro data to identify critical cell-ECM interactions that drive developmental and homeostatic processes, or the progression of diseases. In this review, we focus on mathematical and computational models of the ECM in processes such as cell migration including cancer metastasis, and in tissue structure and morphogenesis. By highlighting the predictive power of these models, we aim to help bridge the gap between experimental and computational approaches to studying the ECM and to provide guidance on selecting an appropriate model framework to complement corresponding experimental studies.

Plasma Levels of Matrix Metalloproteinases 2 and 9 in Patients with Chronic Chagas Heart Disease and Systemic Arterial Hypertension: Correlation with TGF-Beta Plasma Levels

Background

Chronic Chagas heart disease (CCHD) and systemic arterial hypertension (SAH) frequently coexists in areas where Chagas disease is endemic. The effects of the association of both conditions (CCHD-SAH) on the extracellular matrix (ECM) remodeling are unknown. Matrix metalloproteinases (MMP) 2 and 9 are involved in ECM remodeling. The aim of this study was to evaluate MMP 2 and MMP9 in CCHD-SAH patients and to correlate their levels with those of the profibrogenic cytokine TGF-beta.

Methods

We included 19 patients with CCHD-SAH, 14 patients with CCHD alone, and 19 controls matched by sex and age. MMP-2 and MMP-9 plasma levels were studied by gel zymography and showed as optical densities (OD). TGF-beta plasma levels were measured by double-ligand ELISA and expressed as pg/mL.

Results

Median (5^th, 95^th) MMP-2 plasma levels were 1224.7 OD (1160, 1433.5) in patients with CCHD alone, 1424.1 OD (1267.5, 1561) in patients with CCHD-SAH, and 940 OD (898.1, 1000.8) in controls (p=0.001). MMP-9 plasma levels were 1870 OD (1740, 1904.1) in patients with CCHD alone, 1754.6 OD (1650, 2049) in those with CCHD-SAH and 89.7 OD (80, 96) in controls (p=0.0003). MMP-9 plasma levels were higher than those of MMP 2 in patients with CCHD-SAH (p=0.01). No correlation was found between TGF-beta plasma levels with MMP-2 serum levels (r = 0.12; p=0.7), but a moderate negative correlation (r = -0.46; p=0.048) was observed between TGF-beta and MMP-9 plasma levels.

Conclusions

MMP-2 and especially MMP-9 may play a role in the ECM remodeling process in patients with CCHD-SAH. TGF-Beta may counteract the MMP effect on the ECM remodeling process in patients with CCHD-SAH.

The Predictive Values of MMP-9, PLTs, ESR, and CRP Levels in Kawasaki Disease with Cardiovascular Injury

Objective

To explore the levels of matrix metalloproteinase-9 (MMP-9), platelets (PLTs), C reactive protein (CRP), and erythrocyte sedimentation rate (ESR) and their predictive values in Kawasaki disease (KD) with cardiovascular injury.

Methods

128 children were diagnosed with KD in the Lanzhou University Second Hospital. 75 patients had coronary artery lesion (CAL), while 53 patients did not. The levels of MMP-9, PLTs, and CRP and ESR in the two groups were determined. The area under the curve (AUC) of the receiver-operating characteristic (ROC) curve and the Youden index (YI) were used to evaluate the efficacy of MMP-9, PLTs, ESR, and CRP for predicting CALs in KD.

Results

The mean age of the patients was 2.7 ± 2.03 years (range, 2 months to 11 years). There were 87 boys (67.97%) and 41 girls (32.03%). In contrast to the NCAL group, the CAL group had obviously higher levels of MMP-9, PLTs, and CRP and an obviously higher ESR (P < 0.05). MMP-9 showed a linear positive correlation with ESR (P < 0.05) and CRP (P < 0.05). The AUC of the combined detection of the four indicators was 0.877, the sensitivity was 85.07% and the specificity was 78.95%.

Conclusion

MMP-9, PLTs, ESR, and CRP are important indicators for a CAL in KD. The efficacy of the combined detection of MMP-9, PLTs, ESR and CRP is better than that of any single indicator for predicting a CAL in KD.

Expression of Matrix Metalloproteinase-7 Predicts Poor Prognosis in Gastric Cancer

To date, no potential markers have been established for predicting prognosis in gastric cancer. Matrix metalloproteinase-7 (MMP-7) has been suggested as a prognostic marker in several cancers. In this study, we aimed to determine the expression of the MMP-7 protein and its polymorphisms in gastric cancer tissues. The association between MMP-7 expression level and clinicopathological characteristics was also evaluated. MMP-7 protein expression and its polymorphisms were investigated in a total of 400 patients using immunohistochemistry and TaqMan SNP genotyping assays. The correlation of MMP-7 expression with clinicopathological characteristics, including tumor location, tumor size, histologic type, lymphatic invasion, vascular invasion, pathological T stage, pathological TNM stage, residual tumor, and CEA level, was investigated. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated using a multivariate Cox proportional hazards regression model. MMP-7 expression was found in 283 of 400 (70.75%) gastric cancer tissues. Expression of MMP-7 was significantly associated with poor clinicopathological characteristics, including vascular invasion ( $\text{OR}=6.61$ , $95\%\text{CI}=4.26–9.89$ , $p=0.024$ ), lymphatic invasion ( $\text{OR}=8.17$ , $95\%\text{CI}=4.47–12.39$ , $p=0.017$ ), undifferentiated histologic type ( $\text{OR}=2.46$ ; 95% CI, 1.31–4.52; $p=0.014$ ), higher TNM stage (stage IV) ( $\text{OR}=1.48$ , $95\%\text{CI}=1.08–3.08$ , $p=0.047$ ), and high CEA level ( $\text{OR}=5.96$ , $95\%\text{CI}=2.12–8.12$ , $p=0.026$ ). We further observed a significant association of the variant genotype; gastric cancer patients carrying GG of MMP-7 (-181A/G; rs11568818) had a greater increased risk of MMP-7 expression than did wild-type (WT) carriers (AG: odds ratio $\left(\text{OR}\right)=5.67$ ; $95\%\text{CI}=1.57–7.23$ ; $p=0.024$ and GG: $\text{OR}=8.32$ ; $95\%\text{CI}=2.94–11.42$ ; $p=0.016$ ). These findings suggest that MMP-7 expression can be used to predict the prognosis of gastric cancer patients.

Calibrating models of cancer invasion: parameter estimation using approximate Bayesian computation and gradient matching

We present two different methods to estimate parameters within a partial differential equation model of cancer invasion. The model describes the spatio-temporal evolution of three variables-tumour cell density, extracellular matrix density and matrix degrading enzyme concentration-in a one-dimensional tissue domain. The first method is a likelihood-free approach associated with approximate Bayesian computation; the second is a two-stage gradient matching method based on smoothing the data with a generalized additive model (GAM) and matching gradients from the GAM to those from the model. Both methods performed well on simulated data. To increase realism, additionally we tested the gradient matching scheme with simulated measurement error and found that the ability to estimate some model parameters deteriorated rapidly as measurement error increased.

Effect of Doxycycline on Survival in Abdominal Aortic Aneurysms in a Mouse Model

Background

Currently, there is no reliable nonsurgical treatment for abdominal aortic aneurysm (AAA). This study, therefore, investigates if doxycycline reduces AAA growth and the number of rupture-related deaths in a murine ApoE-/- model of AAA and whether gadofosveset trisodium-based MRI differs between animals with and without doxycycline treatment.

Methods

Nine ApoE-/- mice were implanted with osmotic minipumps continuously releasing angiotensin II and treated with doxycycline (30 mg/kg/d) in parallel. After four weeks, MRI was performed at 3T with a clinical dose of the albumin-binding probe gadofosveset (0.03 mmol/kg). Results were compared with previously published wild-type control animals and with previously studied ApoE-/- animals without doxycycline treatment. Differences in mortality were also investigated between these groups.

Results

In a previous study, we found that approximately 25% of angiotensin II-infused ApoE-/- mice died, whereas in the present study, only one out of 9 angiotensin II-infused and doxycycline-treated ApoE-/- mice (11.1%) died within 4 weeks. Furthermore, doxycycline-treated ApoE-/- mice showed significantly lower contrast-to-noise (CNR) values (p=0.017) in MRI compared to ApoE-/- mice without doxycycline treatment. In vivo measurements of relative signal enhancement (CNR) correlated significantly with ex vivo measurements of albumin staining (R ² = 0.58). In addition, a strong visual colocalization of albumin-positive areas in the fluorescence albumin staining with gadolinium distribution in LA-ICP-MS was shown. However, no significant difference in aneurysm size was observed after doxycycline treatment.

Conclusion

The present experimental in vivo study suggests that doxycycline treatment may reduce rupture-related deaths in AAA by slowing endothelial damage without reversing aneurysm growth.

Effects of varying radiation dosages on MMP1 expression, and MMP1 knockdown on the viability and migration of SW620 cells

Colorectal cancer (CRC), also known as bowel cancer, is one of the leading causes of cancer-associated mortality worldwide at present. The aim of the present study was to detect the effects of matrix metalloproteinase 1 (MMP1) on the viability and migration of a CRC cell line in the presence or absence of variation X-ray radiation doses. The CRC cell line, SW620, was cultured and treated with different X-ray doses (0, 0.1, 0.5, 1, 3 and 6 Gy). MMP1 expression was downregulated via the application of a specific small interfering (si)-RNA. The viability and migration of SW620 cells prior to and following transfection were detected with MTT and Transwell chamber assays, respectively. The application of siRNA transfection to silence MMP1 in SW620 cells resulted in reduced cell viability and migration (P<0.05). Compared with the control, the cell viability and migration of cells were significantly reduced when exposed to 0.5, 1, 3, and 6 Gy X-ray radiation (P<0.05). In SW620 cells treated with different X-ray doses, the mRNA expression levels of MMP1 were significantly reduced (P<0.05). Cells treated with 0.5 Gy X-ray exposure exhibited the lowest mRNA expression levels of MMP1 when compared with other doses of X-ray radiation. The expression of MMP1 was associated with the promotion of the viability and migration of SW620 cells. X-ray radiation with 6 Gy dosages significantly reduced cell viability when compared with the control. Thus, MMP1-targeted therapy combined with radiotherapy could be used for treating CRC.

Structured models of cell migration incorporating molecular binding processes

The dynamic interplay between collective cell movement and the various molecules involved in the accompanying cell signalling mechanisms plays a crucial role in many biological processes including normal tissue development and pathological scenarios such as wound healing and cancer. Information about the various structures embedded within these processes allows a detailed exploration of the binding of molecular species to cell-surface receptors within the evolving cell population. In this paper we establish a general spatio-temporal-structural framework that enables the description of molecular binding to cell membranes coupled with the cell population dynamics. We first provide a general theoretical description for this approach and then illustrate it with three examples arising from cancer invasion.

Effect of Rosemarinus officinalis L. on MMP-9, MCP-1 levels, and cell migration in RAW 264.7 and smooth muscle cells

Atherosclerosis is a chronic and progressive inflammatory disease. Novel anti-inflammatory therapies may have promise as treatment strategies for cardiovascular risk reduction. Rosemary (Rosemarinus officinalis L.) has been used in folk medicine to treat headaches, epilepsy, poor circulation, and many other ailments. It was found that rosemary could act as a stimulant and mild analgesic and could reduce inflammation. However, the mechanisms underlying the anti-inflammatory and antiatherosclerotic effects of rosemary need more study. This study investigated effects of the rosemary components, carnosic acid (CA), and carnosol (CAR), on cell migration. Monocyte chemoattractant protein-1 (MCP-1) and matrix metalloproteinase-9 (MMP-9) were determined by Western blot and gelatin zymography, respectively, in RAW 264.7 macrophages and vascular smooth muscle cells (VSMCs). VSMC migration was assessed by a Matrigel migration assay. Active compounds of rosemary extracts were also analyzed using a reversed-phase high-performance liquid chromatography. MMP-9 and MCP-1 activities were markedly diminished with methanol extract (RM), n-hexane fraction (RH), and CA in RAW 264.7 cells. RM, RH, CA, and CAR suppressed tumor necrosis factor-alpha-induced VSMC migration by inhibiting MMP-9 expression. Chromatograms of RM- and RH-containing CA and CAR revealed higher CA contents of RM (9.4%, 93.85 μg/mg dry wt.) and, especially, RH (18.4%, 184.00 μg/mg dry wt.), which were appreciably elevated compared with the similar CAR content in RM and RH (3.7%, 37.30 μg/mg dry wt.; and 2.5%, 25.05 μg/mg dry wt., respectively). Rosemary, especially its CA component, has potential antiatherosclerosis effects related to cell migration.

Association of matrix metalloproteinases-9 gene polymorphisms with genetic susceptibility to esophageal squamous cell carcinoma

Matrix metalloproteinases-9 (MMP-9) plays important roles in tumor invasion and metastasis by degrading extracellular matrix components. Variations in the DNA sequence in the MMP-9 gene may lead to altered MMP-9 production and/or activity, and so this may modulate an individual's susceptibility to esophageal squamous cell carcinoma (ESCC). To test this hypothesis, we investigated the association of the MMP-9 polymorphisms and their haplotypes with the risk of ESCC in a Chinese population. There were significant differences in the genotype and allele distribution of P574R polymorphism of the MMP-9 gene among cases and controls. The P574R GG genotypes were associated with a significantly increased risk of ESCC as compared with the CC genotypes (odds ratio [OR] = 4.08; 95% confidence interval [CI]: 1.58-10.52; p = 0.00). Compared with 279R-574P haplotype, 279R-574R (OR = 3.52; 95% CI: 1.99-6.25) and 279Q-574P (OR = 2.16; 95% CI: 1.07-4.35) haplotypes can increase the onset risk of ESCC statistically, but the role of 279R-574R haplotype is more obvious. MMP-9 P574R polymorphisms and P574R-R279Q haplotype are significantly associated with the risk of ESCC. Our study shows for the first time that MMP-9 gene P574R polymorphism may contribute to a genetic risk factor for ESCC in a Chinese population.

Eradication of Helicobacter pylori infection favourably affects altered gastric mucosal MMP-9 levels

BACKGROUND

Helicobacter pylori gastritis is recognized as an important pathogenetic factor in peptic ulcer disease and gastric carcinogenesis, and is accompanied by strongly enhanced gastric mucosal matrix metalloproteinase-9 (MMP-9) levels.

AIM

This study was performed to investigate whether H. pylori-affected gastric mucosal MMP-2 and MMP-9 levels are reversible by successful treatment of the infection.

PATIENTS AND METHODS

Fifty-eight patients with H. pylori-associated gastritis were treated with a combination regimen of acid inhibitory therapy and antibiotics for 14 days. The levels and isoforms of MMP-2 and MMP-9 were measured by semiquantitative gelatin-zymography, bioactivity assay and enzyme-linked immunosorbent assay in gastric mucosal biopsy homogenates.

RESULTS

Latent, active, and total MMP-9 levels decreased consistently and significantly by successful H. pylori eradication, in antrum as well as corpus mucosa, compared with those prior to treatment, irrespective of the therapy regimen used. The elevated levels remained unchanged, however, when treatment failed. MMP-2 levels did not show major alterations after H. pylori therapy.

CONCLUSION

Elevated MMP-9 levels in H. pylori-infected gastric mucosa are reversible by eradication of the infection. No major changes in mucosal MMP-2 levels were observed by H. pylori eradication.

Relationship between molecular markers and endoscopic findings in laterally spreading tumors

BACKGROUND AND AIM

Characteristic clinicopathological features of laterally spreading tumors (LSTs) have been reported by endoscopists; however, only a few studies have been conducted on the biological features. These studies were not fully associated with the endoscopic findings of LSTs. The aim of this study was to estimate the biological features of each type of endoscopic finding of LST using two molecular markers, matrix metalloproteinase-7 (MMP-7) and beta-catenin.

METHODS

Expression of the molecular markers and the endoscopic findings were compared in 22 LSTs and 14 subpedunculated polyps. MMP-7 and beta-catenin were immunostained. Three types of representative endoscopic findings of LST were defined as segments in LSTs. They were 15 granular segments, seven large nodular segments, and seven flat segments that corresponded to the area composed of aggregates of similar size granules, large nodules of diameter more than 10 mm, and a flat surface with no granule, respectively.

RESULTS

Expression of MMP-7 and coexpression of MMP-7 and beta-catenin were higher in large nodular segments than in granular segments (P < 0.0167). Among the three types of segments, flat segments showed the highest expression densities of beta-catenin accumulated in the nucleus. Large nodular segments and subpedunculated polyps showed similar expression patterns for the molecular markers.

CONCLUSIONS

This study provides new and important information on the relationship between the molecular markers and endoscopic findings of LSTs.

Local delivery of matrix metalloproteinase gene prevents the onset of renal sclerosis in streptozotocin-induced diabetic mice

The present study was undertaken to investigate whether matrix metalloproteinase (MMP) functions to prevent the occurrence of destructive fibrosis in progressive renal disease. As a sustained release carrier of plasmid DNA, biodegradable hydrogels and microspheres were formulated from cationized gelatin prepared through aminization. Plasmid DNA was released from the cationized gelatin hydrogels as a result of hydrogel degradation. A plasmid DNA including a cytomegalovirus promoter and human recombinant MMP-1 gene (pCMV-MMP) was constructed. Gelatin microspheres incorporating pCMV-MMP as well as phosphate-buffered saline (PBS) with or without pCMV-MMP were injected into the renal subcapsule of C57BL/6 mice, which were intraperitoneally injected with streptozotocin (STZ) to induce diabetes 7 days after operation. The mice were killed 4 weeks after STZ injection to sample their blood and kidneys for biochemical and histological examinations. An immunofluorescence study confirmed that MMP protein was expressed around the renal tissue injected with gelatin microspheres incorporating pCMV-MMP. When applied with cationized gelatin microspheres incorporating pCMV-MMP, the mice showed a level of blood urea nitrogen significantly lower than that of other groups. A reduced content of collagen in the kidneys of mice administered gelatin microspheres incorporating pCMV-MMP was histologically observed. Further, the hydroxyproline assay revealed a significantly decreased content of hydroxyproline in kidney. We conclude that sustained release of MMP-1 gene is a promising prophylactic trial for kidney fibrolysis and dysfunction in the STZ-induced diabetic mouse model.

Mast cells--a role in periodontal diseases?

OBJECTIVES

Limited attention has been given to the role mast cells may play in periodontal diseases.

BACKGROUND

Mast cells are indeed found abundantly below and within several types of mucosal epithelia. On the basis of their proteinase content, mast cells are divided into connective tissue (CT) and mucosal phenotypes. The CT phenotype contains both tryptase and chymase (MC(TC)), while the mucosal phenotype contains only tryptase (MC(T)). The in vivo significance of different mast cell phenotypes has not yet been fully established. Mast cells are able to phagocytose, process and present antigens as effectively as macrophages.

RESULTS

Recently mast cells were found in high numbers in chronically inflamed gingival tissue taken from patients with chronic marginal periodontitis (CMP). The number of mast cells was found to be even higher in HIV(+) patients with CMP. Furthermore, mast cells also express strongly matrix metalloproteinases (MMPs), which are key enzymes in degradation of gingival extracellular matrix. Mast cells may release preformed cytokines directing local innate and adaptive immune responses. The present review will focus on possible roles for mast cells in periodontal diseases.

CONCLUSIONS

We certainly feel that this is a key cell in inflamed periodontal tissue and its role in periodontitis needs to be revisited.

Interleukin-4 suppresses IL-1-induced expression of matrix metalloproteinase-3 in human gingival fibroblasts

BACKGROUND

In periodontitis, matrix metalloproteinase-3 (MMP-3, stromelysin 1) is present at increased levels in active disease sites compared to inactive or healthy sites, and the levels are correlated with clinical parameters and associated with progression of the disease. Interleukin (IL)-4 has been shown in human skin and synovial fibroblasts and articular chondrocytes to suppress IL-1-induced expression of MMP-3, but this has not been shown in human gingival fibroblasts. The objective of this study is to determine the effects of IL-4 on the IL-1-induced expression of MMP-3 in human gingival fibroblasts isolated from patients with periodontitis.

METHODS

Northern blot analysis was performed to determine the effects of IL-4 on the IL-1 induction of MMP-3 mRNA. MMP-3 protein levels were determined by enzyme-linked immunosorbent assay (ELISA), and prostaglandin E2 (PGE2) levels were measured by enzyme immunoassay (EIA). DNA binding of activator protein (AP)-1 and nuclear factor (NF)-kappaB was assessed by electrophoretic mobility shift assay (EMSA).

RESULTS

Northern blot analysis revealed that co-incubation of gingival fibroblasts with IL-1 and IL-4 resulted in a significant decrease in MMP-3 mRNA levels compared to IL-1 alone, with a concomitant decrease in protein levels. This inhibition is dose-dependent, and is apparent as early as 3 hours after stimulation. IL-1-induced production of PGE2 was not affected in four of six cultures isolated from different individuals. Addition of exogenous PGE2 had no effect on the suppressive effects of IL-4. DNA binding of transcription factors AP-1 and NF-kappaB was not affected by IL-4.

CONCLUSIONS

IL-4 inhibits the IL-1 induction of MMP-3 in human gingival fibroblasts isolated from patients with periodontitis. This effect is independent of PGE2 and is not due to inhibition of the DNA binding activity of known transcription factors binding to the MMP-3 promoter.

Differential expression of matrix metalloproteinase and tissue inhibitor of MMP in serosal tissue of intraperitoneal organs and adhesions

OBJECTIVE

To comparatively analyse the expression of matrix metalloproteinase (MMP-3) and tissue inhibitor of MMP (TIMP-2) in serosal tissue of intraperitoneal organs and adhesions, as well as peritoneal fluid and serum of subjects with and without adhesions.

DESIGN

Cross sectional study.

SETTING

Academic research centres.

SAMPLE

Patients undergoing abdominal/pelvic surgery.

METHODS

Messenger ribonucleic acid (mRNA) and protein expression using quantitative reverse transcription polymerase chain reaction (Q-RT-PCR), ELISA and immunohistochemistry.

RESULTS

All the tissues examined express MMP-3 and TIMP-2 mRNA and protein at consistently varying levels ranging from 100- to 1000-fold and 2- to 10-fold mRNA and protein, respectively. Serosa of uterine, fallopian tube, ovary and partial peritoneum express a higher MMP-3 mRNA compared with small and large bowels and omentum, while TIMP-2 expression was less variable with the highest level found in uterine serosa (P < 0.05). The expression of MMP-3 and TIMP-2 mRNA in adhesions was not significantly different compared with parietal peritoneum. MMP-3 and TIMP-2 protein content in tissue extracts, peritoneal fluids and serum also varied with higher TIMP-2 than MMP-3 (P < 0.05). TIMP-2 levels were lower in serum of subjects with moderate/extensive adhesions compared with subjects without adhesions. Immunoreactive MMP-3 and TIMP-2 proteins were detected in various cell types in these tissues. There was no correlation between MMP-3 and TIMP-2 expression, and age, gender or menstrual status of subjects with or without adhesions.

CONCLUSION

MMP-3 and TIMP-2 are expressed at varying levels in serosal tissues of peritoneal organs and adhesions, with higher TIMP-2 than MMP-3. Based on the knowledge that tissue injury alters the expression of MMPs and TIMPs, such variations may predispose an organ to develop more adhesions than others. In addition, the results suggest that serum level of TIMP-2 may represent a marker for subjects who will form adhesions with greater severity.

Clinical impact of novel treatment strategies

Following two decades of research on the biology of cancer and in particular of lung cancer, we have now a large number of molecular targets that can be utilized to create specific medicines against these cancers. Non-small cell lung cancer represents numerically the most important solid tumor in Western world, and is poorly affected by current therapies, where surgery represents almost the only curative therapy for about 25% of patients who are resectable at diagnosis. An abundant number of targeted therapies are being investigated in NSCLC. Among them are the metalloproteinase inhibitors, several tyrosine kinase inhibitors and several attempts of gene replacement have also been made. Promising results have so far been obtained with some of these approaches, and the outcome of large randomized studies is awaited. Small cell lung cancer (SCLC) represents about 20% of lung carcinomas, and several of the novel approaches that are being attempted for NSCLC, are also being investigated for SCLC. All these novel therapies open a new era of anticancer treatment that will likely complement the currently available therapies in the near future.

Critical appraisal of the use of matrix metalloproteinase inhibitors in cancer treatment

Experimental studies performed prior to 1990 led to the widely held belief that matrix metalloproteinases (MMPs) produced by cancer cells are of critical importance in tumor invasion and metastasis. Based on this evidence, the pharmaceutical industry produced several well tolerated, orally active MMP inhibitors (MMPIs) which demonstrated efficacy in mouse cancer models. Phase III clinical trials initiated in 1997-98 using marimastat, prinomastat (AG3340), and BAY 12-9566 alone or in combination with standard chemotherapy in patients with advanced cancers (lung, prostate, pancreas, brain, GI tract) have recently been reported; no clinical efficacy was demonstrated. Bayer and Agouron have discontinued their ongoing Phase III drug trials of MMPIs in advanced cancer. In retrospect, the failure of MMPIs to alter disease progression in metastatic cancer might have been anticipated since MMPs appear to be important in early aspects of cancer progression (local invasion and micrometastasis) and may no longer be required once metastases have been established. Our understanding of MMP pathophysiology in cancer has expanded considerably in the past 10 years. Current views indicate that: (1) most MMPs in tumors are made by stromal cells, not carcinoma cells; (2) cancer cells induce stromal cells to synthesize MMPs using extracellular matrix metalloproteinase inducer (EMMPRIN) and cytokine stimulatory mechanisms; and (3) MMPs promote cell migration and the release of growth factors sequestered in the extracellular matrix. MMPs have a dual function in tumor angiogenesis: MMP-2 and MT1-MMP are required in breaking down basement membrane barriers in the early stage of angiogenesis, while other MMPs are involved in the generation of an angiogenic inhibitor, angiostatin. In spite of considerable recent progress in identifying multiple roles of MMPs in disease, our understanding of MMP function in cancer is far from complete (see Table 1). Based on accumulated data, it is recommended that future MMPI trials focus on: (1) patients with early stage cancer; (2) the use of MMPIs along with chemotherapy; (3) the measurement of MMPs in tumor tissue and blood as a means of identifying patients who are more likely to respond to MMPI therapy; and (4) identification of biomarkers that reflect activation or inhibition of MMPs in vivo.

Matrix metalloproteinases and the thyroid

Matrix metalloproteinases (MMPs) are proteolytic enzymes that degrade components of the extracellular matrix (ECM) and basement membrane. They play a critical role in many physiological and pathological processes, such as tumor metastasis. The original concept-that MMP activity during metastasis is restricted solely to invasion of the basement membrane and destruction of ECM components-has been modified to encompass multiple aspects of tumor progression: tumor establishment, growth, angiogenesis, intravasation, extravasation, and almost all metastatic steps. Moreover, the role of tissue inhibitors of matrix metalloproteinases (TIMPs), originally believed to exhibit anti-invasion properties solely by virtue of their inhibition of MMPs, has been extended to include their multiple biological effects, such as growth promotion. In thyroid neoplasia as well, MMPs, in particular MMP-2, seem to be associated with metastatic potential. It would seem that similar and divergent patterns regulate MMP and TIMP gene expression in benign and malignant human thyrocytes, in many instances in agreement with the concept of MMPs playing the role of stimulating, and TIMPs inhibiting cell invasion.

Possible Involvement of Matrix Metalloproteinase-9 in Langerhans Cell Migration and Maturation

Epidermal Langerhans cells (LC) are potent dendritic cells in the induction of primary T cell-mediated immune responses in the skin. They capture foreign Ags and migrate to regional lymph nodes to carry and present these Ags to naive T cells. We investigated the role of matrix metalloproteinase-9 (MMP-9) in LC migration using an anti-MMP-9 mAb. Intradermal injection of anti-MMP-9 mAb before rhodamine B or oxazolone painting markedly inhibited these hapten-induced decreases in LC number in the epidermis and the accumulation of dendritic cells in the regional lymph nodes, indicating that MMP-9 plays some important roles in LC migration in the induction phase of contact sensitization. Treatment with anti-MMP-9 mAb also blocked the increase in cell size, dendrite development, and the enhanced expression of MHC class II Ags in LC induced by hapten painting. In addition, intradermal injection of purified MMP-9 induced marked increases in cell size, dendrite extension, and enhanced expression of MHC class II Ags in LC. These results strongly suggested that MMP-9 is involved not only in LC migration, but also in their morphological and phenotypic maturation in the skin.

Degradation of extracellular matrix by metastatic follicular thyroid carcinoma cell lines: role of the plasmin activation system

The plasmin activation system plays a key role in extracellular matrix degradation in many malignant tumors. Because no data are available on the involvement of the plasmin activation system in matrix degradation by thyroid carcinoma, the present study was performed using follicular thyroid carcinoma cell lines obtained from a primary tumor (FTC-133) and metastases (FTC-236 and FTC-238) of one patient. Matrix degradation by these cell lines was studied assessing the release of radioactivity from S35-methionine labeled extracellular matrix coated onto plastic. The involvement of constituents of the plasmin activation system as well as matrix metalloproteinases (MMPs), another class of proteolytic enzymes, which can be activated by plasmin, were assessed by semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR) and zymography. In the matrix degradation experiment, S35 release by FTC-133 was significantly higher than FTC-236 and FTC-238. S35 degradation could be inhibited by the plasmin inhibitor aprotinin and by anti-human urokinase-type plasminogen activator (uPA) antibody, indicating the involvement of the plasmin activation system. Matrix degradation could also be inhibited by the MMP inhibitor marimastat, thus demonstrating the involvement of MMPs in matrix degradation by these cell lines. Zymographic assays revealed activity of uPA in all cell lines. However, in contrast with FTC-236 and FTC-238, no plasminogen activator inhibitor (PAI) or PAI1 mRNA were found in FTC-133. Therefore, the differences in PAI activity as observed between the cell lines may originate from differences in PAI1 gene transcription. Differences in PAI1 expression did not affect the attachment of these cell lines to vitronectin. We conclude that the plasmin activation system is involved in extracellular matrix degradation by these metastatic follicular thyroid carcinoma cell lines. Differences in extracellular matrix degradation between the cell lines correspond with differences in PAI1 gene expression, indicating the significance of PAI1 in extracellular matrix degradation by metastatic follicular thyroid carcinoma.

A novel in-situ-zymography technique localizes gelatinolytic activity in human skin to mast cells

Matrix-metallo-proteinases play a key role in cutaneous tissue remodeling and wound healing, and have been implicated as the rate-limiting factor in cutaneous tumor invasion and metastasis. We here describe a novel in-situ-zymographic method, which allows to directly localize sites of gelatinolytic activity in human skin. Gelatinolysis was detected through protein-hydrolysis in a 200 microm thick polyacrylamide gel underlying tissue sections. The lysis was substrate-dependent, demonstrated time- and temperature-dependent kinetics, and was inhibited by both EDTA and 1,10-phenanthroline. Normal and diseased skin sections demonstrated multiple focal points of gelatinolysis which co-localized with individual cells. Histochemically, these were shown to represent most likely mast cells (via AS-d-chloroacetate esterase staining and metachromasia). However, immunohistochemical staining for gelatinases A and B showed no immunoreactivity patterns that corresponded to the identified foci of gelatinolysis. The reported in-situ-zymographic technique offers a decisive advantage over immunohistochemistry, since it detects only the activated and catabolically relevant proteases, and provides further evidence for a role of mast cells in extracellular matrix remodeling.