Endostatin inhibits human tongue carcinoma cell invasion and intravasation and blocks the activation of matrix metalloprotease-2, -9, and -13

Recombinant human collagen XV regulates cell adhesion and migration

The C-terminal end of collagen XV, restin, has been the focus of several studies, but the functions of full-length collagen XV have remained unknown. We describe here studies on the production, purification, and function of collagen XV and the production of a monoclonal N-terminal antibody to it. Full-length human collagen XV was produced in insect cells using baculoviruses and purified from the cell culture medium. The yield was 15 mg/liter of cell culture medium. The collagen XV was shown to be trimeric, with disulfide bonds in the collagenous region. Rotary shadowing electron microscopy revealed rod-like molecules with a mean length of 241.8 nm and with a globular domain at one end. The globular domain was verified to be the N-terminal end by N-terminal antibody binding. The molecules show flexibility in their conformation, presumably due to the many interruptions in their collagenous domains. The ability of collagen XV to serve as a substrate for cells was tested in cell adhesion assays, and it was shown that cells did not bind to collagen XV-coated surfaces. When added to the culture medium of fibroblasts and fibrosarcoma cells, however, collagen XV rapidly bound to their fibronectin network. Solid phase assays showed that collagen XV binds to fibronectin, laminin, and vitronectin and that it binds to the collagen/gelatin-binding domain of fibronectin. No binding was detected to fibrillar collagens, fibril-associated collagens, or decorin. Interestingly, collagen XV was found to inhibit the adhesion and migration of fibrosarcoma cells when present in fibronectin-containing matrices.

Angiogenesis in cutaneous disease: part I

Angiogenesis is an important process in normal physiology and disease pathogenesis. Angiogenesis is controlled in a healthy body by a system of angiogenic growth factors and angiogenesis inhibitors. When angiogenic growth factors are predominantly expressed, blood vessel growth occurs and disease may result. Successful therapies have been developed that target growth factors, their receptors, or the cascade pathways that are activated by growth factor/receptor interactions. There is good evidence that angiogenesis plays an important role in a wide range of cutaneous maladies, and angiogenesis-targeting therapies are playing an increasing role in the management of dermatologic disease. Cutaneous angiogenesis offers an exciting new arena for targeted dermatologic therapeutics.

LEARNING OBJECTIVES

After completing this learning activity, participants should be able to distinguish angiogenic growth factors and inhibitors, recognize angiogenic mediating agents and compare their mechanisms of action, and apply the use of angiogenic mediating agents in clinical and research situations.

Proteoglycans: master modulators of paracrine fibroblast-carcinoma cell interactions

Reciprocal interactions between tumor and stromal cells govern carcinoma growth and progression. Signaling functions between these cell types in the tumor microenvironment are largely carried out by secreted growth factors and cytokines. This review discusses how proteoglycans, which are abundantly present in normal and neoplastic tissues, modulate paracrine growth factor signaling events. General principles of proteoglycan involvement in paracrine signaling include stromal induction, core protein processing by proteases and growth factor binding via proteoglycan glycosaminoglycan chains or core protein domains.

The effect of endostatin and gemcitabine combined with HIFU on the animal xenograft model of human pancreatic cancer

OBJECTIVE

To investigate the influence of the recombinant human endostatin and gemcitabine combined with HIFU on the mouse xenograft model of pancreatic cancer.

METHODS

Use human pancreatic cancer cell line PANC-1 to set up the mouse xenograft model, then randomized into four arms. Each arm was treated with gemcitabine, endostatin, gemcitabine combined with endostatin and normal saline respectively. Observe the volume of the tumor, the serum VEGF level and MVD in the tumor tissue among the different arms. All mice were treated with HIFU, then pathological examination was done.

RESULTS

The tumor volume, serum VEGF level and MVD in the combined-therapy arm are all lower than the monotherapy arms and the control arm. The coagulation necrosis occurred in tumors after HIFU treatment.

CONCLUSION

Endostatin and gemcitabine has better effect than gemcitabine or endostatin monotherapy on the animal xenograft model of human pancreatic cancer. HIFU combined with chemotherapy and/or targeted therapy may enhance the effect for pancreatic cancer.

A novel organotypic model mimics the tumor microenvironment

Carcinoma cell invasion is traditionally studied in three-dimensional organotypic models composed of type I collagen and fibroblasts. However, carcinoma cell behavior is affected by the various cell types and the extracellular matrix (ECM) in the tumor microenvironment. In this study, a novel organotypic model based on human uterine leiomyoma tissue was established and characterized to create a more authentic environment for carcinoma cells. Human tongue squamous cell carcinoma cells (HSC-3) were cultured on top of either collagen or myoma. Organotypic sections were examined by immunohistochemistry and in situ hybridization. The maximal invasion depth of HSC-3 cells was markedly increased in myomas compared with collagen. In myomas, various cell types and ECM components were present, and the HSC-3 cells only expressed ECM molecules in the myoma model. Organotypic media were analyzed by radioimmunoassay, zymography, or Western blotting. During carcinoma cell invasion, matrix metalloprotease-9 production and collagen degradation were enhanced particularly in the myoma model. To evaluate the general applicability of the myoma model, several oral carcinoma, breast carcinoma, and melanoma cell lines were cultured on myomas and found to invade in highly distinct patterns. We conclude that myoma tissue mimics the native tumor microenvironment better than previous organotypic models and possibly enhances epithelial-to-mesenchymal transition. Thus, the myoma model provides a promising tool for analyzing the behavior of carcinoma cells.

Therapeutic efficacy of recombinant human endostatin combined with chemotherapeutics in mice-transplanted tumors

Endostatin is an endogenous inhibitor of angiogenesis and has been shown to exhibit potent inhibitory activity in certain mice tumor models. In this study, a treatment strategy of combining recombinant human endostatin (rhEndostatin) and chemotherapeutics was implemented to evaluate the therapeutic efficacy of rhEndostatin against solid tumors. The antitumor effect of rhEndostatin in combination with several chemotherapeutic drugs, e.g., 5-fluorouracil, cyclophosphamide, methotrexate, and mitomycin C, on human QGY liver tumor and mice H22 liver tumor was compared with that of rhEndostatin treatment alone. The results showed that the combination of rhEndostatin and chemotherapeutic drugs resulted in a more potent inhibition of tumor growth. The potential advantages of rhEndostatin plus tumor chemotherapy provide a basis for further clinical trials of rhEndostatin.

FOXO3a promotes tumor cell invasion through the induction of matrix metalloproteinases

The role of the Forkhead transcription factor FOXO3a in processes that promote tumor metastasis is poorly defined. Here, we show that depletion of FOXO3a from cancer cells leads to decreased tumor size specifically due to attenuated invasive migration. During tumor progression, an increase in tumor mass is concomitant with serum deprivation prior to tumor angiogenesis. We show that nuclear retention of FOXO3a due to serum starvation results in greatly increased cancer cell invasion. Exploration of the mechanism by which FOXO3a promotes invasive migration revealed that it induces the expression of matrix metalloproteinase 9 (MMP-9) and MMP-13, both of which have been causally linked to the invasion and progression of numerous human solid tumors. Our results link Forkhead transcription factors to a previously unexplored function in cancer progression by promoting extracellular matrix degradation, allowing tumors to invade neighboring tissues and ultimately metastasize to distant organs.

Type XVIII collagen degradation products in acute lung injury

Introduction

In acute lung injury, repair of the damaged alveolar-capillary barrier is an essential part of recovery. Endostatin is a 20 to 28 kDa proteolytic fragment of the basement membrane collagen XVIII, which has been shown to inhibit angiogenesis via action on endothelial cells. We hypothesised that endostatin may have a role in inhibiting lung repair in patients with lung injury. The aims of the study were to determine if endostatin is elevated in the plasma/bronchoalveolar lavage fluid of patients with acute lung injury and ascertain whether the levels reflect the severity of injury and alveolar inflammation, and to assess if endostatin changes occur early after the injurious lung stimuli of one lung ventilation and lipopolysaccharide (LPS) challenge.

Methods

Endostatin was measured by ELISA and western blotting.

Results

Endostatin is elevated within the plasma and bronchoalveolar lavage fluid of patients with acute lung injury. Lavage endostatin reflected the degree of alveolar neutrophilia and the extent of the loss of protein selectivity of the alveolar-capillary barrier. Plasma levels of endostatin correlated with the severity of physiological derangement. Western blotting confirmed elevated type XVIII collagen precursor levels in the plasma and lavage and multiple endostatin-like fragments in the lavage of patients. One lung ventilation and LPS challenge rapidly induce increases in lung endostatin levels.

Conclusions

Endostatin may adversely affect both alveolar barrier endothelial and epithelial cells, so its presence within both the circulation and the lung may have a pathophysiological role in acute lung injury that warrants further evaluation.

Combination of antiangiogenesis with chemotherapy for more effective cancer treatment

Angiogenesis is a hallmark of tumor development and metastasis and is now a validated target for cancer treatment. However, the survival benefits of antiangiogenic drugs have thus far been rather modest, stimulating interest in developing more effective ways to combine antiangiogenic drugs with established chemotherapies. This review discusses recent progress and emerging challenges in this field; interactions between antiangiogenic drugs and conventional chemotherapeutic agents are examined, and strategies for the optimization of combination therapies are discussed. Antiangiogenic drugs such as the anti-vascular endothelial growth factor antibody bevacizumab can induce a functional normalization of the tumor vasculature that is transient and can potentiate the activity of coadministered chemoradiotherapies. However, chronic angiogenesis inhibition typically reduces tumor uptake of coadministered chemotherapeutics, indicating a need to explore new approaches, including intermittent treatment schedules and provascular strategies to increase chemotherapeutic drug exposure. In cases where antiangiogenesis-induced tumor cell starvation augments the intrinsic cytotoxic effects of a conventional chemotherapeutic drug, combination therapy may increase antitumor activity despite a decrease in cytotoxic drug exposure. As new angiogenesis inhibitors enter the clinic, reliable surrogate markers are needed to monitor the progress of antiangiogenic therapies and to identify responsive patients. New targets for antiangiogenesis continue to be discovered, increasing the opportunities to interdict tumor angiogenesis and circumvent resistance mechanisms that may emerge with chronic use of these drugs.

Endostatin and angiostatin are increased in diabetic patients with coronary artery disease and associated with impaired coronary collateral formation

Coronary artery disease (CAD) is the leading cause of mortality in diabetic patients. Because of the diffuse nature of their disease, diabetic patients may be at risk for incomplete revascularization, highlighting a potential role for proangiogenic therapy in this group. This study investigates molecular mechanisms of angiogenesis in diabetic patients. Myocardial tissue was harvested from patients undergoing coronary artery bypass grafting [nondiabetic (ND) 11, type 2 diabetic (DM) 10]. Expression of angiostatin, endostatin, their precursors (plasminogen and collagen XVIII, respectively), enzymes leading to their production [matrix metalloprotease (MMP)-2 and -9, cathepsin L], and an inhibitor of MMPs (tissue inhibitor of metalloproteinase) was assessed with Western blotting. MMP activity was assessed. Coronary collateralization was graded by Rentrop scoring of angiograms. Plasminogen and collagen XVIII expression were similar between groups. Angiostatin expression trended to increase 1.24-fold (P = 0.07), and endostatin expression increased 2.02-fold in DM patients relative to ND (P = 0.02). MMP-9 expression was no different between groups, whereas MMP-2 expression decreased 1.8-fold in diabetics (P = 0.003). MMP-2 and -9 activity decreased 1.33-fold (P = 0.03) and 1.57-fold (P = 0.04), respectively, in diabetic patients. Cathepsin L expression was 1.38-fold higher in diabetic patients (P = 0.02). Coronary collateralization scores were ND 2.1 +/- 0.37 vs. DM 1.0 +/- 0.4 (P = 0.05). Myocardial endostatin expression correlated strongly with the percentage of hemoglobin A(1c) (r = 0.742, P = 0.0001). Myocardial expression of angiostatin and endostatin demonstrated significant negative linear correlations with coronary collateralization (angiostatin r = -0.531, P = 0.035, endostatin r = -0.794, P = 0.0002). Diabetic patients with CAD exhibit increased levels of the antiangiogenic proteins angiostatin and endostatin and differential regulation of the enzymes governing their production relative to ND patients. Myocardial levels of these proteins show significant correlation to coronary collateralization. These findings offer potential new therapeutic targets for enhancing proangiogenic therapy and insight into the angiogenic impairments seen in diabetes.

Regulation of collagen-derived antiangiogenic factors by p53

BACKGROUND

Evidence suggests that the p53 tumor suppressor protein functions, in part, by limiting tumor angiogenesis. This effect is partly mediated by the ability of p53 to increase production of endogenous angiogenesis inhibitors, such as the collagen-derived antiangiogenic factors (CDAFs), endostatin and tumstatin.

OBJECTIVE

To review the clinical and therapeutic implications of CDAFs and their regulation by p53.

METHODS

We highlight the inhibitory role of CDAFs in angiogenesis and summarize evidence that p53 regulates the transcriptional program leading to their expression, synthesis, assembly and activation.

RESULTS/CONCLUSION

The p53 gene is mutated in half of all human tumors and such cancers would be predicted to produce lower levels of CDAFs. We therefore believe that p53 function can be partially compensated by therapeutic use of CDAFs, which offers a promising new avenue for cancer treatment.

Characterization of the anti-angiogenic properties of arresten, an alpha1beta1 integrin-dependent collagen-derived tumor suppressor

Physiological and pathological turnover of basement membranes liberates biologically active cryptic molecules. Several collagen-derived fragments possess anti-angiogenic activity. Arresten is the 26-kDa non-collagenous domain of type IV collagen alpha1 chain. It functions as an efficient inhibitor of angiogenesis and tumor growth in mouse models, but its anti-angiogenic mechanism is not completely known. Here we show that arresten significantly increases apoptosis of endothelial cells in vitro by decreasing the amount of anti-apoptotic molecules of the Bcl-family; Bcl-2 and Bcl-xL. Although the pro-apoptotic effect of arresten is endothelial cell specific in vitro, in mouse tumors arresten induced apoptosis both in endothelial and tumor cells. The tumor cell apoptosis is likely an indirect effect due to the inhibition of blood vessel growth into the tumor. The active site of arresten was localized by deletion mutagenesis within the C-terminal half of the molecule. We have previously shown that arresten binds to alpha1beta1 integrin on human umbilical vein endothelial cells. However, the microvascular endothelial cells (MLECs) are more important in the context of tumor vasculature. We show here that arresten binds also to the microvascular endothelial cells via alpha1beta1 integrin. Furthermore, it has no effect on Matrigel neovascularization or the viability of integrin alpha1 null MLECs. Tumors implanted on integrin alpha1 deficient mice show no integrin alpha1 expression in the host-derived vascular endothelium, and thus arresten does not inhibit the tumor growth. Collectively, this data sheds more light into the anti-angiogenic mechanism of arresten.

Is collagenase-3 (MMP-13) expression in chondrosarcoma of the jaws a true marker for tumor aggressiveness?

BACKGROUND

Matrix metalloproteinases (MMPs) play an important role in the modeling and remodeling of the extracellular matrix in both physiologic and pathologic states and thus plays an important role in tumor progression. Human collagenase-3 (MMP-13) is a member of matrix metalloproteinase family of enzymes that was originally identified in breast carcinomas and subsequently detected during fetal ossification and in arthritic processes.

AIM

The present study was designed to investigate the expression MMP-13 and to correlate its expression with clinicopathological parameters in chondrosarcoma of the jaws.

METHODS

Archival tumor tissues from 11 patients with chondrosarcoma of the jaws were analyzed by immunohistochemistry for the expression of MMP-13. Clinical information was obtained through the computerized retrospective database from the tumor registry between 1998 to 2006.

RESULTS

Eight of 11 cases (72.8 %) of chondrosarcomas showed a positive reaction for MMP-13, whereas two cases of normal cartilage were negative for this collagenase. As regard the clinicopathological parameters, there was no correlation between MMP-13 expression and sex, age and tumor site. While, there were significant associations between MMP-13 expression and both of mitotic counts and necrosis. On the other hand, there was a significant difference between low and high grade tumors (P < 0.05) regarding MMP-13 expression. Also, there was no significant correlation between MMP-13 expression in primary lesions and their local recurrence.

CONCLUSION

MMP-13 is expressed in the majority of chondrosarcoma of the jaws. It is also noteworthy that the expression of MMP-13 may be related to tumor biological aggressiveness and used to aid in predicting patient's poor prognosis.

Lack of collagen XVIII accelerates cutaneous wound healing, while overexpression of its endostatin domain leads to delayed healing

Endostatin, the C-terminal fragment of collagen XVIII, is known to suppress tumour growth and angiogenesis by inhibiting endothelial cell proliferation and migration. We have previously shown that endostatin and its precursor are important for the structural organization of basement membranes (BM). The aim of this study was to investigate cutaneous wound healing in mice overexpressing endostatin in keratinocytes (ES-tg) and in mice lacking collagen XVIII (Col18a1(-/-)). Excisional wounds were made on the dorsal skin of mice, the wound areas were measured and the wounds were collected for further analyses after 3, 6 or 14 days. The healing of the wounds was delayed in the ES-tg mice and accelerated in the Col18a1(-/-) mice, and the vascularisation rate was accelerated in the Col18a1(-/-) mice, but not affected in the ES-tg mice. Abnormal capillaries with swollen endothelial cells and narrowed lumens were observed in the wounds of the ES-tg mice. In these mice also the formation of the epidermal BM was delayed, and the structure of the epidermal and capillary BMs was more disorganised. Moreover, detachment of the epidermis from the granulation tissue was observed in half (n=10) of the 6-day-old ES-tg wounds, but in none of the controls, suggesting an increased fragility of the epidermal-dermal junction in the presence of an excess of endostatin.

Activation of protein tyrosine kinases and matrix metalloproteinases causes blood-brain barrier injury: Novel mechanism for neurodegeneration associated with alcohol abuse

Blood-brain barrier (BBB) formed by brain microvascular endothelial cells (BMVEC) regulates the passage of molecules and leukocytes in and out of the brain. Activation of matrix metalloproteinases (MMPs) and alteration of basement membrane (BM) associated with BBB injury was documented in stroke patients. While chronic alcoholism is a risk factor for developing stroke, underlying mechanisms are not well understood. We hypothesized that ethanol (EtOH)-induced protein tyrosine kinase (PTK) signaling resulted a loss of BBB integrity via MMPs activation and degradation of BM component, collagen IV. Treatment of BMVEC with EtOH or acetaldehyde (AA) for 2-48 h increased MMP-1, -2 and -9 activities or decreased the levels of tissue inhibitors of MMPs (TIMP-1, -2) in a PTK-dependent manner without affecting protein tyrosine phosphatase activity. Enhanced PTK activity after EtOH exposure correlated with increased phosphorylated proteins of selective receptor and nonreceptor PTKs. Up-regulation of MMPs activities and protein contents paralleled a decrease in collagen IV content, and inhibitors of EtOH metabolism, MMP-2 and -9, or PTK reversed all these effects. Using human BMVEC assembled into BBB models, we found that EtOH/AA diminished barrier tightness, augmented permeability, and monocyte migration across the BBB via activation of PTKs and MMPs. These findings suggest that alcohol associated BBB injury could be mediated by MMPs via BM protein degradation and could serve as a comorbidity factor for neurological disorders like stroke or neuroinflammation. Furthermore, our preliminary experiments indicated that human astrocytes secreted high levels of MMP-1 and -9 following exposure to EtOH, suggesting the role of BM protein degradation and BBB compromise as a result of glial activation by ethanol. These results provide better understanding of multifaceted effects of alcohol on the brain and could help develop new therapeutic interventions.

Endostatin overexpression inhibits lymphangiogenesis and lymph node metastasis in mice

Endostatin, a proteolytic fragment of collagen XVIII, is a potent inhibitor of angiogenesis and tumor growth. We studied the development of carcinogen-induced skin tumors in transgenic J4 mice overexpressing endostatin in their keratinocytes. Unexpectedly, we did not observe any differences in tumor incidence and multiplicity between these and control mice, nor in the rate of conversion of benign papillomas to malignant squamous cell carcinomas (SCC). We did find, however, that endostatin regulates the terminal differentiation of keratinocytes because the SCCs in the J4 mice were less aggressive and more often well differentiated than those in the control mice. We observed an inhibition of tumor angiogenesis by endostatin at an early stage in skin tumor development, but more strikingly, there was a significant reduction in lymphatic vessels in the papillomas and SCCs in association with elevated endostatin levels and also a significant inhibition of lymph node metastasis in the J4 mice. We showed that tumor-infiltrating mast cells strongly expressed vascular endothelial growth factor-C (VEGF-C), and that the accumulation of these cells was markedly decreased in the tumors of the J4 mice. Moreover, endostatin inhibited the adhesion and migration of murine MC/9 mast cells on fibronectin in vitro. Our data suggest that endostatin can inhibit tumor lymphangiogenesis by decreasing the VEGF-C levels in the tumors, apparently via inhibition of mast cell migration and adhesion, and support the view that the biological effects of endostatin are not restricted to endothelial cells because endostatin also regulates tumor-associated inflammation and differentiation, and the phenotype of epithelial tumors.

Endostatin expression in the murine model of ischaemia/reperfusion-induced acute renal failure

BACKGROUND

Renal ischaemia-hypoxia is a leading cause of acute renal failure, a clinical condition associated with rapid loss of renal function and high rates of mortality. Renal proximal tubular cells are the most severely injured during renal ischaemia, caused by the breakdown of the extracellular matrix of the tubular basement membrane. Endostatin is the C-terminal fragment of collagen XVIII generated by proteolytic cleavage and it is well-known as being an inhibitor of angiogenesis. In vitro, endostatin inhibits endothelial cell proliferation and migration, as well as tubule formation. In vivo, it has a potent inhibitory effect on tumour growth. In this study, we analysed endostatin gene expression in C57BL/6 mouse kidneys subjected to ischaemia/reperfusion.

METHODS

Ischaemic renal failure was induced via 45 min of bilateral occlusion of the renal artery and vein, followed by 12 h or 24 h of reperfusion. Whole-kidney homogenate and total RNA were extracted for examination by western blot analysis and quantitative polymerase chain reaction. The immunohistological examination revealed increased endostatin expression in injured kidney, mainly in the proximal tubule and collecting ducts.

RESULTS

Endostatin/collagen XVIII mRNA and protein expression increased during ischaemia and within 12 h of reperfusion. In the western blot assay, we identified increased expression of the 30 kDa endostatin-related fragment and of matrix metalloproteinase-9. CD31 was significantly expressed during reperfusion (P < 0.05). Immunohistological examination revealed glomerular and tubulointerstitial expression of endostatin.

CONCLUSION

These data suggest the local synthesis of a 30 kDa endostatin-related fragment following acute renal failure and suggest its role in the modulation of renal capillary density.

Gene transfer of endostatin enhances the efficacy of doxorubicin to suppress human hepatocellular carcinomas in mice

Hepatocellular carcinoma (HCC) is one of the most common cancer-related causes of death, and is chemoresistant to anticancer drugs. Anti-angiogenic therapy has been shown to enhance the efficacy of chemotherapy to treat solid tumors. The aim of the present study was to determine whether endostatin, a potent antiangiogenic agent, could enhance the efficacy of doxorubicin to combat HCC. An endostatin expression plasmid was constructed and its expression in vitro and in vivo was detected after gene transfer. Recombinant endostatin inhibited angiogenesis in the chorioallantoic membrane assay, and showed synergistic effects with doxorubicin in inhibiting the in vitro proliferation of endothelial cells, but not that of tumor cells. Both endostatin gene therapy and doxorubicin suppressed the growth of subcutaneous human HepG2 tumors established in BALB/c nude mice, and tumor angiogenesis. Combination therapy with endostatin gene therapy and doxorubicin showed a stronger effect in suppressing tumor growth, and tumor angiogenesis, than the respective monotherapies. Gene transfer of endostatin down-regulated the expression of both hypoxia-inducible factor-1alpha and vascular endothelial growth factor (VEGF), whereas doxorubicin only down-regulated VEGF expression. Endostatin and doxorubicin synergized to down-regulate VEGF expression. Endostatin and doxorubicin combination therapy warrants investigation as a therapeutic strategy to combat HCC.

Endostatin gene therapy enhances the efficacy of paclitaxel to suppress breast cancers and metastases in mice

Chemotherapy combined with antiangiogenic therapy is more effective than chemotherapy alone. The aim of this study was to investigate whether endostatin, a potent anti-angiogenic agent, could enhance the efficacy of paclitaxel to combat breast cancer. An expression plasmid encoding mouse endostatin (End-pcDNA3.1) was constructed, which produced intense expression of endostatin and inhibited angiogenesis in the chorioallantoic membrane assay. 4T1 breast tumors were established in BALB/c mice by subcutaneous injection of 1 x 10(5) 4T1 cells. The End-pcDNA3.1 plasmid diluted in the transfection reagent FuGENE was injected into the tumors (around 100 mm(2)), and paclitaxel was injected i.p. into the mice. Endostatin gene therapy synergized with paclitaxel in suppressing the growth of 4T1 tumors and their metastasis to the lung and liver. Both endostatin and paclitaxel inhibited tumor angiogenesis and induced cell apoptosis. Despite the finding that endostatin was superior to paclitaxel at inhibiting tumor angiogenesis, paclitaxel was nevertheless more effective at inducing tumor apoptosis. The combination of paclitaxel and endostatin was more effective in suppressing tumor growth, metastases, angiogenesis, and inducing apoptosis than the respective monotherapies. The combinational therapy with endostatin and paclitaxel warrants future investigation as a therapeutic strategy to combat breast cancer.

Endostar, a novel recombinant human endostatin, exerts antiangiogenic effect via blocking VEGF-induced tyrosine phosphorylation of KDR/Flk-1 of endothelial cells

Endostar, a novel recombinant human endostatin expressed and purified in Escherichia coli with an additional nine-amino acid sequence and forming another his-tag structure, was approved by the SFDA in 2005 for the treatment of non-small-cell lung cancer. But its mechanism of action has not been illustrated before. In this study, we examined the antiangiogenic activities of endostar in vitro and in vivo. The results showed that endostar suppressed the VEGF-stimulated proliferation, migration, and tube formation of human umbilical vein endothelial cells (HUVECs) in vitro. Endostar blocked microvessel sprouting from rat aortic rings in vitro. Moreover, it could inhibit the formation of new capillaries from pre-existing vessels in the chicken chorioallantoic membrane (CAM) assay and affect the growth of vessels in tumor. We further found the antiangiogenic effects of endostar were correlated with the VEGF-triggered signaling. Endostar suppressed the VEGF-induced tyrosine phosphorylation of KDR/Flk-1(VEGFR-2) as well as the overall VEGFR-2 expression and the activation of ERK, p38 MAPK, and AKT in HUVECs. Collectively, these data indicated the relationship between endostar and VEGF signal pathways and provided a molecular basis for the antiangiogenic effects of endostar.

Type I collagen gene suppresses tumor growth and invasion of malignant human glioma cells

Background

Invasion is a hallmark of a malignant tumor, such as a glioma, and the progression is followed by the interaction of tumor cells with an extracellular matrix (ECM). This study examined the role of type I collagen in the invasion of the malignant human glioma cell line T98G by the introduction of the human collagen type I α1 (HCOL1A1) gene.

Results

The cells overexpressing HCOL1A1 were in a cluster, whereas the control cells were scattered. Overexpression of HCOL1A1 significantly suppressed the motility and invasion of the tumor cells. The glioma cell growth was markedly inhibited in vitro and in vivo by the overexpression of HCOL1A1; in particular, tumorigenicity completely regressed in nude mice. Furthermore, the HCOL1A1 gene induced apoptosis in glioma cells.

Conclusion

These results indicate that HCOL1A1 have a suppressive biological function in glioma progression and that the introduction of HCOL1A1 provides the basis of a novel therapeutic approach for the treatment of malignant human glioma.

Endostatin: Current concepts about its biological role and mechanisms of action

Endogenous inhibitors of angiogenesis are proved to be a major factor preventing the emergence of clinically manifested stages of human cancer. The protein endostatin, a 20-kD proteolytic fragment of type XVIII collagen, is one of the most active natural inhibitors of angiogenesis. Endostatin specifically inhibits the in vitro and in vivo proliferation of endothelial cells, inducing their apoptosis through inhibition of cyclin D1. On the surface of endothelial cells, endostatin binds with the integrin alpha(5)beta(1) that activates the Src-kinase pathway. The binding of endostatin with integrins also down-regulates the activity of RhoA GTPase and inhibits signaling pathways mediated by small kinases of the Ras and Raf families. All these events promote disassembly of the actin cytoskeleton, disorders in cell-matrix interactions, and decrease in endotheliocyte mobility, i.e., promote the suppression of angiogenesis. Endostatin displays a high antitumor activity in vivo: it inhibits the progression of more than 60 types of tumors. This review summarizes results of numerous studies concerning the biological activity and action mechanism of endostatin.

Oxidative stress activates protein tyrosine kinase and matrix metalloproteinases leading to blood-brain barrier dysfunction

The blood-brain barrier (BBB) formed by brain microvascular endothelial cells (BMVEC) regulates the passage of molecules and leukocytes in and out of the brain. Oxidative stress is a major underlying cause of neurodegenerative and neuroinflammatory disorders and BBB injury associated with them. Using human BMVEC grown on porous membranes covered with basement membrane (BM) matrix (BBB models), we demonstrated that reactive oxygen species (ROS) augmented permeability and monocyte migration across BBB. ROS activated matrix metalloproteinases (MMP-1, -2, and -9) and decreased tissue inhibitors of MMPs (TIMP-1 and -2) in a protein tyrosine kinase (PTK)-dependent manner. Increase in MMPs and PTK activities paralleled degradation of BM protein and enhanced tyrosine phosphorylation of tight junction (TJ) protein. These effects and enhanced permeability/monocyte migration were prevented by inhibitors of MMPs, PTKs, or antioxidant suggesting that oxidative stress caused BBB injury via degradation of BM protein by activated MMPs and by PTK-mediated TJ protein phosphorylation. These findings point to new therapeutic interventions ameliorating BBB dysfunction in neurological disorders such as stroke or neuroinflammation.

Collagen XVIII modulation is altered during progression of oral dysplasia and carcinoma

BACKGROUND

Collagen XVIII is a ubiquitous basement membrane (BM) component and a precursor of endostatin.

METHODS

Using immunohistochemistry and in situ hybridization, we studied the expression and localization of collagen XVIII in different stages of normal oral wound healing, epithelial dysplasia and squamous cell carcinoma (SCC).

RESULTS

In mild epithelial dysplasias collagen XVIII appeared as a continuous signal in the BM, whereas in severe epithelial dysplasias and in the invasive areas of oral SCCs collagen XVIII was absent. In situ hybridization showed that collagen XVIII mRNA expression did not decrease in severe dysplasia or oral carcinoma samples when compared with the mild dysplasias.

CONCLUSIONS

The results indicate that the absence of collagen XVIII protein in severe oral dysplasias is related to the processing of the protein rather than to changes in mRNA expression.

Reduced nonprotein thiols inhibit activation and function of MMP-9: implications for chemoprevention

Clinical studies demonstrate a positive correlation between the extent of matrix metalloproteinase (MMP) activation and malignant progression of precancerous lesions. Therefore, identification of effective, well-tolerated MMP inhibitors represents a rational chemopreventive strategy. A variety of agents, including proteinases and thiol-oxidizing compounds, activate MMPs by initiating release of the propeptide's cysteine sulfur "blockage" of the MMP active site. Despite the importance of the propeptide's cysteine thiol in preserving MMP latency, limited studies have evaluated the effects of reduced thiols on MMP function. This study investigated the effects of two naturally occurring nonprotein thiols, i.e., glutathione (GSH) and N-acetylcysteine (NAC), on activation, function, and cellular-extracellular matrix interactions of the basement-membrane-degrading gelatinase, MMP-9. Our results reveal that NAC and GSH employ protein S-thiolation to inhibit organomercurial activation of pro-MMP-9. Gelatinase activity assays showed that GSH and NAC significantly inhibited MMP-9 but not MMP-2 function, implying isoform structural specificity. Immunoblot analyses, which suggested GSH interacts with MMP-9's active-site Zn, were corroborated by computational molecular modeling. Cell invasion assays revealed that NAC enhanced endostatin's ability to inhibit human cancer cell invasion. Collectively, these data demonstrate that nonprotein thiols suppress MMP-9 activation and function and introduce the prospect for their use in chemopreventive applications.

Endostatin therapy reveals a U-shaped curve for antitumor activity

Developing continuous systemic delivery of endostatin has been a goal of many laboratories. We have employed a method of gene therapy utilizing different viral constructs. Here, we report that a new serotype of adeno-associated viruses, which incorporates canine endostatin, provides dose-dependent transgene expression in the circulation after intramuscular injection in mice. Elevated levels of endostatin remained stable in the circulation for at least 4 months. In vitro assays determined that the protein expressed was biologically active. Antitumor activities of the above construct demonstrated a U-shape curve, where the maximum activity was observed within a certain critical concentration range. These data suggest that an optimum dose range may be required to achieve therapeutic efficacy in large animal models.

Transformation-specific matrix metalloproteinases, MMP-7 and MMP-13, are present in epithelial cells of keratoacanthomas

Keratoacanthomas are rapidly growing hyperproliferative skin tumors that may clinically or histologically be difficult to distinguish from well-differentiated squamous cell cancers (SCCs). UV light, trauma, and immune suppression represent their etiological factors. As matrix metalloproteinases (MMPs) are implicated at all stages of tumorigenesis, we investigated the expression profile of several cancer-related MMPs to find markers that would differentiate keratoacanthomas from SCCs and shed light to the pathobiology of keratoacanthoma. Samples from 31 keratoacanthomas and 15 grade I SCCs were studied using immunohistochemistry for MMP-2, -7, -8, -9, -10, -13, and -19 and p16 and laminin-5gamma2 chain. In situ hybridization for MMP-7, -10, and -13 was performed in a subset of tumors. Keratinocytes with atypia, presence of neovascularization, and composition of the inflammatory infiltrate were graded from hematoxylin-eosin stainings. MMP-7 was present in the epithelium of 4/31 keratoacanthomas and 9/15 SCCs, MMP-8 in 3/30 keratoacanthomas and 0/15 SCCs, but MMP-13 in 16/31 keratoacanthomas and 10/15 SCCs, and MMP-10 in 28/31 keratoacanthomas and all cancers. MMP-9 was detected in the epithelium in 5/31 keratoacanthomas and 8/15 SCCs, whereas MMP-2 was only present in fibroblasts in both tumors. MMP-19 was upregulated in proliferating epithelium of keratoacanthomas as was p16. Cytoplasmic laminin-5gamma2 was particularly abundant in keratinocytes at the pushing border of MMP-13-positive keratoacanthomas. We conclude that although some MMPs (MMP-10 and -13) are abundantly expressed in keratoacanthomas, the presence of MMP-7 and -9 in their epithelial pushing border is rare and should raise suspicion of SCC. Further, the loss of MMP-19 and p16 could aid in making the differential diagnosis between well-differentiated SCC and keratoacanthoma. Frequent expression of the transformation-specific MMP-13 in keratoacanthomas suggests that they are not benign tumors but incomplete SCCs.

Intraperitoneal gene therapy by rAAV provides long-term survival against epithelial ovarian cancer independently of survivin pathway

Epithelial ovarian carcinoma is the leading cause of death from gynecological malignancies. Owing to the lack of an effective screening method, insidious onset, and non-specific symptoms, a majority of women present with advanced stage disease. Despite improvements from cytoreductive surgery and chemotherapy, recurrent disease remains a formidable challenge. In the present study, we demonstrate for the first time that stable intra-abdominal genetic transfer of endostatin and angiostatin (E+A) by recombinant adeno-associated virus (rAAV) provides sustained antitumor effects on the growth and dissemination of epithelial ovarian cancer in a mouse model. Further, when combined with paclitaxel (taxol), the effect of this therapy was dramatically increased and resulted in long-term tumor-free survival overcoming prior limitations of chemotherapy and gene therapy. The combined effects of angiosuppressive therapy and chemotherapy were found to be independently of survivin pathway. Evidence for the superior effects of the combination therapy was indicated by significantly lower ascites volume with less hemorrhage and tumor conglomerates, lower ascites vascular endothelial growth factor, higher tumor cell apoptosis and decreased blood vasculature, and long-term disease-free survival. Histopathology of visceral organs and liver enzyme assays indicated no toxicity or pathology.

Matrix metalloproteinases and tumor metastasis

Functions of individual matrix metalloproteinases (MMPs) differentially expressed by tumor cells and stromal cells, are finely regulated by their spatial as well as temporal interactions with distinct cellular and extracellular components of the tumor microenvironment and also distant pre-metastatic sites. Certain aspects of MMP involvement in tumor metastasis such as tumor-induced angiogenesis, tumor invasion, and establishment of metastatic foci at the secondary site, have received extensive attention that resulted in an overwhelming amount of experimental and observational data in favor of critical roles of MMPs in these processes. In particular, dependency of tumor angiogenesis on the activity of MMPs, especially that of MMP-9, renders this step possibly the most effective target of synthetic MMP inhibitors. MMP functioning in other stages of metastasis, including the escape of individual tumor cells from the primary tumor, their intravasation, survival in circulation, and extravasation at the secondary site, have not yet received enough consideration, resulting in insufficient or controversial data. The major pieces of evidence that are most compelling and clearly determine the role and involvement of MMPs in the metastatic cascade are provided by molecular genetic studies employing knock-out or transgenic animals and tumor cell lines, modified to overexpress or downregulate a specific MMP. Findings from all of these studies implicate different functional mechanisms for both tumor and stromal MMPs during distinct steps of the metastatic cascade and indicate that MMPs can exhibit pro-metastatic as well as anti-metastatic roles depending on their nature and the experimental setting. This dual function of individual MMPs in metastasis has become a major focus of this review.

Human tongue carcinoma growth is inhibited by selective antigelatinolytic peptides

Matrix metalloproteinases (MMP-2 and MMP-9, or gelatinases) are involved in tongue SCC invasion, metastasis and angiogenesis. We have recently shown that a novel and selective hydrophobic cyclic CTTHWGFTLC (CTT1) peptide is inhibitor for MMP-2 and MMP-9 (Koivunen et al., Nat Biotechnol 1999; 17:768-74). In this study, we demonstrate that both the new hydrophilic derivate GRENYHGCTTHWGFTLC (CTT2) peptide and the CTT1 peptide inhibited specifically the human tongue squamous cell carcinoma (HSC-3) cell-derived gelatinolytic activity and in vitro invasion and migration of these cells (p < or = 0.049). In situ zymography revealed that both peptides also inhibited clearly almost all of the gelatinolytic activity present in the human tongue SCC tissue sections, indicating that MMP-2 and MMP-9 are the major gelatinases detected in the tongue carcinomas. However, CTT2 did not inhibit the type I collagen degradation by human collagenases (MMP-1, MMP-8 and MMP-13). Furthermore, CTT2 reduced the blood vessel density (p < or = 0.043) and clearly improved the survival of the mice bearing human tongue carcinoma xenografts (p < or = 0.012). Overall, we suggest that CTT1 and CTT2 peptides being selective gelatinase inhibitors with significant anti-tumor properties could be useful to diminish the invasion and angiogenesis of human tongue carcinomas characterized by enhanced gelatinolytic activity in tumors.

Collagen XVIII/endostatin shows a ubiquitous distribution in human ocular tissues and endostatin-containing fragments accumulate in ocular fluid samples

BACKGROUND

The endostatin domain of type XVIII collagen (ColXVIII) inhibits neovascularization and regulates cell migration and matrix turnover. This study was designed to demonstrate the protein and gene expression patterns of ColXVIII/endostatin in the human eye and to ascertain whether endostatin is detectable in ocular fluid samples.

METHODS

Twenty human eyes enucleated on account of choroidal melanoma were used for immunohistochemical stainings with antibodies against ColXVIII and endostatin. In situ hybridization was used to localize cells responsible for the production of mRNA for ColXVIII. Tear fluid, aqueous humor, and vitreous gel samples were used for Western immunoblotting to detect endostatin fragments in these samples.

RESULTS

ColXVIII was immunolocalized to almost all ocular structures, namely the basement membranes (BMs) of the corneal and conjunctival epithelia, Descement's membrane, the anterior border layer and posterior pigmented epithelium of the iris, the BMs of the pigmented and non-pigmented ciliary epithelia, the internal wall of Schlemm's canal and trabeculae, the ciliary and iris muscle cells, the BMs of the pigment epithelium of the retina, and the internal limiting membrane. Universal expression was seen in the BMs of vascular endothelial cells, and in fibroblasts located in the conjunctiva, the iris, and the ciliary body. Endostatin showed a corresponding pattern, but additional immunostaining was present in the corneal and conjunctival epithelial cells. Most epithelial and mesenchymal cells expressed the mRNA for ColXVIII. Endostatin-containing fragments varying in size were detected in tear fluid, aqueous humor and vitreous gel samples.

CONCLUSIONS

Practically all structures of the human eye contain ColXVIII/endostatin, emphasizing its possible important structural and functional role in the human eye. Furthermore, ocular fluid samples contain endostatin fragments, which may contribute to the antiangiogenic properties of the eye.

Differential Expression of Collagen Types XVIII/Endostatin and XV in Normal, Keratoconus, and Scarred Human Corneas

PURPOSE

This study was designed to clarify the expression of 2 closely related collagen (Col) types XVIII and XV, and the proteolytically derived endostatin fragment of ColXVIII in normal, keratoconus, and scarred human corneas.

METHODS

Immunohistochemistry, in situ hybridization, immunoelectron microscopy, and Western immunoblotting were used for human corneal samples obtained from penetrating keratoplasty.

RESULTS

In the normal cornea, ColXVIII was immunolocalized to the corneal and conjunctival epithelial basement membrane (EBM), Descemet s membrane, and the limbal and conjunctival capillaries. Immunoreaction for endostatin was otherwise similar, but it also was present in corneal epithelial cells. Western immunoblotting showed that normal cornea contains several endostatin fragments ranging from 20 to 100 kDa. ColXV was present in the EBM of the limbus and conjunctiva, but not in EBM of the clear cornea. In situ hybridization revealed that corneal basal epithelial cells were responsible for the synthesis of ColXVIII mRNA. Keratoconus cases were characterized by an irregular EBM immunoreactivity for ColXVIII and endostatin and patchy immunoreactivity beneath EBM. In scarred corneas, highly increased immunoreactivity for ColXVIII, endostatin, and ColXV was present within stroma.

CONCLUSIONS

The results indicate that ColXVIII and ColXV are differentially expressed in normal human corneas. Constant expression of ColXVIII by corneal EBM suggests that it is an important structural molecule. Aberrant expression of ColXVIII, endostatin, and ColXV in keratoconus and scarred corneas emphasizes the active role these molecules in the wound healing process.

Collagen XVIII/endostatin is associated with the epithelial-mesenchymal transformation in the atrioventricular valves during cardiac development

Type XVIII collagen is a multidomain protein that contains cleavable C-terminal NC1 and endostatin fragments, which have been shown to either induce or inhibit cell migration. Endostatin is being intensely studied because of its anti-angiogenic activity. Three variants of type XVIII collagen have been reported to be distributed in epithelial and endothelial basement membranes in a tissue-specific manner. The single gene encoding collagen XVIII is on chromosome 21 within the region associated with the congenital heart disease phenotype observed in Down's syndrome. In this study, we investigated the expression pattern of collagen XVIII in embryonic mouse hearts during formation of the atrioventricular (AV) valves. We found that collagen XVIII is localized not only in various basement membranes but is also highly expressed throughout the connective tissue core of the endocardial cushions and forming AV valve leaflets. It was closely associated with the epithelial-mesenchymal transformation of endothelial cells into mesenchymal cushion tissue cells and was localized around these cells as they migrated into the cardiac jelly to form the initial connective tissue elements of the valve leaflets. However, after embryonic day 17.5 collagen XVIII expression decreased rapidly in the connective tissue and thereafter remained detectable only in the basement membranes of the endothelial layer covering the leaflets. The staining pattern observed within the AV endocardial cushions suggests that collagen XVIII may have a role in cardiac valve morphogenesis. These results may help us to better understand normal heart development and the aberrant mechanisms that cause cardiac malformations in Down's syndrome.

Hypoxia-induced increase of endostatin in murine aorta and lung

In the lung, hypoxia induces pulmonary hypertension caused by vasoconstriction and vascular remodeling. Additionally, hypoxia is an inducer of angiogenesis, which is assumed to counteract pulmonary hypertension. We asked whether the anti-angiogenic factor endostatin--a cleavage product of collagen XVIII--participates in the vascular alterations induced by hypoxia. By employing Western blotting of tissue extracts of murine brain, liver and heart an endostatin fragment of 22 kDa was detectable, whereas in lung and aorta additional bands of 24 and 26 kDa were found. The amount of these larger fragments was increased in tissues obtained from mice housed for 4 days or 3 weeks at hypobaric hypoxia. By immunohistochemistry endostatin was detected in association with elastic fibers and in close neighborhood to smooth muscle cells of intrapulmonary vessels and the aorta. In the lung, the activity of matrix metalloproteinases (MMP) known to generate endostatin by cleavage of collagen XVIII was increased (MMP-2) and decreased (proMMP-9), respectively, by hypoxia. Elevated amounts of endostatin within the aortic wall of mice exposed to hypobaric hypoxia may stabilize the vascular wall by inhibition of microvascular sprouting. The surprising finding of increased endostatin in the lung presumably contributes to the development of pulmonary hypertension by reduction of angiogenesis.

Pretreatment serum endostatin as a prognostic indicator in metastatic gastric carcinoma

Endostatin is the C-terminal antiangiogenic fragment of the extracellular matrix protein collagen XVIII, and is generated by tumor-derived proteases. The presence of serum endostatin in patients with gastric cancer has not been reported. The authors assessed the serum levels of endostatin in patients with gastric carcinoma and evaluated their association with the levels of vascular endothelial growth factor (VEGF) and the clinical outcome. A total of 107 patients with gastric cancer were included in the study. Pretherapeutic serum levels of endostatin and VEGF were measured using an ELISA, and compared with those in 23 healthy controls. The serum levels of endostatin and VEGF were higher in gastric cancer patients than in healthy controls (endostatin, 70.1 +/- 16.6 vs. 52.2 +/- 6.2 ng/mL [p < 0.001]; VEGF, 55.1 +/- 7.6 vs. 32.1 +/- 2.4 ng/mL [p < 0.001]; mean +/- SD). Serum endostatin levels were significantly associated with the presence of distant metastases (r = 0.556, p < 0.001) and VEGF levels (r = 0.335, p < 0.001), but not with the depth of tumor invasion, differentiation, or regional lymph node status. A serum endostatin level above the 75th percentile of the distribution for the patients (79.2 ng/mL) was associated with a poor outcome (last follow-up at 42 months; median survival time, 9 vs. 20 months [log-rank, p = 0.017]; median time to progression, 5 vs. 10 months [log-rank, p = 0.022]) in the patients with metastatic gastric cancer. The results suggest for the first time that an elevated serum level of endostatin at the diagnosis of metastatic gastric cancer could be predictive of a poor outcome.

Unexpected effect of matrix metalloproteinase down-regulation on vascular intravasation and metastasis of human fibrosarcoma cells selected in vivo for high rates of dissemination

The human tumor/chick embryo model involving grafting of human HT-1080 fibrosarcoma cells on the chorioallantoic membrane was used in conjunction with quantitative real-time Alu PCR to select in vivo a pair of isogenic cell lines (HT-hi/diss and HT-lo/diss), dramatically differing in their ability to disseminate from the primary tumor (i.e., intravasate into the chorioallantoic membrane vasculature and metastasize to the lungs). During an immunohistochemical time course study, HT-hi/diss cells were sequentially visualized having escaped from the primary tumors, engaged with the blood vessels, and eventually observed inside the chorioallantoic membrane capillaries, thus reflecting early intravasating events. In contrast, HT-lo/diss cells seemed restricted to their primary tumor. Importantly, after i.v. inoculation, both variants arrested, extravasated, and proliferated in host tissues with similar efficiencies, highlighting that the observed earlier events at the periphery of the primary tumor could account for their differential dissemination. In a mechanistic probing of these events, we determined that HT-hi/diss intravasation was sensitive to a broad-range matrix metalloproteinase (MMP) inhibitor. To analyze the possible role of individual MMPs, membrane-bound MMP-14 and secreted MMP-9 were individually down-regulated in HT-hi/diss cells with their corresponding small interfering RNAs. Despite efficient down-regulation of MMP-14, neither intravasation nor metastasis of HT-hi/diss cells was affected significantly. However, a substantial down-regulation of MMP-9 was accompanied by a surprising 3-fold increase in intravasation and metastasis. The results emphasize a rising awareness that targeting certain MMPs might result in an enhanced malignancy, exemplified herein at the intravasation level as this step of the metastatic cascade is dissected and quantified.

Generation of biologically active endostatin fragments from human collagen XVIII by distinct matrix metalloproteases

Endostatin, a potent inhibitor of endothelial cell proliferation, migration, angiogenesis and tumor growth, is proteolytically cleaved from the C-terminal noncollagenous NC1 domain of type XVIII collagen. We investigated the endostatin formation from human collagen XVIII by several MMPs in vitro. The generation of endostatin fragments differing in molecular size (24-30 kDa) and in N-terminal sequences was identified in the cases of MMP-3, -7, -9, -13 and -20. The cleavage sites were located in the protease-sensitive hinge region between the trimerization and endostatin domains of NC1. MMP-1, -2, -8 and -12 did not show any significant activity against the C-terminus of collagen XVIII. The anti-proliferative effect of the 20-kDa endostatin, three longer endostatin-containing fragments generated in vitro by distinct MMPs and the entire NC1 domain, on bFGF-stimulated human umbilical vein endothelial cells was established. The anti-migratory potential of some of these fragments was also studied. In addition, production of endostatin fragments between 24-30 kDa by human hepatoblastoma cells was shown to be due to MMP action on type XVIII collagen. Our results indicate that certain, especially cancer-related, MMP family members can generate biologically active endostatin-containing polypeptides from collagen XVIII and thus, by releasing endostatin fragments, may participate in the inhibition of endothelial cell proliferation, migration and angiogenesis.

Endostatin signaling and regulation of endothelial cell-matrix interactions

The growth and survival of a malignant tumor are dependent on the formation and maintenance of its own microvasculature, a process termed angiogenesis. Inhibition of this phenomenon is an emerging strategy in cancer therapy. The extracellular matrix surrounding the vascular endothelial cells contains cryptic protein domains, which are exposed by changes in the proteolytic homeostasis of the tumor microenvironment. These fragments transmit local signals, which regulate vascular endothelial cell proliferation and migration. Endostatin, the proteolytic fragment of collagen type XVIII, is a potent inhibitor of tumor angiogenesis in various mouse models and is currently in clinical trials for therapeutic use in human cancer. Multiple cell surface receptors have been described for endostatin, but the signals transmitted by these receptors resulting in the inhibition of angiogenesis have so far been poorly characterized. Studies on the effects of endostatin on cultured endothelial cells suggest that the antimigratory and antiproliferative properties of this molecule are the major mechanisms underlying its antiangiogenic potential. These effects may be a consequence of endostatin modulation of endothelial cell-matrix interactions and pericellular proteolysis.

Matrix metalloproteinases and angiogenesis

Matrix metalloproteinases (MMPs) are a family of enzymes that proteolytically degrade various components of the extracellular matrix (ECM). Angiogenesis is the process of forming new blood vessels from existing ones and requires degradation of the vascular basement membrane and remodeling of the ECM in order to allow endothelial cells to migrate and invade into the surrounding tissue. MMPs participate in this remodeling of basement membranes and ECM. However, it has become clear that MMPs contribute more to angiogenesis than just degrading ECM components. Specific MMPs have been shown to enhance angiogenesis by helping to detach pericytes from vessels undergoing angiogenesis, by releasing ECM-bound angiogenic growth factors, by exposing cryptic proangiogenic integrin binding sites in the ECM, by generating promigratory ECM component fragments, and by cleaving endothelial cell-cell adhesions. MMPs can also contribute negatively to angiogenesis through the generation of endogenous angiogenesis inhibitors by proteolytic cleavage of certain collagen chains and plasminogen and by modulating cell receptor signaling by cleaving off their ligand-binding domains. A number of inhibitors of MMPs that show antiangiogenic activity are already in early stages of clinical trials, primarily to treat cancer and cancer-associated angiogenesis. However, because of the multiple effects of MMPs on angiogenesis, careful testing of these MMP inhibitors is necessary to show that these compounds do not actually enhance angiogenesis.

Invasive trophoblasts generate regulatory collagen XVIII cleavage products

Endostatin, the C-terminal proteolytic fragment of the noncollagenous domain 1 (NC1) of the basement membrane protein collagen XVIII, inhibits cell proliferation and migration. Placental and decidual expression of the peptide suggested a role in angiogenesis and/or extravillous trophoblast differentiation. Here, we demonstrate that supernatants of trophoblastic SGHPL-5 cells, purified first trimester villous trophoblasts and villous explant cultures contain proteases which in vitro cleave 20kDa endostatin from purified, recombinant NC1 domains. However, supernatants of decidual and villous fibroblasts failed to generate the 20kDa endostatin fragment. Moreover, we show that recombinant endostatin inhibits invasion of SGHPL-5 cells through Matrigel invasion chambers. Since mesenchymal cells but not trophoblasts produce collagen XVIII we suspect that invasive trophoblasts may produce endostatin upon contacting the extracellular matrix deposited by decidual stromal cells. Generation of endostatin through trophoblast-derived proteases could play a role in the regulation of trophoblast invasiveness.

Expression of matrix metalloproteinase (MMP)-7 and MMP-13 and loss of MMP-19 and p16 are associated with malignant progression in chronic wounds

BACKGROUND

The risk of squamous cell carcinoma (SCC) is significantly increased in chronic leg ulcers. Very little is known about the molecular pathogenesis of these tumours, which are often undiagnosed for a long time. As matrix metalloproteinases (MMPs) are implicated at all stages of tumorigenesis, we investigated whether the pattern of epithelial MMP expression can predict development of SCC from pseudoepitheliomatous hyperplasia of chronic wounds.

METHODS

Samples from nine patients with SCCs that had arisen in chronic wounds and 31 with venous leg ulcers were studied using immunohistochemistry for MMP-7, MMP-8, MMP-9, MMP-13, MMP-19 and the tumour suppressor p16. In situ hybridization was performed for MMP-1, MMP-3, MMP-7, MMP-12 and MMP-13.

RESULTS

MMP-7 was expressed by malignantly transformed epithelium, while it was absent from chronic wounds. MMP-9 was detected in the epithelium in both SCCs and chronic wounds. Epithelial MMP-13 expression was strong in SCC, but was absent in chronic wounds. MMP-12 was expressed in the epithelium in two SCCs, while macrophages were positive in chronic wounds. MMP-19 was induced in proliferating epithelium of wounds, but was absent from invasive areas of SCC. p16 was expressed by keratinocytes in half of the chronic wounds and at superficial margins of SCCs, while invasive areas were negative.

CONCLUSIONS

Our results suggest that epithelial expression of MMP-7, MMP-12 and MMP-13, but not that of MMP-1, MMP-3, MMP-8, MMP-9 and MMP-10, in chronic wounds provides a diagnostic clue for distinguishing SCCs from nonmalignant wounds. The loss of MMP-19 and p16 from the epithelium could aid in making the differential diagnosis between well-differentiated SCCs and nonmalignant chronic wounds.