Secreted cathepsin L generates endostatin from collagen XVIII

Overexpression of Collagen XVIII Is Associated with Poor Outcome and Elevated Levels of Circulating Serum Endostatin in Non–Small Cell Lung Cancer

PURPOSE

The aim of this study was to determine whether collagen XVIII expression is correlated with circulating serum endostatin and whether this has any prognostic value in patients with non-small cell lung cancer (NSCLC).

EXPERIMENTAL DESIGN

Serum endostatin levels were measured quantitatively by a competitive enzyme immunoassay, and collagen XVIII expression in tumor tissue was investigated with an immunohistochemical method in a series of 94 patients who underwent surgery for NSCLC.

RESULTS

Sixty cases (63.8%) had positive immunohistochemical staining with anticollagen XVIII polyclonal antibodies, including strongly positive staining in 11 (11.7%) cases. The mean (+/- SD) serum endostatin level was 41.6 +/- 34.4 ng/ml in the patient group and 16.3 +/- 10.3 ng/ml in the control group (P < 0.0001). The 11 cases who were strongly collagen XVIII-positive had significantly higher serum endostatin levels than the cases who were negative or weakly positive (P = 0.0297). The 5-year survival rates of negative, weakly positive, and strongly positive patients were 77.8%, 56.9%, and 43.8%, respectively. The cases with strongly positive collagen XVIII expression had a significantly poorer outcome than cases with negative expression (P = 0.0027). A multivariate analysis with Cox proportional hazards model for disease-specific survival revealed that expression of collagen XVIII (strongly positive versus negative; weakly positive versus negative), tumor classification, and regional lymph node classification were independent prognostic factors.

CONCLUSIONS

Our results suggest that expression of collagen XVIII in tumor tissue is strongly associated with a poorer outcome in NSCLC and correlates with elevated levels of circulating serum endostatin.

Loss of collagen XVIII enhances neovascularization and vascular permeability in atherosclerosis

BACKGROUND

Plaque neovascularization is thought to promote atherosclerosis; however, the mechanisms of its regulation are not understood. Collagen XVIII and its proteolytically released endostatin fragment are abundant proteoglycans in vascular basement membranes and the walls of major blood vessels. We hypothesized that collagen XVIII in the aortic wall inhibits the proliferation and intimal extension of vasa vasorum.

METHODS AND RESULTS

To test our hypothesis, we bred collagen XVIII-knockout (Col18a1(-/-)) mice into the atherosclerosis-prone apolipoprotein E-deficient (ApoE(-/-)) strain. After 6 months on a cholesterol diet, aortas from ApoE(-/-);Col18a1(-/-) and ApoE(-/-);Col18a1(+/-) heterozygote mice showed increased atheroma coverage and enhanced lipid accumulation compared with wild-type littermates. We observed more extensive vasa vasorum and intimal neovascularization in knockout but not heterozygote aortas. Endothelial cells sprouting from Col18a1(-/-) aortas were increased compared with heterozygote and wild-type aortas. In contrast, vascular permeability of large and small blood vessels was enhanced with even heterozygous loss of collagen XVIII but was not suppressed by increasing serum endostatin to wild-type levels.

CONCLUSIONS

Our results identify a previously unrecognized function for collagen XVIII that maintains vascular permeability. Loss of this basement membrane proteoglycan enhances angiogenesis and vascular permeability during atherosclerosis by distinct gene-dose-dependent mechanisms.

The contribution of vascular basement membranes and extracellular matrix to the mechanics of tumor angiogenesis

The goal of this review is to highlight the contribution of extracellular matrix and vascular basement membranes to the regulation of angiogenesis and tumor progression. Here we present a new concept that vascular basement membrane influences endothelial cells and possibly other cell types in a solid state assembled form, and also in a degraded solution state form. Depending on the structural integrity, composition and exposure of cryptic sites, the vascular basement membrane proteome exerts functional influences on proliferating and resting endothelial cells. This review provides the reader with an appreciation of this newly evolved concept in the area of vascular biology.

Angiogenic and antiangiogenic balance regulates concomitant antitumoral resistance

Concomitant antitumoral resistance (CAR), the phenomenon by which the growth of distant secondary tumor implants or metastases in some tumor-bearing hosts is inhibited by the presence of a primary tumor, has been previously ascribed to an antiangiogenic process. Here, we investigated vascular endothelial growth factor (VEGF) and endostatin serum levels in nude or BALB/c mice bearing human lung tumors (Calu-6 and H460) or murine mammary tumors (M3MC, M-234p and M-234m), respectively. In these experimental models we previously found an association between in vivo generation of CAR and in vitro conversion of plasminogen into angiostatin. Serum endostatin level in CAR+ Calu-6-bearing mice was significantly higher than in CAR- H460 counterpart. Sera from mammary tumor-bearing mice showed similar levels of endostatin, regardless of their ability to induce CAR. Conversely, serum VEGF levels in mice bearing CAR+ tumors were lower than those found in CAR- tumor-bearing hosts. Immunostaining with an anti-CD31 antibody revealed that secondary tumors subjected to CAR were significantly less vascularized than primary tumors, while this difference was not observed in CAR- tumors. In vitro studies showed an inhibitory effect of sera from CAR-inducing tumors on endothelial cell proliferation as compared to normal sera, whereas sera from non-CAR-inducing tumors did not alter endothelial proliferation and, in some instances, even caused stimulation of endothelial proliferation. These data suggest that the antiangiogenic mechanism operating in concomitant antitumoral resistance is the result of an increase in the ratio of antiangiogenic/proangiogenic regulators. The levels of the factors involved in this phenomenon can vary in the different tumor models, but the trend favoring the inhibition of angiogenesis is always conserved.

A key angiogenic role of monocyte chemoattractant protein-1 in hemangioendothelioma proliferation

Angiomatous lesions are common in infants and children. Hemangioendotheliomas (HE) represent one type of these lesions. Endothelial cell proliferation and the development of vascular/blood cell-filled spaces are inherent in the growth of HE. Therefore, understanding mechanisms that regulate the proliferation of these lesions should provide key insight into mechanisms regulating angiogenesis. A murine model was used to test the significance of monocyte chemoattractant protein (MCP)-1 in HE proliferation. EOMA cells, a cell line derived from a spontaneously arising murine HE, generate these lesions with 100% efficiency when injected subcutaneously into syngeneic mice. MCP-1 produced by EOMA cells recruit macrophages, which were shown to induce angiogenic behavior in EOMA cells by stimulating transwell migration and inducing sprout formation on type I collagen gels. When EOMA cells were injected into MCP-1(-/-) mice, only 50% of the mice developed tumors, presumably because the low levels of MCP-1 expressed by the injected EOMA cells were enough to overcome any host deficits of this chemokine. When EOMA cells were coinjected with a neutralizing antibody to MCP-1, tumors failed to develop in any of the treated mice, including syngeneic 129P3, C57Bl/6 (wild type), and MCP-1(-/-). These results present the first evidence that MCP-1 is required for HE proliferation and may promote the growth of these lesions by stimulating angiogenic behavior of endothelial cells. This study has produced the first in vivo evidence of a complete response for any neoplasm, specifically a vascular proliferative lesion, to anti-MCP-1 therapy in animals with intact immune systems.

Expression and characterization of cathepsin P

The mouse genome contains a family of clan C1A proteases that appear to be restricted to rodents within Eutherian (placental) mammals. mRNA analysis has shown that these genes are expressed exclusively in placenta. Sequence analysis predicts that the expressed proteins will be functional and consequently it was proposed that this family of proteases may have evolved to perform subspecialized functions of the closely related protease, cathepsin L, that is expressed in placental tissues of all mammalian species. In the present study, it was shown that cathepsin P can be expressed in Pichia pastoris as an inactive zymogen that can be activated with proteinase K, chymotrypsin or pancreatic elastase at neutral pH. Unlike other mammalian cathepsins, cathepsin P could also be autoactivated at neutral pH, but not at acidic pH. The activated enzyme was capable of hydrolysing peptidyl substrates and the protein substrates azocasein and transferrin, with optimal activity at pH 6.5-7.5. Little activity could be detected at pH 5.0 and below. Salts such as Na2SO4 and hyaluronate stimulated the activity of the protease against peptidyl substrates. The properties of cathepsin P appear to be quite distinct from those of cathepsin L, indicating that the duplication that gave rise to cathepsin P has probably not yielded an enzyme that provides a subfunction of cathepsin L in rodents. It seems probable that cathepsin P has evolved to perform a function that is performed by an evolutionarily unrelated protease in other mammalian species.

Cysteine cathepsins (proteases)--on the main stage of cancer?

Cysteine cathepsins are involved in degradation of extracellular matrix, facilitating growth, invasion, and metastasis of tumor cells, in tumor angiogenesis, in apoptosis, and in events of inflammatory and immune responses. In this issue of Cancer Cell, demonstrate association of increased cathepsins activity with angiogenic vasculature and invasive fronts of carcinomas during tumorigenesis in transgenic mouse models using activity-based chemical probes and in vivo imaging. Moreover, this study shows that a broad-spectrum cysteine cathepsin inhibitor effectively blocks several stages of tumorigenesis in the RIP1-Tag2 transgenic mouse model, offering new therapeutic opportunities in cancer treatment.

Inhibition of tumorigenicity and metastasis of human melanoma cells by anti-cathepsin L single chain variable fragment

We demonstrated previously that the switch from nonmetastatic to highly metastatic phenotype of human melanoma cells is directly related to secretion of procathepsin L form. This cysteine proteinase was identified on the basis of its property to cleave human C3, the third component of complement. In an attempt to control procathepsin L secretion, we have recently generated an anti-cathepsin L single chain variable fragment (ScFv) from an anti-cathepsin L monoclonal antibody generated against recombinant cathepsin L. We herein selected clones stably transfected with this anti-cathepsin L ScFv and analyzed them for changes in tumor growth and metastasis. We show that in stably transfected clones, anti-cathepsin L ScFv strongly inhibited the secretion of procathepsin L without modifying the intracellular amount or processing pattern of cathepsin L forms. Confocal analysis demonstrated colocalization of endogenous cathepsin L and anti-cathepsin L ScFv. In addition, expression of this ScFv strongly inhibited generation of tumor and metastasis by these human melanoma clones in nude mice. In vivo, the anti-cathepsin L ScFv-transfected cells produced tumors with decreased vascularization (angiogenesis) concomitant with increased apoptosis of tumor cells. Matrigel assay also demonstrated that melanoma invasiveness was completely abolished. Thus, this is the first demonstration that anti-cathepsin L ScFv could be used to inhibit the tumorigenic and metastatic phenotype of human melanoma, depending on procathepsin L secretion, and could therefore be used as a molecular tool in a therapeutic cellular approach.

Correlation between serum vascular endothelial growth factor and endostatin levels in patients with breast cancer

Serum vascular endothelial growth factor (VEGF) and endostatin levels were detected in 59 patients with breast cancer before surgery and at 3 weeks after surgery. Pre-operatively, their levels were significantly elevated and correlated with each other. Post-operatively, VEGF level decreased significantly and endostatin remained at a high level. Patients with both normalized VEGF and elevated endostatin following surgery had a lower risk of relapse than patients whose VEGF failed to normalize. Univariate and multivariate analyses showed a correlation between elevated VEGF level and short free-relapse survival. These findings suggest a new angiogenesis balance is formed in the patients after surgery and such a resultant balance may be beneficial for the prognosis of breast cancer, which deserves more extensive study.

Matrix metalloproteinases and matrikines in angiogenesis

Neoangiogenesis, the formation of new blood capillaries from pre-existing vessels, plays an important role in a number of physiological and pathological processes, particularly in tumor growth and metastasis. Extracellular proteolysis by matrix metalloproteinases or other neutral proteinases is an absolute requirement for initiating tumor invasion and angiogenesis. Cryptic segments or pre-existing domains within larger proteins, most of them belonging to the extracellular matrix, can be exposed by conformational changes and/or generated by partial enzymatic hydrolysis. They can positively or negatively regulate important functions of endothelial cells including adhesion, migration, proliferation, cell survival and cell-cell interactions. Such regulations by cryptic segments and proteolytic fragments led to the concept of matricryptins and matrikines, respectively. Matrix metalloproteinases and matrikines in conjunction with other pro- or anti-angiogenic factors might act in concert at any step of the angiogenesis process. A number of matrikines have been identified as potent anti-angiogenic factors, which could provide a new alternative to anti-proteolytic strategies for the development of anti-angiogenic therapeutic molecules aimed at inhibiting tumor growth and metastasis. Some of them are currently being investigated in clinical trials.

Raised plasma endostatin levels correlate inversely with breast cancer angiogenesis

BACKGROUND

Angiogenesis is essential for solid tumors, such as breast cancer, to grow. The effect of surgical removal of breast tumors on plasma endostatin and vascular endothelial growth factor (VEGF) levels was evaluated. Tumor tissues were analyzed for expression of Intratumoral microvessel density (IMVD) and endostatin. The effect of VEGF and endostatin in inducing apoptosis on human liver microvascular endothelial cells (HLMVEC) was investigated.

MATERIALS AND METHODS

Plasma from healthy volunteers, patients with fibroadenomas and breast cancer patients were assayed for endostatin and VEGF via immunoassay, pre-operatively and four weeks post-operatively. Expression of endostatin in tumor tissue was determined by Western blotting. IMVD was assessed following immunohistochemical staining with anti-CD34 antibody.

RESULTS

Plasma endostatin levels, in breast cancer patients, were significantly elevated (P = 0.015) in the post-operative (60.59 +/- 7.70 etag/ml) compared with the pre-operative group (30.62 +/- 4.54 etag/ml) and with normal age-matched controls (34.97 +/- 3.76 etag/ml). In patients with high pre-operative plasma endostatin value, IMVD was decreased to 20.1 +/- 3.2 counts compared with 41.9 +/- 5.4 counts in those with low pre-operative endostatin value (P = 0.006). Neither plasma endostatin nor VEGF levels correlated with routine clinico-pathological parameters. Endostatin induced endothelial cell apoptosis and modulated the cytoprotective effect of VEGF in HLMVEC survival.

CONCLUSIONS

Plasma endostatin levels are increased in patients following surgical removal of the primary tumor. The decreased IMVD seen in patients with higher endostatin levels may be due to the apoptosis-inducing effect of endostatin on microvascular endothelial cells.

Anti-neovascular therapy by liposomal drug targeted to membrane type-1 matrix metalloproteinase

Because membrane type-1 matrix metalloproteinase (MT1-MMP) is expressed specifically on the angiogenic endothelium as well as tumor cells, an agent possessing the ability to bind to this molecule might be useful as a tool for active targeting of tumor angiogenic vessels. Based on the sequences of peptide substrates of MT1-MMP, which had been determined by using a phage-displayed peptide library, we examined the binding ability of peptide-modified liposomes for endothelial cells and targeting ability for tumor tissues by positron emission tomography (PET). Liposomes modified with stearoyl-Gly-Pro-Leu-Pro-Leu-Arg (GPLPLR-Lip) showed high binding ability to human umbilical vein endothelial cells and accumulated in the tumor about 4-fold more than did the unmodified liposomes. Because we reported previously that liposomalized 5'-O-dipalmitoylphosphatidyl 2'-C-cyano-2'-deoxy-1-beta-D-arabino-pentofuranosylcytosine (DPP-CNDAC), a hydrophobized derivative of the novel antitumor nucleoside CNDAC, strongly suppressed tumor growth when delivered in liposomes modified with another angiogenic homing peptide, we examined the antitumor activity of DPP-CNDAC entrapped in GPLPLR-Lip. DPP-CNDAC/GPLPLR-Lip showed significant tumor growth suppression compared to DPP-CNDAC/unmodified liposomes. These results suggest that DPP-CNDAC-liposomes modified with MT1-MMP-targeted peptide are useful for cancer anti-neovascular therapy (ANET), namely, tumor growth suppression by damage to angiogenic endothelial cells.

Increased expression of collagen XVIII and its prognostic value in nonsmall cell lung carcinoma

BACKGROUND

Angiogenesis plays a crucial role in tumor growth and metastasis. Recently, some studies have focused on the angiogenesis inhibitor endostatin. However, the biologic role of the precursor of endostatin, collagen XVIII, in human malignancy is unknown. The purpose of the current study was to evaluate whether the expression of collagen XVIII has additional prognostic value for survival in patients with nonsmall cell lung carcinoma (NSCLC).

METHODS

The authors investigated the expression of collagen XVIII in 221 patients using immunohistochemical methods. To confirm the specificity of the collagen XVIII polyclonal antibody used in the current study and to test the expression of collagen XVIII in human lung carcinoma, Western blot analysis was performed on a panel of human lung carcinoma cell lines.

RESULTS

Collagen XVIII expression was detected in 162 of 221 patients with NSCLC (73%), primarily in the tumor cell cytoplasm. Low collagen XVIII expression levels were found in 75 tumor specimens, while high collagen XVIII expression levels were noted in 87 tumor specimens. The prevalence of positive collagen XVIII expression was greater in T2-4 tumors than in T1 tumors (P = 0.0235). The prognosis for patients with strongly collagen XVIII-positive NSCLC was significantly worse than the prognosis for patients with collagen XVIII-positive or collagen XVIII-negative NSCLC (P = 0.0010). Multivariate analysis indicated that T status, lymph node status, and the overexpression of collagen XVIII were independent prognostic factors.

CONCLUSIONS

The results of the current study indicated that the overexpression of collagen XVIII was associated with NSCLC progression and poor outcome. Thus, collagen XVIII expression may serve as a useful prognostic marker in patients with NSCLC.

Collagen XVIII/endostatin is essential for vision and retinal pigment epithelial function

Age-related macular degeneration (ARMD) with abnormal deposit formation under the retinal pigment epithelium (RPE) is the major cause of blindness in the Western world. basal laminar deposits are found in early ARMD and are composed of excess basement membrane material produced by the RPE. Here, we demonstrate that mice lacking the basement membrane component collagen XVIII/endostatin have massive accumulation of sub-RPE deposits with striking similarities to basal laminar deposits, abnormal RPE, and age-dependent loss of vision. The progressive attenuation of visual function results from decreased retinal rhodopsin content as a consequence of abnormal vitamin A metabolism in the RPE. In addition, aged mutant mice show photoreceptor abnormalities and increased expression of glial fibrillary acidic protein in the neural retina. Our data demonstrate that collagen XVIII/endostatin is essential for RPE function, and suggest an important role of this collagen in Bruch's membrane. Consistent with such a role, the ultrastructural organization of collagen XVIII/endostatin in basement membranes, including Bruch's membrane, shows that it is part of basement membrane molecular networks.

Effects of major liver resection, with or without recombinant bactericidal/permeability-increasing protein (rBPI21), on the angiogenic profile of patients with metastatic colorectal carcinoma

BACKGROUND

Surgery induces a process of wound healing, which has immunological and angiogenic aspects. Bactericidal/permeability-increasing protein (BPI) is found in azurophilic granules of human neutrophils, which is bactericidal and neutralizes lipo-polysaccharide (LPS). This may reduce postoperative infectious complications. In addition, BPI has been shown to be an inhibitor of angiogenesis.

METHODS

A total of 18 patients with metastasized colorectal carcinoma to the liver were double blind randomized. The levels of the pro-angiogenic factors interleukin-6 (IL-6) and vascular endothelial growth factor (VEGF) and the angiogenesis inhibitor endostatin were investigated after liver surgery with perioperative administration of either rBPI(21) or placebo.

RESULTS

The highest IL-6 levels were found during the first 24 hr and reached peak levels already at 2 hr postoperatively in both groups. In both groups VEGF levels decreased sharply in the postoperative hours, returning to baseline levels in the days afterwards. In both groups, an immediate decrease in endostatin levels was observed which remained significantly low. RBPI(21) transiently influenced IL-6 and VEGF.

CONCLUSIONS

RBPI(21) only marginally affected IL-6 and VEGF levels. Surgery per se induced an immediate immune response (IL-6) and an immediate angiogenic response, reflected in an initial VEGF decrease and a longer lasting decrease of endostatin. These findings demonstrate the dynamics of tissue responses in the first phase of wound healing.

Phenotypic switching of VEGF and collagen XVIII during hypoxia in head and neck squamous carcinoma cells

The present study sought to determine the potential role of stress activated MAPK and phosphatidylinositol 3-kinase (PI3K) signaling pathways in mediating phenotypic switching between angiogenic and angiostatic elements among squamous cell carcinoma (SCC) cell lines. In particular, we investigated the effects of hypoxia and those of cobalt chloride (CoCl(2)), which mimics the hypoxic response including the production of reactive oxygen species, on such phenotypic shifts. The expression and production of collagen XVIII, and CBP2/Hsp47 provided a measure of an angiostatic phenotype, while vascular endothelial growth factor (VEGF) expression was used to assess potential angiogenic states. These studies revealed that hypoxia produced a slight up-regulation of collagen XVIII and CBP2/Hsp47 that was inhibited by the stress kinase inhibitor SB203580 but was unaffected by N-acetylcysteine (NAC). In addition, VEGF expression was increased following hypoxia and this effect was reversed with inhibition of by SB203580. Conversely, CoCl(2) significantly diminished the expression of both collagen XVIII and CBP2/Hsp47 and enhanced VEGF expression. These changes were reversed by the PI3K inhibitor wortmannin and by treating cells with NAC. These studies show that phenotypic switching between collagen XVIII and VEGF is controlled by stress activated kinases under hypoxia, and PI3K signaling pathways as well as reactive oxygen species (ROS) following CoCl(2) treatment. Furthermore, modulation of the angiogenic switch is most profound during Akt activation than during activation of stress activated kinases.

Functional proteomics of the active cysteine protease content in Drosophila S2 cells

The fruit fly genome is characterized by an evolutionary expansion of proteases and immunity-related genes. In order to characterize the proteases that are active in a phagocytic Drosophila model cell line (S2 cells), we have applied a functional proteomics approach that allows simultaneous detection and identification of multiple protease species. DCG-04, a biotinylated, mechanism-based probe that covalently targets mammalian cysteine proteases of the papain family was found to detect Drosophila polypeptides in an activity-dependent manner. Chemical tagging combined with tandem mass spectrometry permitted retrieval and identification of these polypeptides. Among them was thiol-ester motif-containing protein (TEP) 4 which is involved in insect innate immunity and shares structural and functional similarities with the mammalian complement system factor C3 and the pan-protease inhibitor alpha2-macroglobulin. We also found four cysteine proteases with homologies to lysosomal cathepsin (CTS) L, K, B, and F, which have been implicated in mammalian adaptive immunity. The Drosophila CTS equivalents were most active at a pH of 4.5. This suggests that Drosophila CTS are, similar to their mammalian counterparts, predominantly active in lysosomal compartments. In support of this concept, we found CTS activity in phagosomes of Drosophila S2 cells. These results underscore the utility of activity profiling to address the functional role of insect proteases in immunity.

Cathepsin B in the rat eye

BACKGROUND

Cathepsin B is a mammalian cysteine protease. The enzyme has been suggested to participate in the patophysiological processes of keratoconus as well as in the corneal response to infectious agents. This study describes the localization of cathepsin B in the rat eye.

METHODS

Cathepsin B was identified in rat ocular tissues by Western blotting and immunohistochemistry. Cathepsin B mRNA levels were analyzed in the tissues by quantitative real-time cDNA amplification (QRT-PCR).

RESULTS

Cathepsin B is present in the epithelium, in stromal cells and in the endothelium of the cornea. It is also present in the epithelium lining the ciliary processes, in occasional stromal cells in the iris, in the anterior subcapsular lens epithelium and in various cell types in the retina. At all locations cathepsin B is present in cytoplasmic granules, presumably lysosomes. QRT-PCR analysis detected cathepsin B mRNA in all these tissues in amounts correlating to the immunodetection results, suggesting that the enzyme detected is locally produced.

CONCLUSIONS

Cathepsin B is present in several tissues and cell types throughout the rat eye. It is localized to cytoplasmic granules, presumably lysosomes. Our results suggest that it is probably also produced in the same cell types.

Quantitative analysis of cathepsin L mRNA and protein expression during oral cancer progression

Although an important risk factor for oral cancer is the presence of epithelial dysplasia, most of these lesions will not progress to malignancy. Presently, for the individual patient with dysplasia, there are few reliable markers that may indicate the likelihood of progression to oral cancer. Cathepsin L is a lysosomal protease that degrades extracellular matrix material. Because cathepsin L is frequently overexpressed in oral squamous cell carcinoma (SCC) we hypothesized that it is also overexpressed in oral premalignancy and that premalignant lesions that progressed to oral cancer expressed higher levels of cathepsin L than those premalignant lesions that did not. In this retrospective pilot study we examined changes in cathepsin L expression at the mRNA level using quantitative TaqMan RT-PCR and at the protein level by immunohistochemistry in 33 routinely processed oral dysplastic lesions and 14 SCCs obtained from 33 patients. Sixteen of the dysplastic lesions progressed to oral SCC and 17 did not after several years of follow-up. Cathepsin L mRNA was overexpressed in 16/33 (48%) dysplastic lesions and in 9/14 (64%) oral SCC. Cathepsin L protein was also overexpressed in a large proportion of dysplasias and cancers. Overexpression was independent of dysplasia grade and identified in both those patients who progressed to oral SCC and in those who did not. Levels of cathepsin L mRNA and protein did not differ significantly in the progressing versus non-progressing dysplasias (P=0.27). However, cathepsin L mRNA and protein were significantly lower in the non-progressing dysplasias when compared to the oral cancers (P=0.03) but not in the progressing dysplasias suggesting a trend for dysplasias with overexpressed cathepsin L to be more likely to progress to oral cancer.

Characterization of the human type XVIII collagen gene and proteolytic processing and tissue location of the variant containing a frizzled motif

Human type XVIII collagen was found to be expressed as three variants, termed NC1-303, NC1-493 and NC1-728, differing in their N-terminal non-collagenous domains (NC1). The corresponding gene was found to be approximately 105 kb in size and contain 43 exons. The short variant is derived from utilization of an upstream promoter associated with the first two exons of the gene. The two other variants are derived from a downstream promoter and alternative splicing of exon 3, resulting in 192 residues of shared sequences characterized by a putative approximately 30 residue conserved coiled-coil motif and 235 residues of sequences specific to NC1-728. The NC1-728 variant has a conserved cysteine-rich domain homologous with the ligand-binding part of the frizzled proteins. A polyclonal antibody specific to the NC1-728 variant was generated, and immunostaining of fetal tissues revealed staining in lung and skeletal muscle. Human serum contained 173- and 144-kDa alpha1(XVIII) chains corresponding to the NC1-728 and NC1-493 variants, respectively. A 200-kDa polypeptide was detected in cells transfected with a cDNA construct corresponding to the full-length NC1-728 variant, and EBNA-293 cells endogenously synthesizing low amounts of type XVIII collagen had a 45-kDa fragment in their culture medium that corresponded to most of the NC1 domain of the NC1-728 variant, suggesting processing of the N-terminal frizzled-containing domain.

Regulation of mammary gland branching morphogenesis by the extracellular matrix and its remodeling enzymes

A considerable body of research indicates that mammary gland branching morphogenesis is dependent, in part, on the extracellular matrix (ECM), ECM-receptors, such as integrins and other ECM receptors, and ECM-degrading enzymes, including matrix metalloproteinases (MMPs) and their inhibitors, tissue inhibitors of metalloproteinases (TIMPs). There is some evidence that these ECM cues affect one or more of the following processes: cell survival, polarity, proliferation, differentiation, adhesion, and migration. Both three-dimensional culture models and genetic manipulations of the mouse mammary gland have been used to study the signaling pathways that affect these processes. However, the precise mechanisms of ECM-directed mammary morphogenesis are not well understood. Mammary morphogenesis involves epithelial 'invasion' of adipose tissue, a process akin to invasion by breast cancer cells, although the former is a highly regulated developmental process. How these morphogenic pathways are integrated in the normal gland and how they become dysregulated and subverted in the progression of breast cancer also remain largely unanswered questions.

Cathepsin L plays an active role in involution of the mouse mammary gland

Involution of the mammary gland after weaning occurs in two stages. The first stage is reversible, whereas the second stage is characterized by the irreversible collapse of the alveolar structure. A differential display analysis using cDNAs from tissues obtained at various times after forced weaning of pups identified cathepsin L as up-regulated during early involution. Levels of cathepsin L mRNA were dramatically increased within 24 hr after weaning. Cathepsin L protein detected by immunoblot was also increased during involution, reaching near maximal levels by 36 hr after weaning. In situ immunohistochemistry detected pronounced cathepsin L protein in the cytoplasm and cell periphery. Mice treated with a specific inhibitor of cathepsin L exhibited substantially reduced numbers of apoptotic cells at times up to 72 hr after weaning when compared with untreated animals. The cathepsin L inhibitor did not alter levels of cathepsin L detected in immunoblots or influence molecular weight of the cathepsin L species detected. These data suggest that cathepsin L plays a regulatory role early in the process of mammary gland involution.

Endostatin exhibits a direct antitumor effect in addition to its antiangiogenic activity in colon cancer cells

Endostatin has been considered a highly specific inhibitor of endothelial cell proliferation and/or migration. To explore the use of endostatin in antiangiogenic gene therapy, we generated a recombinant adenovirus, AdEndo, carrying the gene for mouse endostatin. Injection of 10(9) PFU of AdEndo resulted in a low but significant suppression (25%) of preestablished tumor growth in murine models involving murine Lewis lung carcinoma (LLC) and human breast cancer MDA-MB-231 tumors. Greater anticancer activity was observed when the same dose of AdEndo was injected into two other preestablished murine models involving C51 murine colon cancer and HT29 human colon cancer (55 and 47% tumor growth reduction, respectively). In vitro, endostatin derived from AdEndo-infected MRC-5 fibroblasts inhibited the growth of C51 and HT29 cell lines (72 and 61%, respectively). The extent of this inhibition was comparable to that observed in endothelial cells: 75% for microcapillary endothelial cell line HMEC-1, 52% for human dermal microvascular endothelial cells, 46% for human umbilical vein endothelial cells, and 67% for calf pulmonary arterial endothelial cells. Both endothelial and colon cancer cells showed a clear increase in cell apoptosis (4- to 5-fold for endothelial cells and 5- to 10-fold for colon cancer cells) and an accumulation in the G(1) phase of the cell cycle. This antiproliferative activity was not observed in other tumor cell lines: LLC, MDA-MB-231, murine colon adenocarcinoma MC38, human prostate cancer cell line DU145, and human breast cancer cell line CAL51. Taken together, these results provide evidence that, in addition to its antiangiogenic activity, endostatin exerts a direct anticancer action that appears to be restricted to some tumor cell lines. Thus, endostatin could be used in some colon cancer treatments and its clinical efficacy would depend on the response of tumor cells themselves.

Endostatin action and intracellular signaling: beta-catenin as a potential target?

Endostatin, the C-terminal part of collagen XVIII, has been shown to inhibit blood vessel formation in different pathological conditions characterized by increased angiogenesis, such as growing tumors. Subcutaneous injection of endostatin in tumor-bearing mice leads to decreased tumor growth, and even in some cases, cure of tumor disease. Endostatin has been tested in a clinical phase I study and shown not to be toxic. Whether the finding in mice that endostatin treatment does not result in development of resistance will hold true in humans is too early to tell. Endostatin binds to a specific motif in heparan sulfate, which may serve a co-receptor function. The structure of a potential primary receptor is not known. The mechanism of action of endostatin in inhibition of angiogenesis and thereby, inhibition of tumor growth, involves apoptosis of tumor cells. The most consistent effect of endostatin on endothelial cells in vitro is inhibition of endothelial cell migration, which may be due to disturbed cell-matrix interactions. An interesting candidate for transducing endostatin's effect on apoptosis and cell migration is beta-catenin, an intracellular protein which participates both in cell adhesion and in transcriptional regulation.

Cloning and characterization of anti-cathepsin L single chain variable fragment whose expression inhibits procathepsin L secretion in human melanoma cells

We previously demonstrated that increase of procathepsin L secretion by human melanoma cells strongly increased their tumourigenicity and switched their phenotype from low to highly metastatic. Thus, we herein analysed whether it was possible to inhibit procathepsin L secretion using anti-cathepsin L ScFv. For this purpose, we produced different forms of fusion cathepsin L in prokaryotic or eukaryotic expression systems. An anti-cathepsin L monoclonal antibody (mAb), named 3D8, was isolated from mice immunized with purified procathepsin L-His. This 3D8 mAb interacted with an epitope localized on the 156-197 amino acid sequence of cathepsin L and recognized recombinant or native forms of cathepsin L synthesized by human melanoma cells. An active anti-cathepsin L ScFv was generated and characterized from 3D8 mAb heavy and light variable chains. Then, human melanoma cells were transiently co-transfected with 3D8 ScFv and cathepsin L cDNAs. Data demonstrated that increase of 3D8 ScFv expression in human melanoma cells totally inhibited procathepsin L secretion and induced accumulation of intracellular procathepsin L. Our results constitute the first demonstration that anti-cathepsin L ScFv could be used in human melanoma cells to inhibit procathepsin L secretion. This ScFv represents a new molecular tool to explore cell therapy of human melanomas.

Anti-angiogenic property of edible berry in a model of hemangioma

Hemangiomas represent a powerful model to study in vivo angiogenesis. Monocyte chemotactic protein 1 (MCP-1) is known to be responsible for recruiting macrophages to sites of infection or inflammation and facilitate angiogenesis. Recently we have demonstrated that edible berry extracts potently suppress inducible vascular endothelial growth factor expression and in vitro angiogenesis. Comparative analysis of several berry extracts led to the observation that wild blueberry and a berry mix were most effective. Our goal was to follow up on our findings with wild blueberry and the berry mix (OptiBerry). The present work rests on our current finding that these two berry powders significantly inhibit inducible MCP-1 expression in endothelioma cells. Therefore, we sought to examine the effects of wild blueberry and berry mix in an in vivo model of experimental angiogenesis. Reporter studies showed that the berry powders significantly inhibited basal MCP-1 transcription and inducible nuclear factor kappaB transcription. Endothelioma cells pre-treated with berry powders showed diminished ability to form hemangioma. Histological analysis demonstrated markedly decreased infiltration of macrophages in hemangioma of treated mice compared to placebo-treated controls. The current results provide the first in vivo evidence substantiating the anti-angiogenic property of edible berries.

Proteinases and their inhibitors in the immune system

The most important roles of proteinases in the immune system are found in apoptosis and major histocompatibility complex (MHC) class II-mediated antigen presentation. A variety of cysteine proteinases, serine proteinases, and aspartic proteinases as well as their inhibitors are involved in the regulation of apoptosis in neutrophils, monocytes, and dendritic cells, in selection of specific B and T lymphocytes, and in killing of target cells by cytotoxic T cells and natural killer cells. In antigen presentation, endocytosed antigens are digested into antigenic peptides by both aspartic and cysteine proteinases. In parallel, MHC class II molecules are processed by aspartic and cysteine proteinases to degrade the invariant chain that occupies the peptide-binding site. Proteinase activity in these processes is highly regulated, particularly by posttranslational activation and the balance between active proteinases and specific endogenous inhibitors such as cystatins, thyropins, and serpins. This article discusses the regulation of proteolytic processes in apoptosis and antigen presentation in immune cells and the consequences of therapeutic interference in the balance of proteinases and their inhibitors.

Elevated serum endostatin is associated with poor outcome in patients with non-Hodgkin lymphoma

BACKGROUND

Endostatin is a cleaved fragment of collagen Type XVIII and has antiangiogenic activity. The clinical significance of circulating, soluble endostatin (S-endostatin) is not known.

METHODS

Pretreatment S-endostatin and serum vascular endothelial growth factor (S-VEGF) levels were measured in 143 patients with non-Hodgkin lymphoma (NHL) using competitive enzyme immunoassays and were compared with the levels from a control group (n = 24 participants).

RESULTS

S-endostatin levels varied widely from 4.5 ng/mL to 116 ng/mL (median, 29.6 ng/mL), and the median level was higher in patients with NHL compared with patients in the control group (16.4 ng/mL; P = 0.05). High S-endostatin levels were associated with advanced disease stage (P < 0.0001) and high serum VEGF levels at diagnosis (P = 0.017). The median 5-year survival rate for patients who had S-endostatin concentrations within the highest tertile (> 36.0 ng/mL) was only 34% compared with 57% in patients who had lower S-endostatin levels (P = 0.019). A high S-endostatin level also was associated with a poor outcome in patients with large cell diffuse and immunoblastic lymphoma, which was the largest subgroup within the series (n = 60 patients). Patients who had high pretreatment levels of both S-VEGF and S-endostatin had particularly poor outcomes. High S-endostatin levels had an independent, adverse influence on survival it was entered as a factor into a multivariate analysis together with the factors included in the International Prognostic Index (relative risk, 1.80; 95% confidence interval, 1.08-2.98; P = 0.0024).

CONCLUSIONS

High pretreatment levels of S-endostatin are associated with high serum VEGF levels and poor survival in patients with NHL. Prospective studies are warranted to establish the clinical value of longitudinal S-endostatin measurements.

Long-term expression of angiostatin suppresses metastatic liver cancer in mice

Metastatic liver cancer has a very poor prognosis and lacks effective therapy. Anti-angiogenic therapies, which starve tumors of blood supply, have proven to be effective in preclinical models because tumor growth is angiogenesis dependent. However, long-term, high-level, and sustained expression of angiogenesis inhibitors, such as angiostatin, is necessary to prevent dormant tumors from becoming active again. To achieve this objective, we engineered a recombinant adeno-associated virus (AAV) vector encoding mouse angiostatin, an endogenous inhibitor of tumor vascularization. After intraportal delivery of this vector, high-level, stable transgene expression of angiostatin lasting for at least 6 months was observed locally in hepatocytes. Gene transfer of AAV-angiostatin via the portal vein led to significant suppression of the growth of both nodular and metastatic EL-4 lymphoma tumors established in the liver and prolonged the survival time of the mice. The growth of neovessels was inhibited significantly, and extensive apoptosis of tumor cells was observed. The anti-angiogenic activity of angiostatin was independent of vascular endothelial growth factor (VEGF). The AAV-angiostatin viruses did not appear to be toxic to mice, and there was no detectable apoptosis of hepatocytes. In conclusion, these encouraging results warrant future investigation of the use of AAV-mediated anti-angiogenic gene therapy for targeting unresectable liver metastases, especially after surgical removal of primary tumors.

Basement membranes: structure, assembly and role in tumour angiogenesis

In recent years, the basement membrane (BM)--a specialized form of extracellular matrix (ECM)--has been recognized as an important regulator of cell behaviour, rather than just a structural feature of tissues. The BM mediates tissue compartmentalization and sends signals to epithelial cells about the external microenvironment. The BM is also an important structural and functional component of blood vessels, constituting an extracellular microenvironment sensor for endothelial cells and pericytes. Vascular BM components have recently been found to be involved in the regulation of tumour angiogenesis, making them attractive candidate targets for potential cancer therapies.

Immunohistochemical expression of angiogenesis-related markers in oral squamous cell carcinomas with multiple metastatic lymph nodes

The aim of this study was to evaluate the histopathologic features and the expression of angiogenesis-related markers in primary tumors and metastatic lymph nodes of oral squamous cell carcinomas (SCCs) with multiple lymph node involvement in comparison with oral SCCs without nodal metastasis. The protein levels of the angiogenesis inhibitor endostatin, as well as those of the related molecules collagen XVIII, collagen-binding protein (CBP) 2/heat shock protein (HSP) 47, and cathepsin L, were evaluated by immunohistochemical analysis. Compared with nonmetastatic cases, primary tumors of the metastatic group exhibited significantly decreased protein levels of endostatin and its precursor collagen XVIII. Comparison between primary tumors and positive nodes of the metastatic cases revealed decreased expression of collagen XVIII and CBP2/HSP47 in metastases. Angiogenesis is essential for tumor growth and metastasis; accordingly, the observed differences in the immunohistochemical expression of angiogenesis-related proteins in oral SCC with multiple lymph node involvement may provide an explanation for the increased metastatic potential of these tumors.

Serum levels of endostatin and matrix metalloproteinase-9 associated with high stage and grade primary transitional cell carcinoma of the bladder

OBJECTIVES

To analyze the preoperative serum levels of endostatin and matrix metalloproteinase-9 (MMP-9) in patients with primary transitional cell carcinoma of the bladder according to tumor stage and grade and to evaluate their clinical diagnostic application.

METHODS

Preoperative serum levels of endostatin and MMP-9 were determined in 52 patients with transitional cell carcinoma of the bladder (13 with superficial carcinoma and 39 with advanced carcinoma) and 32 healthy controls by enzyme-linked immunosorbent assay.

RESULTS

The serum levels of endostatin and MMP-9 were significantly greater in the 52 patients with bladder cancer than in the healthy controls (endostatin 46.8 ng/mL versus 30.6 ng/mL, P <0.001; MMP-9 786 ng/mL versus 417 ng/mL, P <0.001). The endostatin level correlated positively with the MMP-9 level (R = 0.55, P <0.01). Furthermore, the levels of endostatin and MMP-9 were associated with the tumor stage and grade. Patients with distant metastasis (n = 7) had significantly greater levels of endostatin and MMP-9 than patients without metastasis (n = 45) (endostatin 69.8 ng/mL versus 43.3 ng/mL, P <0.001; MMP-9 1529 ng/mL versus 674 ng/mL, P <0.001).

CONCLUSIONS

Elevated endostatin and MMP-9 levels are associated with a greater stage and grade of primary transitional cell carcinoma of the bladder.

Serum level of the circulating angiogenesis inhibitor endostatin in patients with hyperthyroidism or hypothyroidism

Serum level of endostatin, a natural angiogenesis inhibitor, was measured in 12 patients with hyperthyroidism and 9 patients with hypothyroidism. Control values were obtained from 12 healthy individuals. Hyperthyroidism was shown to be associated with an increased level of endostatin and hypothyroidism with a decreased endostatin level. There was no correlation of serum endostatin with thyroid hormone levels. Endostatin is a fragment of type XVIII collagen, and it is possible that reported changes are related to the effect of thyroid hormones on connective tissue metabolism.

Deficiency of the cysteine protease cathepsin S impairs microvessel growth

During angiogenesis, microvascular endothelial cells (ECs) secrete proteinases that permit penetration of the vascular basement membrane as well as the interstitial extracellular matrix. This study tested the hypothesis that cathepsin S (Cat S) contributes to angiogenesis. Treatment of cultured ECs with inflammatory cytokines or angiogenic factors stimulated the expression of Cat S, whereas inhibition of Cat S activity reduced microtubule formation by impairing cell invasion. ECs from Cat S-deficient mice showed reduced collagenolytic activity and impaired invasion of collagens type I and IV. Cat S-deficient mice displayed defective microvessel development during wound repair. This abnormal angiogenesis occurred despite normal vascular endothelial growth factor and basic fibroblast growth factor levels, implying an essential role for extracellular matrix degradation by Cat S during microvessel formation. These results demonstrate a novel function of endothelium-derived Cat S in angiogenesis.

Differential regulation of cathepsin S and cathepsin L in interferon gamma-treated macrophages

Cathepsin S (catS) and cathepsin L (catL) mediate late stages of invariant chain (Ii) degradation in discrete antigen-presenting cell types. Macrophages (Mphis) are unique in that they express both proteases and here we sought to determine the relative contribution of each enzyme. We observe that catL plays no significant role in Ii cleavage in interferon (IFN)-gamma-stimulated Mphis. In addition, our studies show that the level of catL activity is significantly decreased in Mphis cultured in the presence of IFN-gamma whereas catS activity increases. The decrease in catL activity upon cytokine treatment occurs despite the persistence of high levels of mature catL protein, suggesting that a specific inhibitor of the enzyme is up-regulated in IFN-gamma-stimulated peritoneal Mphis. Similar inhibition of activity is observed in dendritic cells engineered to overexpress catL. Such enzymatic inhibition in Mphis exhibits only partial dependence upon Ii and therefore, other mechanisms of catL inhibition are regulated by IFN-gamma. Thus, during a T helper cell type 1 immune response catL inhibition in Mphis results in preferential usage of catS, such that major histocompatibility complex class II presentation by all bone marrow-derived antigen-presenting cell is regulated by catS.

Expression of collagen XVIII and localization of its glycosaminoglycan attachment sites

Collagen XVIII is the only currently known collagen that carries heparan sulfate glycosaminoglycan side chains. The number and location of the glycosaminoglycan attachment sites in the core protein were determined by eukaryotic expression of full-length chick collagen XVIII and site-directed mutagenesis. Three Ser-Gly consensus sequences carrying glycosaminoglycan side chains were detected in the middle and N-terminal part of the core protein. One of the Ser-Gly consensus sequences carried a heparan sulfate side chain, and the remaining two had mixed chondroitin and heparan sulfate side chains; thus, recombinant collagen XVIII was a hybrid of heparan sulfate and chondroitin proteoglycan. In contrast, collagen XVIII from all chick tissues so far assayed have exclusively heparan sulfate side chains, indicating that the posttranslational modification of proteins expressed in vitro is not entirely identical to the processing that occurs in a living embryo. Incubating the various mutated collagen XVIIIs with retinal basement membranes showed that the heparan sulfate glycosaminoglycan side chains mediate the binding of collagen XVIII to basement membranes.

Phase I pharmacokinetic and pharmacodynamic study of recombinant human endostatin in patients with advanced solid tumors

PURPOSE

Endostatin is the first endogenous angiogenesis inhibitor to enter clinical trials. Laboratory investigations with endostatin have indicated broad antitumor activity coupled with remarkably low toxicity. A phase I trial of recombinant human endostatin was designed to evaluate toxicity and explore biologic effectiveness in patients with refractory solid tumors.

PATIENTS AND METHODS

Endostatin was administered as a 1-hour intravenous infusion given daily for a 28-day cycle. A starting dose of 30 mg/m2 was explored with subsequent dose escalations of 60, 100, 150, 225, and 300 mg/m2. Assessment of serum pharmacokinetics was performed on all 21 patients. Western blot assay and mass spectroscopy were employed to evaluate endostatin metabolism. Circulating levels of endogenous proangiogenic growth factors were examined. Tumor and tumor blood supply were imaged by dynamic computed tomography (CT), magnetic resonance imaging, ultrasound, and positron emission tomography.

RESULTS

Endostatin given on this schedule was essentially free of significant drug-related toxicity. Two transient episodes of grade 1 rash were observed. No clinical responses were observed. Endostatin pharmacokinetics were linear with dose, and serum concentrations were achieved that are associated with antitumor activity in preclinical models. No aggregate effect on circulating proangiogenic growth factors were seen, although several patients exhibited persistent declines in vascular endothelial growth factor levels while enrolled in the study. A few patients demonstrated changes in their dynamic CT scans suggestive of a decline in microvessel density, although overall, no consistent effect of endostatin on tumor vasculature was seen.

CONCLUSION

Endostatin given daily as a 1-hour intravenous infusion was well tolerated without dose-limiting toxicity at doses up to 300 mg/m2.

Branching out: a molecular fingerprint of endothelial differentiation into tube-like structures generated by Affymetrix oligonucleotide arrays

The process of endothelial differentiation into a network of tube-like structures with patent lumens requires an integrated program of gene expression. To identify genes upregulated in endothelial cells during the process of tube formation, RNA was prepared from several different time points (0, 4, 8, 24, 40, and 48 hours) and from three different experimental models of human endothelial tube formation: in collagen gels and fibrin gels driven by the combination of PMA (80), bFGF (40 ng/ml) and bFGF (40 ng/ml) or in collagen gels driven by the combination of HGF (40 ng/ml) and VEGF (40 ng/ml). Gene expression was evaluated using Affymetrix Gene Chip oligonucleotide arrays. Over 1000 common genes were upregulated greater than twofold over baseline at one or more time points in the three different models. In the present study, we discuss the identified genes that could be assigned to major functional classes: apoptosis, cytoskeleton, proteases, matrix, and matrix turnover, pumps and transporters, membrane lipid turnover, and junctional molecules or adhesion proteins.

Retrovirus-mediated gene transfer of human endostatin inhibits growth of human liver carcinoma cells SMMC7721 in nude mice

AIM: To study the effect of human endostatin mediated by retroviral gene transfer on the growth of human hepatocarcinoma cell line SMMC7721 in nude mice.

METHODS: Human endostatin gene together with rat serum albumin signal peptide was transferred into human liver carcinoma SMMC7721 cells by retroviral vector pLncx to build a stable transfectant (SMMC-endo). PCR and Western blot analysis were used to verify the transfection and secretion of human endostatin gene in SMMC7721 cells. The endothelial cell proliferation assay in vitro was conducted to test the biological activity of the expressed human endostatin. The inhibitory effect of endostatin expressed by transfected SMMC7721 on the growth rates of tumor cells in vivo was observed. The mean microvessel density in the specimen was also counted.

RESULTS: PCR amplification proved that the genome of SMMC-endo cells contained a 550 bp specific fragment of endostatin gene. Western blot analysis confirmed the secretion of human endostatin gene in the conditioned medium of transfected SMMC-endo cells. The endothelial proliferation assay showed that the conditioned medium of SMMC-endo cells significantly inhibited the proliferation of human umbilical vein endothelial cells by 48%, significantly higher than that of SMMC-pLncx (10.2%, P < 0.01). In vivo experiments revealed that only in 3 out of 5 mice tumors were formed and the mean size of flank tumors from SMMC-endo cells was 94.5% smaller than that from the control SMMC-pLncx cells 22 days after tumor inoculation (P < 0.001). The mean microvessel density in tumor samples from SMMC-endo cells was only 8.6 ± 1.1, much fewer than that of 22.6 ± 4.5 from SMMC-pLncx cells (P < 0.01).

CONCLUSION: Human endostatin mediated by retroviral gene transfer can inhibit human liver carcinoma cell SMMC7721 growth in nude mice.

Delivery of endostatin in experimental cancer therapy

Endostatin, the 20 kDa C-terminal fragment of collagen XVIII, has been shown to be an effective inhibitor of tumour angiogenesis and growth in different experimental systems and is currently in Phase II/III clinical trials. One challenging aspect of anti-angiogenic treatment is the mode of delivery of the active compound. In this paper we review some of the basic knowledge of endostatin and look specifically into the different possible ways in which endostatin may be administered.

New functional roles for non-collagenous domains of basement membrane collagens

Collagens IV, XV and XVIII are major components of various basement membranes. In addition to the collagen-specific triple helix, these collagens are characterized by the presence of several non-collagenous domains. It is clear now that these ubiquitous collagen molecules are involved in more subtle and sophisticated functions than just the molecular architecture of basement membranes, particularly in the context of extracellular matrix degradation. Degradation of the basement membrane collagens occurs during numerous physiological and pathological processes such as embryonic development or tumorigenesis and generates collagen fragments. These fragments are involved in the regulation of functions differing from those of their original intact molecules. The non-collagenous C-terminal fragment NC1 of collagen IV, XV and XVIII have been recently highlighted in the literature because of their potential in reducing angiogenesis and tumorigenesis, but it is clear that their biological functions are not limited to these processes. Proteolytic release of soluble NC1 fragments stimulates migration, proliferation, apoptosis or survival of different cell types and suppresses various morphogenetic events.

Invariant chain controls the activity of extracellular cathepsin L

Secretion of proteases is critical for degradation of the extracellular matrix during an inflammatory response. Cathepsin (Cat) S and L are the major elastinolytic cysteine proteases in mouse macrophages. A 65 amino acid segment of the p41 splice variant (p41(65aa)) of major histocompatibility complex class II-associated invariant chain (Ii) binds to the active site of CatL and permits the maintenance of a pool of mature enzyme in endosomal compartments of macro-phages and dendritic cells (DCs). Here we show that interaction of p41(65aa) with mature CatL allows extracellular accumulation of the active enzyme. We detected mature CatL as a complex with p41(65aa) in culture supernatants from antigen-presenting cells (APCs). Extracellular accumulation of mature CatL is up-regulated by inflammatory stimuli as observed in interferon (IFN)-gamma-treated macrophages and lipopolysaccharide (LPS)-activated DCs. Despite the neutral pH of the extracellular milieu, released CatL associated with p41(65aa) is catalytically active as demonstrated by active site labeling and elastin degradation assays. We propose that p41(65aa) stabilizes CatL in the extracellular environment and induces a local increase in the concentration of matrix-degrading enzymes during inflammation. Through its interaction with CatL, Ii may therefore control the migratory response of APCs and/or the recruitment of effectors of the inflammatory response.

The antitumoral effect of endostatin and angiostatin is associated with a down-regulation of vascular endothelial growth factor expression in tumor cells

Endostatin and angiostatin are known as tumor-derived angiogenesis inhibitors, but their mechanisms of action are not yet completely defined. We report here that endostatin and angiostatin, delivered by adenoviral vectors, reduced in vitro the neovessel formation in the mouse aortic ring assay by 85 and 40%, respectively. We also demonstrated in vivo that both endostatin and angiostatin inhibited local invasion and tumor vascularization of transplanted murine malignant keratinocytes, and reduced by 50 and 90% the development of highly vascularized murine mammary tumors. This inhibition of tumor growth was associated with a reduction of tumor vascularization. Expression analysis of vascular endothelial growth factor (VEGF) carried out in the mouse aortic ring model revealed a 3- to 10-fold down-regulation of VEGF mRNA expression in endostatin-treated rings. A similar down-regulation of VEGF expression at both mRNA and protein levels was also observed in the two in vivo cancer models after treatment with each angiogenesis inhibitor. This suggests that endostatin and angiostatin effects may be mediated, at least in part, by their ability to down-regulate VEGF expression within the tumor. This work provides evidence that endostatin and angiostatin act on tumor cells themselves.

Cysteine peptidases of mammals: their biological roles and potential effects in the oral cavity and other tissues in health and disease

Cysteine peptidases (CPs) are phylogenetically ubiquitous enzymes that can be classified into clans of evolutionarily independent proteins based on the structural organization of the active site. In mammals, two of the major clans represented in the genome are: the CA clan, whose members share a structure and evolutionary history with papain; and the CD clan, which includes the legumains and caspases. This review focuses on the properties of these enzymes, with an emphasis on their potential roles in the oral cavity. The human genome encodes at least (but possibly no more than) 11 distinct enzymes, called cathepsins, that are members of the papain family C1A. Ten of these are present in rodents, which also carry additional genes encoding other cathepsins and cathepsin-like proteins. Human cathepsins are best known from the ubiquitously expressed lysosomal cathepsins B, H, and L, and dipeptidyl peptidase I (DPP I), which until recently were considered to mediate primarily "housekeeping" functions in the cell. However, mutations in DPP I have now been shown to underlie Papillon-Lefevre syndrome and pre-pubertal periodontitis. Other cathepsins are involved in tissue-specific functions such as bone remodeling, but relatively little is known about the functions of several recently discovered enzymes. Collectively, CPs participate in multiple host systems that are active in health and in disease. They are involved in tissue remodeling and turnover of the extracellular matrix, immune system function, and modulation and alteration of cell function. Intracellularly, CPs function in diverse processes including normal protein turnover, antigen and proprotein processing, and apoptosis. Extracellularly, they can contribute directly to the degradation of foreign proteins and the extracellular matrix. However, CPs can also participate in proteolytic cascades that amplify the degradative capacity, potentially leading to pathological damage, and facilitating the penetration of tissues by cancer cells. We know relatively little regarding the role of human CPs in the oral cavity in health or disease. Most studies to date have focused on the potential use of the lysosomal enzymes as markers for periodontal disease activity. Human saliva contains high levels of cystatins, which are potent CP inhibitors. Although these proteins are presumed to serve a protective function, their in vivo targets are unknown, and it remains to be discovered whether they serve to control any human CP activity.

Prospective analysis of circulating endostatin levels in patients with renal cell carcinoma

BACKGROUND

The aim of the current study was to assess circulating levels of endogenous endostatin in patients with renal carcinoma and to determine the relationship of these levels to circulating levels of vascular endothelial growth factor (VEGF) and prognosis.

METHODS

The authors prospectively studied 66 patients (48 male, 18 female; mean age, 50 years) undergoing nephrectomy for renal carcinoma on clinical trials at the National Cancer Institute. Metastases were present in 51 of 66 patients (77%) at the time of nephrectomy. Preoperative and followup serum endostatin and VEGF levels were determined using competitive enzyme immunoassays and compared to a group of 32 age- and gender-matched healthy controls. Associations between circulating endostatin levels and clinicopathologic variables, including survival, were determined.

RESULTS

Preoperative endostatin levels were higher in renal carcinoma patients than in healthy controls (P = 0.05). There was a weak to moderate correlation between pretreatment serum endostatin levels and serum VEGF levels (r = 0.47; P = 0.001), and levels of both proteins increased significantly following nephrectomy (P < 0.0001 and P < 0.0001, respectively; n = 41). In addition, patients whose endostatin levels increased more than twofold after nephrectomy had significantly poorer prognoses than patients without such an increase (P = 0.018). This association was more pronounced when patients without metastases were excluded (P = 0.0037).

CONCLUSIONS

Circulating endostatin levels are elevated in patients with renal carcinoma and correlate with circulating VEGF levels. Endostatin levels increase after nephrectomy, and patients with the greatest increases experience shortened survival times. These findings suggest an association between tumor aggressiveness and the production of endogenous endostatin in patients with renal carcinoma.

Clinical translation of angiogenesis inhibitors

Angiogenesis inhibitors are a new class of drugs, for which the general rules involving conventional chemotherapy might not apply. The successful translation of angiogenesis inhibitors to clinical application depends partly on the transfer of expertise from scientists who are familiar with the biology of angiogenesis to clinicians. What are the most common questions that clinicians ask as they begin to test angiogenesis inhibitors in cancer clinical trials?

Selective modulation of the secretion of proteinases and their inhibitors by growth factors in cultured differentiated podocytes

Selective modulation of the secretion of proteinases and their inhibitors by growth factors in cultured differentiated podocytes.

BACKGROUND

Podocyte damage is considered to be an important factor in the development of glomerulosclerosis. Morphological studies on experimental models of progressive glomerular disease have identified the detachment of podocytes from the glomerular basement membrane (GBM) as a critical step in the development and progression of glomerulosclerosis. Degradation of the GBM by proteinases also might be a potential mechanism of the detachment because the process impairs the connection between podocytes and the GBM. The present study examined the effects of basic fibroblast growth factor (bFGF), transforming growth factor-beta1 (TGF-beta1) and platelet-derived growth factor (PDGF) on the secretion of proteinases [cathepsin L and matrix metalloproteinases (MMPs)] and their inhibitors [cystatin C and tissue inhibitor of metalloproteinase-2 (TIMP-2)] from differentiated podocytes in culture.

METHODS

Expression of mRNAs for receptors of growth factors (bFGF, PDGF, TGF-beta1), the proteinases and their inhibitors in differentiated podocytes were shown by RT-PCR. The secretion of cathepsin L, cystatin C and TIMP-2 from differentiated podocytes were shown by immunoblot analysis. The activities of MMPs-2 and -9 from differentiated podocytes were shown by gelatin zymography.

RESULTS

Expression of mRNAs for receptors of the growth factors, the proteinases and their inhibitors were confirmed. bFGF increased the secretion of cathepsin L (5.04-fold at 20 ng/mL), but did not alter the secretion of its extracellular inhibitor, cystatin C. In contrast, TGF-beta1 increased the activities of MMPs-2 and -9 (3.23-fold at 10 ng/mL and 25.3-fold at 10 ng/mL, respectively) from differentiated podocytes, but did not enhance the secretion of its inhibitor, TIMP-2. In addition, bFGF enhanced the secretion of TIMP-2 (2.75-fold at 20 ng/mL) and TGF-beta1 enhanced the secretion of cystatin C (2.32-fold at 20 ng/mL). These results demonstrate the imbalance of the secretion of proteinases and their inhibitors after incubation of such growth factors. Of particular interest was the observation of differences in regulation of proteinases and their extracellular inhibitors in response to bFGF and TGF-beta1. PDGF only slightly increased the secretion of cathepsin L (2.54-fold at 20 ng/mL) but exerted no effect on the secretion of cystatin C, MMPs, and TIMP-2 from differentiated podocytes.

CONCLUSION

These results indicate, to our knowledge for the first time, that in differentiated podocytes, both cathepsin L and its inhibitor are independently regulated by different growth factors. It appears that increases in proteolytic activities may induce degradation of the glomerular basement membrane (GBM), which plays an important role in the progression of glomerulosclerosis.

Proteinases of the bone morphogenetic protein-1 family convert procollagen VII to mature anchoring fibril collagen

Collagen VII is the major structural component of the anchoring fibrils at the dermal-epidermal junction in the skin. It is secreted by keratinocytes as a precursor, procollagen VII, and processed into mature collagen during polymerization of the anchoring fibrils. We show that bone morphogenetic protein-1 (BMP-1), which exhibits procollagen C-proteinase activity, cleaves the C-terminal propeptide from human procollagen VII. The cleavage occurs at the BMP-1 consensus cleavage site SYAA/DTAG within the NC-2 domain. Mammalian tolloid-like (mTLL)-1 and -2, two other proteases of the astacin enzyme family, were able to process procollagen VII at the same site in vitro. Immunohistochemical and genetic evidence supported the involvement of these enzymes in cleaving type VII procollagen in vivo. Both BMP-1 and mTLL-1 are expressed in the skin and in cultured cutaneous cells. A naturally occurring deletion in the human COL7A1 gene, 8523del14, which is associated with dystrophic epidermolysis bullosa and eliminates the BMP-1 consensus sequence, abolished processing of procollagen VII, and in mutant skin procollagen VII accumulated at the dermal-epidermal junction. On the other hand, deficiency of BMP-1 in the skin of knockout mouse embryos did not prevent processing of procollagen VII to mature collagen, suggesting that mTLL-1 and/or mTLL-2 can substitute for BMP-1 in the processing of procollagen VII in situ.