Matriptase and HAI-1 are expressed by normal and malignant epithelial cells in vitro and in vivo

Platelet-derived growth factor-C (PDGF-C) activation by serine proteases: implications for breast cancer progression

The PDGF (platelet-derived growth factor) family members are potent mitogens for cells of mesenchymal origin and serve as important regulators of cell migration, survival, apoptosis and transformation. Tumour-derived PDGF ligands are thought to function in both autocrine and paracrine manners, activating receptors on tumour and surrounding stromal cells. PDGF-C and -D are secreted as latent dimers, unlike PDGF-A and -B. Cleavage of the CUB domain from the PDGF-C and -D dimers is required for their biological activity. At present, little is known about the proteolytic processing of PDGF-C, the rate-limiting step in the regulation of PDGF-C activity. In the present study we show that the breast carcinoma cell line MCF7, engineered to overexpress PDGF-C, produces proteases capable of cleaving PDGF-C to its active form. Increased PDGF-C expression enhances cell proliferation, anchorage-independent cell growth and tumour cell motility by autocrine signalling. In addition, MCF7-produced PDGF-C induces fibroblast cell migration in a paracrine manner. Interestingly, PDGF-C enhances tumour cell invasion in the presence of fibroblasts, suggesting a role for tumour-derived PDGF-C in tumour-stromal interactions. In the present study, we identify tPA (tissue plasminogen activator) and matriptase as major proteases for processing of PDGF-C in MCF7 cells. In in vitro studies, we also show that uPA (urokinase-type plasminogen activator) is able to process PDGF-C. Furthermore, by site-directed mutagenesis, we identify the cleavage site for these proteases in PDGF-C. Lastly, we provide evidence suggesting a two-step proteolytic processing of PDGF-C involving creation of a hemidimer, followed by GFD-D (growth factor domain dimer) generation.

Cleavage of hepatocyte growth factor activator inhibitor-1 by membrane-type MMP-1 activates matriptase

Co-expression of membrane-type 1 (MT1)-MMP with hepatocyte growth factor activator inhibitor-1 (HAI-1) in HEK293T cells resulted in cleavage of HAI-1 to produce three fragments. Recombinant MT1-MMP was shown to cleave HAI-1 protein in vitro. Hepatocyte growth factor activator inhibitor-1 was initially identified as the cognate inhibitor of matriptase, a transmembrane serine protease that processes urokinase-type plasminogen activator (uPA). Co-expression of HAI-1 with matriptase suppressed matriptase protease activity, and co-expression of MT1-MMP with them resulted in recovery of matriptase activity by stimulating shedding of HAI-1 fragments. Matriptase protein was detected in squamous carcinoma-derived HSC-4 cells, however, matriptase protease activity was undetectable. Transfection of siRNA for HAI-1 enhanced serine protease activity, which was suppressed by cotransfection of matriptase siRNA. Collagen-gel culture or treatment with concanavalin A (ConA) of HSC-4 cells enhanced MT1-MMP activity, which induced shedding of HAI-1 fragments and conversely stimulated uPA activation by these cells. Serine protease activity, including uPA activation of cells treated with ConA, was abrogated by downregulation of either matriptase or MT1-MMP through the transfection of each siRNA. These results suggest that MT1-MMP induced by collagen-gel culture or ConA treatment causes cleavage and shedding of HAI-1 protein, which allows activation of matriptase in HSC-4 cells. HSC-4 cells showed a characteristic invasive growth by forming vacuole-like structures in collagen gel, which was suppressed by transfection of siRNA for either MT1-MMP or matriptase, suggesting that activation of matriptase through the cleavage of HAI-1 is one of the MT1-MMP multifunctions essential for invasive growth of HSC-4 cells.

Mechanisms for the control of matriptase activity in the absence of sufficient HAI-1

Matriptase proteolytic activity must be tightly controlled for normal placental development, epidermal function, and epithelial integrity. Although hepatocyte growth factor activator inhibitor-1 (HAI-1) represents the predominant endogenous inhibitor for matriptase and the protein molar ratio of HAI-1 to matriptase is determined to be >10 in epithelial cells and the majority of carcinoma cells, an inverse HAI-1-to-matriptase ratio is seen in some ovarian and hematopoietic cancer cells. In the current study, cells with insufficient HAI-1 are investigated for the mechanisms through which the activity of matriptase is regulated. When matriptase activation is robustly induced in these cells, activated matriptase rapidly forms two complexes of 100- and 140-kDa in addition to the canonical 120-kDa matriptase-HAI-1 complex already described. Both 100- and 140-kDa complexes contain two-chain, cleaved matriptase but are devoid of gelatinolytic activity. Further biochemical characterization shows that the 140-kDa complex is a matriptase homodimer and that the 100-kDa complexes appear to contain reversible, tight binding serine protease inhibitor(s). The formation of the 140-kDa matriptase dimer is strongly associated with matriptase activation, and its levels are inversely correlated with the ratio of HAI-1 to matriptase. Given these observations and the likelihood that autoactivation requires the interaction of two matriptase molecules, it seems plausible that this activated matriptase homodimer may represent a matriptase autoactivation intermediate and that its accumulation may serve as a mechanism to control matriptase activity when protease inhibitor levels are limiting. These data suggest that matriptase activity can be rapidly inhibited by HAI-1 and other HAI-1-like protease inhibitors and "locked" in an inactive autoactivation intermediate, all of which places matriptase under very tight control.

Membrane-anchored serine proteases in health and disease

Serine proteases of the trypsin-like family have long been recognized to be critical effectors of biological processes as diverse as digestion, blood coagulation, fibrinolysis, and immunity. In recent years, a subgroup of these enzymes has been identified that are anchored directly to plasma membranes, either by a carboxy-terminal transmembrane domain (Type I), an amino-terminal transmembrane domain with a cytoplasmic extension (Type II or TTSP), or through a glycosylphosphatidylinositol (GPI) linkage. Recent biochemical, cellular, and in vivo analyses have now established that membrane-anchored serine proteases are key pericellular contributors to processes vital for development and the maintenance of homeostasis. This chapter reviews our current knowledge of the biological and physiological functions of these proteases, their molecular substrates, and their contributions to disease.

Endogenous expression of matriptase in neural progenitor cells promotes cell migration and neuron differentiation

Recent studies show that type II transmembrane serine proteases play important roles in diverse cellular activities and pathological processes. Their expression and functions in the central nervous system, however, are largely unexplored. In this study, we show that the expression of one such member, matriptase (MTP), was cell type-restricted and primarily expressed in neural progenitor (NP) cells and neurons. Blocking MTP expression or MTP activity prevented NP cell traverse of reconstituted basement membrane, whereas overexpression of MTP promoted it. The NP cell mobilization induced by either vascular endothelial growth factor or hepatocyte growth factor was also impaired by knocking down MTP expression. MTP acts upstream of matrix metalloproteinase 2 in promoting NP cell mobility. In embryonic stem cell differentiation to neural cells, MTP knockdown had no effect on entry of embryonic stem cells into the neural lineage. High MTP expression or activity, however, shifts the population dynamics from NP cells toward neurons to favor neuronal differentiation. This is the first report to demonstrate the direct involvement of type II transmembrane serine protease in NP cell function.

Epithin/PRSS14 proteolytically regulates angiopoietin receptor Tie2 during transendothelial migration

Epithin/PRSS14, a type II transmembrane serine protease, is involved in normal epithelial development and tumor progression. Here we report, as an interacting substrate of epithin, a receptor tyrosine kinase Tie2 that is well known for important roles in the vessel stability. Epithin interacts with and degrades the Tie2 extracellular portion that contains the ligand-binding domain. Epithin is located in the neighbor of Tie2-expressing vessels in normal tissue. Furthermore, epithin can cleave and degrade Tie2 not only in the same cell but also from neighboring cells nearby, resulting in the degradation of the Tie2 ectodomain. The remaining Tie2 fragment was highly phosphorylated and was able to recruit a downstream effector, phosphatidylinositol 3-kinase. Knocking down epithin expression using short hairpin RNA in thymoma cell severely impaired the migration through endothelial cells that show the actin rearrangement during the process. The diminution of epithin protein expression in 4T1 breast cancer cells caused the significant decrease in the number of transendothelial migrating cells in vitro as well as in those of metastasizing tumor nodules in vivo, Therefore, we propose that epithin, which regulates endothelial Tie2 functions, plays a critical role in the fine tuning of transendothelial migration for normal and cancer cells.

Matriptase is involved in ErbB-2-induced prostate cancer cell invasion

Deregulation of both ErbB-2 signaling and matriptase activity has been associated with human prostate cancer (PCa) progression. In this communication, we investigated the roles of both ErbB-2 signaling in matriptase zymogen activation and matriptase in ErbB-2-induced PCa malignancy. In a human PCa cell progression model, we observed that advanced PCa C-81 LNCaP cells exhibited an aggressive phenotype with increased cell migration and invasion capacity; these cells concurrently showed both enhanced ErbB-2 phosphorylation and increased matriptase zymogen activation compared with parental C-33 LNCaP cells. Moreover, ErbB2 activation, both ligand-dependent (eg, epidermal growth factor treatment) and ligand-independent (eg, overexpression), was able to induce matriptase zymogen activation in this cell line. Inhibition of ErbB-2 activity by either the specific inhibitor, AG825, in epidermal growth factor-treated C-33 LNCaP cells or ErbB-2 knockdown in C-81 LNCaP cells, reduced matriptase activation. These observations were confirmed by similar studies using both DU145 and PC3 cells. Together, these data suggest that ErbB-2 signaling plays an important role in matriptase zymogen activation. ErbB-2-enhanced matriptase activation was suppressed by a phosphatidylinositol 3-kinase inhibitor (ie, LY294002) but not by a MEK inhibitor (ie, PD98059). Suppression of matriptase expression by small hairpin RNA knockdown in ErbB-2-overexpressing LNCaP cells dramatically suppressed cancer cell invasion. In summary, our data indicate that ErbB-2 signaling via the phosphatidylinositol 3-kinase pathway results in up-regulated matriptase zymogen activity, which contributes to PCa cell invasion.

Time-domain in vivo near infrared fluorescence imaging for evaluation of matriptase as a potential target for the development of novel, inhibitor-based tumor therapies

Proteolytic enzymes expressed on the surface of tumor cells, and thus easily accessible to external interventions, represent useful targets for anticancer and antimetastatic therapies. In our study, we thoroughly evaluated matriptase, a trypsin-like transmembrane serine protease, as potential target for novel inhibitor-based tumor therapies. We applied time-domain near infrared fluorescence (NIRF) imaging to characterize expression and activity of matriptase in vivo in an orthotopic AsPC-1 pancreatic tumor model in nude mice. We show strong and tumor-specific binding of intravenously injected Cy5.5 labeled antimatriptase antibody (MT-Ab*Cy5.5) only to primary AsPC-1 tumors and their metastases over time within living mice, taking into account fluorescence intensities and fluorescence lifetimes of the applied probes. Specific binding of MT-Ab*Cy5.5 to tumor sites was confirmed by ex vivo NIRF imaging of tumor tissue, NIRF microscopy and by coregistration of the in vivo acquired NIRF intensity maps to anatomical structures visualized by flat-panel volume computed tomography (fpVCT) in living mice. Moreover, using an activatable synthetic substrate S*DY-681 we could clearly demonstrate that matriptase is proteolytically active in vitro as well as in vivo in tumor-bearing mice, and that application of synthetic active-site inhibitors having high affinity and selectivity toward matriptase can efficiently inhibit its proteolytic activity for at least 24 hr. We thus successfully applied NIRF imaging in combination with fpVCT to characterize matriptase as a promising molecular target for inhibitor-based cancer therapies.

ST14 gene variant and decreased matriptase protein expression predict poor breast cancer survival

BACKGROUND

Matriptase plays a role in carcinogenesis, but the role of its genetic variation or that of the hepatocyte growth factor activator inhibitor-1 (HAI-1) has not been evaluated. This study aimed to examine the genetic variation of matriptase (ST14 gene) and HAI-1 (SPINT1 gene) in breast cancer risk and prognosis, to assess matriptase and HAI-1 gene and protein expression in breast tumors, and to identify their clinicopathologic correlations and prognostic significance.

METHODS

Five single nucleotide polymorphisms in ST14 and three in SPINT1 were genotyped in 470 invasive breast cancer cases and 446 healthy controls. Gene expression analysis was done for 40 breast cancer samples. Protein expression was assessed by immunohistochemical analyses in 377 invasive breast tumors. The statistical significance of the associations among genotypes, clinicopathologic variables, and prognosis was assessed.

RESULTS

The ST14 single nucleotide polymorphism rs704624 independently predicted breast cancer survival, a poor outcome associated with the minor allele (P = 0.001; risk ratio, 2.221; 95% confidence interval, 1.382-3.568). Moreover, ST14 gene expression levels were lower among the minor allele carriers (P = 0.009), and negative/low matriptase protein expression was independently predictive of poorer survival (P = 0.046; risk ratio, 1.554; 95% confidence interval, 1.008-2.396).

CONCLUSIONS

The ST14 variant rs704624 and protein expression of matriptase have prognostic significance in breast cancer. This study adds to the evidence for the role of matriptase in breast cancer and has found new evidence for the genotypes having an impact in breast cancer.

IMPACT

This is the first study showing that genetic variation in matriptase has clinical importance. The results encourage further study on the genetic variation affecting protein levels and function in type II transmembrane serine proteases.

Matriptase activation, an early cellular response to acidosis

Extracellular acidosis often rapidly causes intracellular acidification, alters ion channel activities, and activates G protein-coupled receptors. In this report, we demonstrated a novel cellular response to acidosis: induction of the zymogen activation of matriptase. Acid-induced matriptase activation is ubiquitous among epithelial and carcinoma cells and is characterized by rapid onset, fast kinetics, and the magnitude of activation seen. Trace amounts of activated matriptase can be detected 1 min after cells are exposed to pH 6.0 buffer, and the vast majority of latent matriptase within the cells is converted to activated matriptase within 20 min. Matriptase activation may be a direct response to proton exposure because acid-induced matriptase activation also occurs in an in vitro, cell-free setting in which intracellular signaling molecules and ion channel activities are largely absent. Acid-induced matriptase activation takes place both on the cell surface and inside the cells, likely due to the parallel intracellular acidification that activates intracellular matriptase. Following matriptase activation, the active enzyme is immediately inhibited by binding to hepatocyte growth factor activator inhibitor 1, resulting in stable matriptase-hepatocyte growth factor activator inhibitor 1 complexes that are rapidly secreted. As an early response to acidosis, matriptase activation can also be induced by perturbation of intracellular pH homeostasis by 5-(N-methyl-N-isobutyl)-amiloride and 5-(N-ethyl-N-isopropyl)-amiloride, both of which inhibit Na(+)/H(+) exchangers, and diisothiocyanostilbene-2,2'-disulfonic acid, which can inhibit other acid-base ion channels. This study uncovers a novel mechanism regulating proteolysis in epithelial and carcinoma cells, and also demonstrates that a likely function of matriptase is as an early response to acidosis.

Tissue injury alters the site of expression of hepatocyte growth factor activator inhibitor type 1 in bronchial epithelial cells

Hepatocyte growth factor activator inhibitor-1 (HAI-1) is a Kunitz-type transmembrane serine proteinase inhibitor that inhibits trypsin-like serine proteinases, such as hepatocyte growth factor activator, matriptase, hepsin and prostasin. HAI-1 is expressed in polarized epithelial cells, in which HAI-1 is mainly located on the basolateral membrane. In the present study, we analyzed the expression and distribution of HAI-1 in respiratory epithelium. We found that HAI-1 is expressed by the bronchial respiratory epithelium with basal or basolateral localization and also by the alveolar epithelium. Bronchial expression of HAI-1 was also confirmed using cultured human bronchial epithelial cells. The epithelial expression of HAI-1 was augmented in response to tissue injury such as cancer invasion and inflammation. Surprisingly, in the injured pulmonary tissue, HAI-1 showed distinct apical translocation in ciliated epithelial cells of the bronchiole. We suggest that, in addition to its basolateral surface localization, HAI-1 can transiently localize to the apical surface of respiratory ciliated epithelial cells under conditions of severe inflammation, possibly interacting with a specific cellular proteinase on the apical surface.

Expression of prostasin and its inhibitors during colorectal cancer carcinogenesis

Background

Clinical trials where cancer patients were treated with protease inhibitors have suggested that the serine protease, prostasin, may act as a tumour suppressor. Prostasin is proteolytically activated by the serine protease, matriptase, which has a very high oncogenic potential. Prostasin is inhibited by protease nexin-1 (PN-1) and the two isoforms encoded by the mRNA splice variants of hepatocyte growth factor activator inhibitor-1 (HAI-1), HAI-1A, and HAI-1B.

Methods

Using quantitative RT-PCR, we have determined the mRNA levels for prostasin and PN-1 in colorectal cancer tissue (n = 116), severe dysplasia (n = 13), mild/moderate dysplasia (n = 93), and in normal tissue from the same individuals. In addition, corresponding tissues were examined from healthy volunteers (n = 23). A part of the cohort was further analysed for the mRNA levels of the two variants of HAI-1, here denoted HAI-1A and HAI-1B. mRNA levels were normalised to β-actin. Immunohistochemical analysis of prostasin and HAI-1 was performed on normal and cancer tissue.

Results

The mRNA level of prostasin was slightly but significantly decreased in both mild/moderate dysplasia (p < 0.001) and severe dysplasia (p < 0.01) and in carcinomas (p < 0.05) compared to normal tissue from the same individual. The mRNA level of PN-1 was more that two-fold elevated in colorectal cancer tissue as compared to healthy individuals (p < 0.001) and elevated in both mild/moderate dysplasia (p < 0.01), severe dysplasia (p < 0.05) and in colorectal cancer tissue (p < 0.001) as compared to normal tissue from the same individual. The mRNA levels of HAI-1A and HAI-1B mRNAs showed the same patterns of expression. Immunohistochemistry showed that prostasin is located mainly on the apical plasma membrane in normal colorectal tissue. A large variation was found in the degree of polarization of prostasin in colorectal cancer tissue.

Conclusion

These results show that the mRNA level of PN-1 is significantly elevated in colorectal cancer tissue. Future studies are required to clarify whether down-regulation of prostasin activity via up regulation of PN-1 is causing the malignant progression or if it is a consequence of it.

Polarized epithelial cells secrete matriptase as a consequence of zymogen activation and HAI-1-mediated inhibition

Matriptase, a transmembrane serine protease, is broadly expressed by, and crucial for the integrity of, the epithelium. Matriptase is synthesized as a zymogen and undergoes autoactivation to become an active protease that is immediately inhibited by, and forms complexes with, hepatocyte growth factor activator inhibitor (HAI-1). To investigate where matriptase is activated and how it is secreted in vivo, we determined the expression and activation status of matriptase in seminal fluid and urine and the distribution and subcellular localization of the protease in the prostate and kidney. The in vivo studies revealed that while the latent matriptase is localized at the basolateral surface of the ductal epithelial cells of both organs, only matriptase-HAI-1 complexes and not latent matriptase are detected in the body fluids, suggesting that activation, inhibition, and transcytosis of matriptase would have to occur for the secretion of matriptase. These complicated processes involved in the in vivo secretion were also observed in polarized Caco-2 intestinal epithelial cells. The cells target latent matriptase to the basolateral plasma membrane where activation, inhibition, and secretion of matriptase appear to take place. However, a proportion of matriptase-HAI-1 complexes, but not the latent matriptase, appears to undergo transcytosis to the apical plasma membrane for secretion. When epithelial cells lose their polarity, they secrete both latent and activated matriptase. Although most epithelial cells retain very low levels of matriptase-HAI-1 complex by rapidly secreting the complex, gastric chief cells may activate matriptase and store matriptase-HAI-1 complexes in the pepsinogen-secretory granules, suggesting an intracellular activation and regulated secretion in these cells. Taken together, while zymogen activation and closely coupled HAI-1-mediated inhibition are common features for matriptase regulation, the cellular location of matriptase activation and inhibition, and the secretory route for matriptase-HAI-1 complex may vary along with the functional divergence of different epithelial cells.

Loss of matriptase suppression underlies spint1 mutation-associated ichthyosis and postnatal lethality

Hepatocyte growth factor activator inhibitor-1 (HAI)-1 is an epithelial Kunitz-type transmembrane serine protease inhibitor that is encoded by the SPINT1 gene. HAI-1 displays potent inhibitory activity toward a large number of trypsin-like serine proteases. HAI-1 was recently shown to play an essential role in postnatal epithelial homeostasis. Thus, Spint1-deficient mice were found to display severe growth retardation and are unable to survive beyond postnatal day 16. The mice present histologically with overt hyperkeratosis of the forestomach, hyperkeratosis and acanthosis of the epidermis, and hypotrichosis associated with abnormal cuticle development. In this study, we show that loss of inhibition of a proteolytic pathway that is dependent on the type II transmembrane serine protease, matriptase, underlies the detrimental effects of postnatal Spint1 deficiency. Matriptase and HAI-1 precisely co-localize in all tissues that are affected by the Spint1 disruption. Spint1-deficient mice that have low matriptase levels, caused by a hypomorphic mutation in the St14 gene that encodes matriptase, not only survived the neonatal period but were healthy and displayed normal long-term survival. Furthermore, a detailed histological analysis of neonatal, young adult, as well as aged mice did not reveal any abnormalities in Spint1-deficent mice that have low matriptase levels. This study identifies matriptase suppression as an essential function of HAI-1 in postnatal tissue homeostasis.

Serum active hepatocyte growth factor (AHGF) in benign prostatic disease and prostate cancer

BACKGROUND

Hepatocyte growth factor (HGF) is secreted as an inactive single-chain precursor called pro-HGF. Pro-HGF is converted to an active two-chain form by HGF activator and matriptase. We attempted to clarify whether serum levels of active HGF (AHGF) could be used as a marker of prostate cancer.

METHODS

Serum levels of AHGF and total HGF (THGF; pro-HGF + AHGF) were measured by enzyme-linked immunosorbent assay in 38 patients with benign prostatic disease and 160 patients with prostate cancer.

RESULTS

Serum levels of AHGF in patients with untreated prostate cancer (0.37 +/- 0.12 ng/ml) were significantly higher than those in patients with benign prostatic disease (0.28 +/- 0.08 ng/ml) (P = 0.0001). Serum AHGF levels were increased in patients with stage D or D3 compared with stage B. In addition, there were significant differences in serum AHGF levels between patients with well-differentiated and poorly differentiated adenocarcinoma. Furthermore, the mean serum AHGF/THGF ratio in patients with stage D3 prostate cancer was significantly higher than that in patients with stage B.

CONCLUSIONS

AHGF may be a potential tumor marker for prostate cancer. Further studies in large groups of patients are needed to define the clinical value of AHGF.

Role of matriptase and proteinase-activated receptor-2 in nonmelanoma skin cancer

Matriptase (membrane-type serine proteinase) was reported to play a role in nonmelanoma skin cancer progression. Moreover, it was shown to stimulate proteinase-activated receptor-2 (PAR(2)) in vitro. Hepatocyte growth factor activator inhibitor-1 (HAI-1), the matriptase inhibitor, is an important regulator of enzyme activity. Therefore, the aim of this study was to elucidate the putative role of matriptase, HAI-1, and PAR(2) in normal human skin, as well as in basal cell carcinomas (BCCs) and squamous cell carcinomas (SCCs). In normal human epidermis, PAR(2) colocalized with matriptase and HAI-1. Immunoreactivity of all proteins was found to be diminished in BCCs. Likewise, PAR(2) immunoreactivity was significantly decreased, whereas matriptase immunoreactivity was enhanced with SCC progression. We could also show that matriptase was complexed to HAI-1 in normal human skin, whereas in SCCs, the enzyme was present in an unassociated form. Both a specific peptide agonist for PAR(2) and the proteinase domain of matriptase were able to induce intracellular calcium mobilization and inhibition of proliferation in cultured HaCaT keratinocytes. In conclusion, our results suggest that PAR(2) is a substrate for matriptase in human skin in vivo. Deregulation of these proteins delineates SCC progression.

Protein expression of matriptase and its cognate inhibitor HAI-1 in human prostate cancer: a tissue microarray and automated quantitative analysis

Recent studies have suggested that matriptase, a transmembrane serine protease and its cognate inhibitor hepatocyte growth factor activator inhibitor-1 (HAI-1) are important in the progression of many cancers. Limited quantitative data are available on these proteins in prostate cancer. To validate the roles of matriptase and HAI-1 in prostate cancer and its progression, a prostate cancer tissue microarray was constructed. The tissue microarray includes 41 localized prostate cancers (Pca_local), 18 aggressive prostate cancers, 18 metastatic prostate cancers, 24 benign prostate hyperplasias, 18 high-grade intraepithelial neoplasias (HGPIN), and 41 benign prostate tissues. The cellular expression levels of matriptase and HAI-1 were quantified using automated quantitative analysis. We found that matriptase expression levels were significantly higher in Pca_local (P<0.0001) and HGPIN (P<0.05) compared with benign prostate tissue. Matriptase levels were significantly decreased in metastatic cancer when compared with all other tissue types (P<0.05). Compared with benign prostate tissue, HAI-1 expression levels were significantly higher in all proliferative prostate diseases (benign prostate hyperplasia, HGPIN, localized and aggressive cancers, and metastases) (P<0.001); yet, no significant differences were found in HAI-1 expression levels among the diseased tissue types. These results suggest that an increase of matriptase may be useful as a marker for detection of Pca_local, whereas a decrease of matriptase expression may signal prostate cancer progression. HAI-1 seems to be a marker of prostate epithelial cell proliferation.

Comparative transcriptional analysis of embryoid body versus two-dimensional differentiation of murine embryonic stem cells

Understanding the process of ex vivo embryonic stem (ES) cell differentiation is important for generating higher yields of desirable cell types or lineages and for understanding fundamental aspects of ES differentiation. We used DNA microarray analysis to investigate the differentiation of mouse ES cells cultured under three differentiation conditions. Embryoid body (EB) formation was compared to differentiation on surfaces coated with either gelatin (GEL) or matrigel (MAT). Based on the transcriptional patterns of a list of literature-based "stemness" genes, ES cell differentiation on the two coated surfaces appeared similar but not identical to EB differentiation. A notable difference was the GEL and MAT upregulation but EB downregulation of nine such stemness genes, which are related to cell adhesion and epithelial differentiation. Further, GEL and MAT differentiation showed higher expression of bone formation-related genes (Spp1, Csf1, Gsn, Bmp8b, Crlf1). Gene ontology analysis shows an increase in the expression of genes related to migration and cell structure in all three conditions. Overall, GEL and MAT conditions resulted in a more similar to each other transcriptional profile than to the EB condition, and such differences are apparently related to higher nutrient and metabolite gradients and limitations in the EB versus the GEL or MAT cultures.

Defect of hepatocyte growth factor activator inhibitor type 1/serine protease inhibitor, Kunitz type 1 (Hai-1/Spint1) leads to ichthyosis-like condition and abnormal hair development in mice

Hepatocyte growth factor activator inhibitor type 1 (HAI-1)/serine protease inhibitor, Kunitz type 1 (SPINT1) is a membrane-bound, serine proteinase inhibitor initially identified as an inhibitor of hepatocyte growth factor activator. It also inhibits matriptase and prostasin, both of which are membrane-bound serine proteinases that have critical roles in epidermal differentiation and function. In this study, skin and hair phenotypes of mice lacking the Hai-1/Spint1 gene were characterized. Previously, we reported that the homozygous deletion of Hai-1/Spint1 in mice resulted in embryonic lethality attributable to impaired placental development. To test the role of Hai-1/Spint1 in mice, the placental function of Hai-1/Spint1-mutant mice was rescued. Injection of Hai-1/Spint1(+/+) blastocysts with Hai-1/Spint1(-/-) embryonic stem cells successfully generated high-chimeric Hai-1/Spint1(-/-) embryos (B6Hai-1(-/-High)) with normal placentas. These embryos were delivered without apparent developmental abnormalities, confirming that embryonic lethality of Hai-1/Spint1(-/-) mice was caused by placental dysfunction. However, newborn B6Hai-1(-/-High) mice showed growth retardation and died by 16 days. These mice developed scaly skin because of hyperkeratinization, reminiscent of ichthyosis, and abnormal hair shafts that showed loss of regular cuticular septation. The interfollicular epidermis showed acanthosis with enhanced Akt phosphorylation. Immunoblot analysis revealed altered proteolytic processing of profilaggrin in Hai-1/Spint1-deleted skin with impaired generation of filaggrin monomers. These findings indicate that Hai-1/Spint1 has critical roles in the regulated keratinization of the epidermis and hair development.

psoriasis regulates epidermal development in zebrafish

The zebrafish epidermis completely envelopes the embryo by 14 hours postfertilization, providing an essential barrier between the internal organs and the environment. As the embryo increases in size, keratinocytes in the epidermis must proliferate and differentiate to form the three epidermal layers present in the adult. The mechanisms controlling growth, differentiation, and maintenance of the fish epidermis are mostly unknown. Here, we describe psoriasis, an epidermal mutant that exhibits widespread overproliferation of the epidermis at 3 days postfertilization and a defect in keratinocyte differentiation. Based on mosaic analysis, we show that psoriasis acts non-cell-autonomously, suggesting that psoriasis encodes a secreted factor. Our analysis of the psoriasis mutant indicates that keratinocyte differentiation and proliferation are tightly regulated to maintain a cohesive epidermal sheet around the embryo and that disruptions in these processes result in the formation of epidermal aggregates.

Alpha1-antitrypsin inhibits the activity of the matriptase catalytic domain in vitro

Matriptase is a type II transmembrane protease that is characterized by an N-terminal transmembrane and multiple extracellular domains, in addition to the conserved extracellular serine protease catalytic domain. The expression pattern of matriptase suggests that this protease may play broad roles in the biology of surface lining epithelial cells. In this study we report that alpha1-antitrypsin (AAT), an endogenous inhibitor of serine proteases, inhibits the catalytic domain of human recombinant matriptase in vitro. Co-incubation of AAT with matriptase (at a molar ratio 1:2) resulted in the formation of heat stable complexes, clearly seen in sodium dodecyl sulfate electrophoresis and Western blots. AAT was found to be a slow, tight-binding inhibitor of the catalytic domain of matriptase with a second order reaction rate constant of 0.31 x 10(3) M(-1)s(-1). Notably, the oxidized form of AAT, which lacks serine protease inhibitor activity, failed to generate matriptase complexes and to inhibit matriptase activity. Since matriptase is involved in a number of physiologic processes, including activation of epithelial sodium channels, our findings offer considerable new insights into new regulatory function of AAT in vivo.

Hepatocyte growth factor activator inhibitor-1 has a complex subcellular itinerary

HAI-1 [HGF (hepatocyte growth factor) activator inhibitor-1] is a Kunitz-type transmembrane serine protease inhibitor that forms inhibitor complexes with the trypsin-like serine protease, matriptase. HAI-1 is essential for mouse placental development and embryo survival and together with matriptase it is a key regulator of carcinogenesis. HAI-1 is expressed in polarized epithelial cells, which have the plasma membrane divided by tight junctions into an apical and a basolateral domain. In the present study we show that HAI-1 at steady-state is mainly located on the basolateral membrane of both Madin-Darby canine kidney cells and mammary gland epithelial cells. After biosynthesis, HAI-1 is exocytosed mainly to the basolateral plasma membrane from where 15% of the HAI-1 molecules are proteolytically cleaved and released into the basolateral medium. The remaining membrane-associated HAI-1 is endocytosed and then recycles between the basolateral plasma membrane and endosomes for hours until it is transcytosed to the apical plasma membrane. Minor amounts of HAI-1 present at the apical plasma membrane are proteolytically cleaved and released into the apical medium. Full-length membrane-bound HAI-1 has a half-life of 1.5 h and is eventually degraded in the lysosomes, whereas proteolytically released HAI-1 is more stable. HAI-1 is co-localized with its cognate protease, matriptase, at the basolateral plasma membrane. We suggest that HAI-1, in addition to its protease inhibitory function, plays a role in transporting matriptase as a matriptase-HAI-1 complex from the basolateral plama membrane to the apical plasma membrane, as matriptase is known to interact with prostasin, located at the apical plasma membrane.

Purification from human milk of matriptase complexes with secreted serpins: mechanism for inhibition of matriptase other than HAI-1

Matriptase, a type 2 transmembrane serine protease, is predominately expressed by epithelial and carcinoma cells in which hepatocyte growth factor activator inhibitor 1 (HAI-1), a membrane-bound, Kunitz-type serine protease inhibitor, is also expressed. HAI-1 plays dual roles in the regulation of matriptase, as a conventional protease inhibitor and as a factor required for zymogen activation of matriptase. As a consequence, activation of matriptase is immediately followed by HAI-1-mediated inhibition, with the activated matriptase being sequestered into HAI-1 complexes. Matriptase is also expressed by peripheral blood leukocytes, such as monocytes and macrophages; however, in contrast to epithelial cells, monocytes and macrophages were reported not to express HAI-1, suggesting that these leukocytes possess alternate, HAI-1-independent mechanisms regulating the zymogen activation and protease inhibition of matriptase. In the present study, we characterized matriptase complexes of 110 kDa in human milk, which contained no HAI-1 and resisted dissociation in boiling SDS in the absence of reducing agents. These complexes were further purified and dissociated into 80-kDa and 45-kDa fragments by treatment with reducing agents. Proteomic and immunological methods identified the 45-kDa fragment as the noncatalytic domains of matriptase and the 80-kDa fragment as the matriptase serine protease domain covalently linked to one of three different secreted serpin inhibitors: antithrombin III, alpha1-antitrypsin, and alpha2-antiplasmin. Identification of matriptase-serpin inhibitor complexes provides evidence for the first time that the proteolytic activity of matriptase, from those cells that express no or low levels of HAI-1, may be controlled by secreted serpins.

Live imaging of chronic inflammation caused by mutation of zebrafish Hai1

The hallmark of chronic inflammation is the infiltration and persistence of leukocytes within inflamed tissue. Here, we describe the first zebrafish chronic inflammation mutant identified in an insertional mutagenesis screen for mutants that exhibit abnormal tissue distribution of neutrophils. We identified a mutant line with an insertion in the Hepatocyte growth factor activator inhibitor 1 gene (hai1; also known as Spint1) that showed accumulation of neutrophils in the fin. The mutant embryos exhibited inflammation in areas of epidermal hyperproliferation that was rescued by knock-down of the type II transmembrane serine protease Matriptase 1 (also known as St14), suggesting a novel role for Hai1-Matriptase 1 pathway in regulating inflammation. Using time-lapse microscopy of mutant embryos that express GFP from a neutrophil-specific promoter, we found that individual neutrophils in inflamed tissue displayed random motility characterized by periods of pausing alternating with periods of motility. During periods of persistent movement the cells were highly polarized, while the pausing modes were characterized by a loss of cell polarity. In contrast to responses to acute injury, neutrophils did not exhibit clear retrograde chemotaxis or resolution of inflammation in the mutant. These findings illustrate the utility of zebrafish as a new model system to study chronic inflammation and to visualize immune responses with high resolution in vivo.

Leukocyte cell surface proteinases: regulation of expression, functions, and mechanisms of surface localization

A number of proteinases are expressed on the surface of leukocytes including members of the serine, metallo-, and cysteine proteinase superfamilies. Some proteinases are anchored to the plasma membrane of leukocytes by a transmembrane domain or a glycosyl phosphatidyl inositol (GPI) anchor. Other proteinases bind with high affinity to classical receptors, or with lower affinity to integrins, proteoglycans, or other leukocyte surface molecules. Leukocyte surface levels of proteinases are regulated by: (1) cytokines, chemokines, bacterial products, and growth factors which stimulate synthesis and/or release of proteinases by cells; (2) the availability of surface binding sites for proteinases; and/or (3) internalization or shedding of surface-bound proteinases. The binding of proteinases to leukocyte surfaces serves many functions including: (1) concentrating the activity of proteinases to the immediate pericellular environment; (2) facilitating pro-enzyme activation; (3) increasing proteinase stability and retention in the extracellular space; (4) regulating leukocyte function by proteinases signaling through cell surface binding sites or other surface proteins; and (5) protecting proteinases from inhibition by extracellular proteinase inhibitors. There is strong evidence that membrane-associated proteinases on leukocytes play critical roles in wound healing, inflammation, extracellular matrix remodeling, fibrinolysis, and coagulation. This review will outline the biology of membrane-associated proteinases expressed by leukocytes and their roles in physiologic and pathologic processes.

Activation of hepatocyte growth factor activator zymogen (pro-HGFA) by human kallikrein 1-related peptidases

Hepatocyte growth factor activator (HGFA) is a serine protease and a potent activator of prohepatocyte growth factor/scatter factor (pro-HGF/SF), a multifunctional growth factor that is critically involved in tissue morphogenesis, regeneration, and tumor progression. HGFA circulates as a zymogen (pro-HGFA) and is activated in response to tissue injury. Although thrombin is considered to be an activator of pro-HGFA, alternative pro-HGFA activation pathways in tumor microenvironments remain to be identified. In this study, we examined the effects of kallikrein 1-related peptidases (KLKs), a family of extracellular serine proteases, on the activation of pro-HGFA. Among the KLKs examined (KLK2, KLK3, KLK4 and KLK5), we identified KLK4 and KLK5 as novel activators of pro-HGFA. Using N-terminal sequencing, the cleavage site was identified as the normal processing site, Arg407-Ile408. The activation of pro-HGFA by KLK5 required a negatively charged substance such as dextran sulfate, whereas KLK4 could process pro-HGFA without dextran sulfate. KLK5 showed more efficient pro-HGFA processing than KLK4, and was expressed in 50% (13/25) of the tumor cell lines examined. HGFA processed by these KLKs efficiently activated pro-HGF/SF, and led to cellular scattering and invasion in vitro. The activities of both KLK4 and KLK5 were strongly inhibited by HGFA inhibitor type 1, an integral membrane Kunitz-type serine protease inhibitor that inhibits HGFA and other pro-HGF/SF-activating proteases. These data suggest that KLK4 and KLK5 mediate HGFA-induced activation of pro-HGF/SF within tumor tissue, which may thereafter trigger a series of events leading to tumor progression via the MET receptor.

The roles of proteolytic enzymes in the development of tumour-induced bone disease in breast and prostate cancer

Tumour-induced bone disease is a common clinical feature of advanced breast and prostate cancer and is associated with considerable morbidity for the affected patients. Our understanding of the molecular mechanisms underlying the development of bone metastases is incomplete, but proteolytic enzymes are implicated in a number of processes involved in both bone metastasis and in normal bone turnover, including matrix degradation, cell migration, angiogenesis, tumour promotion and growth factor activation. Malignant as well as non-malignant cells in the primary and secondary sites express these enzymes, the activity of which may be regulated by soluble factors, cell- or matrix-associated components, as well as a number of cell signalling pathways. A number of secreted and cell surface-associated proteolytic enzymes are implicated in tumour-induced bone disease, including the matrix metalloproteinases, lysosomal cysteine proteinases and plasminogen activators. This review will introduce the role of proteolytic enzymes in normal bone turnover and give an overview of the studies in which their involvement and regulation in the development of bone metastases in breast and prostate cancer has been described. The results from trials involving protease inhibitors in clinical development will also be briefly discussed.

Design and synthesis of novel and potent inhibitors of the type II transmembrane serine protease, matriptase, based upon the sunflower trypsin inhibitor-1

Matriptase, initially isolated from human breast cancer cells in culture, is a member of the emerging class of type II transmembrane serine proteases. Matriptase blockade could potentially modulate tumorigenesis and metastasis in vivo. Sunflower trypsin inhibitor-1 (1, SFTI-1), isolated from sunflower seeds, exhibits very potent matriptase inhibitory activity. On the basis of these findings, we designed and synthesized 13 analogues of the naturally occurring peptide 1 with the intention to explore the structure-activity relationships of this type of bicyclic peptides and to improve inhibitory selectivity and metabolic stability of the disulfide-bridge-containing peptide 1. We discovered that the methylenedithioether-bridged compound 14 demonstrates very potent binding affinity to matriptase. Compound 8 exhibits much better selectivity for inhibition of matriptase versus thrombin, whereas compound 2 becomes a more potent thrombin inhibitor, which can be potentially used as an anticoagulant for prophylaxis and therapy of thromboembolism.

Co-localization of the channel activating protease prostasin/(CAP1/PRSS8) with its candidate activator, matriptase

Prostasin (CAP1/PRSS8) is a glycosylphosphatidylinositol-anchored membrane serine protease believed to be critical for the regulation of epithelial sodium channel (ENaC) activity. Prostasin is synthesized as an inactive zymogen that requires a site-specific endoproteolytic cleavage to be converted to an active protease. We have recently reported that the tumor-associated type II transmembrane serine protease, matriptase is necessary and sufficient for prostasin activation in the epidermis. In this study, the interrelationship between the two membrane serine proteases was investigated further by using enzymatic gene trapping combined with immunohistochemistry to delineate the spatial expression of matriptase and prostasin in mouse tissues. We utilized a knock-in mouse with a promoterless beta-galactosidase marker gene inserted into the matriptase locus, as a unique tool for precise assessment of endogenous matriptase expression. The spatial expression of matriptase and prostasin in mouse tissues was delineated by combining in situ beta-galactosidase matriptase staining with immunohistochemical detection of prostasin. We report that prostasin displays a near-ubiquitous co-localization with its candidate activator matriptase in a variety of normal epithelial tissues. These include simple, stratified, and pseudo-stratified epithelium of the integumentary system, digestive tract, respiratory tract, and urogenital tract. However, matriptase and prostasin expression segregates during epithelial multi-stage carcinogenesis to eventually become localized in separate compartments of the tumor. These data suggest that a matriptase-prostasin zymogen activation cascade may be functionally operative in multiple epithelial tissues, but matriptase promotes epithelial carcinogenesis independent of prostasin.

Proteinase-activated receptor-2 induces cyclooxygenase-2 expression through beta-catenin and cyclic AMP-response element-binding protein

Chronic inflammation of mucosae is associated with an increased cancer risk. Tumorigenesis in these tissues is associated with the activity of some proteinases, cyclooxygenase-2 (COX-2), and beta-catenin. Serine proteinases participate in both inflammation and tumorigenesis through the activation of proteinase-activated receptor-2 (PAR(2)), which up-regulates COX-2 by an unknown mechanism. We sought to determine whether beta-catenin participated in PAR(2)-induced COX-2 expression and through what cellular mechanism. In A549 epithelial cells, we showed that PAR(2) activation increased COX-2 expression through the beta-catenin/T cell factor transcription pathway. This effect was dependent upon ERK1/2 MAPK, which inhibited the beta-catenin-regulating protein, glycogen synthase kinase-3beta, and induced the activity of the cAMP-response element-binding protein (CREB). Knockdown of CREB by small interfering RNA revealed that PAR(2)-induced beta-catenin transcriptional activity and COX-2 expression were CREB-dependent. A co-immunoprecipitation assay revealed a physical interaction between CREB and beta-catenin. Thus, PAR(2) up-regulated COX-2 expression via an ERK1/2-mediated activation of the beta-catenin/Tcf-4 and CREB pathways. These findings reveal new cellular mechanisms by which serine proteinases may participate in tumor development and are particularly relevant to cancers associated with chronic mucosal inflammation, where serine proteinases are abundant and COX-2 overexpression is a common feature.

Inactivation of serine protease Matriptase1a by its inhibitor Hai1 is required for epithelial integrity of the zebrafish epidermis

Epithelial integrity requires the adhesion of cells to each other as well as to an underlying basement membrane. The modulation of adherence properties is crucial to morphogenesis and wound healing, and deregulated adhesion has been implicated in skin diseases and cancer metastasis. Here, we describe zebrafish that are mutant in the serine protease inhibitor Hai1a (Spint1la), which display disrupted epidermal integrity. These defects are further enhanced upon combined loss of hai1a and its paralog hai1b. By applying in vivo imaging, we demonstrate that Hai1-deficient keratinocytes acquire mesenchymal-like characteristics, lose contact with each other, and become mobile and more susceptible to apoptosis. In addition, inflammation of the mutant skin is evident, although not causative of the epidermal defects. Only later, the epidermis exhibits enhanced cell proliferation. The defects of hai1 mutants can be phenocopied by overexpression and can be fully rescued by simultaneous inactivation of the serine protease Matriptase1a (St14a), indicating that Hai1 promotes epithelial integrity by inhibiting Matriptase1a. By contrast, Hepatocyte growth factor (Hgf), a well-known promoter of epithelial-mesenchymal transitions and a prime target of Matriptase1 activity, plays no major role. Our work provides direct genetic evidence for antagonistic in vivo roles of Hai1 and Matriptase1a to regulate skin homeostasis and remodeling.

Exploration of target molecules for prostate cancer gene therapy

BACKGROUND

Focusing on Adv-FZ33, a modified adenovirus in which a synthetic 33-amino-acid immunoglobulin G-binding domain was inserted into the adenoviral fiber protein, we tried to identify suitable target molecules for prostate cancer-specific gene therapy.

METHODS

Hybridomas were established from mice immunized with prostate cancer cell lines. The hybridomas were screened using Adv-FZ33 to create monoclonal antibodies (mAbs) that induced high gene transfer efficiency for PC-3 cells. Furthermore, we identified target antigens of the mAbs by immunoprecipitation and mass spectrometry, and investigated the expression of target molecules by flow cytometry and immunocytochemistry.

RESULTS

Using Adv-FZ33, we established four different mouse mAbs that increased transduction efficiency for PC-3. The target antigens identified were Ep-CAM, CD155, HAI-1, and Na,K-ATPase beta1. These antigens were expressed in several cancer cell lines, including prostate cancer. Human prostatic myofibroblast cells lacked expression of Ep-CAM and HAI-1.

CONCLUSIONS

We established anti-Ep-CAM mAb and anti- HAI-1 mAbs. Gene transduction via Ep-CAM and HAI-1 may be a novel strategy for treatment of prostate cancer.

Matriptase-2 inhibits breast tumor growth and invasion and correlates with favorable prognosis for breast cancer patients

PURPOSE

The type II transmembrane serine proteases are cell surface proteolytic enzymes that mediate a diverse range of cellular functions, including tumor invasion and metastasis. Matriptase (matriptase-1) and matriptase-2 belong to the type II transmembrane serine protease family. Matriptase-1 is known to play a role in breast cancer progression, and elevated levels of matriptase-1 correlate with poor patient outcome. The role of matriptase-2 and its cellular function in cancer is unknown. This study aimed to provide new insights into the significance of matriptase-2 in cancer.

EXPERIMENTAL DESIGN

Matriptase-2 expression levels were assessed in a cohort of human breast cancer specimens (normal, n = 34; cancer, n = 95), in association with patient clinical variables, using both quantitative and qualitative analysis of the matriptase-2 transcript along with immunohistochemical techniques. Matriptase-2 was also experimentally overexpressed in the MDA-MB-231 human breast cancer cell line. The effects of matriptase-2 overexpression were examined through a series of in vitro and in vivo studies.

RESULTS

Here, we show that reduced matriptase-2 levels in breast cancer tissues correlate with an overall poor prognosis for the breast cancer patient. This study also reveals that matriptase-2 overexpression in breast cancer cells significantly suppressed tumorigenesis in CD1 athymic mice (P = 0.000003). Furthermore, we report that matriptase-2 overexpression dramatically reduced the invasive (P = 0.0001) and migratory properties (P = 0.01) of the breast cancer cells.

CONCLUSIONS

Matriptase-2 suppresses breast tumor development in vivo, displays prognostic value for breast cancer patients, inhibits both breast cancer cell invasion and motility in vitro, and may play a contrasting role to matriptase-1 in breast cancer.

Autoactivation of matriptase in vitro: requirement for biomembrane and LDL receptor domain

In live cells, autoactivation of matriptase, a membrane-bound serine protease, can be induced by lysophospholipids, androgens, and the polyanionic compound suramin. These structurally distinct chemicals induce different signaling pathways and cellular events that somehow, in a cell type-specific manner, lead to activation of matriptase immediately followed by inhibition of matriptase by hepatocyte growth factor activator inhibitor 1 (HAI-1). In the current study, we established an analogous matriptase autoactivation system in an in vitro cell-free setting and showed that a burst of matriptase activation and HAI-1-mediated inhibition spontaneously occurred in the insoluble fractions of cell homogenates and that this in vitro activation could be attenuated by a soluble suppressive factor(s) in cytosolic fractions. Immunofluorescence staining and subcellular fractionation studies revealed that matriptase activation occurred in the perinuclear regions. Solubilization of matriptase from cell homogenates by Triton X-100 or sonication of cell homogenates completely inhibited the effect, suggesting that matriptase activation requires proper lipid bilayer microenvironments, potentially allowing appropriate interactions of matriptase zymogens with HAI-1 and other components. Matriptase activation occurred in a narrow pH range (from pH 5.2 to 7.2), with a sharp increase in activation at the transition from pH 5.2 to 5.4, and could be completely suppressed by moderately increased ionic strength. Protease inhibitors only modestly affected activation, whereas 30 nM (5 microg/ml) of anti-matriptase LDL receptor domain 3 monoclonal antibodies completely blocked activation. These atypical biochemical features are consistent with a mechanism for autoactivation of matriptase that requires protein-protein interactions but not active proteases.

Expression of EMMPRIN and matriptase in esophageal squamous cell carcinoma: correlation with clinicopathological parameters

Extracellular matrix metalloproteinase inducer (EMMPRIN) and the type II transmembrane serine protease, matriptase, are expressed in several human cancers and play an important role in tumor progression. The aim of the present study was to investigate the immuno-staining patterns of EMMPRIN and matriptase in patients with esophageal squamous cell carcinomas (SCC) and correlate the percentage tumor staining with tumor differentiation and clinical parameters. EMMPRIN and matriptase immunoreactivity was seen on the cell membrane and in the cytoplasm of tumor cells in all 41 cases of esophageal SCC evaluated. The percentage tumor staining of EMMPRIN was 48 +/- 3% for well differentiated, 73 +/- 3% for moderately differentiated, and 92 +/- 3% for poorly differentiated esophageal SCC. Higher percentage tumor staining with EMMPRIN correlated significantly with poorly differentiated esophageal SCC (P < 0.05). The percentage tumor staining with matriptase correlated significantly with tumor differentiation (52 +/- 3% for well differentiated, 85 +/- 2% for moderately differentiated, and 88 +/- 3% for poorly differentiated esophageal SCC). Additionally, higher percentage tumor staining with matriptase was significantly correlated with the advanced N and M stages (P < 0.05). Our results demonstrate that EMMPRIN and matriptase are over-expressed in esophageal SCC and are correlated with advanced clinicopathological stages. Pharmacological agents targeting EMMPRIN and matriptase expressions may be beneficial in the treatment of esophageal SCC.

Matriptase activates stromelysin (MMP-3) and promotes tumor growth and angiogenesis

Matriptase/MT-SP1, a type II membrane serine protease widely expressed in normal epithelial cells and human carcinoma cells, is thought to be involved in cancer progression. To clarify this possibility, we overexpressed exogenous matriptase in the human stomach cancer cell line AZ521. In vitro, the matriptase transfectant (Mat-AZ521) and the control transfectant (Mock-AZ521) showed a similar growth rate, although the saturation cell density was significantly higher with the Mat-AZ521. When implanted into nude mice subcutaneously or intraperitoneally, Mat-AZ521 cells grew faster and produced much larger solid tumors than Mock-AZ521 cells. The overexpression of matriptase in AZ521 cells shortened the survival time of tumor-bearing mice. Histological analysis showed that both the number and the size of blood vessels in tumor tissues were significantly higher in the Mat-AZ521 tumors than the Mock-AZ521 ones. Moreover, it was found that purified matriptase activated one of the important matrix metalloproteinases, stromelysin (MMP-3). These results suggest the possibility that the matriptase-dependent activation of MMP-3, as well as the direct activity of matriptase, promotes tumor growth and angiogenesis by enhancing extracellular matrix degradation in tumor cell microenvironments.

The impact of cell adhesion changes on proliferation and survival during prostate cancer development and progression

In the normal prostate epithelium, androgen receptor (AR) negative basal epithelial cells adhere to the substratum, while AR expressing secretory cells lose substratum adhesion. In contrast, prostate cancer cells both express AR and adhere to a tumor basement membrane. In this review, we describe the differential expression of integrins, growth factor receptors (GFRs), and AR in normal and cancerous epithelium. In addition, we discuss how signals from integrins, GFRs, and AR are integrated to regulate the proliferation and survival of normal and malignant prostate epithelial cells. While cell adhesion is likely of great importance when considering therapeutic approaches for treatment of metastatic prostate cancer, no data on integrin expression are available from tissues of prostate cancer metastasis. However, several drug targets that are upregulated after androgen ablative therapy regulate cell adhesion and thus novel targeted therapies indirectly interfere with cell adhesion mechanisms in prostate cancer cells.

Evidence for a matriptase-prostasin proteolytic cascade regulating terminal epidermal differentiation

Recent gene ablation studies in mice have shown that matriptase, a type II transmembrane serine protease, and prostasin, a glycosylphosphatidylinositol-anchored membrane serine protease, are both required for processing of the epidermis-specific polyprotein, profilaggrin, stratum corneum formation, and acquisition of epidermal barrier function. Here we present evidence that matriptase acts upstream of prostasin in a zymogen activation cascade that regulates terminal epidermal differentiation and is required for prostasin zymogen activation. Enzymatic gene trapping of matriptase combined with prostasin immunohistochemistry revealed that matriptase was co-localized with prostasin in transitional layer cells of the epidermis and that the developmental onset of expression of the two membrane proteases was coordinated and correlated with acquisition of epidermal barrier function. Purified soluble matriptase efficiently converted soluble prostasin zymogen to an active two-chain form that formed SDS-stable complexes with the serpin protease nexin-1. Whereas two forms of prostasin with molecular weights corresponding to the prostasin zymogen and active prostasin were present in wild type epidermis, prostasin was exclusively found in the zymogen form in matriptase-deficient epidermis. These data suggest that matriptase, an autoactivating protease, acts upstream from prostasin to initiate a zymogen cascade that is essential for epidermal differentiation.

Matriptase: potent proteolysis on the cell surface

Matriptase is a type II transmembrane serine protease expressed in most human epithelia, where it is coexpressed with its cognate transmembrane inhibitor, hepatocyte growth factor activator inhibitor (HAI)-1. Activation of the matriptase zymogen requires sequential N-terminal cleavage, activation site autocleavage, and transient association with HAI-1. Matriptase has an essential physiological role in profilaggrin processing, corneocyte maturation, and lipid matrix formation associated with terminal differentiation of the oral epithelium and the epidermis, and is also critical for hair follicle growth. Matriptase and HAI expression are frequently dysregulated in human cancer, and matriptase expression that is unopposed by HAI-1 potently promotes carcinogenesis and metastatic dissemination in animal models.

The molecular and clinical impact of hepatocyte growth factor, its receptor, activators, and inhibitors in wound healing

Wound healing involves a number of cellular and molecular events, many of which are controlled by soluble growth factors. In the process of healing, hepatocyte growth factor, a cytokine known to act as mitogen, motogen, and morphogen, has been postulated to play multiple roles during several stages of this complex biological process. Produced primarily by stromal fibroblasts, hepatocyte growth factor regulates angiogenesis, vascular permeability, cell migration, matrix deposition and degradation, and other biological processes. The current article discusses recent progress in understanding the multiple roles played by this growth factor in tissue repair.

Hepatocyte growth factor activation inhibitors (HAI-1 and HAI-2) regulate HGF-induced invasion of human breast cancer cells

Hepatocyte growth factor (HGF) plays a plethora of roles in cancer metastasis and tumour growth. The interaction between tumour cells and their surrounding stromal environment is a crucial factor regulating tumour invasion and metastasis. Stromal fibroblasts are the main source of HGF in the body, and release HGF as an inactive precursor (pro-HGF). HGF activator (HGFA), matriptase, urokinase-type plasminogen activator and hepsin are the main factors responsible for converting pro-HGF into active HGF. HAI-1 and HAI-2 are 2 novel Kunitz-type serine protease inhibitors that regulate HGF activity through inhibition of HGFA, matriptase and hepsin action. Recent studies demonstrate that HAI-1 and HAI-2 may also potently inhibit a number of other pro-metastatic serine proteases and therefore have direct bearing on the spread of tumours. Our study examined the potential of these HAI's to suppress the influence of HGF and regulate cancer metastasis. We generated a retroviral expression system that induced HAI expression in a human fibroblast cell line. Forced expression of either HAI-1 or HAI-2 in these fibroblasts resulted in a dramatic decrease in the production of bioactive hepatocyte growth factor (HGF). This reduction in HGF activity subsequently suppressed HGF's metastatic influence on breast cancer cells. To further assess the anti-cancer properties of HAI-1 and HAI-2 we generated recombinant HAI proteins. These recombinant HAI proteins possessed the ability to potently quench HGF activity. We also demonstrate that these recombinant HAI's suppressed fibroblast-mediated breast cancer invasion. An additional ribozyme transgenes study revealed that elimination of HAI-1 and HAI-2 expression, in an MDA-MB-231 breast cancer cell line, significantly enhanced the migratory, proliferative and invasive nature of these breast cancer cells. Overall, our data demonstrates the important roles of HAI-1 and HAI-2 in cancer metastasis, and reveals that these serine protease inhibitors display strong therapeutic potential.

Delineation of matriptase protein expression by enzymatic gene trapping suggests diverging roles in barrier function, hair formation, and squamous cell carcinogenesis

The membrane serine protease matriptase is required for epidermal barrier function, hair formation, and thymocyte development in mice, and dysregulated matriptase expression causes epidermal squamous cell carcinoma. To elucidate the specific functions of matriptase in normal and aberrant epidermal differentiation, we used enzymatic gene trapping combined with immunohistochemical, ultrastructural, and barrier function assays to delineate the spatio-temporal expression and function of matriptase in mouse keratinized tissue development, homeostasis, and malignant transformation. In the interfollicular epidermis, matriptase expression was restricted to postmitotic transitional layer keratinocytes undergoing terminal differentiation. Matriptase was also expressed in keratinizing oral epithelium, where it was required for oral barrier function, and in thymic epithelium. In all three tissues, matriptase colocalized with profilaggrin. In staged embryos, the onset of epidermal matriptase expression coincided with that of profilaggrin expression and acquisition of the epidermal barrier. In marked contrast to stratifying keritinized epithelium, matripase expression commenced already in undifferentiated and rapidly proliferating profilaggrin-negative matrix cells and displayed hair growth cycle-dependent expression. Exposure of the epidermis to carcinogens led to the gradual appearance of matriptase in a keratin-5-positive proliferative cell compartment during malignant progression. Combined with previous studies, these data suggest that matriptase has diverging functions in the genesis of stratified keratinized epithelium, hair follicles, and squamous cell carcinoma.

The ratio of Matriptase/HAI-1 mRNA is higher in colorectal cancer adenomas and carcinomas than corresponding tissue from control individuals

Background

It has recently been shown that overexpression of the serine protease, matriptase, in transgenic mice causes a dramatically increased frequency of carcinoma formation. Overexpression of HAI-1 and matriptase together changed the frequency of carcinoma formation to normal. This suggests that the ratio of matriptase to HAI-1 influences the malignant progression. The aim of this study has been to determine the ratio of matriptase to HAI-1 mRNA expression in affected and normal tissue from individuals with colorectal cancer adenomas and carcinomas as well as in healthy individuals, in order to determine at which stages a dysregulated ratio of matriptase/HAI-1 mRNA is present during carcinogenesis.

Methods

Using quantitative RT-PCR, we have determined the mRNA levels for matriptase and HAI-1 in colorectal cancer tissue (n = 9), severe dysplasia (n = 15), mild/moderate dysplasia (n = 21) and in normal tissue from the same individuals. In addition, corresponding tissue was examined from healthy volunteers (n = 10). Matriptase and HAI-1 mRNA levels were normalized to β-actin.

Results

Matriptase mRNA level was lower in carcinomas compared to normal tissue from healthy individuals (p < 0.01). In accordance with this, the matriptase mRNA level was also lower in adenomas/carcinomas combined as compared to their adjacent normal tissue (p < 0.01). HAI-1 mRNA levels in both normal and affected tissue from individuals with severe dysplasia or carcinomas and in affected tissue with mild/moderate dysplasia were all significantly lower than mRNA levels observed in corresponding tissue from healthy control individuals. HAI-1 mRNA was lower in carcinomas as compared to normal tissue from healthy individuals (p < 0.001). HAI-1 mRNA levels were significantly lower in tissue displaying mild/moderate (p < 0.001) and severe (p < 0.01) dysplasia compared to normal tissue from the same patients. Both adenomas and carcinomas displayed a significantly different matriptase/HAI-1 mRNA ratio than corresponding normal tissue from healthy control individuals (p < 0.05). In addition statistically significant difference (p < 0.001) could be observed between mild/moderate and severe adenomas and their adjacent normal tissue.

Conclusion

Our results show that dysregulation of the matriptase/HAI-1 mRNA ratio occurs early during carcinogenesis. Future studies are required to clarify whether the dysregulated matriptase/HAI-1 ratio was causing the malignant progression or is a consequence of the same.

Proteomic analysis of the tetraspanin web using LC-ESI-MS/MS and MALDI-FTICR-MS

Tetraspanins are integral membrane proteins involved in a variety of physiological and pathological processes. In cancer, clinical and experimental studies have reported a link between tetraspanin expression levels and metastasis. Tetraspanins play a role as organizers of a molecular network of interactions, the "tetraspanin web". Here, we have performed a proteomic characterization of the tetraspanin web using a model of human colon cancer consisting of two cell lines derived from primary tumor and metastasis from the same patient. The tetraspanin complexes were isolated after immunoaffinity purification and the proteins were identified by MS using LC-ESI-MS/MS and MALDI-FTICR. The high resolution and mass accuracy of FTICR MS allowed reliable identification using mass finger printing with only two peptides. Thus, it could be used to resolve the composition of complex peptide mixtures from membrane proteins. Different types of membrane proteins were identified, including adhesion molecules (integrins, Lu/B-CAM, GA733 proteins), receptors and signaling molecules (BAI2, PKC, G proteins), proteases (ADAM10, TADG15), and membrane fusion proteins (syntaxins) as well as poorly characterized proteins (CDCP1, HEM-1, CTL1, and CTL2). Some components were differentially detected in the tetraspanin web of the two cell lines. These differences may be relevant for tumor progression and metastasis.

Initiation of plasminogen activation on the surface of monocytes expressing the type II transmembrane serine protease matriptase

uPA (urokinase-type plasminogen activator) activates plasminogen with high efficiency when bound to its cellular receptor uPAR, but only after a prolonged lag phase during which generated plasmin activates pro-uPA. How the activity of this proteolytic system might be rapidly initiated is unknown. We have now found that 2 monocytic cell lines display distinct patterns of plasminogen activation. U937 cells, but not THP-1 cells, displayed the expected lag phase, suggesting a constitutive initiation mechanism on the latter. This was shown to be due to the plasmin-independent activation of uPAR-bound pro-uPA by a cell surface-associated protease and to correlate with the expression of matriptase, a type II transmembrane serine protease that was highly expressed in THP-1 cells but undetectable in U937 cells. Kinetic analysis demonstrated that matriptase is a relatively poor activator of pro-uPA in solution, approximately 100-fold less efficient than plasmin (k(cat)/K(m) 1.16 x 10(5) M(-1)s(-1) cf 1.21 x 10(7) M(-1)s(-1)). However, down-regulation of matriptase expression in THP-1 cells by siRNA reduced the activation of cell-associated pro-uPA and the subsequent rapid initiation of plasminogen activation by 76% to 93%. Matriptase was also found to be expressed by peripheral blood monocytes and may therefore be a specific mechanism for the rapid initiation and regulation of plasminogen activation by these cells.

A novel biomarker for staging human prostate adenocarcinoma: overexpression of matriptase with concomitant loss of its inhibitor, hepatocyte growth factor activator inhibitor-1

BACKGROUND

Matriptase, a type II transmembrane serine protease is involved in angiogenesis, degradation of extracellular matrix, and in the progression of some epithelial cancers. Here, we establish the clinical significance of matriptase and its inhibitor, hepatocyte growth factor activator inhibitor-1 (HAI-1), during the progression of human prostate cancer (CaP).

METHODS

The expression patterns of matriptase and HAI-1 were determined in primary cultures of normal human prostate epithelial (NHPE) cells, human CaP cells LNCaP, DU-145, CWR22Rnu1, and PC-3, and in tissue samples of 172 patients with normal prostate, benign prostatic hyperplasia (BPH), prostatic intraepithelial neoplasia (PIN), and adenocarcinoma of different tumor grades.

RESULTS

The protein and mRNA levels of matriptase were significantly higher in all carcinoma cells as compared with NHPE cells. Conversely, all CaP cells exhibited a reduced expression of HAI-1 as compared with NHPE cells. A progressive increase in the protein levels of matriptase was observed with increasing tumor grade in CaP specimens as compared with normal and BPH tissue specimens. Tissue samples of normal prostate exhibited a high constitutive protein level of HAI-1 compared with BPH and low-grade cancer with a progressive loss with increasing tumor grade.

CONCLUSION

The increased expression of matriptase and loss of HAI-1 may be an important event during the progression of CaP in humans. We suggest that the ratio of these two gene products may serve as a promising biomarker for CaP progression and a potential marker for establishing the efficacy of therapeutic and chemopreventive interventions.