cDNA cloning and expression of a novel serine protease, TLSP

A cDNA for a putative novel serine protease, TLSP, was cloned from human hippocampus cDNA with polymerase chain reaction based strategies. The putative amino acid sequence of TLSP is similar to the trypsin-type serine proteases. TLSP mRNA is expressed in keratinocytes. Overexpressed TLSP protein in neuro2a cells was detected in culture medium.     

Up-regulation of a serine protease inhibitor in astrocytes mediates the neuroprotective activity of transforming growth factor beta1

Serine proteases play a key role in the fundamental biology of the central nervous system (CNS), and recent data suggest their involvement in the pathophysiology of neurodegenerative diseases. Little is known about the physiological regulation of these proteases in the CNS. Among the multiple growth factors present in the brain, transforming growth factor beta1 (TGF-beta1) has been described as an injury-related growth factor. However, its beneficial or deleterious role remains unclear. In the present study, we investigated the influence of TGF-beta1 in apoptosis and necrosis, two mechanisms involved in ischemic neuronal death. We show that TGF-beta1 exerts a neuroprotective role restricted to necrosis induced by N-methyl-D-aspartate. This effect is observable only in the obligatory presence of TGF-beta1-responsive astrocytes. We demonstrate that this neuroprotective activity is mediated through an up-regulation of a serine protease inhibitor (PAI-1) in astrocytes. These results underline the involvement of serine proteases and extracellular matrix components such as the PAI-1/t-PA axis in the excitotoxic cascade. Moreover, regardless of the underlying mechanisms of t-PA involvement in excitotoxic injury, our observations might warn against the use of tissular plasminogen activator as an alternative therapy for the treatment of hypoxic-ischemic injury in the brain.     

Involvement of protease inhibitors in staphylokinase-induced fibrin-specific fibrinolysis

We compared the fibrinolytic properties of recombinant staphylokinase (SAK), a fibrin-specific plasminogen activator, with those of streptokinase and tissue-type plasminogen activator (t-PA) by means of the amidolytic method. We also investigated the involvement of alpha 2-macroglobulin, C1-inactivator and alpha 1-antitrypsin in SAK-induced fibrin-specific fibrinolysis. Both SAK and t-PA activated plasminogen efficiently in the presence of fibrin in human plasma. Although t-PA activated plasminogen dependently on fibrin in the reconstituted plasma system, SAK activated plasminogen independently of fibrin without alpha 2-plasmin inhibitor (alpha 2-antiplasmin, alpha 2-PI). These findings suggest that fibrin and alpha 2-PI play important roles in plasminogen activation by SAK but not by t-PA. Furthermore, protease inhibitors such as alpha 2-PI, alpha 2-macroglobulin, C1-inactivator and alpha 1-antitrypsin inhibited plasminogen activation by SAK and the inhibitory actions of these protease inhibitors disappeared in the presence of fibrin. This shows that alpha 2-macroglobulin, C1-inactivator and alpha 1-antitrypsin, other than alpha 2-PI, contribute to the fibrin-specificity of SAK.     

Characterization of the precursor of prostate-specific antigen. Activation by trypsin and by human glandular kallikrein

The precursor or zymogen form of prostate-specific antigen (pro-PSA) is composed of 244 amino acid residues including an amino-terminal propiece of 7 amino acids. Recombinant pro-PSA was expressed in Escherichia coli, isolated from inclusion bodies, refolded, and purified. The zymogen was readily activated by trypsin at a weight ratio of 50:1 to generate PSA, a serine protease that cleaves the chromogenic chymotrypsin substrate 3-carbomethoxypropionyl-L-arginyl-L-prolyl-L-tyrosine-p-nitroanili ne- HCl (S-2586). In this activation, the amino-terminal propiece Ala-Pro-Leu-Ile-Leu-Ser-Arg was released by cleavage at the Arg-Ile peptide bond. The recombinant pro-PSA was also activated by recombinant human glandular kallikrein, another prostate-specific serine protease, as well as by a partially purified protease(s) from seminal plasma. The recombinant PSA was inhibited by alpha1-antichymotrypsin, forming an equimolar complex with a molecular mass of approximately 100 kDa. The recombinant PSA failed to activate single chain urokinase-type plasminogen activator, in contrast to the recombinant hK2, which readily activated single chain urokinase-type plasminogen activator. These results indicate that pro-PSA is converted to an active serine protease by minor proteolysis analogous to the activation of many of the proteases present in blood, pancreas, and other tissues. Furthermore, PSA is probably generated by a cascade system involving a series of precursor proteins. These proteins may interact in a stepwise manner similar to the generation of plasmin during fibrinolysis or thrombin during blood coagulation.     

Variants of tissue-type plasminogen activator which display substantially enhanced stimulation by fibrin

Unlike most proteases, tissue-type plasminogen activator (t-PA) is secreted from cells as an active, single chain "proenzyme" whose catalytic efficiency is comparable with that of the corresponding mature, two-chain enzyme. We have previously suggested that the absence of the "zymogen triad" (Asp194-His40-Ser32; chymotrypsin numbering) contributes to this unusually high enzymatic activity of single chain t-PA. Consistent with this prediction, the single chain form of a variant of t-PA containing the zymogen triad displayed dramatically reduced activity toward synthetic substrates. Activation cleavage of this variant, however, resulted in a mature, two-chain enzyme with full catalytic activity. To further examine the functional significance of the zymogen triad, we used site-specific mutagenesis to construct a variant of t-PA, t-PA/R275E,A292S,F305H, that contained this triad but could not be converted into its two-chain form by plasmin. Characterization of this variant demonstrated that the presence of the zymogen triad specifically suppressed plasminogen activation by single chain t-PA in the absence of fibrin. In addition, these studies indicated that, like wild type t-PA, zymogen activation of this variant could be accomplished by binding to the co-factor fibrin. The combination of full activity in the presence of fibrin and reduced activity in its absence resulted in novel variants of t-PA that displayed dramatically enhanced stimulation by fibrin. While the presence of fibrin increased the catalytic efficiency of t-PA toward plasminogen by a factor of approximately 520, this stimulation factor increased to 130,000 for t-PA/R275E,A292S,F305H. Plasmin-resistant, zymogen-like variants of t-PA, therefore, may represent thrombolytic enzymes with enhanced "clot selectivity."     

Molecular insights into renal interstitial fibrosis

Progressive interstitial fibrosis accompanied by loss of renal tubules and interstitial capillaries typifies all progressive renal diseases. Dynamic and complex, the process evidently overlaps with matrix remodeling; it may even be reversible. The interstitial fibrous tissue comprises several normal and novel matrix proteins, proteoglycans, and glycoproteins. Interstitial myofibroblasts are a major site of matrix protein overproduction, although resident fibroblasts, tubular cells, and inflammatory cells may contribute. Inadequate matrix degradation also appears to contribute to the fibrogenic process. Two protease cascades, the metalloproteinases and the plasminogen activator/ plasmin family of serine proteases, are implicated in the turnover of interstitial matrix proteins; upregulated expression of protease inhibitors has been observed in each. Increased tissue inhibitor of metalloproteinase-1 and plasminogen activator inhibitor-1 levels suggest that the intrinsic renal activity of the metalloproteinases and serine proteases are inhibited while matrix proteins accumulate in the interstitium. Several signals that may direct the interstitial fibrogenic process have been identified, but not yet proved to cause it. Upregulated expression of transforming growth factor beta-1, the proteotypic fibrogenic cytokine, has been observed in experimental and human models; it probably does not act alone. There may be supportive roles for platelet-derived growth factor, interleukin-1, basic fibroblast growth factor, angiotensin II, and endothelin-1. Although it is not known why interstitial fibrosis compromises renal function, atrophy of renal tubules may be pivotal. Ischemic necrosis and/or apoptosis may generate nonfunctioning atubular and sclerotic glomeruli. Future studies must delineate the molecular basis of the differences between renal repair and renal destruction by fibrosis, two processes that share many common features.     

Prognostic role of cisteine and serin proteases in gastriC cancer

Cysteine proteases (cathepsin B and L), the serine protease urokinase-type plasminogen activator and its inhibitor type-1 play an important part in cancer invasion and metastasis. The authors determined the protease concentrations in gastric cancer tissues, using the ELISA method, in patients with gastric cancer. They evaluated the prognostic role of proteases and the relationship that these proteases may have with other histomorphological prognostic parameters such as tumor staging, grading, histotype, Borrmann classification. The Cox survival analysis showed that cathepsin B (p = 0.002), urokinase-type plasminogen activator (p = 0.0001) and the inhibitor type-1 (p = 0.0004) significantly correlated with poor prognosis. The tumor staging, grading, Borrmann classification correlated also significantly with survival time. Urokinase-type plasminogen activator was selected as the single independent variable in the Cox model (p = 0.0001).     

Interactions of proteases and protease inhibitors in Sertoli-germ cell cocultures preceding the formation of specialized Sertoli-germ cell junctions in vitro

The biochemical mechanism(s) by which germ cells can form specialized junctions with Sertoli cells in the seminiferous epithelium at various stages of the spermatogenic cycle is unknown. This study sought to examine the biochemical changes that are involved when germ cells are cocultured with Sertoli cells in vitro preceding the establishment of specialized Sertoli-germ cell junctions. While isolated germ cells were allowed to attach to Sertoli cells, media from both the apical and basal compartments of bicameral units were collected to assess serine and cysteine protease activity. The expression of selected serine and cysteine proteases and their corresponding inhibitors in these Sertoli-germ cell cocultures was also examined by RT-PCR. Using an [125I]-collagen film assay, a transient but significant increase in serine protease activity was noted in both the apical and basal compartments when germ cells began to settle onto the Sertoli cell monolayer preceding the formation of intercellular junctions. A specific tryptase (RNK-Tryp 2, a serine protease formerly cloned from a rat granular lymphocyte leukemia cell line, RNK-16, cDNA expression library) was shown to be expressed exclusively by Sertoli cells and not germ cells. Furthermore, Sertoli cell tryptase expression as well as urokinase plasminogen activator (u-PA, also a serine protease) increased significantly when germ cells were adhering to Sertoli cells. The decline in total serine protease activity when Sertoli-germ cell junctions were being formed was accompanied by a concomitant increase in alpha2-macroglobulin (alpha2-MG, a nonspecific protease inhibitor) expression. No significant changes in cysteine protease activity in either the apical or basal compartment were noted. However, there was a transient but significant increase in cathepsin L expression when germ cells were adhering to Sertoli cells preceding cell junction formation. The subsequent reduction in cathepsin L expression after this transient increase was accompanied by a concomitant increase in cystatin C expression. These results suggest that proteases and their corresponding inhibitors are working synergistically and are likely to be involved in the adherence of germ cells to Sertoli cells and the subsequent formation of intercellular junctions.     

The sensitivity of biological tissue to ultrasound

Plasminogen activators are serine proteases which play a key role in morphogenesis and tissue remodelling. Two different molecular types, tissue-type and urokinase-type, were identified and they were postulated to play a role in neural development. The developing chick optic lobe plays a central role in processing visual information. In previous studies we demonstrated the occurrence of high levels of plasminogen activator activity in this model. The aim of the present paper is to study the temporal pattern of expression of this activity and characterize the type of plasminogen activator expressed in the developing optic lobe. Using soluble fractions derived by ultracentrifugation from Triton X-100-treated membrane fractions we measured the protease activity with a radial fibrinolytic assay. Employing different inhibitors of fibrinolytic activity and a zymographic assay, we showed that the developing optic lobe expresses only one type of plasminogen activator which corresponds to an urokinase-type of 70 kDa. Our results indicate that peaks of protease activity temporally correlate with massive neuronal migration, neurite outgrowth and synapse formation and maturation. This suggests that a plasminogen activator could play a role in these developmental events. This consistent pattern of variability strongly suggests that it is developmentally regulated and, if so, it could be a reliable parameter to study neural plastic changes induced by modifications in the environmental stimulation.     

Hydrogen peroxide induced impairment of post-ischemic ventricular function is prevented by the sodium-hydrogen exchange inhibitor HOE 642 (cariporide)

Using highly degenerate, serine-protease-specific PCR primers on a midgut-specific cDNA library it was estimated that a minimum of 24 independent serine proteases were expressed in the midgut of Stomoxys calcitrans. The relative abundance of these 24 independent serine proteases has been estimated by restriction analysis of PCR products, showing that 69% fall into six almost equally abundant groups. Two highly abundant serine protease cDNAs (Ssp1 and Ssp2) were isolated and sequenced. They encode preproenzymes of 272 amino acids (Mr 28521) and 255 amino acids (Mr 27097) with putative signal peptides of 17 amino acids and 16 amino acids, putative activation peptides of 15 amino acids and 10 amino acids and mature enzymes of 239 amino acids (Mr 25322; pI 4.89) and 228 amino acids (Mr 24182; pI 7.59), respectively. Both deduced amino acid sequences contain the Asp/His/Ser catalytic triad and the highly conserved sequences surrounding it. Ssp2 also has the aspartate and two glycine residues in the specificity pocket, marking this as a typical trypsin. The positioning of the residues in the specificity pocket of Sspl is unusual; aspartate and glycine residues are present, which is typical of trypsin, but both are separated from surrounding conserved residues by additional amino acids; the second glycine found in the specificity pocket of trypsin is replaced by a serine, which is typical of chymotrypsin. Although a serine protease, the precise substrate specificity of Sspl remains to be determined. Northern analysis shows that both serine proteases are expressed constitutively with only a 20% change in the levels of expression of Ssp1 and Ssp2 through the digestive cycle, and that expression occurs predominantly in the opaque region of the midgut, the region responsible for secretion of digestive enzymes.     

Production of urokinase-type plasminogen activator (u-PA) and plasminogen activator inhibitor-1 (PAI-1) in human brain tumours

We investigated the role of plasminogen activators (PAs) and their inhibitor (plasminogen activator inhibitor-1, PAI-1) in human brain tumours. The amounts of urokinase-type plasminogen activator (u-PA), tissue-type plasminogen activator (t-PA), and plasminogen activator inhibitor-1 (PAI-1), and the activity of u-PA and t-PA were determined by enzyme-linked immunosorbent assay (ELISA), and u-PA and PAI-1 were immunolocalized using monoclonal antibodies in human brain tumours and normal brain tissues. The tissues were surgically removed from 64 patients; normal brain tissue (5 cases), low-grade glioma (4 cases), high-grade glioma (17 cases), metastatic tumour (9 cases), meningioma (benign 12 cases, malignant 6 cases), acoustic schwannoma (11 cases). u-PA activity and u-PA and PAI-1 antigen levels were significantly elevated in malignant brain tumours (malignant meningiomas, high-grade gliomas, and metastatic tumours) and acoustic schwannomas but very low in benign meningiomas, low-grade gliomas and normal brain. There was no difference in t-PA antigen levels among normal and malignant tissues, however levels of t-PA activity were markedly decreased in metastastic tumours. All malignant brain tumour tissues showed positive immunostaining for u-PA and PAI-1, however, some tumour cells showed negative intensity while others showed strong intensity for these antibodies. This contrasts to the homogeneous staining pattern found in acoustic schwannoma. These findings indicate that malignancy in human brain tumours is associated with elevated levels of u-PA and PAI-1 and that an imbalance between these proteins in a micro-environment contributes (ascribes) to tumour cell invasion.     

The fibrinolytic system in neoplasia

During activation of the fibrinolytic system plasminogen is converted to plasmin by tissue plasminogen activator (t-PA) or urokinase-type plasminogen activator (u-PA). t-PA is predominantly released from endothelial cells, u-PA primarily by renal parenchymal cells. The activation of plasminogen is regulated by plasminogen activator inhibitor-1 (PAI-1), plasmin is controlled by alpha 2-plasmin inhibitor. The fibrinolytic system is not only involved in the intravascular dissolution of fibrin (thrombi), it also plays a vital role in normal physiologic reproduction, wound repair, angiogenesis, and tissue remodeling. Fibrinolysis is also a vital component in the pathogenesis of neoplastic disease. It is essential in releasing cells from their primary site of origin, providing nutrition for neoplastic cell growth and promoting cell mobility and motility. In neoplastic cells the degradation of the extracellular matrix proteins is facilitated by excessive expression of u-PA, t-PA, and u-PAR. In many forms of carcinoma increased expression of u-PAR and u-PA is associated with significantly shorter survival. Greater expression of u-PA in breast cancer cells, for example, is associated with shorter survival and increased relapse rate. Progressively aggressive neoplastic cells evidence high expression of u-PA and u-PAR activities, variable expression of t-PA, and enhanced PAI-1 and PAI-2 activities. In acute nonlymphocytic leukemias, poor outcome correlates with high t-PA levels. In acute progranulocytic leukemia there is a high incidence of DIC. Neoplastic prostatic tissue also expresses high u-PA activity and the more aggressive the cell line, the greater the number of u-PAR and the higher the u-PA activity. In gynecologic malignancies, a greater expression of u-PA in combination with cathepsin D is associated with widespread disease and poor prognosis. High u-PA values were also seen in patients with brain, gastric, and hepatic malignancies. It is evident that the plasminogen-plasmin system is a vital component in the biology of neoplastic disease and that it is, in theses conditions, in no way beneficial to the host.     

Balance between matrix synthesis and degradation: a determinant of glomerulosclerosis

In glomerular health and disease, the balance between extracellular matrix (ECM) protein synthesis and degradation determines the amount of matrix that accumulates locally. While cell and whole animal regulation of ECM synthesis has been the subject of ongoing study, attention has become focused on proteases that degrade matrix components only recently. Two major ECM protease systems have been defined. The plasminogen activators (PAs) are serine proteases that have matrix-degrading capability and also activate plasminogen to plasmin. Plasmin not only degrades ECM proteins, but also may activate members of the matrix metalloproteinase (MMP) family which comprise the second major matrix-degrading system. Specific biological antagonists of both the PAs and the MMPs tightly regulate proteolysis by these enzymes. All of these enzymes and inhibitors have been detected in the kidney, and their expression may be altered to facilitate ECM accumulation in conditions associated with matrix expansion, such as glomerulosclerosis. Work is in progress to determine how these systems are regulated in the kidney and to further define their contribution to the sclerotic process.     

Zyme, a novel and potentially amyloidogenic enzyme cDNA isolated from Alzheimer's disease brain

The deposition of the beta amyloid peptide in neuritic plaques and cerebral blood vessels is a hallmark of Alzheimer's disease (AD) pathology. The major component of the amyloid deposit is a 4.2-kDa polypeptide termed amyloid beta-protein of 39-43 residues, which is derived from processing of a larger amyloid precursor protein (APP). It is hypothesized that a chymotrypsin-like enzyme is involved in the processing of APP. We have discovered a new serine protease from the AD brain by polymerase chain reaction amplification of DNA sequences representing active site homologous regions of chymotrypsin-like enzymes. A cDNA clone was identified as one out of one million that encodes Zyme, a serine protease. Messenger RNA encoding Zyme can be detected in some mammalian species but not in mice, rats, or hamster. Zyme is expressed predominantly in brain, kidney, and salivary gland. Zyme mRNA cannot be detected in fetal brain but is seen in adult brain. The Zyme gene maps to chromosome 19q13.3, a region which shows genetic linkage with late onset familial Alzheimer's disease. When Zyme cDNA is co-expressed with the APP cDNA in 293 (human embryonic kidney) cells, amyloidogenic fragments are detected using C-terminal antibody to APP. These co-transfected cells release an abundance of truncated amyloid beta-protein peptide and shows a reduction of residues 17-42 of Abeta (P3) peptide. Zyme is immunolocalized to perivascular cells in monkey cortex and the AD brain. In addition, Zyme is localized to microglial cells in our AD brain sample. The amyloidogenic potential and localization in brain may indicate a role for this protease in amyloid precursor processing and AD.     

Percutaneous fibrin glue therapy of meningeal cysts of the sacral spine

The release of extracellular proteases by the axonal growth cone has been proposed to facilitate its movement by digesting cell-cell and cell-matrix contacts in the path of the advancing growth cone. The serine protease plasminogen activator (PA) has been shown to be secreted and focally concentrated at axonal growth cones of cultured mammalian neurons. Thus, PAs are well-placed to play an active role in growth cone movement and axonal pathfinding in development and regeneration. We discuss recent findings that suggest that the biological action of these proteases is more complex than originally thought.     

Comparison of LHRH-peptidase and plasminogen activator activity in rat testis extracts

Testicular LHRH-peptidase and testicular urokinase-type plasminogen activator are Sertoli cell-secreted proteases which display similar molecular properties. However, there is relatively little information regarding the substrate specificity and potential cross-reactivity of these enzymes. Testicular extracts were prepared from homogenates of whole rat testes and assessed by LHRH-peptidase assay, and by radial caseinolysis assays for plasminogen activator and plasmin-like activity. Following partial purification of the protease activities in testicular extracts by gel filtration and ion-exchange chromatography, it was confirmed that testicular LHRH-peptidase and plasminogen activator are clearly separable. There was no detectable plasmin-like activity in the testicular extracts; however, the extracts were found to contain an inhibitor, or inhibitors, of both plasminogen activator and plasmin activity. In addition to LHRH and Gly6-substituted LHRH analogues, the partially purified LHRH-peptidase degraded both angiotensins I and II, but not the gonadotrophin-releasing-hormone-associated peptide derived from the LHRH precursor molecule. These properties of the LHRH-peptidase provide further evidence that it is a testis-specific prolyl endopeptidase, involved in regulating and/or limiting peptide activity in the testis.     

Retinoic acid-enhanced invasion through reconstituted basement membrane by human SK-N-SH neuroblastoma cells involves membrane-associated tissue-type plasminogen activator

Al-trans retinoic acid (RA) enhanced human, S-type, SK-N-SH neuroblastoma cell invasion of reconstituted basement membrane in vitro but did not induce terminal differentiation of this cell line. In contrast to basal invasion, which was urokinase (uPA)- and plasmin-dependent, RA-enhanced invasion was dependent on tissue-type plasminogen activator (t-PA) and plasmin activity. Neither basal nor RA-enhanced invasion involved TIMP-2 inhibitable metalloproteinases. Enhanced invasion was associated with the induction of t-PA expression, increased expression of the putative t-PA receptor amphoterin, increased association of t-PA with cell membranes and increased net membrane-associated PA activity. Enhanced invasion was not associated with significant changes in the expression of uPA or its membrane receptor UPAR; plasminogen activator inhibitors PAI-1 and PAI-2; metalloproteinases MMP-1, MMP-2, MMP-3, MMP-9 and membrane type MMP1; or tissue inhibitors of metalloproteinases TIMP-1 and TIMP-2. RA stimulated the association of t-PA with the external cell membrane surface, which could be inhibited by heparin sulphate but not by mannose sugars or chelators of divalent cations, consistent with a role for amphoterin. Our data indicate that RA can promote the malignant behavior of S-type neuroblastoma cells refractory to RA-mediated terminal differentiation by enhancing their basement membrane invasive capacity. We suggest that this results from the action of a novel, RA-regulated mechanism involving stimulation of t-PA expression and its association with the cell membrane leading to increased PA-dependent matrix degradation.     

Hemoptysis caused by pulmonary arterial aneurysm, disclosing Beh?et disease. Apropos of 2 cases]

MCF7 and ZR75-1 breast cancer cells grow as adherent monolayers in tissue culture. Treatment with the serum serine protease plasmin causes them to detach and to grow as floating multicellular spheroids. Two plasmin activators, urokinase plasminogen activator and streptokinase, induce the same growth pattern changes in the presence of plasminogen. Serum contains also plasminogen activator inhibitors. Aged serum, deficient in plasminogen activator inhibitors, converts spontaneously monolayer breast cancer cells into multicellular spheroids which readily revert to monolayer growth after addition of fresh serum. Urokinase blocks the reversion. The formation of multicellular spheroids does not affect the proliferative rate of breast tumor cells but endows tumor cells with increased resistance to the chemotherapeutic drugs, doxorubicin and paclitaxel.     

Production of tissue-type plasminogen activator (t-PA) and type-1 plasminogen activator inhibitor (PAI-1) in mildly cirrhotic rat liver

We have studied the production of tissue-type plasminogen activator (t-PA) and type-1 plasminogen activator inhibitor (PAI-1) in liver of normal rats and in rats with mild cirrhosis induced by carbon tetrachloride inhalation, to demonstrate the production of these fibrinolytic components and their pathophysiologic role in the liver in vivo. Immunohistochemical study of paraffin-embedded liver sections and fibrin autography of frozen sections showed that the normal rat liver produces very little t-PA or PAI-1. On the contrary, striking t-PA activity and both t-PA and PAI-1 antigens were observed in the cirrhotic liver. Both t-PA and PAI-1 in plasma were also markedly increased in the cirrhotic rats. Because the hepatocyte can internalize t-PA or PA/PAI-1 complexes from circulation, Northern blot analysis of the total liver RNA was performed to demonstrate the endogenous synthesis of t-PA and PAI in the liver. Although the normal liver hardly expresses either t-PA or PAI-1 mRNA, striking t-PA and PAI-1 mRNA expression was observed in the liver of rats with mild cirrhosis. These data demonstrate that t-PA and PAI-1 production is strongly upregulated in the liver in rats with mild cirrhosis. These fibrinolytic components, whose production is closely associated with liver failure, may play important roles in the regulation of hepatocyte proliferation and liver regeneration in vivo.     

Expression of the plasminogen activation system in kidney cancer correlates with its aggressive phenotype

Malignant tumors contrast with benign ones in their ability to invade adjacent tissue and to metastasize. The urokinase plasminogen activator is a proteolytic enzyme that can facilitate these processes. In many carcinomas, the concentration of the urokinase plasminogen activator system is high. The high expression of these enzymes is related to tumor grade. In this study, we have investigated whether secretion of the urokinase plasminogen activator, urokinase plasminogen activator receptor, and plasminogen activator inhibitor 1 in normal kidney tissue and kidney cancer tissue follows this pattern. We have found that urokinase plasminogen activator, urokinase plasminogen activator receptor, and plasminogen activator inhibitor 1 were expressed in higher levels in kidney cancers (squamous cell carcinoma and renal cell carcinoma) than in normal kidney tissue and that these differences were statistically significant (P < or = 0.05). In renal cell carcinomas, we have observed differences between normal kidney tissue and renal cell carcinomas in males and Caucasians but not in females and African Americans (P < or = 0.05). Expression of the urokinase plasminogen activator system was also higher in grade III tumors when compared with lower-grade tumors or normal tissue.