Modulation of substance P signaling by dipeptidyl peptidase-IV enzymatic activity in human glioma cell lines.

Dipeptidyl peptidase-IV (DPP-IV, CD26) is a serine protease almost ubiquitously expressed on cell surface and present in body fluids. DPP-IV has been suggested to proteolytically modify a number of biologically active peptides including substance P (SP) and the chemokine stromal cell derived factor-1alpha (SDF-1alpha, CXCL12). SP and SDF-1alpha have been implicated in the regulation of multiple biological processes and also induce responses that may be relevant for glioma progression. Both SP and SDF-1alpha are signaling through cell surface receptors and use intracellular calcium as a second messenger. The effect of DPP-IV on intracellular calcium mobilization mediated by SP and SDF-1alpha was monitored in suspension of wild type U373 and DPP-IV transfected U373DPPIV glioma cells using indicator FURA-2. Nanomolar concentrations of SP triggered a transient dose dependent increase in intracellular calcium rendering the cells refractory to repeated stimulation, while SDF-1 had no measurable effect. SP signaling in DPP-IV overexpressing U373DPPIV cells was not substantially different from that in wild type cells. However, preincubation of SP with the DPP-IV overexpressing cells lead to the loss of its signaling potential, which could be prevented with DPP-IV inhibitors. Taken together, DPP-IV may proteolytically inactivate local mediators involved in gliomagenesis.

Dietary habits and lung cancer risk among non-smoking women.

A case-control study was conducted to investigate the relationship between diet and the risk of lung cancer among women non-smokers and to compare with women smokers in the same population. Data collected by personal interviews from 435 microscopically confirmed cases and 1710 controls were analysed using unconditional logistic regression. In addition to results for all study subjects, associations between diet and lung cancer risk were compared between two highly contrasting groups: smokers (odds ratio (OR) 7.03) and non-smokers (OR 1.00). A protective effect of frequent (daily or several times per week) black tea drinking appeared among non-smoking women (OR 0.65, 95% confidence interval (CI) 0.43-0.99). Among smoking women, protective effects were observed for frequent intake of milk/dairy products (OR 0.56, 95% CI 0.32-0.96), coffee (OR 0.47, 95% CI 0.25-0.88), and wine consumption (daily or weekly OR 0.60, 95% CI 0.37-0.98; monthly OR 0.60, 95% CI 0.39-0.94). Inverse associations with the risk appeared for physical exercise for smokers only, and for the body mass index both among non-smoking and smoking women. Some items of diet may contribute to variation in risk among women in the Czech Republic; their importance seems to vary in relation to their status in smoking, the dominant factor in the aetiology of lung cancer.

Tracheal stenosis complicated with tracheoesophageal fistula.

OBJECTIVE: The aim of the present study was to evaluate the results of surgical treatment in patients with simultaneous occurrence of postintubation tracheal stenosis (TS) and tracheoesophageal fistula (TEF). METHODS: In the group of 51 patients with postcannulation tracheal stenosis who underwent segmental resection, TEF was identified simultaneously in five (10%) of them. The mean age of the TS-TEF patients was 43 years (range 35-60 years). The patients underwent a single-stage operation during which TEF was sealed and resection of the stenotic tracheal segment was performed. RESULTS: The cause of TEF and of TS was artificial pulmonary ventilation by tracheostomy tube (n=4) or by endotracheal tube (n=1) with a simultaneous insertion of nasogastric tube. In one of the patients with tracheostomy the fistula resulted from an injury to the pars membranacea tracheae and the esophageal wall during tracheostomy. All the patients were respiring spontaneously before the surgical treatment. The mean length of the fistula was 24.0 mm (range 15-30 mm), the fistulae were located at the junction of the upper and middle third of the trachea. The mean length of the resected tracheal segment was 29.6 mm (range 26-32 mm). Postoperative complications were not observed in the group of the TS-TEF patients, none of them died. CONCLUSIONS: The method of choice of the surgical treatment of TEF associated with TS is a single-stage procedure in the patient who respires spontaneously.

Bronchial carcinoid tumors: long-term outcome after surgery.

The objective of the present study was to evaluate clinical condition and results of surgical treatment of patients with typical and atypical bronchial carcinoids. The study was based on retrospective analysis of a total of 96 patients (mean age 47.3 year, age range 21-76, 44 men and women 52), who were surgically treated for bronchial carcinoid between 1985-2001. We assessed symptomatology of the disease, type of surgical intervention, tumor histology and staging, and postoperative 5-year and 10 year survival rates. The main sign of disease was respiratory inflammation. The carcinoid syndrome was not found in any patient. Most patients (n=68) were operated for central form of the tumor. The micromorphological tumor diagnosis was established prior to surgery in 76.5% patients with the central form of carcinoid. Surgical treatment included lobectomy (n=49), bronchoplastic procedure (n=14), sleeve lobectomy (n=9), atypical resection and segmentectomy (n=11), pneumonectomy (n=7) and tumor enucleation (n=5). Histological analysis revealed typical carcinoid in 77 cases (80.2%) and atypical carcinoid in 19 (19.8%). Lymph nodes (N1 and/or N2) were examined by histology in 84 patients and lymph node metastases were found in 13 (19.4%) of 67 patients with typical carcinoid and in 5 cases (29.4%) of 17 with atypical carcinoid. In the postoperative period on patient died from embolism to the arteria pulmonalis. Postoperative complications (atelectasis, prolonged air leak, bronchopleural fistula) were observed in 11.4% of patients. Tumor relapse occurred only in two patients with typical carcinoid. Postoperative 5-year and 10-year rates amounted to 98.6% and 87.3%, respectively, in typical carcinoid 94.5% and 73.5% in atypical carcinoid. The survival rates of patients with typical and atypical bronchial carcinoids were not significantly different (p>0.05). The surgical management is the treatment of choice in bronchial carcinoids. Results of this study indicate that the 5-year survival in patients with either histological type of bronchial carcinoid is excellent and the prognosis of operated patients is very good even in the case of regional lymph nodes infiltration by the tumors.

Cysteine proteinases in tumor cell growth and apoptosis.

During their evolution tumor cells acquire and mobilize various mechanisms that crucially affect their capability of proliferation, invasiveness and metastasis. Recent findings provide evidence that tumor cell associated cysteine proteinases such as some lysosomal cathepsins and apoptotic caspases are fundamentally involved in specific developmental traits of tumor cell populations. Tumor cell exterior-associated cysteine cathepsins B and L promote tumor growth, invasion and metastasis through degradation of extracellular connective matrices and through endothelial cell growth-directed activities. On the other hand, caspases -3, -7 and -6, generated in tumor cell cytoplasm via a robust activation of their zymogens, suppress tumor cell growth, invasion and metastasis through proteolytic devitalizing and remodeling of tumor cells into readily phagocytable apoptotic corpses. Tumor cell variants that are deficient in expression of effector caspase zymogens or are capable to suppress the extrinsic and intrinsic activation mechanisms of effector caspase zymogens and the activity of effector caspases have a significant survival advantage in environments of various death stimuli. Advancements in pharmacological targeting of tumor associated pathogenic lysosomal cysteine cathepsins and in apoptotic caspases-oriented conditioning of tumor cells may substantially contribute to therapeutic control of tumor diseases.

Regulation of cathepsin B activity by cysteine and related thiols.

We studied the mode of regulation of the activity of mature cathepsin B (CB) by L-cysteine and some related thiols. The activity of CB with Z-Arg-Arg-NHMec as substrate was gradually inhibited over a range of increasing concentration of Cys, Cys methyl ester (CysOMe), Cys ethyl ester (CysOEt), N-acetyl-Cys (N-AcCys) and 3-mercaptopropionic acid. However, the inhibition of CB peaked at a definite value of [Cys], [CysOMe], [CysOEt] and [N-AcCys] and was gradually reversed over a range of higher concentrations of Cys and its esters. The maximum inhibitory concentrations of Cys, CysOME, CysOEt and N-AcCys showed a positive relationship to the pKa(RSH) values of the thiols and those of CysOEt and Cys decreased with increasing pH. The capability of the thiols to overcome their own inhibitory effect on CB was dependent on the concentration of their thiolate anion (RS-). However, the preincubation-dilution experiments showed that Cys and N-AcCys did not interact with active CB via a covalent mode. The inhibition of CB by N-AcCys was competitive and could be reversed by CysOMe. This activity-recovering effect of CysOMe was concentration-dependent and obeyed the Michaelis-Menten saturation kinetics over a profound increase of [RS-]. CB reacting in an environment of concurrently decreasing [RS-] and increasing [RSH], which was achieved by means of carboxylesterase-catalyzed deesterification of CysOEt to Cys, was progressively inhibited. Cys and N-AcCys also inhibited the fragmentation of histone H4 by CB and their concentration-dependent inhibitory profiles were qualitatively similar to those observed with Z-Arg-Arg-NHMec. Taken together, the results indicate that the RSH form of Cys and related thiols inhibits the activity of CB while the RS- form of these thiols counteracts or reverses the inhibitory action of the RSH form. This previously unrecognized thiol-thiolate anion regulation mechanism might be involved in a dynamic regulation of CB activity in endosomes and lysosomes and at the sites of lysosome-driven pericellular proteolysis.

Dipeptidyl peptidase IV in C6 rat glioma cell line differentiation.

The C6 rat glioma cell line is broadly used as a model in studies of glial cell differentiation. In the present study we demonstrated a significantly higher total cellular, but especially membrane-associated, activity of dipeptidyl peptidase IV in differentiated C6 cells in comparison with their proliferating counterparts. The majority, but not all, of enzyme isoelectric focusing isoforms from differentiated C6 cells displayed a substantially higher activity compared to the proliferating cells, with G-P-NHMec as the substrate. Non-denaturing polyacrylamide gradient gel electrophoresis showed the presence of one major peak of activity, dipeptidyl peptidase IV (Mr of about 220000), in both proliferating and differentiated C6 cells. The results indicate that dipeptidyl peptidase IV regulation is associated with C6 rat glioma cell differentiation.

Cysteine proteases and cysteine protease inhibitors in non-small cell lung cancer.

In this study we investigated the levels of two lysosomal cysteine protease proteins cathepsin B (CB) and cathepsin L (CL) and the levels of three cysteine protease inhibitor proteins stefin A (SFA), stefin B (SFB) and cystatin C (CNC) in squamous-cell lung carcinoma (SQCLC) and matched lung parenchyma specimens and examined the inhibition of CB and cathepsin C (CC) activities by endogenous inhibitors in extracts from SQCLC, lung adenocarcinoma (LAC) and lung parenchyma specimens. We found that Stage I SQCLCs contained significantly increased levels of CB protein, CB activity and SFA protein as compared to matched lungs. Neither the levels of CL protein nor the levels of SFB protein nor the levels of CNC protein in Stage I SQCLCs and the lungs were significantly different, but the levels of CB and CL proteins as well as the levels of SFA and SFB proteins showed significant positive correlation in SQCLCs. In SQCLCs as well as in the lungs the level of SFB protein was significantly higher than the level of SFA protein or the level of CNC protein. In the lungs the levels of SFA protein and CNC protein revealed a weak negative correlation trend. In extracts from SQCLCs the level of SFA protein showed a weak negative correlation with the residual CB activity (i.e. the activity remaining after extract preincubation) whereas in extracts from the lungs the level of CNC protein displayed a weak negative correlation trend with the residual CB activity and with the residual CC activity. We observed that SQCLCs and LACs contained not only a significantly increased activity of CB but also a significantly higher inhibitory potential against the activity of endogenous CB as compared to matched lungs. Leupeptin, a small inhibitor of CB, was capable to protect CB in lung carcinoma and lung parenchyma extracts from preincubation-induced inhibition, revealing an active-site directed and competitive nature of CB inhibition by endogenous cystatins. Ultrafiltration passaged protein preparations of nominal Mr < or = 30,000 obtained from extracts of SQCLCs inhibited significantly higher quantities of activity of purified bovine spleen CC than did such protein preparations from matched lungs. Reaction courses of purified bovine spleen CC that had been preincubated with such protein preparations resembled those of endogenous CC from SQCLC and lung extracts showing a slow steady-state approach. These observations and the relaxation kinetics of CC from SQCLC and lung extracts suggest that CC in the extracts may be complexed with some cystatins. In conclusion, our results indicate that quantitatively different combinations of cystatins are the major constituents of the inhibitory potential against CB and CC in SQCLCs and the lungs.

Cathepsin B, thiols and cysteine protease inhibitors in squamous-cell lung cancer.

We investigated activities of the cysteine protease cathepsin B (CB; EC 3.4.22.1), the levels of reduced glutathione (GSH) and cysteine and the activity of gamma-glutamyltransferase (gamma-GT; EC 2.3.2.2) in squamous-cell lung carcinoma (SQCLC) and the lung parenchyma specimens from surgically treated patients. The basal CB activity, assayed in tissue extracts in the absence of exogenous activators, was significantly higher in SQCLC compared to the lung. The residual CB activity, remaining in tissue extracts after preincubation at 37 degrees C, was not any longer significantly different in SQCLC and the lungs. The inhibited CB activity, calculated as the difference between the basal and residual CB activities, was significantly higher in SQCLC compared to the lung. In the case of the cysteine protease cathepsin C (CC; EC 3.4.14.1), neither the basal nor the residual nor the inhibited CC activities in SQCLC and the lung were significantly different. Compared to CC, the powerfulness of endogenous cysteine protease inhibitors to inhibit CB was much higher in both SQCLC and the lung. The cysteine protease inhibitors from SQCLC and the lung which effectively inhibited CB could be related to the inhibitors with an apparent M(r) ranging from 10,000 to 30,000. Isoelectric focusing studies indicated significant differences in the progress of inhibition of the activity of CB isoforms in SQCLC and lung parenchyma extracts. The levels of both GSH and Cys were significantly higher in SQCLC compared to the lung and the level of GSH was significantly higher in Stage III tumors compared to Stage I tumors. The activity of gamma-GT was not significantly different in SQCLC and the lung but it was significantly higher in Stage I tumors compared to Stage III tumors and showed a significant negative correlation with GSH level in SQCLC. Dithiothreitol did not increase the basal activity of CB from SQCLC and the lung which indicates that reversibly oxidized forms of CB do not accumulate in the tumors and the lungs. The basal activity of CB from SQCLC and the lung was competitively inhibited by Cys. Moreover, increasing Cys concentrations had a modulatory effect on the basal activity of CB from SQCLC and the lung which was featured by Cys-induced inhibition of CB activity and by subsequent Cys-effected recovery of CB activity from its previous inhibition by Cys.

Cell membrane-bound proteases: not "only" proteolysis.

Ectopeptidases are widely distributed among various cell systems. Their expression on an appropriate cell type is finely regulated, reflecting the specific functional cell implications and engagement in defined physiological pathways. Protein turnover, ontogeny, inflammation, tissue remodelling, cell migration and tumor invasion are among the many physiological and pathological events in which cell-surface proteases play a crucial role, both as effector as well as regulatory molecules. It has recently become clear that also non-catalytic effects of membrane-bound proteases are of great importance in some biological regulations. They may generate specific signal transduction intracellularly, after reacting with certain target molecules. They may also play a pivotal role in cell-cell and cell-virus contact and recognition, as well as in binding to the extracellular matrix. This short review provides some insight into the multifunctional mechanisms attributed to cell membrane-bound proteases.

Lysosomal dipeptidyl-peptidases I and II in human squamous cell lung carcinoma and lung parenchyma.

In the present work we studied the levels of activities of dipeptidyl-peptidase I (or cathepsin C, DPP-I) and dipeptidyl-peptidase II (DPP-II) and examined their isoelectric focusing profiles in matched pairs of human squamous cell lung carcinoma (SQCLC) and the lung from surgically treated patients (n = 33). The mean specific activities of DPP-I and DPP-II were higher in SQCLC (Stages I and II) than in the lung, but only the activity of DPP-II in Stage I SQCLC was significantly higher compared to the lung. The activities of both enzymes were higher in the tumor than in the lung in 10 of 20 Stage I SQCLC patients, but only in 3 of 13 Stage II SQCLC patients. The specific activities of DPP-I and DPP-II in the lungs showed a good correlation while the correlation of both enzyme activities in SQCLCs was poor. We observed only a small and mutually comparable activation of DPP-I in extracts from SQCLCs and from the lungs by dithiothreitol. The isoelectric focusing profile of several DPP-II forms in SQCLCs and the lungs was similar and the single major DPP-II isoform revealed in the tumors and lungs showed a pIapp of 5.3-5.2. The isoelectric focusing profile of DPP-I showed multiple enzyme forms in SQCLCs (pIapp 6.3-4.5) as well as in the lungs (pIapp 6.4-4.8). In SQCLCs, as well as in the lungs, the activities of the DPP-I forms with pIapp values < or = 5.6 were shifted by neuraminidase treatment to the site of the major DPP-I isoform with pIapp of about 6.0 and the zymograms then showed an another DPP-I with pIapp of 5.7, which was less discernible in the lung. In some patients, the DPP-I forms with pIapp values < or = 5.6 from SQCLC retained a greater percentage of activity distribution than did the DPP-I pIapp-counterparts from the lung.

Multiple forms of cathepsin B in human lung cancer.

In this study we have examined, by means of isoelectric focusing (IEF) in native polyacrylamide gel and contact-print fluorescence zymography, whether human lung carcinomas and the lung parenchyma contain different pools of multiple charge forms of the cysteine proteinase cathepsin B. The isoelectric point (pI) patterns of cathepsin B from lung carcinoma and matched lung were similar, particularly with regard to 2 major intermediate acidic enzyme pI forms designated as I and II (pIapp of 5.10 and 4.93 in tumors, and 5.11 and 4.94 in lungs, respectively). The slightly acidic cathepsin B pI forms (pIapp 5.47-5.19) in squamous-cell lung carcinoma (SQCLC) were significantly more numerous than such enzyme pI forms in lungs. The numbers of the highly acidic cathepsin B pI forms (pIapp 4.82-4.33) were significantly higher in SQCLC and lung adenocarcinoma (ACL) than in matched lung. The activity distribution percentage in the set of highly acidic cathepsin B pI forms was significantly higher in SQCLC and ACL than in matched lung. We also observed that cathepsin B from SQCLC and matched lung was fully recoverable by IEF from inhibition by leupeptin. Using the cysteine-proteinase-specific inactivator E-64, we revealed by IEF that some cathepsin B isoforms (charge forms) from SQCLC were more resistant to inactivation by this compound than the corresponding enzyme isoforms from lungs. After IEF, the enzyme isoforms apparently lost their resistance to E-64. Our results indicate that the pool of multiple charge forms of cathepsin B in SQCLC and ACL is different from that in the lung, and also that there may be an increased level of loose complexes between cathepsin B and some proteins or polypeptides in SQCLC compared to the lung.

Two-step generation of spirocyclic dipeptides from linear peptide ethyl ester precursors.

Linear tri- and tetrapeptide precursors of 2,5-piperazinedione were prepared and their conversion to spirocyclic dipeptidase enzymes, the spirocyclic dipeptides (SpDp) were generated from the precursors by a two-step mechanism consisting in the proteolytic release of the C-terminal dipeptide ethyl ester and its subsequent spontaneous cyclization. After intraperitoneal administration of urokinase and Ac-Leu-Lys-Gly-Acp-OEt, a SpDp precursor targeted to endogenous plasmin, or the administration of the activated Hageman factor fragment and Ac-Leu-Arg-Ala-Acp-OEt, a SpDp precursor, targeted to endogenous kallikrein, the generated corresponding C-terminal dipeptide ethylester intermediates and SpDp, cyclo(Gly-Acp) and cyclo (Ala-Acp), respectively, were detected in the blood serum of C57B1 mice. Suppression of partial amnesia induced by sodium nitrite was observed in rats where it was subcutaneously administered with H-Leu-Ala-Acp-OEt, a peptide precursor of alaptide, the active SpDp, i.e. cyclo(1-amino-1-cyclopentanecarbonyl-L-alanyl).

Dipeptidyl peptidase IV, prolyl endopeptidase and cathepsin B activities in primary human lung tumors and lung parenchyma.

The activities of dipeptidyl peptidase IV (DPP-IV), prolyl endopeptidase (PE) and cathepsin B (CB) were investigated in primary human lung tumours and matched lung parenchyma, using continuous-rate fluorometric assays of the enzymes. Squamous-cell lung carcinomas showed significantly higher specific activities of all three enzymes studied. In lung adenocarcinomas only activities of PE and CB were increased significantly. In a limited number of primary human lung tumours of other histological types the activities of DPP-IV, PE and CB were also elevated. Mixing the matched homogenates of lung tumours and lung parenchyma gave additive activities for each enzyme studied. A significant correlation between tumour/lung ratios of specific activities of DPP-IV and CB was observed.

The malignant phenotype and cysteine proteinases.

Expression, membrane association and secretion of both cathepsin B and cathepsin L have been associated with the malignant phenotype of murine B16 melanomas. Only native forms of the two enzymes were found in the lysosomal fractions, whereas both native and latent forms were found in the membrane fractions. Brief exposure to acid pH induced secretion of only native forms of both cathepsin B and cathepsin L and a concomitant reduction in membrane-associated activities. Thus, the pericellular acidification associated with malignant tumors may provide optimal conditions for proteolysis by the cysteine proteinases in terms of their enhanced stability and their induced release in native forms not requiring proteolytic activation.

Aminopeptidases and angiotensin I-converting enzyme activities in primary human lung tumors and lung parenchyma.

The activities of alanyl aminopeptidase (AAP), arginyl aminopeptidase (RAP), alpha-glutamyl aminopeptidase (EAP) and angiotensin I-converting enzyme (ACE) were investigated in primary human lung tumors of different histological types and in matched lung parenchyma. In contrast to the studied aminopeptidases whose activity differences between tumor and lung tissues were infrequently significant, the activity of ACE was decreased highly significantly in the majority of lung tumors.

Dipeptidyl peptidase IV in the human lung and spinocellular lung cancer.

The isoelectric point and proportions of soluble and membrane bound dipeptidyl peptidase IV (DPP-IV) in human lung and spinocellular lung cancer tissue were tested. It was found that soluble DPP-IV is relatively less frequent in the cancer than in normal lung tissue. We demonstrated multiple molecular forms of DPP-IV in normal and cancer lung tissues, differing probably not only in the degree of sialylation. DPP-IV from lung cancer tissue consists of more basic molecular forms than that from normal lung tissue. These results suggest that the molecular properties of DPP-IV in normal and cancerous lung tissues may be different.

Cathepsin B and its endogenous inhibitors: the role in tumor malignancy.

Several lysosomal proteinases including the cysteine proteinase cathepsin B have been implicated in malignant progression of tumors. Many investigators have demonstrated correlations between increased activity of cathepsin B and increased metastatic capability of animal tumors or malignancy of human tumors. Such increases in cathepsin B activity in malignant tumors may reflect alterations in synthesis, in activation and processing, and/or in intracellular trafficking and delivery as well as in the endogenous inhibitors of cathepsin B. Increases in mRNA transcripts for cathepsin B have been observed in both murine and human tumors and multiple transcripts for cathepsin B have been identified, but an association of multiple transcripts with malignancy has not been confirmed. Cathepsin B precursors found in human malignant ascites fluid do not possess mannose-rich carbohydrates suggesting that a defect in the post translational processing of carbohydrate moieties on tumor cathepsin B may be responsible for the release of cathepsin B observed in many tumor systems. However, the intracellular trafficking of cathepsin B responsible for its association with plasma membrane/endosomal systems and for its release will require further study as both latent, precursor forms of cathepsin B and native forms of cathepsin B are involved. We speculate that malignant tumor cells adherent to basement membrane are capable of forming a digestive microenvironment in which lysosomal proteinases such as cathepsin B function optimally, a microenvironment similar to that formed between adherent osteoclasts and bone. One of the endogenous cysteine proteinase inhibitors, stefin A, also is affected by malignancy. Reduced expression (mRNA and protein) of stefin A is found as well as a reduction in its inhibitory capacity against cysteine proteinases. The data to date at both the molecular and protein levels supporting a functional role(s) for cathepsin B and its endogenous inhibitors in cancer progression are only correlative. Experimental approaches utilizing well-defined model systems in conjunction with genetic manipulation of cathepsin B and its endogenous inhibitors are needed to provide convincing evidence that cathepsin B has an important role in cancer.

Increased cathepsin B activity in human lung tumors.

The occurrence and levels of cathepsin B activity were investigated in primary human lung tumors and lung metastases of renal, colorectal and urinary bladder carcinomas as well as in the associated apparently normal lung parenchyma using a continuous rate enzyme assay with Ac-Leu-Arg-Arg-NHMec (7-(N-acetyl-L-leucyl-L-arginyl-L-arginylamido)-4-methylcoumarin) as the fluorogenic substrate. The inhibition studies of the enzymic hydrolysis of the substrate provided evidence for the catalytic action of the cysteine proteinase cathepsin B (CB) in the lung tumor tissues and the lung parenchyma under the assay conditions used. In the studied group of twenty-four patients with primary lung tumors of all major histological types, the level of CB activity in the tumor tissue was increased twofold and more over that in the associated lung parenchyma in 83% and 75% of cases, when expressed on the basis of wet tissue weight and tissue DNA, respectively. In patients with primary lung adenocarcinoma, the activity of the enzyme in the tumor tissue was elevated over that in the lung parenchyma in all cases studied. In both subgroups of patients with squamous cell lung carcinoma and adenocarcinoma, the mean cathepsin B activity was significantly higher in the tumor tissue than in the lung parenchyma. No obvious correlation was found between the tissue level of cathepsin B activity and the stage of primary lung tumor disease. In a limited number of patients with lung metastases, the level of cathepsin B activity was also higher in the tumor tissue than in the lung parenchyma.

A kinetic fluorometric assay of dipeptidyl peptidase IV in viable human blood mononuclear cells.

A continuous-rate fluorometric assay of dipeptidyl peptidase IV (DP-IV) in viable human blood mononuclear cells using 7-(L-glycyl-L-prolylamido)-4-methylcoumarin as the substrate is described. The assay method is accurate, rapid, and highly sensitive for measuring the level of cell-surface bound DP-IV activity in suspension of blood mononuclear cells, as well as of other viable cells bearing this enzyme. We believe that the kinetic assay is suitable for studying the regulation of expression and the role of plasma membrane-bound DP-IV on the cellular level.