Clinicopathologic Significance of Cathepsin B and Urokinase-type Plasminogen Activator Immunostaining in Colorectal Adenocarcinoma

Acetone-fixed cryostat sections of 52 colorectal adenocarcinomas (26 stage B, 26 stage C) were immunostained with antibodies for two "invasion-associated" proteolytic enzymes—cathepsin B and urokinase-type plasminogen activator. Cathepsin B immu nostaining of neoplastic cells was observed in 21 tumors (40%). It was generally accompanied by staining among peritumoral host cells. There was no correlation be tween neoplastic cell cathepsin B staining and tumor stage (stage B, 42% positive vs stage C, 38% positive) however staining was more frequent in tumors that recurred (cathepsin B negative, 23% recurred vs cathepsin B positive, 48% recurred, P = .05-.06,25 months follow-up). Significant neoplastic cell urokinase-type plasminogen activator staining was present in only six cases (12%); however, peritumoral spindle and inflammatory cells exhibited positivity in 35% of tumors. There was no correlation between host cell derived urokinase-type plasminogen activator staining and either node metastasis or patient outcome. Tumors that stained for both neoplastic cell ca thepsin B and stromal cell urokinase-type plasminogen activator (12%) characterized a morphologically and clinically aggressive subset, compared to cases that stained for only one (51%) or neither (37%) enzyme (both positive, 83% recurred, 83% poorly differentiated vs neither positive, 26% recurred, 5% poorly differentiated). These data imply that invasion-associated proteases are derived from heterogeneous cellular sources in colorectal tumors. Further, synergistic protease activity may promote aggres sive clinical behavior accounting, in part, for the adverse prognostic significance of poor differentiation. Int J Surg Pathol 1(4):227-234, 1994

Abstract P1-05-11: Biological characterization of tumor-associated leukocytes in positive and negative lymph node breast cancer patients

Background: Leukocytes plays crucial role in breast cancer progression and lymph node metastasis. Veins draining the breast through the axillary tributaries contain tumor-associated leukocytes migrating away from tumor microenvironment. Collecting tumor-associated leukocytes and characterizing their immunophenotype and biological properties in positive and negative lymph node patients may elucidate their role in lymph node metastasis.

Aims: Using an innovative surgical approach previously described, wecollectedtumor-associated leukocytes from venous drainage of the breast during breast cancer surgery of positive and negative lymph node (LN)metastasis patients. Isolated leukocytes were subjected to: 1) immunophenotyping; 2) cytokine profiling; and 3) assessment of the expression level of total and phospho NF-kβ.

Material and Methods: We enrolled 40 patients diagnosed with breast cancer from Ain Shams University Hospitals. Patients were sub-grouped into negative (zero) and positive (4) LN metastasis patients. All enrolled patients had not received neo-adjuvant chemotherapy. During modified radical mastectomy or conservative breast surgery, 15–20 ml of blood were collected from axillary vein tributaries for the isolation of tumor-associated leukocytes by Ficoll-Hypaque density gradient centrifugation. The immunophenotype of the isolated mononuclear cells was assessed using flow cytometry to identify the percentage of T lymphocytes (CD3+) and their subpopulations (CD4+ and CD8+), NK cells (CD56+) and B-lymphocytes (CD19+). Tumor-associated leukocytes isolated from positive and negative LN patients were seeded overnight in appropriate culture media at 37°C in a humidified CO2 incubator. Conditioned media containing secreted cytokines/chemokines were profiled using RayBio human cytokine antibody arrayIIIand then analyzed and quantified using ImageJ software. In addition, using immunoblottingwe assessed the level of expression of total and phospho NF-kβ in leukocyte lysates from positive and negative LN patients.

Result: Flow cytometric analysis revealed a significant increase in the percentage of T lymphocytes and T helper(CD3+/CD4+) cells collected from axillary tributaries of positive LN patients as compared to negative LN patients. Leukocytesisolated from positive LN patients were characterized by more than five-foldincreases in IL-12, Thrombopoietin, IL-13, INF-ϒ, TARC, IGF-1, IL-3, TNF-α, IL-4, GCSF, IL-5 and IL-1α. Moreover, we detected an increase in cellular expression of total and phospho NF-kβ in leukocytes isolated from positive LN as compared to negative LN breast cancer patients.

Conclusion: Our results demonstrate for the first time that tumor-associated leukocytes of positive LN patients possess different cytokine patterns than those ofnegative LN patients. Moreover, we identified major cytokines that may contribute to LN metastasis and could be therapeutically targeted.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P1-05-11.

Monocytes/macrophages and natural killer cells characterize the tumor microenvironment of inflammatory breast cancer in Egyptian patients

Abstract #1054

Background: Inflammatory breast cancer (IBC) is the most aggressive form of breast cancer. IBC incidence appears to be higher in Egypt as compared to USA. Although the role of leukocytes in regulating breast cancer dissemination has been studied extensively, their role in IBC progression is not well understood. Previously, we showed that human monocytes augment the invasiveness and proteolytic activity of IBC cell lines. Aim: To compare the immunophenotype of IBC and non-IBC and to identify IBC tumor-infiltrated immune cell that may be associated with poor prognosis of IBC.
 Methods: We enrolled two groups of patients: IBC (n=13) and non-IBC (n=27) being treated at Ain Shams University hospitals. All patients underwent modified radical mastectomy. IBC patients had 7 or more metastatic axillary lymph nodes whereas non-IBC patients had 3 or less metastatic axillary lymph nodes. During surgery, blood draining from the breast tumor microenvironment, through branches of axillary vein, and peripheral blood was collected. Total mononuclear cells were isolated from collected blood and their phenotype was examined using flow cytometry. Monoclonal antibodies specific for cell surface markers for particular cells types were used: namely T-helper cells (CD3+CD4+), T-cytotoxic cells (CD3+CD4-), natural killer (NK) cells (CD56+) and monocytes/macrophages (CD14+). Results: Within each group we compared the leukocytic composition of blood collected from the tumor drainage to that of peripheral blood in IBC and non-IBC patients. 1) In IBC, we detected a significant increase in the mean percentage of NK cells and monocytes collected from the tumor site, but no significant difference in CD8+ and CD4+ cells. 2) In non-IBC, the percentage of CD4+ T cells collected from the tumor site was significantly higher than from peripheral blood. No significant differences were detected in CD8+, CD56+ and CD14+ cells.
 We compared the leukocyte composition of blood collected from both IBC and non-IBC patients. 1) In peripheral blood of IBC patients, we detected a significant increase in CD4+ T cells, but no significant differences in CD8+, CD56+ and CD14+ cells when compared to non-IBC patients. 2) When we compared the leukocyte content of blood collected from the tumor site in IBC and non-IBC, we found a significant increase in CD56+, and CD14+ cells and a significant decrease in CD4+ T cells in IBC, but no significant difference in CD8+ T cells. Conclusion: Differences in the immunophenotype of IBC versus non-IBC suggests a role for these immune cells in the metastatic dissemination and progression of IBC.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 1054.

Cathepsin K in the bone microenvironment: link between obesity and prostate cancer?

The skeleton is the most common site of metastasis in patients with advanced prostate cancer. Despite many advances in targeting skeletal metastases, the mechanisms behind the attraction of prostate cancer cells to the bone are not known. Osteoclast cathepsin K, due to its ability to effectively degrade bone matrix collagen I, has been implicated in colonization and growth of prostate tumours in the bone. Identification of new cathepsin K substrates in the bone microenvironment and the recent findings demonstrating its involvement in obesity and inflammation suggest additional roles for this enzyme in skeletal metastases of prostate cancer.

Invasion of ras-transformed breast epithelial cells depends on the proteolytic activity of cysteine and aspartic proteinases

It has been suggested that the lysosomal proteinases cathepsin B, L and D participate in tumour invasion and metastasis. Whereas for cathepsins B and L the role of active enzyme in invasion processes has been confirmed, cathepsin D was suggested to support tumour progression via its pro-peptide, rather than by its proteolytic activity. In this study we have compared the presence of active cathepsins B, L and D in ras-transformed human breast epithelial cells (MCF-10A neoT) with their ability to invade matrigel. In this cell line high expression of all three cathepsins was detected by immunofluorescence microscopy. The effect of proteolytic activity on cell invasion was studied by adding various natural and synthetic cysteine and aspartic proteinase inhibitors. The most effective compound was chicken cystatin, a general natural inhibitor of cysteine proteinases, (82.8+/-1.6% inhibition of cell invasion), followed by the synthetic inhibitor trans-epoxysuccinyl-L-leucylamido-(4-guanidino) butane (E-64). CLIK-148, a specific inhibitor of cathepsin L, showed a lower effect than chicken cystatin and E-64. Pepstatin A weakly inhibited invasion, whereas the same molar concentrations of squash aspartic proteinase (SQAPI)-like inhibitor, isolated from squash Cucurbita pepo, showed significant inhibition (65.7+/-1.8%). We conclude that both cysteine and aspartic proteinase activities are needed for invasion by MCF-10A neoT cells in vitro.

Expression of cathepsins B, D and L in mouse corneas infected with Pseudomonas aeruginosa

C57BL/6J naïve and immunized mice were intracorneally infected with Pseudomonas aeruginosa. Semi-quantitative RT-PCR was performed to detect cathepsin gene expression and the results were further confirmed by immunoblot analysis. The enzymatic activities of cathepsins B, D and L were measured by peptidase assays. Immunohistochemical staining was carried out to localize the expression of the cathepsins. Cathepsins B, D and L were detected in the normal cornea by RT-PCR. A peptidase assay revealed activities of all three cathepsins under normal physiological conditions. In naïve mice, enzymatic activities of cathepsins B, D and L were all significantly enhanced when the corneas were infected with P. aeruginosa and the peak of the induction appeared around day 6 postinfection. Immunoblot analysis showed increased expression of cathepsins B, D and L. The infected corneal samples from immunized mice exhibited much lower induction of enzymatic activities compared to those from naïve mice. Immunohistochemistry showed that the expression of cathepsins in the normal cornea was restricted to the epithelial tissue while the induced expression of cathepsins was predominantly in the substantia propria. Our data revealed up-regulated enzymatic activities of cathepsins B, D and L in the naïve corneas infected with P. aeruginosa, which correlated well with the inflammatory response. Immunization of mice against P. aeruginosa attenuated the inducing effect on cathepsin expression caused by infection. The time sequence for induction of cathepsin proteins and enzymatic activities suggests a mechanism of host proteolytic degradation of the extracellular matrix resulting in corneal destruction after P. aeruginosa infection.

Plasma membrane association of cathepsin B in human prostate cancer: biochemical and immunogold electron microscopic analysis

BACKGROUND

Cathepsin B (CB), a cysteine protease, is usually found in perinuclear lysosomes of epithelial cells of normal organs and non-malignant tumors, but is associated with the plasma membranes of many solid organ malignant tumors. Plasma membrane localized CB facilitates degradation of extracellular matrix proteins and progression of tumor cells from one biological compartment to another. The activities of CB and its subcellular distribution have not been investigated in malignant prostate. Our objective was to examine the subcellular distribution of CB by determining the activities of CB in lysosome and plasma membrane/endosome subcellular fractions and its subcellular localization by immunogold electron microscopy.

METHODS

Prostate tissue pieces obtained immediately after prostatectomy were homogenized and fractionated into subcellular components for determining biochemical activities of CB and cysteine protease inhibitors (CPIs). Distribution of CB was compared with that of prostate specific antigen (PSA, a serine protease), which is abundant in secretory vesicles and granules of normal prostate, benign prostatic hyperplasia (BPH) and malignant prostate cells. Localization of CB was investigated in resin embedded lysosomes and plasma membrane/endosome subcellular fractions and in prostate tissue sections by immunogold electron microscopy.

RESULTS

We have demonstrated the specificity of CB activity in human prostate homogenates by using a variety of inhibitors in our assay. We did not find any difference in the specific activity of CB based on protein or DNA content in homogenates of malignant prostate (Gleason histologic scores 5-7) and BPH (no histological evidence of cancer) whether it was measured by chromogenic or fluorogenic peptide substrate assay techniques. We found significantly higher activities of CB in the plasma membrane/endosome fractions of malignant prostate than in BPH. In contrast, CPI activity was increased relative to CB activity in plasma membrane/endosome fraction of BPH versus prostate cancer. Our data indicated a shift in the balance of enzyme to inhibitor that would favor increased activities of CB in prostate cancer. The immunogold microscopic study showed specific localization of CB in plasma membrane. They also showed localization of CB in lysosomes that were often adjacent to luminal and/or basal surfaces of malignant cells in contrast to the usual perinuclear distribution of lysosomes in hyperplastic prostate glands. PSA was localized in secretory granules and vesicles, including the plasma membranes and secretory blebs in malignant prostate cells. Occasional PSA positive secretory vesicles or membrane profiles were seen in the plasma membrane/endosomal and lysosomal fractions.

CONCLUSIONS

The increased activity of CB in plasma membrane/endosomal fractions is associated with malignant prostate and not with BPH or normal prostate. Morphologic distribution CB is associated with the plasma membranes or lysosomes adjacent to apical and basal cell surfaces. This distribution is characteristic feature prostate cancer cells, but not in BPH or normal prostate cells. Subcellular distribution of PSA occurs in secretory vesicles and granules of the cytoplasm, but not in lysosomes. Our biochemical and morphological data could be used to distinguish malignant prostates from non-malignant tumors.

Ratio of cathepsin B to stefin A identifies heterogeneity within Gleason histologic scores for human prostate cancer

BACKGROUND

Cathepsin B (CB), a lysosomal cysteine protease, is involved in degradation of extracellular matrix proteins and progression of tumor cells from one biological compartment to another in many solid organ cancers, including prostate cancer. Our objective was to identify patterns of distribution of CB and its endogenous cellular inhibitor stefin A in cryostat sections of frozen BPH and prostate cancer tissue samples and to define these patterns in relation to Gleason histologic scores, clinical stages, and serum total PSA levels.

METHODS

We localized CB and stefin A in the same sections using polyclonal and monoclonal antibody immunoglobulin G (IgGs) against CB and stefin A using immunofluorescence and confocal microscopic techniques. Only cryostat sections of frozen prostates were used in localizations of CB and stefin A.

RESULTS

Benign prostatic hyperplasia (BPH) showed similar localization patterns for CB and stefin A and a ratio of 1 was indicated by CB = stefin A. Confocal studies indicated that most CB and stefin A sites in BPH glandular cells overlapped as shown by the yellow fluorescence of their co-localization. We found considerable variability in individual localization of CB and stefin A within and between Gleason histologic scores for prostate cancers. This variability was also found in Gleason score 6 tumors that are otherwise considered similar histologically and morphologically. Negative control sections did not show localization of CB by FITC, stefin A by Cy3 or yellow fluorescence for co-localization. Our analysis of the ratio of CB to stefin A showed three patterns, namely CB = stefin A, CB > stefin A, and CB < stefin A, within each Gleason score evaluated by us. Confocal microscopy showed more sites of yellow fluorescence when the ratio was CB = stefin A than those found in CB > stefin A or CB < stefin A. Statistical analyses showed prostate cancer cases with ratios of CB > stefin A (P < 0.05) and CB < stefin A (P < 0.05) significantly different from normal prostate and BPH which had ratios of CB = stefin A. Regression analysis did not show any specific relationship between the ratio of CB to stefin A and Gleason scores, clinical stages, and serum total prostate specific antigen (PSA) levels in prostate cancers. Analysis of our data indicates that the homeostatic balance between the enzyme and inhibitor was altered even in Gleason histologic score 6 tumors that are usually considered histologically similar by glandular differentiation.

CONCLUSIONS

We have shown that prostate cancer is a heterogeneous tumor within each Gleason histological score regardless of the progression indicated by lower to higher Gleason score tumors. The ratio of CB > stefin A would indicate a preponderance of enzyme that would favor degradation of extracellular matrix proteins and progression of tumor cells in biological compartments. These tumors are expected to be aggressive prostate cancers. In contrast, prostate tumors showing ratios of CB < stefin A and CB = stefin A are expected to be less aggressive prostate cancers. This is the first report to define heterogeneity within any Gleason score for prostate cancers by the ratios of CB to stefin A.

Invasion of ras-transformed breast epithelial cells depends on the proteolytic activity of cysteine and aspartic proteinases

It has been suggested that the lysosomal proteinases cathepsin B, L and D participate in tumour invasion and metastasis. Whereas for cathepsins B and L the role of active enzyme in invasion processes has been confirmed, cathepsin D was suggested to support tumour progression via its pro-peptide, rather than by its proteolytic activity. In this study we have compared the presence of active cathepsins B, L and D in ras-transformed human breast epithelial cells (MCF-10A neoT) with their ability to invade matrigel. In this cell line high expression of all three cathepsins was detected by immunofluorescence microscopy. The effect of proteolytic activity on cell invasion was studied by adding various natural and synthetic cysteine and aspartic proteinase inhibitors. The most effective compound was chicken cystatin, a general natural inhibitor of cysteine proteinases, (82.8+/-1.6% inhibition of cell invasion), followed by the synthetic inhibitor trans-epoxysuccinyl-L-leucylamido-(4-guanidino) butane (E-64). CLIK-148, a specific inhibitor of cathepsin L, showed a lower effect than chicken cystatin and E-64. Pepstatin A weakly inhibited invasion, whereas the same molar concentrations of squash aspartic proteinase (SQAPI)-like inhibitor, isolated from squash Cucurbita pepo, showed significant inhibition (65.7+/-1.8%). We conclude that both cysteine and aspartic proteinase activities are needed for invasion by MCF-10A neoT cells in vitro.

Imaging proteolysis by living human glioma cells

Degradation of basement membrane is an essential step for tumor invasion. In order to study degradation in real time as well as localize the site of proteolysis, we have established an assay with living human cancer cells in which we image cleavage of quenched-fluorescent basement membrane type IV collagen (DQ-collagen IV). Accumulation of fluorescent products is imaged with a confocal microscope and localized by optically sectioning both the cells and the matrix on which they are growing. For the studies described here, we seeded U87 human glioma cells as either monolayers or spheroids on a 3-dimensional gelatin matrix in which DQ-collagen IV had been embedded. As early as 24 hours after plating as monolayers, U87 cells were present throughout the 3-dimensional matrix. Cells at all levels had accumulated fluorescent degradation products of DQ-collagen IV intracellularly within vesicles. Similar observations were made for U87 spheroids and the individual cells migrating from the spheroids into the gelatin matrix. Both the migrating cells and those within the spheroid contained fluorescent degradation products of DQ-collagen IV intracellularly within vesicles. Thus, glioma cells like breast cancer cells are able to degrade type IV collagen intracellularly, suggesting that this is an important pathway for matrix degradation.

Expression of cathepsins B and S in the progression of prostate carcinoma

Cathepsins B and S (CatB, CatS) are lysosomal cysteine proteases which, among other functions, appear to play a role in cancer progression in different tumor models due to their matrix-degrading properties. To investigate their possible involvement in the development of prostate carcinoma, we immunohistochemically analyzed CatB and CatS in 38 primary human prostatic adenocarcinomas, as well as concomitant high-grade prostatic intra-epithelial neoplasia, nodular hyperplasia and normal tissue. CatB expression was observed in 28 (74%) and CatS in 32 (84%) carcinomas, being concomitant in 24 cases (63%). High-grade intra-epithelial neoplasia expressed CatB in 20/23 cases (87%), and a similar result was obtained for CatS, with expression of both coinciding in 18 cases (78%). In non-neoplastic tissue, strong expression of both proteases was observed in macrophages, inflamed glands and transitional metaplasia, whereas atrophic glands and basal cells of normal glands displayed intense CatB positivity. We conclude that CatB and CatS are often expressed together in neoplastic prostatic cells from pre-invasive to invasive and clinically detectable stages, suggesting a putative role in local invasion, though other functions cannot be ruled out.

Observing proteases in living cells

The lysosomal cysteine protease cathepsin B has been implicated in tumor progression and metastasis in part due to its altered trafficking. In order to analyze the trafficking of cathepsin B in living cells, we utilized enhanced green fluorescent protein (EGFP) fused to various cathepsin B constructs for transfecting two cell lines: an invasive human breast adenocarcinoma cell line (BT20) and a cathepsin B deficient mouse embryonic fibroblast cell line (MEF T -/-). The cells were transiently transfected with four cathepsin B-EGFP fusion constructs: full-length preprocathepsin B-EGFP, cathepsin B preregion-EGFP, cathepsin B prepro region-EGFP, and cathepsin B prepro region-EGFP with a mutation of the glycosylation site in the pro region. The full length construct showed vesicular distribution throughout the cells in both cell lines. In both BT20 and MEF T -/- cells, preregion-EGFP was localized in a ring tightly associated with the cell nucleus, suggesting distribution to the endoplasmic reticulum. The distribution of the prepro region-EGFP construct was similar except that it also included some patchy areas adjacent to the nucleus. This suggested that the cathepsin B prepro region-EGFP might have entered the Golgi. Distribution of the mutated cathepsin B prepro region-EGFP was similar to that of wild-type prepro region-EGFP in the MEF T -/-. In the invasive BT20 cells, however, the mutated prepro region-EGFP showed a vesicular distribution throughout the cytoplasm and in cell processes. This distribution is similar to that of endogenous cathepsin B in these cells. Our results suggest that: 1) tumor cells have an alternative mechanism for trafficking of cathepsin B which is independent of the mannose-6-phosphate receptor pathway, and 2) the pro region of cathepsin B may contain the sorting sequence necessary for its trafficking via this pathway.

Expression of cathepsins B and S in the progression of prostate carcinoma

Cathepsins B and S (CatB, CatS) are lysosomal cysteine proteases which, among other functions, appear to play a role in cancer progression in different tumor models due to their matrix-degrading properties. To investigate their possible involvement in the development of prostate carcinoma, we immunohistochemically analyzed CatB and CatS in 38 primary human prostatic adenocarcinomas, as well as concomitant high-grade prostatic intra-epithelial neoplasia, nodular hyperplasia and normal tissue. CatB expression was observed in 28 (74%) and CatS in 32 (84%) carcinomas, being concomitant in 24 cases (63%). High-grade intra-epithelial neoplasia expressed CatB in 20/23 cases (87%), and a similar result was obtained for CatS, with expression of both coinciding in 18 cases (78%). In non-neoplastic tissue, strong expression of both proteases was observed in macrophages, inflamed glands and transitional metaplasia, whereas atrophic glands and basal cells of normal glands displayed intense CatB positivity. We conclude that CatB and CatS are often expressed together in neoplastic prostatic cells from pre-invasive to invasive and clinically detectable stages, suggesting a putative role in local invasion, though other functions cannot be ruled out.

Imaging proteolysis by living human breast cancer cells

Malignant progression is accompanied by degradation of extracellular matrix proteins. Here we describe a novel confocal assay in which we can observe proteolysis by living human breast cancer cells (BT20 and BT549) through the use of quenched-fluorescent protein substrates. Degradation thus was imaged, by confocal optical sectioning, as an accumulation of fluorescent products. With the BT20 cells, fluorescence was localized to pericellular focal areas that coincide with pits in the underlying matrix. In contrast, fluorescence was localized to intracellular vesicles in the BT549 cells, vesicles that also label for lysosomal markers. Neither intracellular nor pericellular fluorescence was observed in the BT549 cells in the presence of cytochalasin B, suggesting that degradation occurred intracellularly and was dependent on endocytic uptake of substrate. In the presence of a cathepsin B-selective cysteine protease inhibitor, intracellular fluorescence was decreased approximately 90% and pericellular fluorescence decreased 67% to 96%, depending on the protein substrate. Matrix metallo protease inhibitors reduced pericellular fluorescence approximately 50%, i.e., comparably to a serine and a broad spectrum cysteine protease inhibitor. Our results suggest that: 1) a proteolytic cascade participates in pericellular digestion of matrix proteins by living human breast cancer cells, and 2) the cysteine protease cathepsin B participates in both pericellular and intracellular digestion of matrix proteins by living human breast cancer cells.

Rac1-induced endocytosis is associated with intracellular proteolysis during migration through a three-dimensional matrix

Transfection of Rat1 fibroblasts with an activated form of rac1 (V12rac1) stimulated cell migration in vitro compared to transfection of Rat1 fibroblasts with vector only or with dominant negative rac1 (N17rac1). To investigate the involvement of proteases in this migration, we used a novel confocal assay to evaluate the ability of the Rat1 transfectants to degrade a quenched fluorescent protein substrate (DQ-green bovine serum albumin) embedded in a three-dimensional gelatin matrix. Cleavage of the substrate results in fluorescence, thus enabling one to image extracellular and intracellular proteolysis by living cells. The Rat1 transfectants accumulated degraded substrate intracellularly. V12rac1 increased accumulation of the fluorescent product in vesicles that also labeled with the lysosomal marker LysoTracker. Treatment of the V12rac1-transfected cells with membrane-permeable inhibitors of lysosomal cysteine proteases and a membrane-permeable selective inhibitor of the cysteine protease cathepsin B significantly reduced intracellular accumulation of degraded substrate, indicating that degradation occurred intracellularly. V12rac1 stimulated uptake of dextran 70 (a marker of macropinocytosis) and polystyrene beads (markers of phagocytosis) into vesicles that also labeled for cathepsin B. Thus, stimulation of the endocytic pathways of macropinocytosis and phagocytosis by activated Rac1 may be responsible for the increased internalization and subsequent degradation of extracellular proteins.

Ulcerative balanoposthitis of the foreskin as a manifestation of chronic lymphocytic leukemia: case report and review of the literature

Ulcerative lesions of the penis have many possible etiologies, including infectious, neoplastic, traumatic, drug-induced, and autoimmune. Although the most frequent neoplasm presenting as an ulcerative penile lesion is squamous cell carcinoma, it may rarely be a manifestation of other malignancies, including those of hematolymphoid origin. We report a case of ulcerative balanoposthitis as a manifestation of chronic lymphocytic leukemia. Chronic lymphocytic leukemia and other hematolymphoid malignancies should be considered in the large differential diagnosis of nonhealing penile ulcers.

Fluorescent microplate assay for cancer cell-associated cathepsin B

Cathepsin B and in particular cell-surface and secreted cathepsin B has been implicated in the invasive and metastatic phenotype of numerous types of cancer. We describe here a method to easily survey cancer cell lines for cathepsin B activity using the highly selective substrate Z-Arg-Arg-AMC. Intact human U87 glioma cells hydrolyze Z-Arg-Arg-AMC with a Km of 460 microM at pH 7.0 and 37 degrees C. This is nearly the same as the Km of 430 microM obtained with purified cathepsin B assayed under the same conditions. The pericellular (i.e. both cell-surface and released) cathepsin B activity was inhibited by the cysteine protease inhibitors E-64, leupeptin, Mu-Np2-HphVS-2Np, Mu-Leu-HpHVSPh and the cathepsin B selective inhibitor Mu-Tyr(3,5 I2)-HphVSPh with IC50 values similar to those observed for the inhibition of purified human liver cathepsin B. Other human cancer cell lines with measurable pericellular cathepsin B activity included HT-1080 fibrosarcoma, MiaPaCa pancreatic, PC-3 prostate and HCT-116 colon. Cathepsin B activity correlated with protein levels of cathepsin B as determined by immunoblot analysis. Pericellular cathepsin B activity was also detected in the rat cell lines MatLyLu prostate and Mat B III adenocarcinoma and in the murine lines B16a melanoma and Lewis lung carcinoma. The ability to determine pericellular cathepsin B activity will be useful in selecting appropriate cell lines for use in vivo when analyzing the effects of inhibiting cathepsin B activity on tumor growth and metastasis.

Human procathepsin B interacts with the annexin II tetramer on the surface of tumor cells

To study potential roles of plasma membrane-associated extracellular cathepsin B in tumor cell invasion and metastasis, we used the yeast two-hybrid system to screen for proteins that interact with human procathepsin B. The annexin II light chain (p11), one of the two subunits of the annexin II tetramer, was one of the proteins identified. We have confirmed that recombinant human procathepsin B interacts with p11 as well as with the annexin II tetramer in vitro. Furthermore, procathepsin B could interact with the annexin II tetramer in vivo as demonstrated by coimmunoprecipitation. Cathepsin B and the annexin II tetramer were shown by immunofluorescent staining to colocalize on the surface of human breast carcinoma and glioma cells. Taken together, our results indicate that the annexin II tetramer can serve as a binding protein for procathepsin B on the surface of tumor cells, an interaction that may facilitate tumor invasion and metastasis.

Cell surface complex of cathepsin B/annexin II tetramer in malignant progression

The cysteine protease cathepsin B is upregulated in a variety of tumors, particularly at the invasive edges. Cathepsin B can degrade extracellular matrix proteins, such as collagen IV and laminin, and can activate the precursor form of urokinase plasminogen activator (uPA), perhaps thereby initiating an extracellular proteolytic cascade. Recently, we demonstrated that procathepsin B interacts with the annexin II heterotetramer (AIIt) on the surface of tumor cells. AIIt had previously been shown to interact with the serine proteases: plasminogen/plasmin and tissue-type plasminogen activator (tPA). The AIIt binding site for cathepsin B differs from that for either plasminogen/plasmin or tPA. AIIt also interacts with extracellular matrix proteins, e.g., collagen I and tenascin-C, forming a structural link between the tumor cell surface and the extracellular matrix. Interestingly, cathepsin B, plasminogen/plasmin, t-PA and tenascin-C have all been linked to tumor development. We speculate that colocalization through AIIt of proteases and their substrates on the tumor cell surface may facilitate: (1) activation of precursor forms of proteases and initiation of proteolytic cascades; and (2) selective degradation of extracellular matrix proteins. The recruitment of proteases to specific regions on the cell surface, regions where potential substrates are also bound, could well function as a 'proteolytic center' to enhance tumor cell detachment, invasion and motility.

Unraveling the role of proteases in cancer

Investigators have been studying the expression and activity of proteases in the final steps of tumor progression, invasion and metastasis, for the past 30 years. Recent studies, however, indicate that proteases are involved earlier in progression, e.g., in tumor growth both at the primary and metastatic sites. Extracellular proteases may co-operatively influence matrix degradation and tumor cell invasion through proteolytic cascades, with individual proteases having distinct roles in tumor growth, invasion, migration and angiogenesis. In this review, we use cathepsin B as an example to examine the involvement of proteases in tumor progression and metastasis. We discuss the effect of interactions among tumor cells, stromal cells, and the extracellular matrix on the regulation of protease expression. Further elucidation of the role of proteases in cancer will allow us to design more effective inhibitors and novel protease-based drugs for clinical use.

Transcription of human cathepsin B is mediated by Sp1 and Ets family factors in glioma

Cathepsin B expression is increased at both the mRNA and protein levels in a wide variety of tumors. The mechanisms responsible for this regulation are not well elucidated. We have isolated a 2.2-kb cathepsin B genomic fragment that contains the 5'-flanking region of the cathepsin B gene. Using reporter gene analysis in human glioblastoma U87MG cells, we have mapped a 228-bp fragment (-172 to +56) having high promoter activity. This promoter region has a high G+C content; contains potential Spl, Ets, and USF binding motifs; and lacks canonical TATA and CAAT boxes immediately upstream of the major transcriptional initiation site. Cotransfection experiments demonstrated that Spl and Ets1 could trans-activate cathepsin B transcription, whereas Ets2 could not. Electrophoretic mobility shift assays and supershift assays revealed that three of the four putative Sp1 sites in this promoter region form a specific complex containing the Sp1 transcription factor. Mutating all four of the Spl binding sites individually markedly reduced the promoter activity of transfected reporter genes in U87 cells. Cotransfection of this cathepsin B promoter construct with Spl family expression vectors in Schneider's Drosophila line 2 (SL2) cells demonstrated that Spl and Sp3, but not Sp4, activated cathepsin B transcription. Taken together, these results suggest that Sp1, Sp3, and Ets1 are important factors in cathepsin B transcription. The regulation of cathepsin B transcription by Sp1- and Sp1-related factors is mediated through multiple GC boxes.

Differentiating agents regulate cathepsin B gene expression in HL-60 cells

We utilized HL-60 cells as a model system to examine the regulation of ctsb gene expression by differentiating agents. Inducers of monocytic differentiation [phorbol ester (PMA), calcitriol (D3), and sodium butyrate (NaB)] and inducers of granulocytic differentiation [all-trans retinoic acid (RA) and 9-cis retinoic acid (9-cis RA)] increase ctsb mRNA levels in a dose-dependent manner as determined by Northern blot hybridization. D3 and retinoids exert additive effects, suggesting that these agents act in part through distinct pathways. Actinomycin D decay experiments indicate that D3, NaB, RA, and 9-cis RA do not alter mRNA stability. In contrast, PMA markedly increases the half-life of ctsb mRNA. In transient transfection assays, PMA and NaB both stimulate transcription of the luciferase reporter gene placed under the control of ctsb promoter fragments. Thus, inducers of HL-60 cell differentiation can regulate the expression of the ctsb gene at both transcriptional and posttranscriptional levels.

Cathepsin B and glioma invasion

Increased expression of cathepsin B has been reported in a number of human and animal tumors. This has also been observed in human gliomas where increases in cathepsin B mRNA, protein, activity and secretion parallel malignant progression. In the present study, we showed that cathepsin B was directly involved in glioma cell invasion. Activity of cathepsin B was an order of magnitude higher in glioma tissue than in matched normal brain. Inhibitors of cysteine proteases reduced invasion of glioma cells in two in vitro models: invasion through Matrigel and infiltration of a glioma spheroid into a normal brain aggregate. Glioma spheroids expressed higher levels of cathepsin B than did monolayers and the ability of subclones differing in cathepsin B activity to infiltrate normal brain aggregates paralleled their cathepsin B activity. We confirmed that intracellular staining for cathepsin B occurs at the cell periphery and in cell processes and observed extracellular staining on the cell surface. In addition, we demonstrated that intracellular cathepsin B located at the cell periphery and in processes was active. The cell surface cathepsin B colocalized with areas of degradation of an extracellular matrix component. We hypothesize that the increased expression of active cathepsin B in gliomas leads to increases in invasion in vitro and in vivo and have developed a xenotransplant model in which this hypothesis can be tested.

Exocytosis of active cathepsin B enzyme activity at pH 7.0, inhibition and molecular mass

Lysosomal cathepsin B has been implicated in parasitic, inflammatory and neoplastic diseases. Most of these pathologies suggest a role for cathepsin B outside the cells, although the origin of extracellular active enzyme is not well defined. The activity of extracellular cathepsin B is difficult to assess because of the presence of inhibitors and inactivation of the enzyme by oxidizing agents. Therefore, we have developed a continuous assay for measurement of cathepsin B activity produced pericellularly by living cells. The kinetic rate of Z-Arg-Arg-NHMec conversion was monitored and the assay optimized for enzyme stability, cell viability and sensitivity. To validate the assay, we determined that human liver cathepsin B was stable and active under the conditions of the assay and its activity could be inhibited by the selective epoxide derivative CA-074. Via this assay, we were able to demonstrate that active cathepsin B was secreted pericellularly by viable cells. Both preneoplastic and malignant cells secreted active cathepsin B. Pretreatment of cells with the membrane-permeant proinhibitor CA-074Me completely abolished pericellular and total cathepsin B activity whereas pretreatment with the active drug CA-074 had no effect. Immunoprecipitation and immunoblotting experiments suggested that the active enzyme species was 31-kDa single-chain cathepsin B. Exocytosis of cathepsin B was not related to secretion of proenzyme or secretion from mature lysosomes. Our results suggest an alternative pathway for exocytosis of active cathepsin B.

The relationship of cathepsin B and stefin A mRNA localization identifies a potentially aggressive variant of human prostate cancer within a Gleason histologic score

Cathepsin B (CB) is involved in degradation of extracellular matrix proteins during tumor progression in human solid organ tumors (such as colorectal, bladder, and breast cancers), including human prostate cancer. Its activities are regulated by endogenous inhibitors (such as stefins or cystatins). Increased expression of cathepsin B message, protein, and membrane association have been linked to malignancy, but there are very few studies of their mRNA expression in prostate cancer using in situ hybridization techniques. Our objective was to determine the relationship of CB and stefin A (cystatin A) mRNA localization to the Gleason grading system for histologic scores in the hope of distinguishing aggressive and less aggressive variants of prostate cancer. We used a 25-base biotinylated oligonucleotide CB cDNA antisense probe to localize CB message and a 27-base biotinylated oligonucleotide stefin A cDNA antisense probe to localize stefin A message. Prostate samples from 41 prostatectomy patients were collected along with their pre-surgery serum PSA levels and clinical stage of the disease. Sections prepared from frozen prostate tissue samples were hybridized with the CB and stefin A and control pBR 322 probes using techniques reported by Sinha et al. [1] and their distribution quantitated by an image analysis system. Prostate sections treated with RNAse before hybridization or incubated with the pBR 322 control probe showed little or no reaction products, confirming that localization of CB and stefin A probes was specific. In prostate cancer, the reaction products were found in neoplastic and invasive cells and occasionally in stromal cells. The ratios of CB to stefin A were similar in normal prostate and benign prostatic hyperplasia (BPH) whereas they varied consistently within and between Gleason histologic scores for prostate cancer. These variations showed three localization patterns; namely, prostate cancers with higher levels of CB than stefin A, lower levels of CB than stefin A, and similar levels of CB and stefin A. All three patterns and ratios for CB and stefin A were found in prostate samples (22/41) represented by the Gleason histologic score 6 tumors. In these tumors, serum PSA levels ranged from 1 to 78 ng/ml and prostate cancers showed B, C, and D clinical stages. There was no correlation of CB/stefin A ratio and serum PSA values or clinical stage in a limited number of prostate cancer cases. Our data showed that there were prostate cancer cases within Gleason histologic scores which expressed high, similar, and low levels of CB when compared to stefin A. We postulate that prostate cancer cases showing higher levels of CB compared to stefin A probably represent an aggressive variant of this cancer within any one Gleason histologic score. If this is the case, aggressive variants of prostate cancer would occur within Gleason scores 3 to 10 even though higher scores are usually considered more aggressive forms of prostate cancers. Since our study is based upon a very limited number of frozen prostate samples, we emphasize that a larger series of archival prostate cancer samples along with their survival data should be analyzed to establish any relationship of CB/stefin A ratio and aggressive variants of this cancer. Therefore, our conclusion is tentative. Our study provides a partial explanation for differences in the clinical course of prostate cancer in patients. This is the first study to show that determination of CB and stefin A mRNA ratios may lead to identification of aggressive and less aggressive variants of prostate cancer within a Gleason histologic score.

Molecular regulation, membrane association and secretion of tumor cathepsin B

Upregulation, membrane association and secretion of cathepsin B have been shown to occur in many types of tumors and to correlate positively with their invasive and metastatic capabilities. To further understand changes in cathepsin B activity and localization, we have been examining its regulation at many levels including transcription and trafficking. Our studies indicate that there may be three promoter regions in the cathepsin B gene. Of these, continued examination of the promoter upstream of exon 1 has indicated possible control by several regulatory factors including E-box and Sp-1 binding elements. Upregulation of cathepsin B at this level may account for some of the secretion of cathepsin B found in tumors. We have also gathered evidence that endo- and exocytosis of cathepsin B may be regulated by ras and ras-related proteins in addition to previously described trafficking systems. There is also evidence that several populations of lysosomes may exist and that trafficking to different populations may determine whether cathepsin B is secreted from the tumor cell or remains intracellular. Our results indicate that membrane association and secretion of cathepsin B is not a random process in the tumor cell, but rather part of a tightly controlled system.

Intracellular accumulation of the amyloidogenic L68Q variant of human cystatin C in NIH/3T3 cells

AIM

To study the cellular transport of L68Q cystatin C, the cystatin variant causing amyloidosis and brain haemorrhage in patients suffering from hereditary cystatin C amyloid angiopathy (HCCAA).

METHODS

Expression vectors for wild-type and L68Q cystatin C were constructed and used to transfect mouse NIH/3T3 cells. Stable cell clones were isolated after cotransfection with pSV2neo. Clones expressing human wild-type and L68Q cystatin C were compared with respect to secreted cystatin C by enzyme linked immunosorbent assay (ELISA), and for intracellular cystatin C by western blotting and immunofluorescence cytochemistry. Colocalisation studies in cells were performed by double staining with antibodies against human cystatin C and marker proteins for lysosomes, the Golgi apparatus, or the endoplasmic reticulum, and evaluated by confocal microscopy.

RESULTS

Concentrations of human cystatin C secreted from transfected NIH/3T3 cells were similar to those secreted from human cells in culture. In general, clones expressing the gene encoding L68Q cystatin C secreted slightly lower amounts of the protein than clones expressing wild-type human cystatin C. Both immunofluorescence cytochemistry and western blotting experiments showed an increased accumulation of cystatin C in cells expressing the gene encoding L68Q cystatin C compared with cells expressing the gene for the wild-type protein. The intracellularly accumulating L68Q cystatin C was insoluble and located mainly in the endoplasmic reticulum.

CONCLUSIONS

The cellular transport of human cystatin C is impeded by the pathogenic amino acid substitution Leu68-->Gln. The resulting intracellular accumulation and increased localised concentration of L68Q cystatin C might be an important event in the molecular pathophysiology of amyloid formation and brain haemorrhage in patients with HCCAA.

Codistribution of procathepsin B and mature cathepsin B forms in human prostate tumors detected by confocal and immunofluorescence microscopy

Cathepsin B (CB) is involved in invasion and metastasis of a variety of solid organ tumors, including human prostate cancer. The tertiary structures of the proenzyme and mature forms of CB are related closely, as revealed by crystallographic studies. However, the cellular distributions of the CB forms have not been defined in human prostate and its tumors. Our objective was to investigate the distribution and codistribution of CB and procathepsin B (proCB) in human prostate tumors. Human prostate tissue samples that were obtained from 21 prostatectomy and/or cystectomy patients were collected immediately after surgery and processed for this study. We used a rabbit antihuman liver CB immunoglobulin G (IgG) that recognizes both mature CB and proCB and a mouse antipropeptide monoclonal antibody IgG that recognizes only proCB. Fluorescein isothiocyanate (FITC)-conjugated donkey antirabbit IgG and indocarbocyanine (Cy3; rhodamine)-conjugated donkey antimouse IgG were used to differentiate localization of the enzyme forms. Immunofluorescence of FITC and Cy3 was examined in prostate sections by using epifluorescence and confocal laser-scanning microscopy. Because fluorescence is dependent on section thickness, time needed for study and photography, and the antigenic sites of proCB and mature CB localized by antibodies and by fluorescent markers (Cy3 vs. FITC), the cellular distributions and the relative intensity of fluorescence on cryostat sections were assessed qualitatively. Immunofluorescence of Cy3 for localizing proCB and of FITC for localizing mature CB were observed in prostatic epithelial cells and their tumors and in stromal connective tissue cells. By using confocal microscopy, colocalization of the enzyme forms in the same cells was indicated by yellow fluorescence. In stromal cells (such as smooth muscles, fibroblast, and macrophages), the distribution of proCB and relative fluorescence intensity was moderate to predominant in human prostate and its tumors. In neoplastic prostate, the cellular distributions of CB ranged from low to predominant levels. In some neoplastic glands, Cy3 fluorescence for proCB was absent, whereas the mature form of CB localized in cancer cells and in the subjacent extracellular matrix. Confocal microscopy showed a close association of CB with extracellular matrix surrounding neoplastic acini and invasive cells, indicating that the enzyme form was probably involved in degradation of the matrix proteins. The negative control study showed no specific immunofluorescence for proCB or CB in prostate cancer cases. We have shown a differential distribution of proenzyme and mature forms of CB in normal prostate, benign prostatic hyperplasia, and neoplastic prostate. The enzyme forms were assessed by determining the cellular distributions of CB and proCB. Our study indicates that the differential distribution of proCB and CB might provide clues into aggressiveness of prostate cancers within Gleason grades. However, we emphasize that our observation should be evaluated in a larger series of prostate samples before a definitive conclusion can be reached. This is the first report to show codistribution of proenzyme and mature forms of CB by using confocal microscopy.

Cathepsin B on invasion and metastasis of gastric carcinoma

OBJECTIVE

To investigate the expression of cathepsin B (CB) in human gastric carcinoma tissue.

METHODS

The expression of CB in human gastric tissue was studied by using monospecific polyclonal rabbit antibody raised against human liver CB for immunohistochemistry, and full length cDNA of CB for in situ hybridization and dot blot.

RESULTS

CB overexpression in gastric carcinoma was found when compared with non-neoplastic gastric tissue at both mRNA and protein levels. Diffuse cytoplasmic CB staining of mRNA and protein were identified in malignant cells of 53.3% and 69.1% of gastric adenocarcinoma respectively. The increased staining of CB in malignant cells was associated with the depth of the invasiveness and growth pattern as well as metastasis of lymph nodes, but not with the histological classification. It was also found that there were the expression of CB in stromal cells of the tumor and the expression localized mainly in the endothelial cells of the microvessels which correlated with angiogenesis.

CONCLUSION

These results indicate that the expression of CB in gastric carcinoma is related to tumor progression, and leads to development of the invasive phenotype.

Tumor cell membrane cathepsin B

The lysosomal cysteine peptidase cathepsin B was found to be associated with plasma membrane/endosomal fractions of murine B16 amelanotic melanoma cells. Confocal microscopy with three dimensional image analysis indicated that cathepsin B was associated with the external basal cell surface, which would be consistent with its proposed role in degradation of extracellular matrix proteins. We purified and partially characterized cathepsin B from homogenates of murine liver and B16 amelanotic melanoma cells and from lysosomal and membrane/endosomal fractions of the B16 tumor cells. By SDS-PAGE under reducing conditions, the purified cathepsin B from the tumor homogenates was resolved as a single protein band of Mr 31000, corresponding to the single chain form of cathepsin B. In contrast, cathepsin B from liver homogenates was resolved as two bands of Mr 31000 and 24000, corresponding to the single chain and the heavy chain of the double chain form, respectively. The tumor cathepsin B consisted of four isozymes with pIs of 5.64, 5.33, 5.2 and 5.1, whereas the liver cathepsin B consisted of five isozymes with pIs of 5.64, 5.5, 5.45, 5.35 and 5.3. The additional acidic isoforms of cathepsin B in the B16 tumor probably reflect altered glycosylation in tumors. The commonality of isoforms in the B16 plasma membrane/endosomal and lysosomal fractions suggests that retrograde trafficking of cathepsin B from the lysosome to the endosome and its exocytotic release result in the association of cathepsin B with the tumor cell membrane.

Differential localization of cysteine protease inhibitors and a target cysteine protease, cathepsin B, by immuno-confocal microscopy

The cystatin superfamily of cysteine protease inhibitors and target cysteine proteases such as cathepsin B have been implicated in malignant progression. The respective cellular/extracellular localization of cystatins and cysteine proteases in tumors may be critical in regulating activity of the enzymes. Confocal microscopy has enabled us to demonstrate the differential localization of cystatins and cathepsin B in an embryonic liver cell line and an invasive hepatoma cell line. In both, stefins A and B were distributed diffusely throughout the cytoplasm, whereas cystatin C was distributed in juxtanuclear vesicles. Stefin A and cystatin C, but not stefin B, were present on the cell surface. Cystatin C was found on the top surfaces of both cell lines, whereas stefin A was found only on the top surface of the embryonic liver cells. Cathepsin B staining was concentrated in perinuclear vesicles in the embryonic liver cells. In the hepatoma cells, staining for cathepsin B was also present in vesicles adjacent to the cell membrane and on localized regions of the bottom surface. Such a disparate distribution of cathepsin B and its endogenous inhibitors may facilitate proteolysis by the hepatoma cells and thereby contribute to their invasive phenotype.

Cathepsin B and human tumor progression

Cathepsin B has been implicated in progression of various human tumors. Overexpression of cathepsin B mRNA, increased cathepsin B staining and elevated cathepsin B activity have been found in different human cancers. These occur especially at the invasive edges of cancers, suggesting a role for cathepsin B in tumor invasion. In some tumors, mRNA expression and protein staining for cathepsin B correlate with clinical progression. Cathepsin B can facilitate tumor progression directly through degradation of components of the basement membrane and extracellular matrix. In vitro studies show that cathepsin B may exert its degradative effects intracellularly or extracellularly, depending on the cell type and location of cathepsin B. Cathepsin B can also facilitate tumor progression indirectly through activation of other latent proteases and/or degradation of protein inhibitors of other proteases. Thus cathepsin B may be an integral component of the proteolytic cascade linked to malignant progression of human tumors.

Malignant transformation alters intracellular trafficking of lysosomal cathepsin D in human breast epithelial cells

Increased expression and alteration of intracellular trafficking of lysosomal cathepsins have been reported in malignant tumors, or in cells transformed by the transfection with the ras oncogene. In the present study, immortal MCF-10A human breast epithelial cells were transformed with the mutated ras oncogene. Both cell lines were investigated for changes in the intracellular localization of lysosomal cathepsin D and lamp-1 (lysosome-associated membrane protein) employing specific antibodies and confocal immunofluorescence microscopy. The results revealed that staining for cathepsin D along with for lamp-1 was mostly localized in the perinuclear region of MCF-10A cells. In contrast, the staining for these proteins was found to be widely distributed throughout the cytoplasm and at the cell periphery in MCF-10AneoT cells. The organization of microtubules, but not actin, appeared to differ between MCF-10A cells and their oncogenic ras transfectants. When the microtubules were depolymerized by treatment of MCF-10A cells with nocodazole, vesicles containing the lysosomal cathepsin D were dispersed in the cytoplasm and translocation of these vesicles to the cell periphery was observed. The intracellular localization of cathepsin D in the nocodazole-treated MCF-10A cells seemed to be similar to that observed in the oncogenic ras transfectants of these cells. When taxol, which inhibits microtubule depolymerization, was added to the culture medium of neoT cells, a polymerized microtubule network was observed, and the reclustering of cathepsin D and lamp-1 occurred in an unidirectional manner towards the perinuclear region. These findings support a model in which cytoskeletal microtubule organization is closely related to the trafficking of lysosomes/endosomes, and in which oncogenic ras interferes with such organization in human breast epithelial cells.

Exon 2 of human cathepsin B derives from an Alu element

Transcripts for the cysteine protease cathepsin B are alternatively spliced in the untranslated regions (UTRs). We show that a cathepsin B probe containing 5'-UTR sequences hybridized to an RNA of approximately 300 nt in addition to the typical 2.2 and 4.0 kbp mRNAs. Within this 5'-UTR, exon 2 was found to be homologous to Alu repetitive elements. Specifically, exon 2 was part of an Alu element interspersed with the cathepsin B gene. The approximately 300 nt band that hybridized to our cathepsin B probe likely corresponds to Alu transcripts, which are known to accumulate in human cells. Indeed, a similarly migrating band was detected with an authentic Alu probe. Thus, we suggest that primary transcripts for cathepsin B contain Alu sequences which are preserved as exon 2 in some fully spliced mRNAs.

Cathepsin B and middle cerebral artery occlusion in the rat

Lysosomal proteases, although tightly regulated under physiological conditions, are known to contribute to cell injury after various forms of tissue ischemia have occurred. Because cathepsin B is a prominent lysosomal protease found in brain parenchyma, the authors hypothesized that it may contribute to neuronal cell death after focal cerebral ischemia. The authors measured the expression and spatial distribution of cathepsin B within the ischemic brain in 43 animals by means of immunohistochemical analysis in a rat model of transient middle cerebral artery (MCA) occlusion. Cathepsin B activity was also measured within specific ischemic brain regions by using an in vitro assay (22 animals). In addition, the authors tested the therapeutic effect of preischemic intraventricular administration of stefin A, a cysteine protease inhibitor, on the volume of cerebral infarction after transient MCA occlusion (15 animals). Increased cathepsin B immunoreactivity was detected exclusively within the ischemic neurons after 2 hours of reperfusion following a 2-hour MCA occlusion. Cathepsin B immunolocalization in the ischemic region decreased by 24 hours of reperfusion, but then increased by 48 hours of reperfusion because the infarct was infiltrated by inflammatory cells. Increased immunolocalization of cathepsin B in the inflammatory cells located in the necrotic infarct core continued through 7 days of reperfusion. Cathepsin B enzymatic activity was significantly increased in the ischemic tissue at 2, 8, and 48 hours, but not at 24 hours of reperfusion after 2 hours of MCA occlusion. Continuous intraventricular infusion of stefin A, before 2 hours of MCA occlusion (15 animals), significantly reduced infarct volume compared with control animals (12 animals): the percentage of hemispheric infarct volume was 20+/-3.9 compared with 33+/-3.5 (standard error of the mean; p = 0.025). These data indicate that neuronal cathepsin B undergoes increased expression and activation within 2 hours of reperfusion after a 2-hour MCA occlusion and may be a mechanism contributing to neuronal cell death. Intraventricular infusion of stefin A, an inhibitor of cathepsin B, significantly reduces cerebral infarct volume in rats.

Oncogenic c-Ki-ras but not oncogenic c-Ha-ras up-regulates CEA expression and disrupts basolateral polarity in colon epithelial cells

Colon carcinomas commonly contain mutations in Ki-ras4B, but very rarely in Ha-ras, suggesting that different Ras isoforms may have distinct functions in colon epithelial cell biology. In an earlier study we had demonstrated that oncogenic Ki-ras4BVal-12, but not oncogenic Ha-rasVal-12, blocks the apicobasal polarization of colon epithelial cells by preventing normal glycosylation of the integrin beta1 chain of the collagen receptor. As a result, only the Ki-ras mutated cells exhibited altered cell to substratum attachment, whereas mutation of either Ras isoform activated mitogen-activated protein kinases. We have now asked whether intercellular adhesion proteins implicated in establishing basolateral polarity in colon epithelial cells are modulated by oncogenic Ki-Ras4BVal-12 proteins but not oncogenic Ha-RasVal-12 proteins. The embryonic adhesion protein carcinoembryonic antigen (CEA) was up-regulated on the mRNA and protein levels in each of three stable Ki-rasVal-12 transfectant lines but in none of three stable Ha-rasVal-12 transfectant lines. The elevated protein levels of CEA in Ki-ras4BVal-12 transfectant cells were decreased by blocking expression of Ki-ras4BVal-12 with antisense oligonucleotides. N-cadherin levels were decreased in only the Ki-ras transfectants, whereas E-cadherin levels were unchanged. Immunohistochemical analysis demonstrated that Ki-ras4BVal-12 transfectant cells did not polarize into cells with discrete apical and basal regions and so could not restrict expression of CEA to the apical region. These unpolarized cells displayed elevated levels of CEA all along their surface membrane where CEA mediated random, multilayered associations of tumor cells. This aggregation was both calcium-independent and blocked by Fab' fragments of anti-CEA monoclonal antibody col-1. Trafficking of the lysosomal cysteine protease cathepsin B may also be altered when cell polarity cannot be established. Ki-ras4BVal-12 transfectant cells expressed 2-fold elevated protein levels of the lysosomal cysteine protease cathepsin B but did not up-regulate cathepsin B mRNA expression. One function of oncogenic c-Ki-Ras proteins in colon cancer progression may be to up-regulate CEA and thus to prevent the lateral adhesion of adjacent colon epithelial cells that normally form a monolayer in vivo.

Expression of functional recombinant human procathepsin B in mammalian cells

Cathepsin B has been implicated in numerous pathobiological processes. In order to study its interactions with other proteins implicated in these processes, quantities of functional recombinant cathepsin B are needed. Therefore, we expressed recombinant human procathepsin B in mammalian cells (BSC-1 monkey kidney cells and HeLa human cervical carcinoma cells) using a vaccinia virus expression system. The recombinant human procathepsin B appeared to be authentic and expressed in its native conformation as indicated by: (1) N-terminal sequencing; (2) molecular size; (3) processing intracellularly to mature double-chain cathepsin B; (4) in vitro cleavage by pepsin to mature cathepsin B coincident with appearance of activity against a selective synthetic substrate; and (5) substrate/inhibitor profiles. This is the first report of the expression of functional recombinant human procathepsin B in mammalian cells. We also report a single-step immunoaffinity purification procedure for the isolation of electrophoretically pure proenzyme. By the methodologies described, human procathepsin B can now be obtained in high yield. This should facilitate studies of its interactions with protease inhibitors, other proteases, extracellular matrices, cell-surface proteins and biological substrates that may be of relevance to the pathobiological functions of this enzyme.

Gene trapping in differentiating cell lines: regulation of the lysosomal protease cathepsin B in skeletal myoblast growth and fusion

To identify genes regulated during skeletal muscle differentiation, we have infected mouse C2C12 myoblasts with retroviral gene trap vectors, containing a promoterless marker gene with a 5' splice acceptor signal. Integration of the vector adjacent to an actively transcribed gene places the marker under the transcriptional control of the endogenous gene, while the adjacent vector sequences facilitate cloning. The vector insertionally mutates the trapped locus and may also form fusion proteins with the endogenous gene product. We have screened several hundred clones, each containing a trapping vector integrated into a different endogenous gene. In agreement with previous estimates based on hybridization kinetics, we find that a large proportion of all genes expressed in myoblasts are regulated during differentiation. Many of these genes undergo unique temporal patterns of activation or repression during cell growth and myotube formation, and some show specific patterns of subcellular localization. The first gene we have identified with this strategy is the lysosomal cysteine protease cathepsin B. Expression from the trapped allele is upregulated during early myoblast fusion and downregulated in myotubes. A direct role for cathepsin B in myoblast growth and fusion is suggested by the observation that the trapped cells deficient in cathepsin B activity have an unusual morphology and reduced survival in low-serum media and undergo differentiation with impaired cellular fusion. The phenotype is reproduced by antisense cathepsin B expression in parental C2C12 myoblasts. The cellular phenotype is similar to that observed in cultured myoblasts from patients with I cell disease, in which there is diminished accumulation of lysosomal enzymes. This suggests that a specific deficiency of cathepsin B could contribute to the myopathic component of this illness.

Cathepsin B expression in human tumors

Cathepsin B has been linked to tumor progression through observations that its activity, secretion or membrane association are increased. The most malignant tumors, and specifically the cells at the invasive edge of those tumors, express the highest activity. Cathepsin B may facilitate invasion directly by dissolving extracellular matrix barriers like the basement membrane, or indirectly by activating other proteases capable of digesting the extracellular matrix. Cathepsin B also might play a role in tumor growth and angiogenesis. Cathepsin B activity is the result of several levels of regulation: transcription, post-transcription processing, translation and glycosylation, maturation and trafficking, and inhibition. The majority of reports on cathepsin B expression in tumors have focused on measurements of activity or protein staining. In some tumors, e.g. gliomas, a correlation between the amounts of cathepsin B mRNA, protein and activity and tumor progression has been established. Regulation of cathepsin B at the transcriptional and post-transcriptional levels is still poorly understood. Although the putative promoter regions have characteristics of housekeeping-type promoters, cathepsin B mRNA expression varies depending on the cell type and state of differentiation. We have evidence that more than one promoter could direct expression of human cathepsin B. Multiple transcript species have been detected, resulting from alternative splicing in the 5'- or 3'-untranslated regions, and possibly the use of alternative promoter regions. The existence of transcript variants indicates a potential for post-transcriptional control of expression. In support of this, ras-transformation of MCF-10A human breast epithelial cells results in an increase in protein levels without a concomitant increase in mRNA levels. Cathepsin B mRNA species with distinct 5'- or 3'-untranslated regions may differ in their stability and translatability. Variations in the coding region may also alter cathepsin B properties. We and Frankfater's group have observed transcript species that would encode a truncated protein, lacking the prepeptide and about half of the propeptide. This truncated protein, if synthesized in cells, would be expected to be cytosolic; therefore its function is unclear. Once the several mechanisms of regulation of cathepsin B expression and activity are better understood, they could provide us with new strategies to specifically reduce cathepsin B activity in tumors.

Tumor progression and angiogenesis: cathepsin B & Co

Experimental and clinical evidence reveals that the growth of solid tumors is dependent on angiogenesis. Proteolytic enzymes such as plasminogen activators and matrix metalloproteinases have been implicated in this neovascularization. The role of lysosomal proteases in this process has yet to be explored. Increased expression of the lysosomal cysteine protease cathepsin B has been observed in many etiologically different tumors, including human brain, prostate, breast, and gastrointestinal cancers. Immunohistochemical and in situ histochemical studies have demonstrated expression of cathepsin B in neovessels induced during malignant progression of human glioblastoma and prostate carcinomas. In these two tumor types, neovessels stain strongly for cathepsin B compared with the normal microvasculature. As an initial point to elucidate whether cathepsin B is an important component of the angiogenic response in tumours, we analyzed expression of cathepsin B in endothelial cells during neovessel formation. We present evidence for strong immunostaining of cathepsin B in rat brain microvascular endothelial cells as they form capillary tubes in vitro. This finding is discussed within the general framework of the role of proteolytic enzymes in tumor invasion and angiogenesis.

Cathepsin B: multiple enzyme forms from a single gene and their relation to cancer

Overexpression and altered trafficking of cathepsin B characterize the malignant phenotype of tumor cells. Human cathepsin B is encoded by a single-copy gene located on chromosome 8p22. With its 13 exons, the gene encompasses at least 27 kb of DNA. Expression of cathepsin B can be regulated at transcriptional and posttranscriptional levels. Multiple cathepsin B mRNA species arising from alternative splicing may be related to tissue- and tumor-specific differences in expression. There is selective overexpression, increased activity, membrane association and secretion of cathepsin B in many etiologically different cancers. This suggests that cathepsin B may play a functional role in malignant progression. Recent clinical studies provide confirmatory evidence in that cathepsin B expression is a prognostic indicator in colon carcinoma.

Microglial cathepsin B: an immunological examination of cellular and secreted species

The cysteine proteinase cathepsin B (CB) was isolated from immortalized murine BV-2 microglial cells and examined via sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting to establish physicochemical properties of CB from what is generally considered the resident CNS macrophage. Microglial proteases have been implicated in several pathological processes occurring in the CNS, including neurodegeneration. Murine microglial CB was observed to consist of two major single-chain species of 32 and 34 kDa, with pls of 5.5-5.2 and 5.1-4.5, respectively. In addition, a minor 24-kDa CB species was also observed in some microglial preparations. The major CB isozymes in microglia differed from those observed in murine liver and brain, which consisted of both single- and double-chain CB variants of 31 and 24-25 kDa/5 kDa, respectively, with pl values of 5.5-4.5. A microglial pro-CB of 37 kDa was also isolated, which could be processed to the 34-kDa single-chain CB species. Cystatin was observed to prevent pro-CB processing, whereas E-64 and leupeptin were only partially inhibitory. The 37-kDa pro-CB species was observed to undergo processing into the 34-kDa CB species when incubated at pH 5.5 but remained stable with respect to molecular mass when incubated at pH 7.0. In contrast, the 34-kDa single-chain CB species was observed to autodegrade when incubated at pH 7.0, whereas incubation at pH 5.5 did not affect the integrity of the species as monitored by immunoblotting. Both pro-CB and 32-kDa single-chain CB species were observed extracellularly following lipopolysaccharide activation of BV-2 microglial cells.

Immunolocalization of cathepsin B in human glioma: implications for tumor invasion and angiogenesis

The poor prognosis of patients with malignant gliomas is at least partially due to the invasive nature of these tumors. In this study, the authors investigated the possibility that the cysteine protease cathepsin B (CB) is a participant in the process of glial tumor cell invasion. To accomplish this, an immunohistochemical analysis was made of the localization of antibodies to CB in biopsies of five specimens of normal brain, 16 astrocytomas, 33 anaplastic astrocytomas, and 33 glioblastomas multiforme. Staining was scored according to the percentage of positive cells and the intensity of the stain, graded from 0 to 3+. Staining for CB was not seen in any of five samples of normal brain except for occasional neuronal cell bodies and microglia. Only five (31%) of 16 astrocytomas showed a small percentage of positive cells (0.01%-3%) that were stained in a light, diffuse cytoplasmic pattern (1+). Twenty-nine (87.8%) of 33 anaplastic astrocytomas showed positive light, granular staining in 2% to 40% of cells. In anaplastic astrocytoma, the staining within a tumor was heterogeneous with intensities of 1+ (17%), 1+ to 2+ (29%), or 2+ (55%). In contrast, all 33 (100%) glioblastomas were positive in 10% to 90% of cells. The staining was present in a coarse, granular pattern with an intensity of 2+ (12%) or 3+ (88%). Tumor cells infiltrating into brain adjacent to malignant gliomas stained positively in 26 cases that could be evaluated for glioblastoma multiforme; these invading cells frequently followed penetrating blood vessels as typical "secondary structures of Scherer." Moderate to intense CB staining associated with endothelial proliferation in high-grade tumors was also observed, especially in regions of tumor infiltration into adjacent normal brain. These results provide evidence consistent with the hypothesis that CB is functionally significant in the process of tumor invasion and angiogenesis in the clinical progression of the malignant phenotype in astrocytes.

Identification of two new exons and multiple transcription start points in the 5'-untranslated region of the human cathepsin-B-encoding gene

Transcripts for cysteine protease cathepsin B (CTSB) were found to be highly variable in the 5'-UTR (untranslated region). In cDNA clones from a human gastric adenocarcinoma cDNA library, we have identified two new exons (designated 2a and 2b) between exons 2 and 3 in the 5'-UTR of the gene. All of the exons of the 5'-UTR could be alternatively spliced to produce several transcript species. In addition, transcription was initiated from more than one promoter region. Using RT-PCR (reverse transcription-polymerase chain reaction) and primer extension assays, CTSB mRNA species were found to differ among tissues and between a glioblastoma sample and a cell line derived from it. Exons 2a and 2b were detected more frequently in tumor samples than in matched normal samples. Thus, factors related to the cell differentiation and environment seem likely to determine the types of transcripts that are expressed which in turn could influence the overall steady-state level of CTSB mRNAs and their rate of translation. Interestingly, at least three upstream translation initiation codons were observed and could constitute a means of controlling translation initiation.

Immunohistochemical localization of cathepsin B in neoplastic human prostate

Cathepsin B (CB) has been shown to degrade extracellular matrix (ECM) proteins, and has been reported to be involved in invasion and metastasis of several types of solid organ tumors in human and animals, but CB has not been studied in human prostate cancer (CAP). Our objective was to determine the CB protein immunostaining pattern in CAP and to correlate the immunostaining with the degree of malignancy as reflected in the Gleason grading system. We used two types of CB antibodies (namely, monospecific, polyclonal antibodies to human liver CB prepared in rabbits, and polyclonal antibody produced in sheep) to establish CB localization patterns in neoplastic prostate. Our analysis showed a heterogeneous CB immunostaining pattern in the neoplastic human prostate. CB immunostaining occurred in many, but not all, of the neoplastic columnar/cuboidal cells of acini and isolated cells, i.e., in small ragged glands and clusters (groups) of invasive cells in the prostatic stroma. We have shown that, in general, there was a positive correlation of the intensity of CB immunostaining with the Gleason histologic score (or Gleason grade sum) tumors, i.e., from the lowest scores through score 8, but many of the tumors with scores 9 and 10 showed little CB immunostaining. Our study indicated that the increased CB immunostaining in the Gleason grade sum 5-8 tumors may be associated with increased degradation of ECM, but not in 9 and 10 despite the fact that the latter tumors are more malignant clinically. In well-differentiated tumors, fewer CB immunostaining cells were present than the moderately-differentiated tumors. In other words, most of the stromal invasion of the prostatic ECM occurred in tumors of Gleason grade sums 5-8. We suggest that CB immunostaining might be a useful method to assess stromal invasion of prostatic carcinoma, especially in the higher grade tumors.

Cathepsin B in angiogenesis of human prostate: an immunohistochemical and immunoelectron microscopic analysis

BACKGROUND

Angiogenesis (or neovascularization) is required for the growth of solid organ tumors and precedes invasion of the adjacent stroma by neoplastic cells. We investigated the relative density and distribution of cathepsin B (CB) immunostained microvessels (i.e., small blood vessels and capillaries) in benign prostatic hyperplasia (BPH), prostatic intraepithelial neoplasia (PIN), and prostatic adenocarcinoma (CAP) by immunocytochemical localization of an antibody directed against a cathepsin B-derived synthetic peptide (Syn-CB).

METHODS

We studied 16 formalin-fixed, prostatectomy specimens that were embedded in paraffin/paraplast for histological examination by hematoxylin and eosin and immuno-localization of the Syn-CB antibody. Selected paraformaldehyde-fixed specimens were embedded in K4M Lowicryl or LRWhite resins. We localized the antibody in thin sections using immunoelectron microscopy techniques.

RESULTS

Eight patients had BPH [4 patients with BPH alone, 2 with BPH and PIN, and 2 with BPH and CAP]. Ten cancer cases included one with Gleason histologic score 4, two with score 6, four with score 7, and three with score 8. In CAP cases, Gleason score 6 and 7 tumors had more microvessels than the score 4 or 8 tumors. In both BPH and CAP cases, the antibody was localized chiefly in the endothelial cells of microvessels, but occasionally in ductal and glandular epithelial cells. Ultrastructurally, CB-immunoreactive gold particles were markedly increased at the luminal and basal plasma membrane surfaces and folds of endothelial cells in neoplastic prostate, but not in the endothelial cells of BPH. Furthermore, the presence of CB localizing gold particles in collagen and smooth muscle fibers near the microvessels indicated leakage of the enzyme in prostatic stroma of neoplastic prostate. Similar leakage was not observed in BPH. Morphometric analysis showed that the relative density of microvessels increased two to three times in cancer patients when compared to patients with BPH alone. Our study also indicated that BPH associated with PIN or CAP had an increased density of microvessels when compared to BPH alone.

CONCLUSIONS

Our study showed that the relative density and distribution of microvessels are the most important features of neovascularization in prostatic tumors. The relative density of microvessels increased in PIN and CAP when compared to BPH alone. Although the localization of CB is associated with lysosomes of endothelial cells in both BPH and CAP, there is a greater association of CB with the plasma membranes of endothelial cells in CAP than BPH. Immunoelectron microscopy provided evidence that CB might be involved in dissolution of basement membranes in neoplastic tumors during angiogenesis. CB localization has the potential of defining a role for this protease in degradation of extracellular matrix constituents during early steps of angiogenesis.