Thrombomodulin modulates growth of tumor cells independent of its anticoagulant activity.

Thrombomodulin (TM), recognized as an essential vessel wall cofactor of the antithrombotic mechanism, is also expressed by a wide range of tumor cells. Tumor cell lines subcloned from four patients with malignant melanoma displayed a negative correlation between TM expression and cell proliferation in vitro and in vivo. Overexpression of wild-type TM decreased cell proliferation in vitro and tumor growth in vivo. TM mutants with altered protein C activation capacity lead to a similar effect. In contrast, transfection of melanoma cells with mutant TM constructs, in which a portion of the cytoplasmic or lectin domain was deleted, abrogated the antiproliferative effect associated with overexpression of wild-type TM. Experiments performed with either peptide agonists/antagonists of the thrombin receptor, with hirudin, or with inhibitors of thrombin-TM interaction did not alter the growth inhibitory effect of TM overexpression. These data suggest that TM exerts an effect on cell proliferation independent of thrombin and the thrombin receptor, possibly related to the binding of novel ligands to determinants in the lectin domain which might trigger signal transduction pathways dependent on the cytoplasmic domain.

beta(3)A-integrin downregulates the urokinase-type plasminogen activator receptor (u-PAR) through a PEA3/ets transcriptional silencing element in the u-PAR promoter.

Migration of cells requires interactions with the extracellular matrix mediated, in part, by integrins, proteases, and their receptors. Previous studies have shown that beta(3)-integrin interacts with the urokinase-type plasminogen activator receptor (u-PAR) at the cell surface. Since integrins mediate signaling into the cell, the current study was undertaken to determine if in addition beta(3)-integrin regulates u-PAR expression. Overexpression of beta(3)-integrin in CHO cells, which are avid expressers of the receptor, downregulated u-PAR protein and mRNA expression. The u-PAR promoter (-1,469 bp) that is normally constitutively active in CHO cells was downregulated by induced beta(3)-integrin expression. A region between -398 and -197 bp of the u-PAR promoter was critical for beta(3)-integrin-induced downregulation of u-PAR promoter activity. Deletion of the PEA3/ets motif at -248 bp substantially impaired the ability of beta(3)-integrin to downregulate the u-PAR promoter, suggesting that the PEA3/ets site acts as a silencing element. An expression vector encoding the transcription factor PEA3 caused inhibition of the wild-type but not the PEA3/ets-deleted u-PAR promoter. The PEA3/ets site bound nuclear factors from CHO cells specifically, but binding was enhanced when beta(3)-integrin was overexpressed. A PEA3 antibody inhibited DNA-protein complex formation, indicating the presence of PEA3. Downregulation of the u-PAR promoter was achieved by the beta(3)A-integrin isoform but not by other beta(3)-integrin isoforms and required the cytoplasmic membrane NITY(759) motif. Moreover, overexpression of the short but not the long isoform of the beta(3)-integrin adapter protein beta(3)-endonexin blocked u-PAR promoter activity through the PEA3/ets binding site. Thus, besides the physical interaction of beta(3)-integrin and u-PAR at the cell surface, beta(3) signaling is implicated in the regulation of u-PAR gene transcription, suggesting a mutual regulation of adhesion and proteolysis receptors.

Assessment of axillary lymph node involvement in breast cancer patients with positron emission tomography using radiolabeled 2-(fluorine-18)-fluoro-2-deoxy-D-glucose.

BACKGROUND: The presence of metastatic tumor cells in the axillary lymph nodes is an important factor when deciding whether or not to treat breast cancer patients with adjuvant therapy. Positron emission tomography (PET) imaging with the radiolabeled glucose analogue 2-(fluorine-18)-fluoro-2-deoxy-D-glucose (F-18 FDG) has been used to visualize primary breast tumors as well as bone and soft-tissue metastases. PURPOSE: This study was undertaken to evaluate before surgery the diagnostic accuracy of PET for detection of axillary lymph node metastases in patients suspected of having breast cancer. METHODS: Women who were scheduled to undergo surgery for newly discovered, suspected breast cancers were referred for PET imaging of the axilla region. The women were first clinically examined to determine the status of their axillary lymph nodes (i.e., presence or absence of metastases). Fifty-one women were intravenously administered F-18 FDG and were studied by PET imaging. Attenuation-corrected transaxial and coronal images were visually evaluated by two nuclear medicine physicians (blinded to the patient's medical history) for foci of increased F-18 FDG uptake in the axilla region. All patients underwent surgery for their suspected breast cancers. Axillary lymph node dissection was also performed on all patients with breast cancer, with the exception of four patients who received primary chemotherapy for locally advanced breast cancer. A single pathologist analyzed breast tumor and lymph node tissue specimens. RESULTS: The overall sensitivity (i.e., the ability of the test to detect disease in patients who actually have disease) and specificity (i.e., the ability of the test to rule out disease in patients who do not have disease) of this method for detection of axillary lymph node metastases in these patients were 79% and 96%, respectively. When only patients with primary breast tumors larger than 2 cm in diameter (more advanced than stage pT1; n = 23) were considered, the sensitivity of axillary PET imaging increased to 94%, and the corresponding specificity was 100%. Lymph node metastases could not be identified in four of six patients with small primary breast cancers (stage pT1), resulting in a sensitivity of only 33%. Axillary PET imaging provided additional diagnostic information in 12 (29%) of 41 breast cancer patients with regard to the extension of disease to other sites (i.e., other lymph nodes, skin, bone, and lung). CONCLUSIONS: PET imaging with F-18 FDG allowed accurate and noninvasive detection of axillary lymph node metastases, primarily in patients with breast cancer more advanced than stage pT1. Detection of micrometastases and small tumor-infiltrated lymph nodes is limited by the currently achievable spatial resolution of PET imaging. IMPLICATIONS: In clinical practice, PET imaging cannot substitute for histopathologic analysis in detecting axillary lymph node metastases in breast cancer patients. PET imaging, however, improves the preoperative staging of the disease in breast cancer patients and, therefore, might alter therapeutic regimen options.

Randomized adjuvant chemotherapy trial in high-risk, lymph node-negative breast cancer patients identified by urokinase-type plasminogen activator and plasminogen activator inhibitor type 1.

BACKGROUND: Most patients with lymph node-negative breast cancer are cured by locoregional treatment; however, about 30% relapse. Because traditional histomorphologic and clinical factors fail to identify the high-risk patients who may benefit from adjuvant chemotherapy, other prognostic factors are needed. In a unicenter study, we have found that levels of urokinase-type plasminogen activator (uPA) and plasminogen activator inhibitor type 1 (PAI-1) in the primary tumor are predictive of disease recurrence. Thus, we designed the Chemo N(0) prospective randomized multicenter therapy trial to investigate further whether uPA and PAI-1 are such prognostic factors and whether high-risk patients identified by these factors benefit from adjuvant chemotherapy. After 4.5 years, we present results of the first interim analysis. METHODS: We studied 556 patients with lymph node-negative breast cancer. The median follow-up was 32 months. All patients with low tumor levels of uPA (< or = 3 ng/mg of protein) and of PAI-1 (< or = 14 ng/mg of protein) were observed. Patients with high tumor levels of uPA (> 3 ng/mg of protein) and/or of PAI-1 (> 14 ng/mg of protein) were randomly assigned to combination chemotherapy or subjected to observation only. All statistical tests were two-sided. RESULTS: A total of 241 patients had low levels of uPA and PAI-1, and 315 had elevated levels of uPA and/or PAI-1. The estimated 3-year recurrence rate for patients with low tumor levels of uPA and PAI-1 (low-risk group) was 6.7% (95% confidence interval [CI] = 2.5% to 10.8%). This rate for patients with high tumor levels of uPA and/or PAI-1 (high-risk group) was 14.7% (95% CI = 8.5% to 20.9%) (P = 0.006). First interim analysis suggests that high-risk patients in the chemotherapy group benefit, with a 43.8% lower estimated probability of disease recurrence at 3 years than high-risk patients in the observation group (intention-to-treat analysis: relative risk = 0.56; 95% CI = 0.25 to 1.28), but further follow-up is needed for confirmation. CONCLUSIONS: Using uPA and PAI-1, we have been able to classify about half of the patients with lymph node-negative breast cancer as low risk, for whom adjuvant chemotherapy may be avoided, and half as high risk, who appear to benefit from adjuvant chemotherapy.

Both the cytosols and detergent extracts of breast cancer tissues are suited to evaluate the prognostic impact of the urokinase-type plasminogen activator and its inhibitor, plasminogen activator inhibitor type 1.

The serine protease urokinase-type plasminogen activator (uPA) plays a key role in tumor-associated proteolysis in malignant solid tumors. Proteolytic activity of uPA is controlled by its naturally occurring plasminogen activator inhibitor type 1. As an initial observation, a correlation of enzymatic uPA activity in breast cancer cytosols with prognosis was described in 1988 (Duffy et al., Cancer (Phila.), 62: 531-533, 1988). A pronounced prognostic impact of uPA, independent of classical risk parameters, was then first demonstrated in detergent-extracted (Triton X-100) breast cancer tissues by applying enzyme-linked immunosorbent assay techniques (Jänicke et al., Lancet, 2: 1049, 1989; Fibrinolysis, 4:69-78, 1990; Duffy et al., Cancer Res., 50: 6827-6829, 1990). In addition, not only uPA but also plasminogen activator inhibitor type 1 were shown to be of prognostic value in breast cancer (Jänicke et al., Semin. Thromb. Hemostasis, 17: 303-312, 1991; Breast Cancer Res. Treat., 24: 195-208, 1993). Subsequently, the prognostic value of uPA and plasminogen activator inhibitor type 1 was also confirmed in studies using archived "cytosol fractions" of breast cancer tissues (Foekens et al., Cancer Res., 52: 6101-6105, 1992; Spyratos et al., J. Natl. Cancer Inst., 84: 1266-1272, 1992; Grondahl-Hansen et al., Cancer Res., 53: 2513-2521, 1993; Sumiyoshi et al., Int. J. Cancer, 50: 345-348, 1992). A direct comparison of both methods with regard to prognosis, however, was lacking. We therefore prepared both the detergent-treated tissue extracts and the cytosol fractions from the same breast cancer specimens to allow a direct comparison of both methods. In 247 breast cancer patients investigated, the Triton X-100-extracted tissues revealed about twice as much uPA antigen (uPATx: median, 2.32 ng/mg protein) than the cytosol fractions (uPAcyt: median, 1.07 ng/mg protein). In contrast, the presence of Triton X-100 did not result in an increase of PAI-1 (PAI-1Tx: median, 6.34 ng PAI-1/mg protein) compared to the cytosol fractions (PAI-1cyt: median, 7.15 ng PAI-1/mg protein). Good correlations between uPATx and uPAcyt (R = 0.72) and between PAI-1Tx and PAI-1cyt (R = 0.88) were observed. Furthermore, PAI-1 and uPA are moderately correlated with each other (uPATx versus PAI-1Tx: R = 0.40; uPAcyt versus PAI-1cyt: R = 0.39). The prognostic power of uPA showed its best advantage in Triton X-100-extracted tissues (RR = 3.22), most pronounced in the subgroups of node-negative and premenopausal patients, respectively.(ABSTRACT TRUNCATED AT 400 WORDS)

Fibrin-fibronectin compounds in human ovarian tumor ascites and their possible relation to the tumor stroma.

Covalently linked heterogeneous fibrin-fibronectin compounds were detected in ascitic fluid of 31 patients with advanced ovarian cystadenocarcinoma by means of enzyme-linked immunosorbent assay techniques, immunoaffinity chromatography, and Western blot analysis. Deposition of fibrin and fibronectin could also be demonstrated immunohistochemically in Carnoy-fixed tissue sections. Fibrin and fibronectin were found in the tumor stroma within tumor nests and more prominently in stroma surrounding the tumor nests. The association of fibrin and fibronectin was especially pronounced in the stroma surrounding the tumor islands. Fibronectin was also found to be associated with stroma cells. Areas within the tumor stroma showed superimposed staining for both fibrin and fibronectin supporting the assumption that the covalently linked fibrin-fibronectin conjugates found in ascitic fluid may stem from the provisional tumor stroma by proteolytic release.

Primary tumor and metastasis in ovarian cancer differ in their content of urokinase-type plasminogen activator, its receptor, and inhibitors types 1 and 2.

The relevance of urokinase-type plasminogen activator (uPA) and plasminogen activator inhibitor (PAI) type 1 in predicting the survival probability of patients with advanced ovarian cancer after radical surgery and adjuvant chemotherapy by assessing the patients' primary tumors has recently been shown by us (W. Kuhn et al., Gynecol. Oncol., 55: 401-409, 1994). In the present study, we determined uPA, uPA receptor, PAI-1, and PAI-2 concentrations in primary tumors and tumor-infiltrated omentum and retroperitoneal lymph nodes of ovarian cancer patients. The group consisted of 39 patients with advanced ovarian carcinoma stages Fédération Internationale de Gynécologie et d'Obstétrique (FIGO) IIIc or IV; for comparison 7 patients with early carcinoma stage FIGO I were also included. In metastases of the omentum from ovarian cancer stage FIGO IIIc or IV patients, we noted a 4-fold elevated uPA content, a 2-fold increase in PAI-1, and also a significant increase in uPA receptor and PAI-2 over primary tumors. In metastases of the lymph nodes the levels of the respective antigens were also increased when compared to primary tumors. These data may indicate that elevated levels of components of the fibrinolytic system at sites of metastases may contribute to the aggressive potential of cancer cells by favoring their reimplantation and/or the consolidation of a new tumor stroma.

Rac1 in human breast cancer: overexpression, mutation analysis, and characterization of a new isoform, Rac1b.

Rac1 is a member of the Ras superfamily of small guanosine triphosphatases (GTPases) that act as molecular switches to control cytoskeletal rearrangements and cell growth. Analogous to Ras, constitutively activating point mutations of Rac1 cause tumorigenic transformation of cell lines. However, there is no information about whether Rac1 is also mutated in vivo. After RT - PCR of Rac1, several clones of seven benign and 10 malignant breast cancer tissues as well as eight breast cancer cell lines were sequenced. Only single-nucleotide polymorphisms of Rac1 could be detected, and none of these corresponded to constitutively activating point mutations that have been used in cell lines for transformation. While sequencing Rac1 in breast tissues, a new Rac1 isoform with an insertion of 19 codons within the reading frame of Rac1 close to switch region II was identified and named Rac1b. The Rac1b protein acts like a fast cycling GTPase in GTP binding and hydrolysis assays. In Northern and Western blot experiments both Rac1 RNA and Rac1 protein had a significantly higher expression in breast cancer tissues compared to normal breast tissue samples. Immunohistochemical staining of Rac1 showed weak Rac1 expression in benign breast disease but high expression level in ductal carcinoma-in-situ, primary breast cancer, and lymph node metastases. In addition, breast tumor cells from patients with recurrent disease had Rac1 expression at the plasma membrane, suggesting activation of Rac1, in patients with aggressive breast cancer. Oncogene (2000).

Breast imaging with positron emission tomography and fluorine-18 fluorodeoxyglucose: use and limitations.

PURPOSE: To evaluate the diagnostic value of positron emission tomography (PET) using fluorine-18 fluorodeoxyglucose (FDG) for the diagnosis of primary breast cancer. PATIENTS AND METHODS: Preoperatively, 144 patients with masses suggestive of breast cancer underwent PET imaging of the breast. To identify breast cancer by increased metabolic activity, parametric FDG-PET images were analyzed for increased tracer uptake applying conventional image reading (CIR) and sensitive image reading (SIR). One hundred eighty-five breast tumors were evaluated by histology, revealing 132 breast carcinomas and 53 benign masses. RESULTS: Breast carcinomas were identified with an overall sensitivity of 64.4% (CIR) and 80.3% (SIR). The increase in sensitivity (SIR) resulted in a noticeable decrease in specificity, from 94.3% (CIR) to 75.5% (SIR). At stage pT1, only 30 (68.2%) of 44 breast carcinomas were detected, compared with 57 (91.9%) of 62 at stage pT2. A higher percentage of invasive lobular carcinomas were false-negative (65.2%) compared with invasive ductal carcinomas (23.7%). Nevertheless, positive PET scans provided a high positive-predictive value (96.6%) for breast cancer. CONCLUSION: Partial volume effects and varying metabolic activity (dependent on tumor type) seem to represent the most significant limitations for the routine diagnostic application of PET. The number of invasive procedures is therefore unlikely to be significantly reduced by PET imaging in patients presenting with abnormal mammography. However, the high positive-predictive value, resulting from the increased metabolic activity of malignant tissue, may be used with carefully selected subsets of patients as well as to determine the extent of disease or to assess therapy response.

Positron emission tomography using [(18)F]Fluorodeoxyglucose for monitoring primary chemotherapy in breast cancer.

PURPOSE: To address the role of positron emission tomography (PET) using [(18)F]fluorodeoxyglucose (FDG) to monitor primary (neoadjuvant) chemotherapy in patients with locally advanced breast cancer. PATIENTS AND METHODS: Quantification of regional FDG uptake of the breast acquired after the first and second courses of chemotherapy was compared with the baseline scan in 22 patients with a total of 24 breast carcinomas. To evaluate the predictive value of PET imaging, histopathologic response after completion of chemotherapy classified as gross residual disease (GRD) or minimal residual disease (MRD) served as the gold standard. RESULTS: Significant differences in tracer uptake between nonresponding tumors (GRD) and responding lesions (MRD) were observed (P <.05) as early as after the first course of chemotherapy. Tracer uptake showed little change in tumors with GRD found later in pathologic analysis but decreased sharply to the background level in most tumors with MRD. After the first course, all responders were correctly identified (sensitivity 100%, specificity 85%) by a standardized uptake value decrease below 55% of the baseline scan. At this threshold, histopathologic response could be predicted with an accuracy of 88% and 91% after the first and second courses of therapy, respectively. CONCLUSION: This study demonstrates that in patients with advanced breast cancer undergoing primary chemotherapy, FDG-PET differentiates responders from nonresponders early in the course of therapy. This may help improve patient management by avoiding ineffective chemotherapy and supporting the decision to continue dose-intensive preoperative chemotherapy in responding patients.

Metabolic characterization of breast tumors with positron emission tomography using F-18 fluorodeoxyglucose.

PURPOSE: To evaluate the diagnostic value of position emission tomographic (PET) imaging with F-18 fluorodeoxyglucose (FDG) in differentiating between benign and malignant breast tumors. PATIENTS AND METHODS: Fifty-one patients, with suspicious breast lesions newly discovered either by physical examination or by mammography, underwent PET imaging before exploratory surgery. FDG-PET images of the breast were analyzed visually and quantitatively for objective assessment of regional tracer uptake. RESULTS: Primary breast cancer was identified visually with a sensitivity of 68% to 94% and a specificity of 84% to 97% depending on criteria used for image interpretation. Quantitative analysis of FDG uptake in tumors using standardized uptake values (SUV) showed a significant difference between benign (1.4 +/- 0.5) and malignant (3.3 +/- 1.8) breast tumors (P < .01). Receiver operating characteristic (ROC) curve analysis exhibited a sensitivity of 75% and a specificity of 100% at a threshold SUV value of 2.5. Sensitivity increased to 92% with a corresponding specificity of 97% when partial volume correction of FDG uptake was performed based on independent anatomic information. CONCLUSION: PET imaging allowed accurate differentiation between benign and malignant breast tumors providing a high specificity. Sensitivity for detection of small breast cancer ( < 1 cm) was limited due to partial volume effects. Quantitative image analysis combined with partial volume correction may be necessary to exploit fully the diagnostic accuracy. PET imaging may be helpful as a complimentary method in a subgroup of patients with indeterminate results of conventional breast imaging.

Gender differences in myocardial blood flow dynamics: lipid profile and hemodynamic effects.

OBJECTIVES: The purpose of the study was to compare myocardial blood flow (MBF) in hyperlipidemic postmenopausal women and age-matched hyperlipidemic men, and to analyze the relationship between cholesterol subfractions and myocardial blood flow in men and women. BACKGROUND: Women are protected from coronary artery disease (CAD) events until well after menopause, in part due to gender-specific differences in lipid profiles. METHODS: To examine the effect of these influences on coronary microcirculation, MBF was quantitated with N-13 ammonia/PET (positron emission tomography) at rest and during adenosine hyperemia in 15 women and 15 men, all nondiabetic, who were matched for age and total cholesterol levels (53+/-4 vs. 50+/-8 years, p = NS, 6.44+/-1.1 vs. 6.31+/-0.85 mmol/liter, or 249+/-41 vs. 244+/-33 mg/dl, p = NS). RESULTS: Women had significantly higher high density lipoprotein (HDL) and lower triglyceride (Tg) levels than did men, and they showed significantly higher resting MBF and stress MBF levels. Significant correlations were found between resting and hyperemic MBF and HDL and Tg levels (r = 0.44, p < 0.02 for stress MBF vs. HDL; r = 0.48, p < 0.007 for stress MBF vs. Tg). Gender was the strongest predictor of hyperemic MBF in multivariate analysis. Women responded to adenosine hyperemia with a significantly higher heart rate than did men, and hemodynamic factors correlated significantly with blood flow both at rest and during stress. CONCLUSIONS: These data suggest that the favorable lipid profile seen in women may be associated with preserved maximal blood flow in the myocardium.

Prognostic value of the cysteine proteases cathepsins B and cathepsin L in human breast cancer.

The lysosomal cysteine proteases cathepsin B and cathepsin L have been implicated in tumor spread and metastasis. To evaluate the prognostic impact of these proteases for disease-free survival and overall survival in breast cancer, the antigen content of cathepsin B and cathepsin L was determined using ELISA in tumor cytosol fractions of 167 breast cancer patients and in cytosols of 29 benign breast tissue specimens. Median values of 856 ng versus 76 ng cathepsin B/mg protein and of 428 ng versus 56 ng cathepsin L/mg protein were found in tumor versus benign cytosol fractions. A positive correlation between cathepsin B and cathepsin L (r = 0.32, P = 0.0000, Spearman test) was found. Cathepsin L was inversely correlated to hormone receptor status (P = 0.0014, Mann-Whitney U test) and to the presence of tumor necrosis (P = 0.009, Mann-Whitney U test). There were no correlations of cathepsin B or cathepsin L to tumor size, axillary lymph node status, age, menopausal status, tumor grading, and vessel invasion. To perform univariate analyses of disease-free survival, optimal cutoff points were determined by isotonic regression and classification and regression trees analysis. Patients with a high content of cathepsin B (>1092 ng/mg protein) or cathepsin L (>376 ng/mg protein) in their primary tumors had a statistically significantly higher risk of recurrence than patients with a low content of cathepsin B or cathepsin L (5-year disease-free survival: cathepsin B, 70% versus 52%, P = 0.04; cathepsin L, 83% versus 52%, P = 0.0002). Median follow-up was 39 (range, 6-73) months. Multivariate analysis for disease-free survival showed that cathepsin L is a strong and independent prognostic factor with a prognostic impact comparable to that of axillary lymph node status and grading. We conclude that both cathepsin B and cathepsin L may serve as prognostic factors for tumor recurrence in human breast cancer. These data underline the significance of tumor-associated proteolysis for invasion and metastasis.

Elastase released from human granulocytes stimulated with N-formyl-chemotactic peptide prevents activation of tumor cell prourokinase (pro-uPA).

Proteolytic enzymes released from granulocytes upon stimulation with the chemotactic N-formyl peptide FNLPNTL (in the presence of cytochalasin B) prevented activation of tumor cell single-chain urokinase-type plasminogen activator (pro-uPA) by plasmin. Elastase was identified by the use of eglin C (elastase inhibitor) and a monoclonal antibody to elastase as the functional proteolytic enzyme in granulocyte supernatants. Action of purified granulocyte elastase on pro-uPA generated enzymatically inactive two-chain uPA linked by disulfide bridges which was indistinguishable by SDS-PAGE from plasmin-generated HMW-uPA. The major elastase cleavage site in pro-uPA was located between Ile159 and Ile160. a minor one between Thr165 and Thr166. Elastase cannot substitute for plasmin in the proteolytic activation of pro-uPA to enzymatically active HMW-uPA. However, when pro-uPA was first activated by plasmin to form enzymatically active HMW-uPA, this enzymatic activity was not impaired by subsequent elastase treatment.

Recombinant soluble urokinase receptor as a scavenger for urokinase-type plasminogen activator (uPA). Inhibition of proliferation and invasion of human ovarian cancer cells.

A recombinant soluble human urokinase receptor comprising amino acids 1-277 was cloned and transfected into CHO cells. The mutant protein (rec-uPAR277), purified from the CHO cell supernatant by affinity chromatography on immobilized urokinase (uPA), in a four-fold excess, completely abolished the binding of FITC-labeled pro-uPA to the human ovarian cancer cell line, OV-MZ-6. This invasive and tumorigenic cancer cell line expresses uPA, its inhibitor PAI-1, and the high-affinity receptor for uPA, uPAR. Rec-uPAR277 significantly reduced the proliferation of OV-MZ-6 cells in a concentration-dependent manner without altering the viability of the cells. Invasion of OV-MZ-6 cells tested in an in vitro Matrigel invasion assay was inhibited by rec-uPAR277 up to 75%. In conclusion, these results demonstrate that rec-uPAR277 can function as a scavenger for uPA in vitro by inhibiting proliferation and invasion of human cancer cells.

Effective activation of the proenzyme form of the urokinase-type plasminogen activator (pro-uPA) by the cysteine protease cathepsin L.

Increased levels of both the cysteine protease, cathepsin L, and the serine protease, uPA (urokinase-type plasminogen activator), are present in solid tumors and are correlated with malignancy. uPA is released by tumor cells as an inactive single-chain proenzyme (pro-uPA) which has to be activated by proteolytic cleavage. We analyzed in detail the action of the cysteine protease, cathepsin L, on recombinant human pro-uPA. Enzymatic assays, SDS-PAGE and Western blot analysis revealed that cathepsin L is a potent activator of pro-uPA. As determined by N-terminal amino acid sequence analysis, activation of pro-uPA by cathepsin L is achieved by cleavage of the Lys158-Ile159 peptide bond, a common activation site of serine proteases such as plasmin and kallikrein. Similar to cathepsin B (Kobayashi et al., J. Biol. Chem. (1991) 266, 5147-5152) cleavage of pro-uPA by cathepsin L was most effective at acidic pH (molar ratio of cathepsin L to pro-uPA of 1:2,000). Nevertheless, even at pH 7.0, pro-uPA was activated by cathepsin L, although a 10-fold higher concentration of cathepsin L was required. As tumor cells may produce both pro-uPA and cathepsin L, implications for the activation of tumor cell-derived pro-uPA by cathepsin L may be considered. Different pathways of activation of pro-uPA in tumor tissues may coexist: (i) autocatalytic intrinsic activation of pro-uPA; (ii) activation by serine proteases (plasmin, kallikrein, Factor XIIa); and (iii) activation by cysteine proteases (cathepsin B and L).

Urokinase induces proliferation of human ovarian cancer cells: characterization of structural elements required for growth factor function.

Ovarian cancer metastasis is associated with an increase in the urokinase-type plasminogen activator (uPA) and its receptor uPAR. We present evidence that binding of uPA to uPAR provokes a mitogenic response in the human ovarian cancer cell line OV-MZ-6 in which endogenous uPA production had been significantly reduced by stable uPA 'antisense' transfection. High molecular weight (HMW) uPA, independent of its enzymatic activity, produced an up to 95% increase in cell number concomitant with 2-fold elevated [3H]thymidine incorporation as did the catalytically inactive but uPAR binding amino-terminal fragment of uPA, ATF. uPA-induced cell proliferation was significantly decreased by blocking uPA/uPAR interaction by the monoclonal antibody IIIF10 and by soluble uPAR. The efficiency of the uPAR binding synthetic peptide cyclo19,31 uPA19-31 to enhance OV-MZ-6 cell growth proved this molecular domain to be the minimal structural determinant for uPA mitogenic activity. Dependence of uPA-provoked cell proliferation on uPAR was further demonstrated in Raji cells which do not express uPAR and were thus not induced by uPA. However, upon transfection with full-length uPAR, Raji cells acquired a significant growth response to HMW uPA and ATF.

Reduction of breast carcinoma tumor growth and lung colonization by overexpression of the soluble urokinase-type plasminogen activator receptor (CD87).

The serine protease urokinase-type plasminogen activator, uPA, when bound to its specific receptor, uPAR (CD87), plays a significant role in tumor cell invasion and metastasis. In breast cancer, enhanced uPA antigen in the primary tumor is correlated with poor prognosis of the patient. In an in vivo nude mouse model, we tested tumor growth and metastasis of human breast carcinoma cells that had been transfected with an expression plasmid encoding a soluble form of uPAR (suPAR). We explored, whether suPAR/uPA interaction reduces the binding of uPA to cell surface-associated uPAR, and, as a consequence, could suppress tumor growth and metastasis of the human breast cancer cell line MDA-MB-231 BAG. Overexpressed, secreted suPAR was shown to bind and thus scavenge the uPA secreted by the transfected lines suPAR3 and suPAR10. In vitro, an overexpression of suPAR did not alter the proliferation rate of the transfected tumor cells, nor did it affect the expression of uPA. Overexpression of suPAR led to a reduction in the plasminogen activation-related proteolytic activity of breast carcinoma cells. Primary tumor growth in the mammary fat pad of nude mice was followed up for 52 days. Overexpression of suPAR correlated with a reduction in tumor growth (from day 21, reaching 30% by day 34) as well as lung colonization (lung metastasis-positive mice in suPAR3: 4 of 17; suPAR10: 3 of 10; parental MDA-MB-231 BAG: 13 of 18). We conclude that suPAR overexpression leading to effective scavenge of uPA impairs proteolysis as well as the tumor growth and metastatic potential of breast carcinoma cells in vivo.

Antisense inhibition of urokinase reduces spread of human ovarian cancer in mice.

Urokinase-type plasminogen activator (uPA) is a protease involved in the process of tissue remodelling and cell migration in vitro. To explore whether uPA is a prerequisite for human ovarian cancer spread in vivo the expression of uPA was suppressed in human ovarian cancer cells by antisense phosphorothioate oligonucleotides (PS-ODN). The suppression of uPA expression was dependent on PS-ODN concentration and only observed in the presence of liposomes. This phenomenon seemed to be due to the fact that PS-ODNs were taken up by the cancer cells only in concert with liposomes as studied by fluorescently-labeled PS-ODNs using flow cytofluorometry and laser scanning microscopy. uPA-deprived cancer cells exhibited a significantly reduced invasive capacity in vitro compared with untreated cancer cells or cells treated with control PS-ODNs (P = 0.003). The intraperitoneal spread of the cancer cells in vivo was significantly diminished when nude mice were treated with uPA antisense PS-ODNs in comparison with control mice (P = 0.009). These results suggest that uPA expression may be required for spread of human ovarian cancer and that its inhibition could provide a therapeutic approach.

FDG PET evaluation of granular cell tumor of the breast.

Granular cell tumor is a rare, usually benign neoplasm of neural origin that may arise in virtually any site and, when situated in the breast, can mimic breast carcinoma. We describe a case of granular cell tumor of the breast in a 57-yr-old woman. Clinical evaluation, mammography, sonography and MRI suggested a carcinoma with infiltration of skin and muscle. However, the tumor did not display increased glucose metabolism on PET. Clinical findings, imaging results, histological characteristics and surgical management are discussed.