Plasminogen activators and plasminogen activator inhibitors in human colorectal carcinoma tissues are not expressed by the tumour cells

The effect of anti-VEGF therapy on immature myeloid cell and dendritic cells in cancer patients

Impairment of dendritic cells (DC), the most effective activators of anticancer immune responses, is one mechanism for defective antitumor immunity, but the causes of DC impairment are incompletely understood. We evaluated the association of impaired DC differentiation with angiogenesis-associated molecules D-dimer, vascular endothelial growth factor (VEGF), urokinase plasminogen activator (uPA), and plasminogen activator inhibitor (PAI-1) in peripheral blood from 41 patients with lung, breast, and colorectal carcinoma. Subsequently, we studied the effect of administration of the anti-VEGF antibody (bevacizumab) on DC maturation and function in vivo. Compared with healthy volunteers, cancer patients had a bias toward the immunoregulatory DC2, had deficits in DC maturation after overnight in vitro culture, and had a significant increase in immature myeloid cell progenitors of DC (0.50 +/- 0.31% vs. 0.32 +/- 0.16% of peripheral blood mononuclear cells, respectively, P = 0.011). A positive correlation was found between the percentage of DC2 and PAI-1 (R = 0.50) and between immature myeloid cells and VEGF (R = 0.52). Bevacizumab administration to cancer patients was associated with a decrease in the accumulation of immature progenitor cells (0.39 +/- 0.30% vs. 0.27 +/- 0.24%, P = 0.012) and induced a modest increase in the DC population in peripheral blood (0.47 +/- 0.23% vs. 0.53 +/- 0.30%). Moreover, anti-VEGF antibody treatment enhanced allo-stimulatory capacity of DC and T cell proliferation against recall antigens. These data suggest that DC differentiation is negatively associated with VEGF levels and may be one explanation for impaired anticancer immunity, especially in patients with advanced malignancies.

Functional Imaging of Proteolysis: Stromal and Inflammatory Cells Increase Tumor Proteolysis

The underlying basement membrane is degraded during progression of breast and colon carcinoma. Thus, we imaged degradation of a quenched fluorescent derivative of basement membrane type IV collagen (DQ-collagen IV) by living human breast and colon tumor spheroids. Proteolysis of DQ-collagen IV by HCT 116 and HKh-2 human colon tumor spheroids was both intracellular and pericellular. In contrast, proteolysis of DQ-collagen IV by BT20 human breast tumor spheroids was pericellular. As stromal elements can contribute to proteolytic activities associated with tumors, we also examined degradation of DQ-collagen IV by human monocytes/macrophages and colon and breast fibroblasts. Fibroblasts themselves exhibited a modest amount of pericellular degradation. Degradation was increased 4–17-fold in cocultures of fibroblasts and tumor cells as compared to either cell type alone. Inhibitors of matrix metalloproteinases, plasmin, and the cysteine protease, cathepsin B, all reduced degradation in the cocultures. Monocytes did not degrade DQ-collagen IV; however, macrophages degraded DQ-collagen IV intracellularly. In coculture of tumor cells, fibroblasts, and macrophages, degradation of DQ-collagen IV was further increased. Imaging of living tumor and stromal cells has, thus, allowed us to establish that tumor proteolysis occurs pericellularly and intracellularly and that tumor, stromal, and inflammatory cells all contribute to degradative processes.

Urokinase gene expression indicates early invasive growth in squamous cell lesions of the uterine cervix

The plasminogen activating system plays a key role in the cascade of tumour-associated proteolysis leading to extracellular matrix degradation and stromal invasion. Changes in the expression of this system, consisting of urokinase- and tissue-type plasminogen activators (uPA and tPA, respectively), plasminogen activator inhibitors (PAI-1, PAI-2) and uPA receptor, have been associated with tumour aggressiveness in a variety of solid malignant tumours. This paper describes a study of squamous intraepithelial lesions (SILs, n=36), squamous cell carcinomas (SCCs, n=42), and normal mucosa (n=5) of the uterine cervix by in situ hybridization with (35)S-labelled RNA probes. uPA transcripts were absent from normal mucosa and non-invasive lesions, but present in atypical epithelial cells of all microinvasive carcinomas ( n=19) and in some of the more advanced invasive carcinomas (n=11). PAI-1 transcripts were found in stromal cells of most tissue samples with, however, significantly increased levels in invasive SCC compared with SIL, microinvasive SCC, and normal mucosa. uPA-positive invasive carcinomas often displayed additional PAI-1 expression by tumour cells. At variance with uPA, tPA transcripts were found in atypical epithelial cells of low- and high-grade SILs. In the majority of SCCs tested (27/29 cases), the HPV 16 E6/E7 oncogene and uPA transcription were correlated. uPA and PAI-1 expression indicates invasive growth when expressed by atypical epithelial cells of squamous cervical lesions. Moreover, the presence of uPA transcripts is indicative of early invasive growth. uPA and tPA seem to have different functions in the development of invasive properties in uterine cervical squamous epithelium.

Different mechanisms are involved in the antibody mediated inhibition of ligand binding to the urokinase receptor: a study based on biosensor technology

Certain monoclonal antibodies are capable of inhibiting the biological binding reactions of their target proteins. At the molecular level, this type of effect may be brought about by completely different mechanisms, such as competition for common binding determinants, steric hindrance or interference with conformational properties of the receptor critical for ligand binding. This distinction is central when employing the antibodies as tools in the elucidation of the structure-function relationship of the protein in question. We have studied the effect of monoclonal antibodies against the urokinase plasminogen activator receptor (uPAR), a protein located on the surface of various types of malignant and normal cells which is involved in the direction of proteolytic degradation reactions in the extracellular matrix. We show that surface plasmon resonance/biomolecular interaction analysis (BIA) can be employed as a highly useful tool to characterize the inhibitory mechanism of specific antagonist antibodies. Two inhibitory antibodies against uPAR, mAb R3 and mAb R5, were shown to exhibit competitive and non-competitive inhibition, respectively, of ligand binding to the receptor. The former antibody efficiently blocked the receptor against subsequent ligand binding but was unable to promote the dissociation of a preformed receptor-ligand complex. The latter antibody was capable of binding the preformed complex, forming a transient trimolecular assembly, and promoting the dissociation of the uPA/uPAR complex. The continuous recording of binding and dissociation, obtained in BIA, is central in characterizing these phenomena. The identification of a non-competitive inhibitory mechanism against this receptor reveals the presence of a determinant which influences the binding properties of a remote site in the molecular structure and which could be an important target for a putative synthetic antagonist.

Alterations in plasminogen activation correlate with epithelial cell dysplasia grading in colorectal adenomas

Proteases are important for neoplastic invasion but a specific role for the plasminogen activator system in the progression of colorectal epithelial dysplasia to adenomatous lesions remains unclear. Consecutive tissue cryosections of 51 adenomas, 49 distant mucosa samples and five mucosa samples from control subjects were histopathologically analysed for dysplasia grade and tissue type, urokinase plasminogen activator levels and plasminogen activator inhibitor type 1 (PAI-1) using immunosorbent methods. Plasminogen activation and urokinase-mediated proteolytic activity levels were assessed using in situ zymography. Plasminogen activation and tissue-type activator levels were lower in adenomas than in mucosae (P < 0.001). PAI-1 concentration and urokinase levels were higher in adenomas than in mucosae (P < 0.001 and P < 0.001 respectively). In adenomas, urokinase concentration increased in parallel with PAI-1, but only the urokinase levels correlated with the dysplasia grade (P < 0.01). Thus, the alterations in plasminogen activation correlated with epithelial cell dysplasia grading. In the mucosa to adenoma transition, a marked decrease in tissue-type plasminogen activator occurred. In adenomas, this decrease was accompanied by a concomitant increase in urokinase and PAI-1. The urokinase level only continued to rise in parallel with the dysplasia grade. Resulting protease-antiprotease imbalance in high-grade dysplasia may represent the phenotypic change associated with malignant transformation and invasive behaviour.

Comparative evaluation of integrin alpha- and beta-chain expression in colorectal carcinoma cell lines and in their tumours of origin

The integrin family consists of broadly expressed cell surface adhesion receptors, each member of which is composed of a non-covalently linked alpha/beta heterodimer. Integrin receptors are involved in the interaction with matrix proteins and may contribute to invasion and metastasis of carcinomas. To examine the biological role integrins play in colorectal carcinoma we compared the expression of integrin alpha- and beta-subunits in situ and in vitro. Eight newly established cell lines derived from immunohistochemically characterized colorectal carcinomas together with two sublines obtained after nude mouse passage and the commonly used colon carcinoma lines HT-29, SW480, SW620, and COLO 205 were investigated by immunocytochemistry and flow cytometry. The carcinomas in situ expressed alpha 1-, alpha 2-, alpha 3-, alpha 6-, alpha v- and beta 1-subunits in variable amounts while being devoid of alpha 4, alpha 5, and beta 3. The individual integrin profile of the tumour in tissue was essentially maintained in vitro. However, a neo expression of the alpha 5 chain was found, together with an induction or increase in alpha 1, alpha 2, alpha 3, alpha v and beta 1 levels. No decrease in integrin subunit expression was observed. Standard-serum and serum-free medium revealed no striking differences in alpha- and beta-chain expression in the cell lines HT-29 and COLO 205. In serum-free medium, SW480 showed a slight increase of alpha 1 and alpha 5 and a decrease of alpha 3 and alpha v while SW620 expressed more alpha 1. We conclude that the great variability of adhesion receptor expression of the integrin family in colorectal carcinomas in situ is essentially maintained in vitro, although culture conditions which are only marginally influenced by serum factors unpredictably lead to some increase in expression or even induction of several integrin subunits.

Secretion of urokinase and plasminogen activator inhibitor-1 by normal colonic epithelium in vitro

Urokinase is a neutral protease whose major site of action is the external surface of the plasma membrane of cells and whose major function seems to be modulation of cell adhesion, such as that which occurs during cell migration. This study aimed to determine whether colonic epithelium is involved with the urokinase system. The contents of urokinase and one of its specific inhibitors, plasminogen activator inhibitor-1, were measured in culture supernatant and cell homogenates of isolated human colonic crypt cells. The amounts of both factors increased in supernatants over 24 hours, and approximately twice the amount was found in supernatants than in autologous cell homogenates. The secretion of both factors was similar in serum free and serum containing media. Northern blot analysis showed that messenger ribonucleic acid specific for urokinase and plasminogen activator inhibitor-1 was present in colonic crypt cells and that expression over 18 hours of culture was increased 12 fold for urokinase type plasminogen activator and two to fourfold for the inhibitor compared with values found in autologous freshly isolated cells. Urokinase activity was detected in crypt cell homogenates and supernatants indicating that it was present in excess of its inhibitors. Control experiments indicated that the epithelial cells themselves were responsible for the observations and excluded artefactual effects of the isolation procedure. In conclusion, isolated human colonic epithelial cells secrete urokinase and at least one of its specific inhibitors. Further investigation of the role of urokinase in the physiology and pathophysiology of colonic epithelium is indicated.