Tumor cell surface-associated binding site for the M(r) 72,000 type IV collagenase.

We have studied the capacity of two human breast adenocarcinoma cells, MDA-MB231 and MCF-7, to bind exogenous M(r) 72,000 type IV collagenase by both morphological and radioreceptor binding assays. By indirect immunofluorescence, staining with a specific anti-M(r) 72,000 type IV collagenase antibody was strongly induced when cells were preincubated with the purified enzyme. Scatchard plot analysis indicated the existence of a binding site for the M(r) 72,000 type IV collagenase with high affinity for both cell lines (Kd = 2 x 10(-9) M). These results are the first demonstration of the existence of a tumor cell membrane-associated putative receptor for a member of the matrix metalloproteinase family, as previously evidenced for the urokinase-type plasminogen activator.     

Pregnancy outcome following frozen embryo transfer after artificial cycle or treatment by clomiphene citrate

The optimal method to prepare endometrium before frozen embryo transfer (FET) is not yet established. We retrospectively studied 4496 FET and detailed pregnancy and miscarriage rates in three groups of patients according to the endometrium preparation they have followed before their successive FET: clomifene citrate (CC, group 1), artificial cycle (AC, group 2) or switch between CC and AC (group 3). The overall pregnancy rates per transfer were 24.3, 20.8 and 17.3% while the miscarriage rates reached 23.2, 29.8 and 42.5%, respectively. Group 1 experienced the highest ongoing pregnancy rate (18.6%), the lowest being observed in group 3 (10.0%, p?相似文献   

Thymic extracellular matrix in myasthenia gravis. II. Immunohistochemical evidence for increased type I collagen degradation

By immunohistochemistry, we studied the breakdown of type I collagen in frozen sections of normal and hyperplastic (myasthenia gravis-associated) human thymuses. This analysis was carried out using a specific polyclonal antibody directed against the alpha 2-CB(3,5) peptide, a degradation product of type I collagen. In the normal thymus, virtually no labeling was observed within thymic septae or intralobular regions. In contrast, bright fluorescent staining was consistently detected in myasthenia gravis-associated hyperplastic thymuses. Such immunoreactivity was found not only in septal regions but also in the intralobular connective tissue meshwork that exists in these thymuses. Our results represent further evidence for a defect in extracellular matrix metabolism in hyperplastic thymuses, which may be related to the abnormal intrathymic penetration of B cells, known to occur in this disease.     

Regulation of LRP-1 expression: Make the point

The low-density lipoprotein receptor-related protein-1 (LRP-1) is a membrane receptor displaying both scavenging and signaling functions. The wide variety of extracellular ligands and of cytoplasmic scaffolding and signaling proteins interacting with LRP-1 gives it a major role not only in physiological processes, such as embryogenesis and development, but also in critical pathological situations, including cancer and neurological disorders. In this review, we describe the molecular mechanisms involved at distinct levels in the regulation of LRP-1, from its expression to the proper location and stability at the cell surface.     

Coordinate enhancement of gelatinase a mRNA and activity levels in human fibroblasts in response to breast-adenocarcinoma cells

Gelatinases/type-IV collagenases are metalloproteinases involved in some carcinoma invasion and metastatic processes. The exact cellular source of the 72-kDa gelatinase A is controversial. We have analyzed the expression of mRNA coding for gelatinase A in vivo by in situ hybridization on breast-cancer tissues. The mRNA for gelatinase A was present in fibroblasts. We have therefore evaluated the gelatinase-A activity in vitro, in co-cultures of different breast adenocarcinoma cell lines and human fibroblasts. In monoculture, none of the tumor cells tested produced detectable amounts of gelatinase A. The gelatinase-A activity was enhanced in cultures of fibroblasts maintained in the presence of MDA-MB 231 or SKBR3 cells, or their conditioned medium. This increased enzymatic activity was evidenced both in the culture medium and in the membrane fraction and was paralleled by enhancement of the steady-state levels of mRNA. These results are an in vitro demonstration of a regulation of fibroblasts gelatinase-A production by soluble factors secreted by breast-tumor cells.     

Matrix-directed regulation of pericellular proteolysis and tumor progression

The microenvironment of cancer cells, composed of extracellular matrix (ECM) macromolecules, plays a pivotal function in tumor progression. ECM preexisting modules or cryptic sites revealed by partial enzymatic hydrolysis positively or negatively regulate matrix metalloproteinase (MMP) expression and activation, further influencing matrix invasion by cancer cells. Pericellular activation of gelatinase A (MMP-2) proceeds via the formation of a complex involving its inhibitor, TIMP-2, its activator(s), MT-MMPs and alphavbeta3 integrin forming a docking system. This proteinase has been invariably linked to cancer cell invasive potential and is often predictive of a poor survival. MMP-2 degrades most ECM macromolecules and appears to act as a main 'decryptase'. ECM modulation of MMP-2 activation pathway thus influences angiogenesis and tumor growth. For instance the noncollagenous domain of alpha3 chain of type IV collagen, through alphavbeta3 integrin binding, inhibits both MT1-MMP and alphavbeta3 integrin expression from melanoma cells and empedes cell migration and proliferation. At the opposite, a particular module in elastin (VGVAPG) with type VIII beta turn conformation stimulates MT1-MMP and proMMP-2 activation through binding to S-gal elastin receptor, and increases the matrix invasive capacity of several cancer cell lines and endothelial cells. Endocytosis emerges as a main mechanism controlling MMP-2, and also other MMPs; it proceeds via the formation of a MMP-thrombospondin(s) complex further recognized by the LRP scavenger receptor. ECM undergoes conspicuous variations with aging linked to alterations of tissue organization and post-translational modifications of matrix constituents that modify cell-matrix interactions and MMP-2 activation pathway.     

Invasion of reconstituted basement membrane matrix is not correlated to the malignant metastatic cell phenotype

Interactions between tumor cells and basement membranes represent a critical step in the progression of neoplasia and in the metastatic process. Reconstituted basement membrane matrix, matrigel, has been recently used with the aim of developing an in vitro assay of tumor cell invasiveness. We have extended these studies by comparing the invasiveness of a large series of normal and malignant epithelial and mesenchymal cells of human and animal origin cultured on matrigel. Normal cells (fibroblasts, glomerular mesangial cells, keratinocytes), human fibrosarcoma cells (HT1080), and reticular sarcoma cells (M5076) clearly established invasive capabilities in the matrix. However, all the other tested cell lines, malignant or virally transformed cells invasive in vivo (MCF7, T47D, SA52, SW613, MO4, A431, BeWo), as well as normal nontransformed cells (MOH22) were incapable of penetration. The morphological features of matrigel invasion by normal fibroblasts and HT1080 cells are described at the light and electron microscope levels. The extent of degradation of a radiolabeled matrigel is minimal and similar in several cell lines reported to be noninvasive or invasive in vivo. Our data suggest that matrigel does not provide a universal model to correlate the invasiveness of cells in vivo and in vitro.     

Collagen isotypes, laminin, and fibronectin in granulomas of the liver and intestines of Schistosoma mansoni-infected mice

Patterns of fibrosis within hepatic and intestinal granulomas of Schistosoma mansoni-infected mice were analyzed by indirect immunofluorescence. Deposition of collagen isotypes, laminin, and fibronectin was evaluated semiquantitatively between 8 and 20 weeks of the infection. Liver granulomas were the largest at 8 weeks and contained low amounts of type I and higher amounts of type III collagen and fibronectin. Collagen deposition became pronounced as infection progressed. The relative amounts of type I collagen deposits rose and equalled that of type III. In the smaller immunomodulated granulomas at 20 weeks both types I and III were high, and type IV collagen deposition was observed. Fibronectin and laminin deposits were also detected. The small ileal granulomas did not change their size during the course of the infection. At 8 weeks, connective tissue matrix deposition was barely detectable within these lesions. Gradually, small deposits of types I and III appeared in equal amounts and attained highest levels by 20 weeks of the infection. Fibronectin deposits at that time were very prominent but laminin and type IV collagen were absent. Colon granulomas at 8 weeks of the infection were only somewhat smaller than those of the liver, yet contained very sparse deposits of types I and III collagen. During the ensuing weeks collagen deposits rose only slightly. By 20 weeks the granulomas diminished in size and within those lesions type III collagen was predominant. Whereas the presence of fibronectin was pronounced, type IV collagen and laminin were detectable only in trace amounts. These observations indicate the existence of important organ-related differences in the intragranulomatous deposition of connective tissue matrix.     

Mechanisms of pericyte recruitment in tumour angiogenesis: a new role for metalloproteinases

Pericytes occur in tumour blood vessels and are critical for the development of a functional vascular network. Targeting tumour pericytes is a promising anti-angiogenic therapy but requires identifying the mechanisms of their recruitment in tumour and addressing whether these mechanisms can be selectively harnessed. Among the pathways involved in pericyte recruitment during embryonic development, the contribution of platelet-derived growth factor B and sphingosine 1-phosphate is confirmed in tumour angiogenesis. The effect of angiopoietin 1 depends on the tumour model. Transforming growth factor-beta1 enhances tumour vascularization and microvessel maturation. Recent reports suggest a participation of matrix metalloproteinases (MMP) in tumour pericyte recruitment that is consistent with the effect of certain MMPs in the development of microvasculature in embryonic development and in in vitro models of vascular remodelling. Here, we discuss the possibility for MMPs to contribute to pericyte recruitment at six levels: (1) direct promotion of pericyte invasion by extracellular matrix degradation; (2) stimulation of pericyte proliferation and protection against apoptosis by modification of the ECM; (3) activation of pericytes through the release of growth factor bound to the ECM; (4) transactivation of angiogenic cell surface receptor; (5) propagation of angiogenic signalling as cofactor; and (6) recruitment of bone marrow-derived stem cells.     

Post-translational proteolytic events influence LRP-1 functions

The low-density lipoprotein receptor-related protein (LRP-1) is a membrane receptor displaying both endocytic scavenging and signaling functions. In this review, we briefly present post-translational proteolytic processes targeting this receptor and speculate on their possible influence on LRP-1 biological functions.