No abstract

Human MCF-7 breast carcinoma cells possess a receptor-like moiety on their surface that has a high binding affinity (Kd = 2 nM) for laminin, a glycoprotein localized in basement membranes. Laminin preferentially stimulates (8-fold) MCF-7 cells to attach to type IV (basement membrane) collagen, whereas fibronectin stimulates attachment only 2-fold for these cells on type I collagen. The attachment properties of two other human breast carcinoma cell lines to type IV collagen were also studied. The attachment of ZR-75-1 cells was stimulated 4-fold by laminin and 5-fold by fibronectin, whereas T47-D cell attachment was stimulated 2-fold by laminin and 7-fold by fibronectin. By employing protease-derived fragments oflaminin, the major domains of the laminin molecule that participate in MCF-7 cell attachment to type IV collagen were identified. The whole laminin molecule has the configuration of a four-armed cross with three short arms and one long arm. A major cell-binding domain was found to reside near the intersection point of the short arms, and the type IV collagen-binding domain was associated with the globular end regions of the short arms. The receptor for laminin on the surface of these tumor cells may be involved in the initial interaction oftumor cells via laminin with the vascular basement membrane to facilitate invasion and subsequent promotion of metastasis.

No abstract

Laminin is a multifunctional protein with diverse biological activities. Like fibronectin, it can influence cell adhesion, growth, morphology, differentiation, migration, and agglutination as well as the assembly of the extracellular matrix. Laminin primarily affects cells of epithelial origin, and the response varies depending on the cell. Because most differentiated cells are difficult to maintain in culture, laminin may be an important supplement in studies on cell differentiation in vitro.

One objective of periodontal therapy after resolution of the infectious process is to facilitate a new connective tissue attachment to the root dentin surface. Here we report that a selective advantage for attachment and growth can be conferred on human gingival fibroblasts by biochemical manipulation of the dentin surface. Tetracycline HCL treatment of the dentin surface increases binding of fibronectin. The adsorbed fibronectin stimulates fibroblast attachment and growth, while suppressing epithelial cell attachment and growth. This biochemical manipulation may provide a useful approach for the treatment of periodontally involved teeth.

The response of human endothelial cell migration to various extracellular matrix components and growth factors has been assessed. Human endothelial cells demonstrate increased chemotaxis and chemokinesis when placed in a modified Boyden chamber with endothelial cell growth factor (ECGF) used at a concentration of 10 -9 M. Anti-ECGF antibody inhibits the chemotactic response. Heparin (10 -a to 10 -l° M) was also chemotactic and was shown to potentiate the chemotactic activity of ECGF. Although laminin, fibronectin, the polypeptide (epidermal, fibroblast, and nerve) growth factors, and collagen types I, II, Iit, IV, and V demonstrate a chemotactic response, these activities were one third to one half less than observed with ECGF. These data suggest that ECGF and heparin may play a significant role as response modifiers of human endothelial cell migration which may be relevant to tumor metastasis, wound healing, and atherogenesis.

Metastatic mouse melanoma cells have a high affinity for the basement membrane and the ability to degrade it; these properties may allow tumor cells to invade the membrane and disseminate. In this study it was found that the metastatic potential of mouse melanoma cells varied when the cells were exposed in culture to fibronectin or laminin. After removal of fibronectin or exposure to laminin, the cells had an increased affinity for basement membrane collagen, were more invasive of basement membranes in vitro, and produced more lung colonies in vivo. These changes are correlated with and may be due to an increase in the laminin-binding capacity of the tumor cell surface.

Selective use of tetracyciine HCl was studied to evaluate a potential treatment methodology. Tetracycline HCl adsorbed to dentin surfaces, binding 4.7 /ig/mm-after a 5 min exposure to a 50 mg/ml tetracycline HCl solution. Desorption in a discontinuous flow assay maintained biologically active concentrations of tetracycline HCl in the fluid phase for at least 48 h. The tetracycline HCl bound, and subsequently released from dentin retained antimicrobial activity with an ID50 of 3.7 ,«g/ml. Tetracycline HCl conditioning removed an amorphous surface layer, thereby exposing dentin with open tubules, as determined by scanning electron microscopy. These data suggest that tetracycline HCl-treated root surfaces may act as a depot for release of active antibiotic, as well as serve as an improved substrate for connective tissue components vital to healing at the interface between hard and soft tissues.