Metastasis.

We examined the role of individual integrins in promoting human keratinocyte migration. In short-term assays on collagen type I- or fibronectin-coated substrates, migration was blocked by antibody to the alpha 2 integrin and the alpha 5 integrin, respectively. Unexpectedly, antibodies to integrin alpha 3 also significantly inhibited cell locomotion on both ligands. Time-course immunofluorescence staining revealed that keratinocyte migration was accompanied by deposition of endogenous laminin 5. Since alpha 3 beta 1 is a known receptor for this ligand, this observation suggested that migrating keratinocytes use freshly deposited laminin 5 in locomotion. Indeed, further investigation showed that anti-laminin 5 blocking antibodies effectively inhibited keratinocyte motility on both collagen and fibronectin substrates. Furthermore, cell migration on laminin 5-coated substrates was blocked by both anti-alpha 3 and anti-laminin 5 antibodies. Laminin 5 did not appear important in the initial attachment of keratinocytes, since adhesion of cells to collagen type I- or fibronectin-coated surfaces was not blocked by antibody to alpha 3 integrin or to laminin 5, but could be inhibited by antibody to alpha 2 or alpha 5, respectively. Using an in vitro wound assay, blocking antibodies to alpha 3 integrin and to laminin 5 also blocked reepithelization of the denuded monolayer. These results show that alpha 3 beta 1 integrin plays an important role in the migration of keratinocytes via their interaction with laminin 5. Furthermore, they suggest that cell migration is dependent not only on exogenous ligands but, importantly, on endogenously secreted laminin 5. Finally, the data are consistent with our earlier finding that laminin 5 is the first extracellular matrix component to be expressed and deposited by migrating keratinocytes during wound healing in vivo.

Cell Adhesion↗

PubMed1996

Specific accumulation of tumor-derived adhesion factor in tumor blood vessels and in capillary tube-like structures of cultured vascular endothelial cells.

Tumor-derived adhesion factor (TAF) was previously identified as a cell adhesion molecule secreted by human bladder carcinoma cell line EJ-1. To elucidate the physiological function of TAF, we examined its distribution in human normal and tumor tissues. Immunochemical staining with an anti-TAF monoclonal antibody showed that TAF was specifically accumulated in small blood vessels and capillaries within and adjacent to tumor nests, but not in those in normal tissues. Tumor blood vessel-specific staining of TAF was observed in various human cancers, such as esophagus, brain, lung, and stomach cancers. Double immunofluorescent staining showed apparent colocalization of TAF and type IV collagen in the vascular basement membrane. In vitro experiments demonstrated that TAF preferentially bound to type IV collagen among various extracellular matrix components tested. In cell culture experiments, TAF promoted adhesion of human umbilical vein endothelial cells to type IV collagen substrate and induced their morphological change. Furthermore, when the endothelial cells were induced to form capillary tube-like structures by type I collagen, TAF and type IV collagen were exclusively detected on the tubular structures. The capillary tube formation in vitro was prevented by heparin, which inhibited the binding of TAF to the endothelial cells. These results strongly suggest that TAF contributes to the organization of new capillary vessels in tumor tissues by modulating the interaction of endothelial cells with type IV collagen.

Cell Adhesion↗