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Distribution of integrins and their matrix ligands in osteogenic sarcomas

We studies the expression of the members of the β1 integrin family and extracellular matrix ligands in osteosarcoma tissues. Immunostaining of primary osteosarcomas with use of specific antibodies for α1‐α6 integrin subunits, fibronectin, type‐I collagen, and laminin gave characteristic patterns: despite the diffuse expression of type‐I collagen in all 16 osteosarcomas, collagen receptors were detected in only one. Laminin and laminin receptors were expressed poorly. In contrast, the α4 and α5 fibronectin receptors were found in 100 and 75%, respectively, which correlates very well with the strong expression of fibronectin in the stroma. The other ligand for α4, vascular cell adhesion molecule‐1, was not expressed in the seven specimens tested. Therefore, primary osteosarcomas closely interact with fibronectin through α4 and possibly α5 subunits of the β1 integrin. We also examined the expression the expression was detected in all six specimens, however, the change varied. In contrast, osteosarcoma cells obtained from invasive portions of tumors exhibited new and augmented expression of certain integrins in two of the three cases in which their ligands were also expressed.