Adhesion molecules in high-grade soft tissue sarcomas: correlation to clinical outcome

The extracellular matrix (ECM) forms a framework for cell adhesion, but it also regulates growth and differentiation. Normal and malignant cells interact with the ECM via specific receptors, the integrins. To explore the mechanisms of growth and spread in soft tissue sarcomas the expression of the major ECM molecules and their corresponding integrin receptors were studied by immunohistochemistry in high-grade soft tissue sarcomas: malignant fibrous histiocytoma (20 cases), malignant peripheral nerve sheath tumour (17 cases) and synovial sarcoma (21 cases). The expression pattern was compared with cell proliferation and clinical outcome. Integrins were found to be expressed according to histological pattern. In synovial sarcomas, the epithelial component showed a high alpha 2 but negative or minimal detection of alpha 5 expression, while a weak alpha 2 expression and a moderate alpha 5 expression were found in the spindle cell component. No alpha 2 expression was detected in malignant fibrous histiocytoma, and minimal alpha 5 expression was detected in malignant schwannoma. The alpha 6 expression levels were positively correlated with the occurrence of metastases in all types of sarcomas studied. The expression of ECM molecules was downregulated and irregular in most tumours. In conclusion, the divergent integrin expression pattern could be useful in the diagnosis and classification of soft tissue sarcomas. Furthermore, since high laminin receptor expression correlates with occurrence of metastases, it could become a useful prognostic marker.