Cell-extracellular matrix interaction in glioma invasion.

Astrocytic tumours of the central nervous system express cell adhesion receptors of the integrin superfamily, CD44 and adhesion receptors of the immunoglobulin superfamily. Glioma cells utilize these receptors to adhere to and migrate along components of the extracellular matrix (ECM), which is uniquely distributed and regulated within the brain and the spinal cord. For penetration into healthy brain tissue a number of proteases are expressed, which degrade proteins of the extracellular matrix. Thus, glioma cell invasion into the adjacent brain tissue is dependent on the interaction of glioma cells with the extracellular matrix and the subsequent destruction of matrix barriers. There is a critical balance between expression of various adhesion receptors and proteases. The tight regulation of critical levels of proteases and receptors expressed by glioma cells or other cells is necessary for the "physiological" behaviour of glioma cells. Shifts in the balance of protein expression determine glioma cell behaviour in their micro-environment and can initiate or influence the complex process of glioma cell invasion. The complex receptor-ECM interaction in glioma cell invasion is discussed focussing upon the role of integrin receptors and matrix-metalloproteinases. Influencing these molecules or their regulation may lead to novel therapeutic approaches in the treatment of malignant glioma.