THE BASEMENT-MEMBRANE AND ITS ROLE IN CANCER

The basement membrane (BM) is an important component of the cellular s tructure, acting as a support system for the epithelium while also sep arating it from the underlying stroma. During the development of invas ive tumors, malignant cells disobey the social order of organ boundari es and cross into tissues they do not belong to. The general observati on of defective BM during cancer invasion and progression indicates th e aggressive behaviour of tumor cells when they interact with BMs in a manner fundamentally different from that of normal cells. The main co nstituents of BM include type IV collagen, laminin, fibronectin, hepar an sulfate proteoglycans, nidogen and entactin. Immunohistochemical st udies have shown a discontinuous BM deposition at the epithelial strom al interface in many carcinomas. This discontinuity may be attributed to the production of proteolytic enzymes including matrix metalloprote inases. These proteolytic enzymes have been demonstrated to have a cha racteristic role in the process of BM degradation during tumor invasio n and metastases. It has also been demonstrated that as a tumor progre sses from a benign to an invasive stage, significant alterations occur in the expression of the BM proteins. In addition, increase in proteo lytic enzyme activity including activation of metalloproteinases is al so seen to occur during tumor invasion. This study discusses the vario us components of the BM, its structure and role in neoplastic progress ion.