Invasiveness

The extracellular matrix supports the adhesion of cells and transmits signals through cell surface adhesion receptors. The basement membrane separates the epithelial cells from the underlying stroma, thereby providing the first barrier against invasion of malignant growths. The destruction of the basement membrane is a prerequisite for the dissemination of cancer cells and loss of its continuity is distinguishing the earliest sign of invasiveness. This is followed by intravasation into local blood or lymph vessels. The basement membrane is 20–200 nm thick and consists of Collagens, noncollagenous glycoproteins, and proteoglycans. Networks are formed through the self-organization of Laminins and Collagen IV. Entactin forms connections between these two networks. Heparan sulfate proteoglycans are linked to the membrane through their interactions with Laminin. Alternative extracellular matrix constituents, such as Tenascin, Fibronectin, and variant forms of Laminin, are existent in tumors and can affect cancer progression.