Intercellular invasion and the organizational stability of tissues: a rolefor fibronectin

Intracellular invasion is the movement of cells of one type into the fabric of other, contiguous tissues. Invasion is a signature behavior of the mali gnant tumor and also is found as part of the normal behavior of inflammator y blood cells and tissues engaged in the morphogenetic movements of normal embryogenesis and in a number of instances of normal and pathological tissu e remodeling in the adult. Informed by the view that the underlying mechani sms of invasion will be similar for tumor cells and invasive blood and embr yonic cells, this review adopts a comparative approach to the analysis of i nvasion, Invasion results in the development of a diffuse interface between contiguous tissues. Its alternative is the maintenance of stable, planar t issue boundaries. This is the more usual condition for contiguous tissues i n the animal. This review will focus on the processes that, on the one hand , stabilize planar contact interfaces between tissues, and, on the other, p romote the destabilization of tissue integrity by fostering intercellular i nvasion. Particular attention is devoted to a role for adhesive interaction s mediated by the matrix adhesion molecule, fibronectin. In certain instanc es, fibronectin in the matrix promotes invasion whereas in others, the pres ence of fibronectin prevents invasion. The distinction appears to depend on whether the invasive tissue is migrating into an acellular extracellular m atrix or whether invasion involves densely cellular tissues. In the first i nstance, fibronectin promotes invasion, whereas in the second, it stabilize s the interface of the contacting tissues and prevents invasion. (C) 2000 E lsevier Science B.V. All rights reserved.