INTEGRINS AND EXTRACELLULAR MATRIX-PROTEINS IN THE DIFFERENT COMPONENTS OF THE WILMS-TUMOR

The Wilms' tumour (WT) is composed of blastema, epithelium and mesench yme; the epithelium and possibly also the mesenchyme develop from the blastema, parallel to embryonal development. Since interactions betwee n cell adhesion receptors and extracellular matrix (ECM) proteins play an important role in tissue maturation, we examined the expression of the integrin subunits alpha 1-alpha 6, beta 1 and beta 4, and of the ECM proteins fibronectin, laminin and collagen I and IV, in 20 frozen WT samples and in 5 fetal and 2 adult kidneys. The integrin and ECM pr otein distribution in tumour epithelium and mesenchyme showed strong s imilarities to that in their fetal counterparts, whereas the tumour bl astema differed strongly from the fetal blastema. In the WT blastema d ifferent components were recognized Undifferentiated blastema, charact erized by expression of alpha 3 and alpha 6 and the virtual absence of ECM proteins. Blastema with epithelial commitment, showing increased expression of alpha 3 and alpha 6 and the appearance of alpha 2 and, a s a very early phenomenon, production of laminin. Blastema with mesenc hymal commitment, with loss of alpha 3 and alpha 6 and expression of a lpha 1, alpha 4 and alpha 5 and presence of ECM proteins. It is specul ated that the inability of the (undifferentiated) blastema to produce ECM proteins is related to its relatively high metastatic potential wh en compared with epithelium and mesenchyme.