Using an indirect immunoperoxidase technique, we tested frozen specimens from 12 Wilms'
tumors with
monoclonal antibodies (MoAbs) reacting against a large panel of molecules including
laminin,
fibronectin,
cytokeratin,
vimentin,
villin, CD24, CALLA/CD10, CR1, CD26, class I and class II major histocompatibility complex (MHC) molecules, and endothelium
factor VIII. These molecules were chosen because they are markers of specific segments of the mature kidney and because their loss or acquisition is indicative of different steps of human nephrogenesis. KI67 MoAb was used to evaluate the proliferating activity of the cells. The blastemal component (cell compact areas) of Wilms'
tumors consisted of
vimentin-positive cells with a
fibronectin network. However, signs of epithelial maturation were present in compact areas where
cytokeratin-positive cells producing
laminin were observed. The cells exhibited a high degree of proliferating activity. The tubule formations consisted of
cytokeratin-positive cells and had a defined
laminin border. All the cells, whether in compact areas or in tubules, were strongly CD24-positive. Some tubular formations showed signs of proximal maturation with the presence of CALLA, CD26, and even
villin. In four cases class I-MHC molecules were expressed by some tubular cells. Large cystic cavities present in five cases were edged by
cytokeratin, CD24-positive cells, or by
vimentin, CALLA, CR1-positive cells. Some glomeruloid bodies, present in two cases, were also composed of
vimentin, CALLA, and CR1-positive cells which correspond to the mature podocyte phenotype. The interstitial tissue contained mainly
laminin and
fibronectin network with macrophages and few CD3 lymphocytes. The presence of large cells with muscular differentiation was noted; round
vimentin and CD26-positive cells were also seen. The endothelial cells of the vessels exhibited
vimentin,
factor VIII, and class I and class II MHC molecules as do mature cells, but in some cases the endothelial cells lacked class II molecule expression and were CALLA-positive. These results which confirmed and extended those previously described show that cell differentiation in
Wilms' tumor mimics that observed during metanephros development. Moreover, this study shows that tumoral cells in
nephroblastoma share several
antigens with cells from lymphoid lineage (CD24, CALLA, and CD26) as do developing and mature kidney cells. Such cell phenotype dissection provides a useful and reliable tool for testing the influence of various factors on the development of hetero-transplanted or cultured Wilms'
tumors.