Frozen sections of human
renal carcinomas were studied in indirect immunofluorescence using
antibodies against intermediate filaments of
cytokeratin,
desmin and
vimentin type, and against proximal tubular brush border and distal tubular
Tamm-Horsfall glycoprotein antigens, as well as with
fluorochrome-labeled
lectins in an attempt to study the origin and stage of differentiation of
renal carcinomas. Eighty per cent of the
renal carcinomas expressed the brush border
antigens, whereas the
Tamm-Horsfall glycoprotein could not be found.
Antibodies against epidermal cytokeratins reacted only with collecting ducts in normal kidney, whereas
antibodies against cytokeratins of Madin-Darby canine kidney epithelial cell line also reacted with glomerular and tubular epithelium. In 93% of the
carcinomas tumor cells showed reactivity with both types of antikeratin
antibodies.
Vimentin, the cytoskeletal
protein of mesenchymal cells, was present in the
carcinoma cells of 53% of the
tumors, although it was not present in normal tubular epithelium. Moreover,
vimentin was expressed together with
cytokeratin in the
carcinoma cells in 57% of the
keratin-positive samples as judged by double immunostaining, whereas the muscle type of intermediate filament
protein,
desmin, was not seen in the malignant cells. Binding sites for
Lotus tetragonolobus agglutinin and
soybean agglutinin, normally present in the cells of proximal tubules, were lacking or only faintly detectable in the neoplastic cells.
Dolichos biflorus agglutinin, normally present in collecting ducts, was not detected in the
tumors. The results show that most
renal carcinomas express
cytokeratin antigens as a sign of their epithelial origin and also show characteristics of proximal tubular cells. On the other hand, the results indicate that
lectin-binding sites typical for normal differentiated tubular cells are profoundly modified in
renal carcinomas. Ulex europaeus
agglutinin did not bind to the malignant cells but decorated the endothelial cells of the
tumors.