Aberrant Expression of Polycystin-1 in Renal Cell Tumors

Polycystin-1 (PC1) is a cellular transmembrane protein coded by the polycystic kidney disease (PKD1) gene, prevalently expressed in developing/mature kidney and in autosomal polycystic kidney disease (ADPKD). Limited data are available concerning the PC1 involvement in renal tumorigenenesis. Polycystin-1 expres- sion was evaluated in 8 clear cell renal cell carcinomas (RCCs), 7 tubulopapillary cell type tumors, 3 solid RCCs developed in patients with von Hippel-Lindau disease (VHLD), one RCC developed in a patient on chronic haemodialysis and one angiomyolipoma in a patient with Tuberous sclerosis (TS). In the normal kidney, consistent level of polycystin-1 was detected in distal tubules, collecting duct, glomerular podocytes and vascular smooth muscle cells. The strongest immunoreactivity against polycystin-1 was observed in epithelial cells lining the cystic components in all ADPKD tissues. Five cases of clear cell type RCCs and two-tubulopapillary cell type RCCs consistently expressed PC1. In the VHL disease associated renal carcinomas, both the neoplastic cells and cystic tissue areas weakly expressed PC1. In TS-associated angiomyolipoma, the vascular compo- nent was PC1 positive, while the tumoral cells were scarcely stained. The present report indicates consistent expression of the PKD1 gene product polycystin-1, in normal kidney, ADPKD tissues, and renal cell carcinomas. The findings suggest that the level of PC1 expression is linked to tumor cell type, being a more frequent event in clear cell RCC.