Renin gene expression in nephroblastoma

Demonstration of renin gene expression in nephroblastoma by in situ hybridization

Most patients with nephroblastoma have high levels of plasma renin and some are hypertensive. Blood pressure falls after removal of the affected kidney, suggesting that nephroblastoma is associated with renin production either by the tumour or by the kidney. In this study, direct evidence was sought of renin gene expression in nephroblastoma using in situ hybridization. Digoxigenin-labelled riboprobes and an immunoperoxidase technique were used to detect cells containing renin mRNA: this showed renin gene expression in 9 out of 12 cases. There were positive cells within metanephric blastema and in occasional neoplastic glomeruloid structures, confirming that in seven cases nephroblastoma tumour cells expressed the renin gene. However, renin gene expression was also demonstrated in perivascular cells of uncertain lineage in seven cases; in five cases there was evidence of renin gene expression in both tumour cells and perivascular cells. The latter finding raises the possibility that some of the cells expressing the renin gene could be stromal cells. It is concluded that nephroblastomas contain cells that express the renin gene and that some are tumour cells, while other perivascular cells may be stromal cells.

Morphological characteristics of a transplantable nephroblastoma (NB-Y) in F344 rats and the relation of tumour growth to hyper-reninaemia in NB-Y-bearing rats

A transplantable tumour, designated NB-Y, was established from a spontaneous nephroblastoma in an F344 rat. NB-Y was serially passaged in syngeneic rats by subcutaneous implantation up to the 49th generation. The transplants grew into nodules with an average diameter of 5 cm and average weight of 92.9 g 4 weeks after implantation. The primary tumour and NB-Y consisted mainly of sheets or clusters of undifferentiated blastemal cells, which reacted immunohistochemically for vimentin but not for keratin. Renin-containing cells were observed in the small blood vessel walls within the primary tumour, but neoplastic cells of both primary tumour and NB-Y failed to stain for renin. Plasma renin activity was significantly higher (40.7 ng per ml per h) in transplanted rats 4 weeks after implantation compared with non-transplanted controls (28.0 ng per ml per h). Hyperplastic juxtaglomerular cells were often observed in rats bearing NB-Y. Sinusoidal dilatation was present in the liver, adrenal glands, pituitary gland and bone marrow of recipients, suggesting abnormal blood flow provoked via the renin-angiotensin system. The present study revealed the development of hyper-reninaemia in NB-Y-bearing rats, but its pathogenesis remains unknown.