Experimental Models for the Sequential Analysis of Chemically-Induced Renal Carcinogenesis

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Abstract
In order to discriminate non-specific toxicity from the early precursor lesions of neoplasia, emphasis in these studies has been on the use of models requiring only a single administration of chemical. Our interests have focussed on three neoplastic entities in the kidney, renal mesenchymal neoplasia, renal cell carcinoma, and nephroblastoma. Dimethylnitrosamine administered as a single intraperitoneal injection to immature female Wistar rats, pre-conditioned for several days with a no-protein/sugar-only diet, has been used for investigating the complex morphological nature of renal mesenchymal tumors, their pathogenesis and the development of cell culture correlates. The near 100% tumor incidence and its facility for cell culture manipulation makes this a particularly potent model for studying chemical carcinogenesis and the evolution of cell transformation. Discovery that the rat kidney response to DMN was biphasic with respect to the time of treatment led to the subsequent development of a high incidence system for inducing renal adenocarcinoma, using older rats. Renal cell carcinomas could also be induced in mice by a single intravenous injection of streptozotocin. The tumor frequency in female CBA/H/T6J mice was almost 100%, providing a new model for the investigation of renal carcinogenesis in this species. Nephroblastoma has been a poorly comprehended neoplasm in both lower animals and man because of the lack of a high incidence model in conventional laboratory mammals. Recently, we have exploited an increased spontaneous predisposition of the Nb rat to nephroblastoma using a single intraperitoneal dose of N-ethylnitrosourea in pregnant females on day 18 of gestation, producing a frequency of 50% for this tumor type. More potent however, was a system which utilized the partially inbred III VO/J strain of rabbit using the same carcinogen and transplacental route of administration. The resultant incidence of nephroblastomas in the progeny was in excess of 90%, and like their counterparts in man, the neoplasms developed rapidly and had a potential for distant metastasis. Each one of these animal models is suitable for the sequential tracing of tumor pathogenesis, and in depth analysis of the biochemical and molecular mechanisms involved in the initiation and formation of different types of renal cancer.

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