Type I 5'-iodothyronine deiodinase activity and mRNA are remarkably reduced in renal clear cell carcinoma.

The purpose of this study was to compare thyroid hormone metabolism between non-cancerous tumor-surrounding human kidney tissues and renal clear cell carcinomas (RCCC). The material consisted of samples taken from 10 RCCC patients of both sexes and three grades of differentiation, G1 to G3. We showed that, similar to rat tissue, type I 5' monodeiodinase (5'DI) expression is heterogeneous within the human kidney. We also found a poor correlation between 5'DI activity and mRNA level in non-cancerous tumor-surrounding tissue suggesting significant post-transcriptional regulation of 5'DI expression by an unidentified process in the human kidney. In all RCCC tissues both 5'DI activity and mRNA levels were undetectable. This suggests either loss of human 5'DI gene expression during neoplastic transformation or the origination of RCCC from a tubular cell type that does not express 5'DI.