Renal cell carcinoma and normal kidney protein expression

Renal cell carcinoma (RCC), a human kidney cancer from the proximal tubular epithelium, accounts for about 3% of adult malignancies. Molecular and cytogenetic analysis have highlighted deletions, translocations, or loss of heterozygosity in the 3p21–p26, a putative RCC locus, as well as in 6q, 8p, 9pq, and 14pq. Studies on phenotypic expression of human kidney tissue and on post‐translational modifications in RCC have not yet provided a marker for early renal cell carcinoma diagnosis. Current dignostic methods do not help to detect the tumor before advanced stages. We therefore used two‐dimensional polyacrylamide gel electrophoresis (2‐D PAGE) to study normal and tumor kidney tissues in ten patients suffering from RCC. A human kidney protein map in the SWISS‐2DPAGE database accessible through the ExPASy WWW Molecular Biology Server was established. Of 2789 separated polypeptides, 43 were identified by gel comparison, amino acid analysis, N‐terminal sequencing, and/or immunodetection. The comparison between normal and tumor kidney tissues showed four polypeptides to be absent in RCC. One of them was identified as ubiquinol cytochrome c reductase (UQCR), whose locus has elsewhere been tentatively assigned to chromosome 19p12 or chromosome 22. A second polypeptide was identified as mitochondrial NADH‐ubiquinone oxido reductase complex I whose locus is located on chromosome 18p 11.2 and chromosome 19q 13.3. These result suggest that the lack of UQCR and of mitochondrial NADH‐ubiquinone oxidoreductase complex I expression in RCC may be caused by unknown deletions, or by changes in gene transcription or translation. It might indicate that mitochondrial disfunction plays a major role in RCC genesis or evolution.