Identification of metabolic enzymes in renal cell carcinoma utilizing PROTEOMEX analyses.

PROTEOMEX, an approach which combines conventional proteome analysis with serological screening, is a powerful tool to separate proteins and identify immunogenic components in malignant diseases. By applying this approach, we characterized nine metabolic enzymes which were differentially expressed in renal cell carcinoma (RCC) cell lines and compared their expression profiles to that of normal kidney epithelium cells. Four of these proteins, superoxide dismutase (SODC), triosephosphatase isomerase (TPIS), thioredoxin (THIO) and ubiquitin carboxyl-terminal hydrolase (UBL1) were further analysed for both their constitutive and interferon (IFN)-gamma inducible protein expression pattern in cell lines or tissue specimens derived from RCC or normal kidney epithelium using Western blot analysis and immunohistochemistry, respectively. With the exception of the RCC cell line MZ1940RC, which completely lacks the expression of UBL1, a heterogeneous and variable expression pattern of the different metabolic enzymes was detected in RCC and normal renal epithelium. The highest differences in the expression levels were found for THIO in the RCC cell lines, which was 2-fold upregulated when compared to autologous normal kidney epithelium. Moreover, IFN-gamma treatment did not influence the constitutive expression of these metabolic enzymes. Thus, PROTEOMEX represents a valuable approach for the identification of metabolic enzymes which might be used as markers for the diagnosis of RCC.