Expression of C-reactive protein by renal cell carcinomas and unaffected surrounding renal tissue.

Background: Elevation of plasma C-reactive protein (CRP) is common in patients with renal cell carcinoma (RCC). Renal tubular epithelial cells are capable of synthesizing CRP. Although production of interleukin (IL)-6 has been described in RCC, CRP expression by carcinoma cells has yet not been investigated.

Methods: In the present study we analyzed CRP plasma levels as well as intratumoral CRP and IL-6 expression of RCC from 40 patients who underwent radical nephrectomy by means of quantitative real-time polymerase chain reaction (PCR) and immunohistochemistry. For each tumor, specimens were obtained from tumor center, tumor margin, and unaffected surrounding renal tissue.

Results: Preoperative plasma CRP levels correlated significantly with tumor stage (P = 0.05) and grade (P < 0.01). CRP mRNA expression was detected in 26 of 33 (79%), 30 of 36 (83%), and 32 of 36 (89%) samples from tumor center, tumor margin, and unaffected surrounding tissue, respectively. However, levels of CRP mRNA were significantly higher in tumor tissue compared to adjacent renal tissue (P < 0.01). Clear cell carcinoma exhibited significantly higher CRP mRNA levels than papillary carcinoma (P < 0.05). CRP plasma levels correlated significantly with quantitative levels of CRP mRNA within tumors (P < 0.0001). Immunohistochemically, strong CRP production was observed both in tumor cells and in tubular epithelial cells in unaffected tissue, respectively. All kidneys expressed IL-6 mRNA in the tumor and/or the unaffected tissue, but levels of intratumoral IL-6 mRNA showed no significant correlation with CRP plasma levels or local CRP transcription.

Conclusion: In patients with RCC, a tumor-derived origin of some plasma CRP is likely. Activity of the IL-6/CRP network in RCC contributes to the accumulating evidence of the acute-phase reaction as a local inflammatory process.