Up-regulation of Endothelin-2 as a Common andEarly Event in localized Clear Cell Renal Cell Carcinoma Free

Purpose: Despite incidence rates that have been rising for decades, the molecular underpinnings that support the development of clear cell renal cell carcinoma (ccRCC) remain unclear. Herein, we evaluate expression levels of the hypoxia-induced autocrine survival factor endothelin-2 (EDN2) in patient-matched ccRCC and normal kidney samples.

Methods: We identified 169 patients who underwent nephrectomy for histologically confirmed, localized ccRCC at our institution from 2000 to 2003 and had fresh-frozen tumor and normal kidney samples available. After mRNA was extracted from microdissected tissue, we conducted real time PCR to determine expression levels of EDN2. We normalized the expression data using four control genes and then fit linear mixed models to evaluate differential expression between tumor and normal samples. In addition, we explored potential interactions with relevant clinicopathologic characteristics including tumor stage and grade.

Results: Of the 161 patients analyzed, 65% were male, 58% were stage pT1, and 43% were nuclear grade 1 or 2. Overall, EDN2 expression was higher in tumor samples compared to paired normal samples with an average fold change (FC) of 2.0 (P-value < 0.0001). This over-expression in tumor versus normal tissue was apparent in early stage (pT1) tumors but not later stage (pT2, pT3) tumors (FC of 2.9 v. 1.1 respectively; interaction P-value = 0.001). Similarly, over-expression was more pronounced in low grade (1, 2) tumors compared to high grade (3, 4) tumors (FC of 3.5 v. 1.3 respectively; interaction P-value = 0.0002).

Conclusions: While independent validation is required, our patient-based data suggest that up-regulation of EDN2 is a common and early event in localized ccRCC. If confirmed in future studies, EDN2 could represent a target for the development of novel chemopreventive or neo-adjuvant therapeutics for ccRCC.