Expression level of CXCL7 in peripheral blood cells is a potential biomarker for the diagnosis of renal cell carcinoma

There are no blood biomarkers for the diagnosis of renal cell carcinoma (RCC) in routine clinical use. We focused on the gene expression profile of peripheral blood cells obtained from RCC patients to discover novel biomarkers for RCC diagnosis. Using microarray analysis and quantitative verification, CXCL7 was shown to be significantly upregulated in the peripheral blood cells of RCC patients. Importantly, aberrant CXCL7 expression was confirmed even in peripheral blood cells obtained from early stage (pT1a) RCC patients, and the expression level of CXCL7 in peripheral blood cells was a potential independent biomarker for the diagnosis of RCC by receiver operating characteristic curve analysis (sensitivity, 70.0%; specificity, 64.0%; area under the curve=0.722; multiple logistic regression analysis: odds ratio, 1.07; 95% confidence interval, 1.03-1.11; P=0.0004). Moreover, CXCL7 expression in peripheral blood cells significantly decreased after resection of the primary tumor. CXCL7 is more highly expressed in PBMCs than in neutrophils from both healthy controls and RCC patients. Interestingly, CXCL7 expression in PBMCs from healthy volunteers was significantly elevated following coculture with RCC cells compared to those cocultured with normal cells as a control. These results suggest that aberrant CXCL7 expression in peripheral blood cells is induced by RCC cells and may serve as a novel biomarker in the diagnosis of RCC.