Relationship between VHL mutation status, tumor VEGF expression and plasma VEGF measurement in sporadic renal cell carcinoma

Abstract

4602 Background: The relationship between VHL mutation status and prognosis in renal cell carcinoma (RCC) remains controversial. The aim of this study was to evaluate prospectively the association between VHL status, tumor VEGF expression, plasma VEGF levels and usual prognostic parameters in RCC. Methods: 70 patients with clear cell RCCs were included in this study. Genomic DNA was extracted using the QIAmp DNA mini kit (Qiagen) from frozen tumor samples. Four amplimers covering the whole coding sequence and exon/intron junctions of the VHL gene were synthetized by PCR followed by Big Dye sequencing (Applied Biosystems). Mutation bearing sequences were confirmed in a second round of PCR and sequencing reactions. Tumor VEGF expression was determined by immunohistochemistry and plasma VEGF was measured by enzyme-linked immunosorbent assay (Quantikine immunoassay, R&D systems). Results were expressed in pg/ml. Qualitative and quantitative variables were compared by using Chi-square (Fischer exact test) and Student t tests, respectively. Results: A VHL mutation was found in 46 cases (65.7%). VHL mutations were localized in exon 1, 2 and 3 in 23, 16 and 7 cases respectively. Median tumor VEGF expression was 45% (5–100). Median plasma VEGF was 104 pg/ml (13–1430). A significant association was found between VHL mutation and N stage (p: 0.01), Fuhrman grade, symptoms at presentation (p: 0.02) or tumor size (p: 0.007). A VHL mutation was found in 83.5% of low grade (G1–2) and 80% of incidental tumors respectively. A trend towards more frequent VHL mutations was observed in T1 tumors (87% mutation rate, p: 0.07) and in good performance status patients. Interestingly, VEGF tumor expression and plasma VEGF levels were not significantly different among patients with tumors having or not mutated VHL (p: 0.7). Conclusion: VHL mutations are more frequent in small incidental low stage or low grade tumors. Although VHL inactivation was not specifically determined in this study, we failed to show any association between VHL mutational status and VEGF tumor or plasma expression suggesting that other pathways than the VHL/HIF axis are required for explaining the angiogenic phenotype of RCC. No significant financial relationships to disclose.