Receptor tyrosine kinases and growth factors expression in tumor thrombus cells in patients with renal cell carcinoma (RCC).

Abstract

e17073 Background: To our knowledge, this is a first study describing the expression of the receptor tyrosine kinases (RTKs) and growth factors (GFs) in venous tumor thrombus cells and comparing results with the expression in primary RCC. Methods: Formalin-fixed paraffin-embedded specimens of tumor thrombus and primary tumor removed from 25 untreated pT3a-T4N0-1M0-1 RCC patients were evaluated by immunohistochemistry with primary antibodies to VEGF-A, FGF2, VEGFR1, VEGFR2, FGFR1, FGFR2, PDGFRα, and PDGFRβ (Abcam/Santa Cruz Biotech) and REAL™ EnVision™ Detection System (Agilent). The extent of expression was compared with 25 specimens of primary tumor tissue (selected from the same patients). Significant differences in the expression among these groups were assessed by chi-squared and Fisher's exact tests using a semi-quantitative method (H-score). The analysis of the correlation between expression levels and RCC characteristics was also performed. Results: Mean age was 62.0 (35-74) years. pT3a, pT3b, pT3c and pT4 stages were detected in 4 (16.0%), 13 (52.0%), 7 (28.0%), and 1 (4.0%) patients. Lymph node metastases were found in 9 (36.0%) cases, 15 (60.0%) patients had 1 or more metastatic sites. All RTKs and GFs were heavily expressed in primary tumor cells. Tumor thrombus cells were characterized by significant lower expression levels of VEGFR1, VEGFR2, and PDGFRα (p < 0.05 for all). Tendency to lower expression of VEGF-A (p = 0.06), FGF-2 (p = 0.046), FGFR1 (p = 0.077), and FGFR2 (p = 0.09) was observed in tumor thrombus cells (Table). VEGFR2 expression levels were 2-times reduced in patients with supradiaphragmatic thrombus (H-score = 21.4±12.0) compared to infradiaphragmatic thrombus (H-score = 55.0±8.5, p = 0.042). Furman grade correlated with the expression levels of VEGFR1 (p = 0.035) and FGFR1 (p = 0.022) in primary tumor cells; tumor invasion into venous wall correlated with the expression levels of VEGFR1 (p = 0.023) and FGFR2 (p = 0.005) in thrombus cells. Conclusions: RCC invasion into veins is accompanied by a decrease in expression of RTKs and GFs. Further studies are needed to understand the biological significance. [Table: see text]