Vascular endothelial growth factor as a biomarker for endostatin gene therapy

Renal cell carcinoma (RCC) is characterized by high vascular endothelial growth factor (VEGF) production and, consequently, excessive angiogenesis. Several strategies have been developed to target angiogenesis as a method for treating metastatic RCC (mRCC). Endostatin (ES) is a C-terminal fragment of collagen XVIII that has antiangiogenic activity. The aim of this study was to investigate the predictive value of circulating VEGF-A in a murine model of mRCC after ES gene therapy. ES therapy did not affect the levels of collagen XVIII/ES or ES in the tissue. The circulating level of ES was increased in the control and ES-treated groups (normal vs. control, P < 0.05 and ES-treated vs. control, P < 0.001), and the intratumoral vessels were significantly decreased (ES-treated vs. control, P < 0.05). ES therapy decreased the VEGF mRNA levels. The tissue and circulating levels of VEGF in the control group were significantly higher than normal (P < 0.01 and P < 0.05, respectively). Treatment with ES significantly reduced the VEGF concentrations in both compartments (P < 0.001 for tissue and P < 0.05 for plasma). Our findings indicate that in addition to the directly targeted tumor vessels, ES exerts its antitumor effect by down-regulating VEGF gene expression in renal tumor cells. Additionally, our findings point to the predictive value of VEGF for ES therapy.