Tumour vascular endothelial growth factor (VEGF) mRNA in relation to serum VEGF protein levels and tumour progression in human renal cell carcinoma

Angiogenesis is gaining interest because of its importance in tumour growth and metastasis. Renal cell carcinoma (RCC) is known to be a well-vascularized tumour. The aim of this study was to evaluate the expression of VEGF mRNA and receptor flt-1 mRNA (VEGF R1) in a clinical material of RCCs compared with clinicopathological variables and serum VEGF levels. Total RNA was extracted from snap-frozen tumour tissue obtained from 61 patients. Expression of mRNA for VEGF₁₂₁, VEGF₁₆₅ and flt-1 were analysed using quantitative RT-PCR. Relative VEGF mRNA levels, corrected for corresponding cyclophilin value, were related to stage, grade, RCC type and survival time. Serum VEGF₁₆₅ protein was analysed using a quantitative ELISA. Papillary RCC had significantly lower VEGF₁₂₁ and flt-1 mRNA levels compared with conventional RCC (p=0.001). VEGF₁₂₁ mRNA levels were significantly lower in locally advanced tumours in relation to tumours limited to the kidney and those with metastatic disease (p=0.047 and p=0.036). This statistical difference disappeared when only conventional RCCs were evaluated. No association was found between VEGF mRNA levels and nuclear grade. Patients with lower VEGF₁₂₁ mRNA levels had significantly longer survival time compared with those with higher levels (when adjusted to stage, p=0.0097, log rank test). There was an inverse relation between VEGF₁₆₅ mRNA and serum VEGF₁₆₅ levels. The trend to lower VEGF₁₂₁ mRNA levels in locally advanced RCC indicate that angiogenic activity and degradation might be up-regulated in tumours with a high ability to invade. The association with tumour progression shows that VEGF is a promising angiogenic factor especially important in conventional RCCs. VEGF expression might possibly be of help to identify RCCs susceptible for anti-angiogenic therapies.