Tumor-infiltrating lymphocytes express vascular endothelial growth factor in renal cell carcinomas

Background: Known influence of the immune system on metastases of renal cel l cancer (RCC) has led to the development of several therapeutic approaches for further stimulation of the host immune system by cytokines and the ret ransfusion of tumor-infiltrating lymphocytes (TIL). Based on observations i n human prostate adenocarcinomas and transitional cell carcinomas, we have investigated the presence of TIL in different stages of RCC in correlation to vascular endothelial growth factor (VEGF) expression as a parameter for tumor progression and adverse survival in RCC patients. Methods: Samples fr om surgically obtained RCC (n = 28) and benign renal parenchyma (n=10) were snap-frozen and processed by double-immunofluorescence staining with CD4/C D8 and VEGF antibodies. Results: In 20 of 28 RCCs a coexpression of TIL-spe cific markers CD4 and/or CD8 and VEGF was demonstrated. Control tissues wer e VEGF-negative and showed only negligible infiltration by CD4- or CD8-posi tive lymphocytes. Conclusion: The results indicate that at least 71% of TIL produce VEGF and may promote tumor progression rather than represent an ab ortive antitumor response of the host immune system.