Microvascular density, macrophages, and mast cells in human clear cell renal carcinoma with and without bevacizumab treatment

Background: Clear cell renal cell carcinoma (ccRCC)represents a highly vascularized aggressive kidney cancer. Due to ccRCC chemotherapy resistance, antiangiogenesis is one of the most innovative targeted therapies for this tumor. The tumor microenvironment exerts important roles in tumor growth, angiogenesis, and metastatic escape. Materials and methods: In this study, we investigated the composition of tumor cell microenvironment including mast cells, macrophages, and microvascular density in ccRCC tumor tissues collected from patients who underwent nephrectomy treated or not with bevacizumab as neoadjuvant therapy before surgery. Results: The results of this study indicate that bevacizumab-treated ccRCC samples present reduced microvascular density as well as a lower number of CD68-positive macrophages and tryptase-positive mast cells in comparison with the untreated patients. Conclusions: It follows that the antiangiogenic activity of bevacizumab may be due to a direct effect on angiogenic cytokines released by tumor cells and an indirect effect on the release of pro-angiogenic factors by inflammatory stromal cells.