Primitive and Bone Metastatic Renal Carcinoma Cells Promote Osteoclastogenesis through Endothelial Cells

Background: The contribution of angiogenesis to renal carcinoma bone metastases is virtually unknown. Materials and Methods: The effect of a cell line from a renal carcinoma bone metastasis (CRBM) was compared in vitro with the primitive renal adenocarcinoma line ACHN, by evaluating the influence on the ability of bone endothelial cells to activate osteoclasts. Results: The ACHN-conditioned medium produced a significant expression of macrophage-colony-stimulating factor mRNA. The conditioned medium from ACHN, CRBM, or from endothelial cells previously stimulated with the neoplastic cell-conditioned media, had no direct effect on osteoclast differentiation from blood precursors (PBMC), such as CRBM and ACHN co-cultured with PBMC. However, PBMC co-cultured with endothelial cells previously stimulated with the CRBM-conditioned medium showed significantly higher levels of tartrate-resistant acid phosphatase. Conclusion: It is possible that the bone metastatic line CRBM releases factors that induce endothelial cells to favor osteoclast differentiation.