Macrophage Inflammatory Protein–1δ: A Novel Osteoclast Stimulating Factor Secreted by Renal Cell Carcinoma Bone Metastasis

Approximately 30% of patients with renal cell carcinoma (RCC) develop bone metastasis, which is characterized by extensive osteolysis leading to severe bone pain and pathologic fracture. Although the mechanism of RCC-induced osteolysis is unknown, studies of bone metastasis have shown that tumor-induced changes in bone remodeling are likely mediated by alterations in the bone microenvironment. Here, we report the discovery of a novel osteoclast stimulatory factor secreted by RCC bone metastasis (RBM). Through microarray analysis, we found expression of the chemokine, macrophage inflammatory protein-1δ (MIP-1δ), to be increased in RBM versus patient-matched primary RCC tissues and confirmed this finding by quantitative reverse transcription-PCR (qRT-PCR) and ELISA ( P P