CCR2 and prostate cancer: In the bone marrow milieu, C-C motif chemokine ligand 2 (CCL2; also known as monocyte chemoattractant protein 1), the primary ligand for C-C motif chemokine receptor 2 (CCR2) [18], is produced in bone marrow osteoblasts, endothelial cells, stromal cells, and prostate cancer cells [19].