We have previously shown that IL-6 mediates direct paracrine–autocrine signaling between cells of the osteoblast lineage and cancer cells, thereby enhancing the growth of breast cancers in bone.22 The reduced growth of VDR knockdown cells and tumors derived from such cells may, at least in part, be due to their diminished expression and secretion of interleukins like IL-6. Here, IL6 is linked to breast cancer.