IL6 and breast cancer: Breast cancer cell is known to produce numerous osteolytic factors including parathyroid hormone-related protein (PTHrP), IL-1, IL-6, IL-8, IL-11, vascular endothelial growth factor (VEGF), connective tissue growth factor (CTGF), matrix metallopeptidase 1 (MMP1), hepatocyte growth factor, etc12–16.