The secretion from breast cancer cells of signalling molecules like vascular endothelial growth factor (VEGF), interleukin-6 (IL-6), IL-8,IL-11, macrophage colony-stimulating factor (MCSF), receptor activator of nuclear factor kappa-B ligand (RANKL), sonic hedgehog (SHH) and parathyroid hormone-related protein (PTHrP) (Figure 3), results in an inbalance toward osteoclasts hyper-activation with consequent increased bone degradation leading to pathological bone tissue loss and micro-fractures as cause of CABP. This evidence concerns the gene IL6 and breast cancer.