IL6 and breast cancer: In addition, estrogen influences the production of cytokines and growth factors, such as insulin-like growth factor (IFG-1), interleukin-6 (IL-6), osteoprotegerin (OPG), and receptor activator of nuclear factor kappa-B ligand (RANKL), which are involved in bone turnover [1, 36, 37] and mammary cancer [38, 39].