TNFSF11 and breast cancer: While thought to be predominantly produced by osteoblasts, RANKL is also secreted by breast cancer cells.29–31 In contrast to RANKL, osteoprotegerin (OPG) suppresses osteoclast formation by acting as a decoy receptor for RANKL.31 Exposure of MDA-MB-231 cells to twice-daily LIV reduced RANKL expression by 51.3% (P < 0.05).