Cathepsin-driven collagen and bone ECM proteolysis sets the stage for tumor cell infiltration, and bone metastatic tumor cells elevate local MMP expression, increasing presentation or activity of RANKL (Receptor Activator of Nuclear factor Kappa-Β Ligand), thereby promoting osteoclast differentiation and bone breakdown [176,177,178,179]. Here, TNFSF11 is linked to neoplasm.