RUNX2 and osteosarcoma: Based on the fact that RUNX2 is capable of inhibiting the osteoclastic differentiation by promoting the expression of osteoprotegerin (OPG), a potent inhibitor of osteoclast differentiation39, and that T63 was consistently found to increase the OPG/RANKL ratio in human osteosarcoma cells40, it is thus possible the anti-osteoclastic effect of T63 in vivo might be mediated by the elevated RUNX2 activity as well.