VDR and osteosarcoma: It was shown that activation function 2 (AF-2; ligand-dependent domain localized on C-terminus of VDR (Figure 3) [73, 74]) domain of human VDR interacts with suppressor for gal 1 (SUG1, component of the 26S proteasome) in ROS17/2.8 cell line (rat osteosarcoma).