VDR and cancer: We conclude that the synergism between rexinoids and vitamin D may represent an untapped pathway to explore the feasibility of combinatorial therapeutic treatment strategies since some diseases (e.g., cancers) are thought to be amenable to treatment by both rexinoids and vitamin D. Thus, it may be useful to elucidate the presence of multi-ligand pathways that may facilitate synergistic activation of VDR signaling.