5(OH)DFor decades, scientists have been trying to increase the amount of activated vitamin D in cancer cells, in the hope that it will slow cancer’s growth, without causing high blood calcium at the same time. In many ways, activated vitamin D is the ideal anticancer drug, as it forces cells to die when they are supposed to do so (apoptosis) and it increases specialization (differentiation) of cells, unlike cancer cells that try to avoid dying and are often highly undifferentiated.
Although many cancers destroy the vitamin D system as soon as they can, not all cancers do. That is, some cancer cells retain both the enzymes and the receptors needed for the vitamin D system to work. Therefore, beginning in the 1980s, the search was on for an activated vitamin D-like molecule that would go inside cancer cells but not cause high blood calcium at the same time.