fig2

Figure 2. When the “Kill Switch” tumor suppression mechanism fails due to age-related decline in circulating dehydroepiandrosterone sulfate (DHEAS), many human tumors are subsequently able to appropriate elements of the “Kill Switch” for their own use. A: organic anion transporting polypeptide (OATP) that transport DHEAS into the cell, and SS that de-sulfates DHEAS to dehydroepiandrosterone (DHEA) are two examples of “Kill Switch” elements that are frequently usurped by human tumors; B: such appropriation of “Kill Switch” elements by human tumors makes them susceptible to selective killing by such drugs as fluasterone sulfate, a fluorinated analog of DHEAS that cannot be metabolized to steroid hormones, and is therefore of particular use in SS-expressing hormone sensitive tumors. Most human tumors may be rendered sensitive to fluasterone or fluasterone sulfate treatment by pretreatment with fluorodeoxyglucose (FDG), a fluorinated analog of FDG that is selectively taken up by human tumors, where it accumulates. FDG is metabolized to FDG6P, a fluorinated analog of glucose-6-phosphate (G6P)