The clinical effectiveness of ablative radioiodine treatment of thyroid tumors is limited by the availability of the sodium iodide symporter (NIS) at the plasma membrane (PM) for uptake of 131I. A significant proportion of well-differentiated thyroid tumors are unable to concentrate sufficient radioiodine for effective therapy, and in other tumor models such as breast tumors, where radioiodine uptake would be an attractive therapeutic option, uptake is insufficient. The gene discussed is SLC5A5; the disease is thyroid tumor.