SLC5A5 and oncocytic neoplasm: Some studies have been demonstrating that MAPK and TGF-β1/Smad/FoxP3 are involved in the re-differentiation of thyroid tumors and in the re-expression of the sodium-iodine symporter (NIS, also known as solute carrier family 5 member 5 - SLC5A5) in non-oncocytic tumors (87–89).