INCREASED EXPRESSION OF THE SODIUM IODIDE SYMPORTER IN PAPILLARY THYROID CARCINOMAS/

Iodide is concentrated to a much lesser extent by papillary thyroid ca rcinoma as compared with the normal gland, The Na+/I- symporter (NIS) is primarily responsible for the uptake of iodide into thyroid cells, Our objective was to compare NIS mRNA and protein expression in papill ary carcinomas with those in specimens with normal thyroid, Northern b lot analysis revealed a 2.8-fold increase in the level of NIS mRNA in specimens with papillary carcinoma versus specimens with normal thyroi d. Immunoblot analysis using anti-human NIS antibody that tvas produce d with a glutathione S-transferase fusion protein containing NIS prote in (amino acids 466-522) showed the NIS protein at 77 kD. The NIS prot ein level was elevated in 7 of 17 cases of papillary carcinoma but was not elevated in the normal thyroid, Immunohistochemical staining reve aled abundant NIS in 8 of 12 carcinomas, whereas NIS protein was barel y detected in specimens with normal thyroid, Although considerable pat ient-to-patient variation was observed, our results indicate that NIS mRNA is elevated, and its protein tends to be more abundant, in a subs et of papillary thyroid carcinomas than in normal thyroid tissue.