Molecular characteristics in papillary thyroid cancers (PTCs) with no 131I uptake

Objective: Papillary thyroid cancers (PTCs) with no iodine uptake have an aggressive behaviour and a poor prognosis. The aim of our study was to characterize, at molecular level, a subset of PTC with no 131 iodine ( ¹³¹I) uptake. Design and methods: Forty-eight cancer tissues were divided into three groups: Group 1, 28 primary cancers; Group 2, 7 recurrences capable of trapping ¹³¹I; and Group 3, 13 recurrences incapable of trapping ¹³¹I. mRNA levels of thyroid genes (sodium/iodide symporter NIS, thyroglobulin, thyroperoxidase and pendrin) and glycolytic metabolism genes (GLUT-1, hexokinase I and II) and BRAF mutations were evaluated in the different groups. Results: Cancers with no ¹³¹I uptake had slightly reduced NIS, significantly reduced thyroglobulin (P <0.01), thyroperoxidase (P = 0.01) and pendrin (P = 0.03) and significantly increased GLUT-1 (P = 0.01) gene expression levels; and a high frequency of BRAF mutations (77%). BRAF ^V600E mutation, in both primary and metastatic thyroid cancers, is associated with a marked drop in thyroperoxidase (29-fold) and pendrin (20-fold) expression and a considerable increase (five-fold) in GLUT-1 expression. Conclusions: (1) The loss of ¹³¹I uptake in recurrences depends not only on a decrease in NIS gene, but possibly on a reduction in the molecules regulating its intracellular metabolism; (2) the high GLUT-1 gene expression supports the use of positron emission tomography with specific tracers in clinical management of such cancers; and (3) BRAF ^V600E point mutations may lead to less differentiated phenotypes, suggesting a worse prognosis.