BRAF mutations in papillary thyroid carcinomas inhibit genes involved in iodine metabolism.
BACKGROUND
BRAF mutations are common in papillary thyroid carcinomas (PTCs). By affecting the expression of genes critically related to the development and differentiation of thyroid cancer, they may influence the prognosis of these tumors.


OBJECTIVE
Our objective was to characterize the expression of thyroid-specific genes associated with BRAF mutation in PTCs. DESIGN/SETTING AND PATIENTS: We examined the expression of key markers of thyrocyte differentiation in 56 PTCs with BRAF mutations (BRAF-mut) and 37 with wild-type BRAF (BRAF-wt). Eight samples of normal thyroid tissue were analyzed as controls. Quantitative PCR was used to measure mRNA levels for the sodium/iodide symporter (NIS), apical iodide transporter (AIT-B), thyroglobulin (Tg), thyroperoxidase (TPO), TSH receptor (TSH-R), the transcription factor PAX8, and glucose transporter type 1 (Glut1). NIS protein expression and localization was also analyzed by immunohistochemistry.


RESULTS
mRNA levels for all thyroid-specific genes were reduced in all PTCs vs. normal thyroid tissues. NIS, AIT-B, Tg, and TPO expression was significantly lower in BRAF-mut tumors than in the BRAF-wt group. Glut-1 transcript levels were increased in all PTCs, and additional increases were noted in BRAF-mut tumors. In both tumor subsets, the NIS protein that was expressed was abnormally retained in the cytoplasm.


CONCLUSIONS
BRAF V600E mutation in PTCs is associated with reduced expression of key genes involved in iodine metabolism. This effect may alter the effectiveness of diagnostic and/or therapeutic use of radioiodine in BRAF-mut PTCs.
Durante
C
C
Department of Clinical Sciences, University of Rome La Sapienza, 00161 Rome, Italy.
Puxeddu
E
E
Ferretti
E
E
Morisi
R
R
Moretti
S
S
Bruno
R
R
Barbi
F
F
Avenia
N
N
Scipioni
A
A
Verrienti
A
A
Tosi
E
E
Cavaliere
A
A
Gulino
A
A
Filetti
S
S
Russo
D
D
D000328:Adult; D000368:Aged; D002291:Carcinoma, Papillary / Q000235:genetics* / Q000378:metabolism; D002454:Cell Differentiation; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D005819:Genetic Markers; D006801:Humans; D007455:Iodine / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D017354:Point Mutation; D048493:Proto-Oncogene Proteins B-raf / Q000235:genetics*; D012333:RNA, Messenger / Q000378:metabolism; D013964:Thyroid Neoplasms / Q000235:genetics* / Q000378:metabolism
D005819:Genetic Markers; D012333:RNA, Messenger; D007455:Iodine; C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf