Expression of cAMP-responsive element binding protein and inducible cAMP early repressor in hyperfunctioning thyroid adenomas.
OBJECTIVE
The pathogenesis of thyroid hyperfunctioning adenomas is still only partially understood and controversy exists about the frequency of gain-of-function mutations of the TSH receptor or G(s)alpha gene, which activate the cAMP pathway. The nuclear transcription factors cAMP-responsive element binding protein (CREB) and inducible cAMP early repressor (ICER) are among the final targets of this signalling cascade.


METHODS
In our study we focused on the expression of CREB and ICER genes in the nodular as well as in the extranodular tissue of hyperfunctioning tumours of the thyroid.


METHODS
RT-PCR and Western blot analysis were performed in a series of 14 patients. The presence of an activating mutation of the TSH receptor or of the G(s)alpha gene was ascertained by direct sequencing.


RESULTS
The levels of CREB transcripts did not significantly differ in the adenomas and in the normal tissues (CREB/GAPDH, mean optical density+/-s.e.: 0.98+/-0.18 vs 0.88+/-0.27 respectively, P = not significant (N.S.)), although case-to-case variability was observed. The absence of a significant difference between the adenoma and the surrounding normal tissue was maintained after dividing the patients into two groups, according to TSH receptor status. Accordingly, no significant difference in the levels of CREB protein (total and Ser(133)-phosphorylated) was observed between the nodular and the extranodular tissue. In addition, no difference was found in the levels of ICER transcripts (ICER/GAPDH, mean optical density+/-s.e.: 0.52+/-0.11, nodule vs 0.36+/-0.11, normal thyroid, P=N.S.), independently of the TSH receptor gene status (i.e. wild-type or mutated).


CONCLUSIONS
Our results support the recent hypothesis that the activation of the cAMP pathway in hyperfunctioning adenomas of the thyroid might be counteracted by opposite events and suggest that complex molecular mechanisms might take part in the pathogenesis of hyperfunctioning tumours.
Peri
Alessandro
A
Endocrine Unit, Department of Clinical Physiopathology, University of Florence, Viale Pieraccini 6, 50139 Florence, Italy. a.peri@dfc.unifi.it
Luciani
Paola
P
Tonacchera
Massimo
M
Agretti
Patrizia
P
Baglioni-Peri
Silvana
S
Buci
Lisa
L
Conforti
Barbara
B
Cioppi
Federica
F
Biliotti
Giancarlo
G
Serio
Mario
M
Vitti
Paolo
P
Chiovato
Luca
L
D051697:Activating Transcription Factor 1; D000236:Adenoma / Q000097:blood / Q000378:metabolism*; D000328:Adult; D000368:Aged; D015153:Blotting, Western; D000242:Cyclic AMP / Q000378:metabolism*; D051786:Cyclic AMP Response Element Modulator; D004268:DNA-Binding Proteins / Q000096:biosynthesis* / Q000235:genetics; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008163:Luminescent Measurements; D008297:Male; D008875:Middle Aged; D009154:Mutation; D010766:Phosphorylation; D012333:RNA, Messenger / Q000032:analysis; D011989:Receptors, Thyrotropin / Q000235:genetics*; D012097:Repressor Proteins / Q000096:biosynthesis* / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D015398:Signal Transduction; D013963:Thyroid Hormones / Q000097:blood*; D013964:Thyroid Neoplasms / Q000097:blood / Q000378:metabolism*; D014157:Transcription Factors / Q000096:biosynthesis* / Q000235:genetics
D051697:Activating Transcription Factor 1; D004268:DNA-Binding Proteins; D012333:RNA, Messenger; D011989:Receptors, Thyrotropin; D012097:Repressor Proteins; D013963:Thyroid Hormones; D014157:Transcription Factors; D051786:Cyclic AMP Response Element Modulator; D000242:Cyclic AMP