Down-regulation of NR4A1 in follicular thyroid carcinomas is restored following lithium treatment.
BACKGROUND
The identification of follicular thyroid adenoma-associated transcripts will lead to a better understanding of the events involved in pathogenesis and progression of follicular tumours. Using Serial Analysis of Gene Expression, we identified five genes that are absent in a malignant follicular thyroid carcinoma (FTC) library, but expressed in follicular adenoma (FTA) and normal thyroid libraries.


METHODS
NR4A1, one of the five genes, was validated in a set of 27 normal thyroid tissues, 10 FTAs and 14 FTCs and three thyroid carcinoma cell lines by real time PCR. NR4A1 can be transiently increased by a variety of stimuli, including lithium, which is used as adjuvant therapy of thyroid carcinoma with (131)I. We tested if lithium could restore NR4A1 expression. The expression of other genes potentially involved in the same signalling pathway was tested. To this end, lithium was used at different concentration (10 mm or 20 mm) and time (2 h and 24 h) and the level of expression was tested by quantitative PCR. We next tested if Lithium could affect cell growth and apoptosis.


RESULTS
We observed that NR4A1 expression was under-expressed in most of the FTCs investigated, compared with expression in normal thyroid tissues and FTAs. We also found a positive correlation between NR4A1 and FOSB gene expression. Lithium induced NR4A1 and FOSB expression, reduced CCDN1 expression, inhibited cell growth and triggered apoptosis in a FTC cell line.


CONCLUSIONS
NR4A1 is under-expressed in most of FTCs. The loss of expression of both NR4A1 and the Wnt pathway gene FOSB was correlated with malignancy. This is consistent with the hypothesis that its loss of expression is part of the transformation process of FTCs, either as a direct or indirect consequence of Wnt pathway alterations. Lithium restores NR4A1 expression, induces apoptosis and reduces cell growth. These findings may explain a possible molecular mechanism of lithium's therapeutic action.
Camacho
Cléber P
CP
Genetic Bases of Thyroid Tumors Laboratory, Division of Genetics, Department of Morphology, Federal University of São Paulo, São Paulo, Brazil.
Latini
Flavia R M
FR
Oler
Gisele
G
Hojaij
Flavio C
FC
Maciel
Rui M B
RM
Riggins
Gregory J
GJ
Cerutti
Janete M
JM
D018263:Adenocarcinoma, Follicular / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology; D000236:Adenoma / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology; D017209:Apoptosis / Q000187:drug effects; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D017024:Chemotherapy, Adjuvant; D019938:Cyclin D1 / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation / Q000187:drug effects*; D006801:Humans; D018020:Lithium Compounds / Q000494:pharmacology / Q000627:therapeutic use; D057105:Nuclear Receptor Subfamily 4, Group A, Member 1; D016760:Proto-Oncogene Proteins c-fos / Q000235:genetics / Q000378:metabolism; D011987:Receptors, Steroid / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D013964:Thyroid Neoplasms / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology; D051153:Wnt Proteins / Q000235:genetics / Q000378:metabolism
C530104:CCND1 protein, human; D004268:DNA-Binding Proteins; C064269:FOSB protein, human; D018020:Lithium Compounds; C539821:NR4A1 protein, human; D057105:Nuclear Receptor Subfamily 4, Group A, Member 1; D016760:Proto-Oncogene Proteins c-fos; D011987:Receptors, Steroid; D051153:Wnt Proteins; D019938:Cyclin D1