Hypermethylation of a New Distal Sodium/Iodide Symporter (NIS) Enhancer (NDE) Is Associated With Reduced NIS Expression in Thyroid Tumors

Autor(es)

Galrao, Ana Luiza ^[1] ; Camargo, Rosalinda Y. ^[1] ; Friguglietti, Celso U. ^[2] ; Moraes, Lais ^[3] ; Cerutti, Janete Maria ^[3] ; Serrano-Nascimento, Caroline ^[4] ; Suzuki, Miriam F. ^[5] ; Medeiros-Neto, Geraldo ^[1] ; Rubio, Ileana G. S. ^[6]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, Sch Med FM USP, Cellular & Mol Endocrine Lab, Thyroid Unit, BR-01246903 Sao Paulo - Brazil

^[2] Head & Neck Surg Santa Catarina Hosp, BR-01310000 Sao Paulo - Brazil

^[3] Univ Fed Sao Paulo UNIFESP, Dept Morphol & Genet, Div Genet, Genet Bases Thyroid Tumors Lab, BR-04039032 Sao Paulo - Brazil

^[4] Univ Sao Paulo, Inst Biomed Sci, Dept Physiol & Biophys, BR-05508900 Sao Paulo - Brazil

^[5] IPEN CNEN SP, Inst Pesquisas Energet & Nucl, Ctr Biotechnol, BR-05508000 Sao Paulo - Brazil

^[6] UNIFESP, Dept Biol Sci, BR-09972270 Diadema, SP - Brazil

• Tipo de documento: Artigo Científico
• Fonte: JOURNAL OF CLINICAL ENDOCRINOLOGY & METABOLISM; v. 99, n. 6, p. E944-E952, JUN 2014.
• Citações Web of Science: 12

Resumo

Context: In thyroid tumors, reduced radioiodine uptake is associated with worse patient outcome concomitantly with low sodium/iodide symporter (NIS) mRNA expression. Previous studies showed that CpG-island methylation in the NIS proximal promoter does not correlate with mRNA expression. Objectives: The aim of the study was to identify new CpG-islands within the NIS 5' region and investigate the involvement of their methylation in NIS expression. Design: DNA was obtained from 30 pairs of thyroid samples: tumor (T) and surrounding nontumor (NT) samples. All T samples had reduced NIS mRNA expression compared to NT samples. Main Outcome Measures: Methylation degree was quantified by bisulfite sequencing, and NIS expression by real-time PCR and Western blot. Reporter gene assays were performed to determine CpG-island functionality. Tumor cell cultures were treated with 5-Aza demethylating agent to determine NIS expression, methylation status, and I-125 uptake. Results: We identified a new CpG-island2 with 14 CpG sites, located -2152/-1887 relative to ATG site. CpG-island2 was hypermethylated in T compared to NT samples, in both benign and malignant tumor groups. There was a significant inverse correlation between NIS mRNA expression and degree of CpG-island2 methylation in NT and T samples. This sequence increased the expression of a reporter gene; thus, it was considered a new enhancer. Cell culture treatments with 5-Aza reduced CpG-island2 methylation levels concomitantly with restoration of NIS mRNA and protein expression and I-125 uptake. Conclusions: We identified a new distal enhancer, NIS distal enhancer, that regulates gene expression through DNA methylation. This enhancer is hypermethylated in T compared to NT samples and is associated with decreased NIS expression in tumors. This epigenetic deregulation may be an early event in tumorigenesis. (AU)

• Processo FAPESP: 07/51236-3 - Metilacao do gene simportador sodio-iodo (nis) em tumores de tireoide.
• Beneficiário: Ana Luiza Resende Galrão
• Modalidade de apoio: Bolsas no Brasil - Mestrado
• Processo FAPESP: 07/51235-7 - Metilacao do gene simportador sodio-iodo (nis) em tumores de tireoide.
• Beneficiário: Geraldo Antônio de Medeiros Neto
• Modalidade de apoio: Auxílio à Pesquisa - Regular
• Processo FAPESP: 09/52517-1 - Metilação do gene simportador sódio-iodo (NIS) em tumores de tireoide
• Beneficiário: Ana Luiza Resende Galrão
• Modalidade de apoio: Bolsas no Brasil - Doutorado Direto