Transcriptional regulation of the potential tumor suppressor ABI3 gene in thyroid carcinomas: interplay between methylation and NKX2-1 availability

Autor(es)

Moraes, Lais ^[1] ; Galrao, Ana Luiza R. ^[1] ; Rubio, Ileana ^[2] ; Cerutti, Janete M. ^[1]

Afiliação do(s) autor(es)

^[1] Univ Fed Sao Paulo, Escola Paulista Med, Dept Morphol & Genet, Genet Bases Thyroid Tumors Lab, Div Genet, Sao Paulo, SP - Brazil

^[2] Univ Fed Sao Paulo, Dept Biol Sci, Sao Paulo, SP - Brazil

• Tipo de documento: Artigo Científico
• Fonte: ONCOTARGET; v. 7, n. 18, p. 25960-25970, MAY 3 2016.
• Citações Web of Science: 5

Resumo

We previously reported that ABI3 expression was decreased in thyroid cancer tissues and that ectopic expression of ABI3 in a follicular thyroid carcinoma cell line delayed cell cycle progression and inhibited cell proliferation, invasion, migration and tumor formation in athymic mice. These data indicated that ABI3 is a tumor suppressor gene; however the mechanism through which ABI3 is silenced in thyroid carcinomas is unknown. We here show that treatment of four follicular thyroid carcinoma cell lines with 5-aza-dC induced demethylation of a specific region of the ABI3 promoter and restored ABI3 expression. In contrast, 5-aza-dC treatment did not restore ABI3 expression in a non-thyroid cell line, suggesting a tissue-specific regulation. We additionally show that 8 CpG sites located within the ABI3 promoter are hypermethylated in most thyroid carcinoma samples and the degree of methylation correlated with ABI3 expression. Narrowing the region to specific CpG sites, the CpG(4-6) sites showed the largest difference between benign and malignant lesions. In silico analysis revealed that these CpG sites flank a canonical binding site for NKX2-1, a thyroid specific transcriptional factor. Analysis of thyroid samples shows a correlation between NKX2-1 and ABI3 expression. In vitro assays demonstrate that NKX2-1 was required for ABI3 expression. Luciferase assay further confirmed the promoter activity of this region, which was increased when the cells were co-transfected with NKX2-1. Our study shows that the transcriptional silencing of ABI3 in cancer cells occurs via methylation and uncovered a previously unrecognized role for NKX2-1 in the regulation of ABI3. (AU)

• Processo FAPESP: 13/03867-5 - Análise da variação no número de cópias (CNV) de segmentos de DNA em pacientes de uma família com síndrome nem 2ª e mutação p.G533C no gene RET: identificação de regiões associadas à gênese e progressão do carcinoma medular da tiróide
• Beneficiário: Janete Maria Cerutti
• Modalidade de apoio: Auxílio à Pesquisa - Regular