Overexpression of TTF-1 and PAX-8 restores thyroglobulin gene promoter activity in ARO and WRO cell lines

Background. In anticipation of developing gene therapy against thyroid carcinoma we created an expression vector using the thyroglobulin (Tg) gene promoter. The inhibition of both Tg and thyroid-specific transcription factor (TTF-1 and PAX-8) gene expression, however, has been well documented in thyroid carcinomas. We therefore examined the effects of overexpression of TTF-1 and PAX-8 on Tg gene promoter activity in the human thyroid carcinoma cell lines, ARO (anaplastic) and WRO (follicular). Methods. ARO, WRO, and nonthyroid cells were transfected with an expression vector in which β- galactosidase (β-gal) is driven by the Tg gene promoter (β-gal). Tg, TTF- 1, and PAX-8 gene expression were also examined by reverse transcriptase- polymerase chain reaction (RT-PCR). Results. ARO and WRO exhibited decreased gene expression of Tg, TTF-1, and PAX-8. Transfection with TG-gal alone exhibited minimal β-gal expression, whereas cotransfection with TTF-1 and PAX-8 resulted in markedly increased expression. There was no evidence of β- gal expression with or without TTF-1 and PAX-8 in nonthyroid cells. Conclusions. Weak Tg gene promoter activity in ARO and WRO is associated with decreased expression of transcription factors TTF-1 and PAX-8 but can be restored with their overexpression. This model may serve as a template on which to further develop cell-specific gene therapy against thyroid carcinoma.