Journal of Korean Endocrine Society 2004;19(2):127-140.
Published online April 1, 2004.
Effects of USF-1, USF-2, PTEN and Thyroid Transcription Factors on the Function and Growth in FRTL-5 Cells.
Yun Jae Chung, eun Sook Kim, Yong Ki Min, Myung Shik Lee, Moon Kyu Lee, Kwang Won Kim, Jae Hoon Chung
1Division of Endocrinology and Metabolism, Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Korea.
2Samsung Biomedical Research Institute, Seoul, Korea.
Upstream stimulatory factors (USFs) and PTEN are known to be tumor suppressants. USFs and PAX-8 were reported to be the functional competitors in sodium iodide symporter (NIS) gene expression. We investigated the effects of USF-1, USF-2, PTEN, and thyroid-specific transcription factors (TTF-1, PAX-8) on the function and growth of thyrocytes of FRTL 5 rat thyroid cells. METHODS: Complementary DNAs of the USF-1, USF-2, PTEN, TTF-1 (homeodomain), and PAX-8 were synthesized from RNA extracted from FRTL-5using an RT-PCR kit. Each of them was transiently transfected to the FRTL-5 cells using the lipofectamine after being cloned into the pcDNA3.1 vectors. Stable cell lines, which were transfected by USF-1, PTEN, TTF-1, and PAX-8, were also obtained from the FRTL-5 cells, respectively. Extracellular cAMP concentrations were measured after 24 hours of incubation with varying concentrations of bTSH (0.1~100 mIU/mL). After, [Methyl-3H] thymidine uptake or 5-bromo-2'-deoxyuridine (BrdU) assay was performed. RESULTS: USF-1 and USF-2 significantly increased cAMP levels and decreased thymidine uptake in both transiently and stably transfected cells (p<0.01). PTEN had a tendency to increase both the cAMP levels and BrdU uptake in stable cells, but had a tendency to decrease thymidine uptake in transiently transfected cells. TTF-1 significantly increased the cAMP levels and either thymidine or BrdU uptake in both transiently and stably transfected cells (p<0.05). PAX-8 significantly increased both the cAMP levels and BrdU assay in stable cells, but in transiently transfected cells, it significantly decreased cAMP concentrations (p<0.01). CONCLUSIONS: These results suggested that both the USF-1 and USF-2 play a role in suppressing the growth of thyrocytes but at the same time, they kept the ability to produce cAMP after TSH stimulation. They had opposing effects on TTF-1 and PAX-8 in terms of the proliferation of thyrocytes
Key Words: USF-1, USF-2, PTEN, TTF-1, PAX-8, FRTL-5 cells

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