USF inhibits cell proliferation through delay in G2/M phase in FRTL-5 cells.
Upstream stimulatory factor (USF) has a negative effect on the cell proliferation in some cell types. However, its effect on thyrocytes is not clear. Therefore, we investigated the effects of USF on the proliferation and function of thyroid follicular cells. Complementary DNAs of the USF-1 and USF-2 were synthesized using RT-PCR from FRTL-5 cells, and each was transfected to FRTL-5 cells and papillary thyroid carcinoma cell lines. Cyclic AMP (cAMP) production and [methyl-3H] thymidine uptake after thyroid stimulating hormone (TSH) treatment were measured in FRTL-5 cells. In the carcinoma cell lines, 5-bromo-2'-deoxyuridine (BrdU) uptake was assayed to evaluate cell proliferation. Apoptosis was tested by Hoechst staining and cell cycle analysis was done using a fluorescence activated cell sorting. Expression of cell cycle regulating genes was evaluated by Northern and Western blotting. Overexpression of USF-1 and USF-2 significantly suppressed TSH-stimulated [methyl-3H] thymidine uptake (p<0.05), while it maintained TSH-stimulated cAMP production in FRTL-5 cells. Overexpression of USF significantly suppressed BrdU uptake in each carcinoma cell line, NPA and TPC-1 cells (p<0.05). It induced delay of cell cycle at the G2/M phase, but did not increase apoptosis in FRTL-5 cells. It was accompanied by a decrease of cyclin B1 and cyclin-dependent kinase (CDK)-1, and an increase of p27 expression. USF-1 and USF-2 suppressed cell proliferation of normal thyrocytes and thyroid carcinoma cells. However, they retained the ability to produce cAMP after TSH stimulation. Their inhibitory effect on cell proliferation might be caused partly by the delay in G2/M phase.
Jung
Hye Seung
HS
Division of Endocrinology and Metabolism, Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Korea.
Kim
Keun-Sook
KS
Chung
Yun Jae
YJ
Chung
Hyun-Kyung
HK
Min
Yong-Ki
YK
Lee
Myung-Shik
MS
Lee
Moon-Kyu
MK
Kim
Kwang-Won
KW
Chung
Jae Hoon
JH
D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D001973:Bromodeoxyuridine / Q000493:pharmacokinetics; D016203:CDC2 Protein Kinase / Q000037:antagonists & inhibitors; D002291:Carcinoma, Papillary / Q000473:pathology*; D002455:Cell Division / Q000187:drug effects*; D049109:Cell Proliferation / Q000187:drug effects*; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000096:biosynthesis; D019926:Cyclin B / Q000037:antagonists & inhibitors; D056744:Cyclin B1; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000378:metabolism; D016195:G2 Phase / Q000187:drug effects*; D013936:Thymidine / Q000037:antagonists & inhibitors / Q000493:pharmacokinetics; D013961:Thyroid Gland / Q000166:cytology*; D013964:Thyroid Neoplasms / Q000473:pathology*; D013972:Thyrotropin / Q000494:pharmacology; D014162:Transfection; D051720:Upstream Stimulatory Factors / Q000235:genetics / Q000494:pharmacology*
C534699:CCNB1 protein, human; D019926:Cyclin B; D056744:Cyclin B1; C497181:USF1 protein, human; C497184:USF2 protein, human; D051720:Upstream Stimulatory Factors; D050760:Cyclin-Dependent Kinase Inhibitor p27; D013972:Thyrotropin; D000242:Cyclic AMP; D016203:CDC2 Protein Kinase; D001973:Bromodeoxyuridine; D013936:Thymidine