Expression of NAG-1, a transforming growth factor-beta superfamily member, by troglitazone requires the early growth response gene EGR-1.
Troglitazone (TGZ) and 15-deoxy-Delta(12,14)-prostaglandin J2 (PGJ2) are peroxisome proliferator-activated receptor-gamma (PPARgamma) ligands that have been shown to possess pro-apoptotic activity in human colon cancer. Although these compounds bind to PPARgamma transcription factors as agonists, emerging evidence suggests that TGZ acts independently of PPARgamma in many functions, including apoptosis. We previously reported that TGZ induces an early growth response transcription factor (EGR-1) by the ERK phosphorylation pathway rather than by the PPARgamma pathway (Baek, S. J., Wilson, L. C., Hsi, L. C., and Eling, T. E. (2003) J. Biol. Chem. 278, 5845-5853). In this report, we show that the expression of the antitumorigenic and/or pro-apoptotic gene NAG-1 (nonsteroidal anti-inflammatory drug-activated gene-1) is induced by TGZ and correlates with EGR-1 induction. In cotransfection and gel shift assays, we show that EGR-1-binding sites are located within region -73 to -51 of the NAG-1 promoter and have an important role in the transactivation of TGZ-induced NAG-1 expression. In contrast, PGJ2 induced NAG-1 protein expression, but PGJ2 may not affect the same region that TGZ does in the NAG-1 promoter. The effect of PGJ2 is probably PPARgamma-dependent because a PPARgamma antagonist inhibited the PGJ2-induced expression of NAG-1. TGZ-induced NAG-1 expression was not inhibited by the PPARgamma antagonist. The fact that TGZ-induced NAG-1 expression was accompanied by the biosynthesis of EGR-1 also suggests that EGR-1 plays a pivotal role in TGZ-induced NAG-1 expression. Our results suggest that EGR-1 induction is a unique property of TGZ, but is independent of PPARgamma activation. The up-regulation of NAG-1 may provide a novel explanation for the antitumorigenic property of TGZ.
Baek
Seung Joon
SJ
Laboratory of Molecular Carcinogenesis, NIEHS, National Institutes of Health, Research Triangle Park, North Carolina 27709, USA.
Kim
Jong-Sik
JS
Nixon
Jennifer B
JB
DiAugustine
Richard P
RP
Eling
Thomas E
TE
D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis; D001665:Binding Sites; D015152:Blotting, Northern; D015153:Blotting, Western; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism; D002839:Chromans / Q000494:pharmacology*; D016207:Cytokines / Q000096:biosynthesis*; D004268:DNA-Binding Proteins / Q000378:metabolism / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D051766:Early Growth Response Protein 1; D055436:Growth Differentiation Factor 15; D006801:Humans; D017874:Immediate-Early Proteins; D008024:Ligands; D008156:Luciferases / Q000378:metabolism; D008954:Models, Biological; D008957:Models, Genetic; D005810:Multigene Family; D009841:Oligonucleotides / Q000737:chemistry; D010766:Phosphorylation; D010957:Plasmids / Q000378:metabolism; D011401:Promoter Regions, Genetic; D015230:Prostaglandin D2 / Q000031:analogs & derivatives* / Q000494:pharmacology; D011485:Protein Binding; D012313:RNA / Q000378:metabolism; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism; D016329:Sp1 Transcription Factor / Q000737:chemistry; D045162:Thiazolidinediones / Q000494:pharmacology*; D013997:Time Factors; D014157:Transcription Factors / Q000378:metabolism / Q000502:physiology*; D015533:Transcriptional Activation; D014162:Transfection; D016212:Transforming Growth Factor beta / Q000096:biosynthesis*; D000077288:Troglitazone; D015854:Up-Regulation
C097240:15-deoxy-delta(12,14)-prostaglandin J2; D000970:Antineoplastic Agents; D002839:Chromans; D016207:Cytokines; D004268:DNA-Binding Proteins; C497325:EGR1 protein, human; D051766:Early Growth Response Protein 1; C526140:GDF15 protein, human; D055436:Growth Differentiation Factor 15; D017874:Immediate-Early Proteins; D008024:Ligands; D009841:Oligonucleotides; D018160:Receptors, Cytoplasmic and Nuclear; D016329:Sp1 Transcription Factor; D045162:Thiazolidinediones; D014157:Transcription Factors; D016212:Transforming Growth Factor beta; D012313:RNA; D008156:Luciferases; D000077288:Troglitazone; D015230:Prostaglandin D2