Knockdown of NFAT3 blocked TPA-induced COX-2 and iNOS expression, and enhanced cell transformation in Cl41 cells.
The nuclear factor of activated-T-cells (NFAT) family is a ubiquitous transcription factor that mediates regulation on various gene expressions. Recent studies indicate that NFAT may implicate in cancer process, mainly through its direct regulation on the cyclooxygenase-2 (COX-2) gene expression. There is also evidence suggesting another aspect of NFAT in tumor suppression. However, the according mechanism remains unknown. In this study, we used a small interfering RNA (siRNA) expression construct to study the role of NFAT3 in the 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced cell transformation with the tumor promotion-sensitive mouse epidermal Cl41 cells. Our results showed that TPA was able to induce NFAT3 activation in Cl41 cells. Stable transfection of NFAT3 siRNA specifically reduced endogenous NFAT3 expression. At the same time, TPA-induced expression of both COX-2 and inducible nitric oxide synthase (iNOS) were blocked. However, anchorage-independent transformation in response to TPA was significantly enhanced in NFAT3 siRNA stable transfectants as compared with vector transfectants. Moreover, treatment with the iNOS specific inhibitor aminoguanidine (AG) also enhanced Cl41 cells transformation induced by TPA. As COX-2 expression is proved to be required for cell transformation in Cl41 cells in our recent studies, our results demonstrate that the inducible NFAT3-mediated iNOS upregulation represents a novel potent tumor-suppressing pathway and may contribute to the tumor suppressor functions of NFAT protein.
Li
Jingxia
J
Nelson Institute of Environmental Medicine, New York University School of Medicine, Tuxedo, New York 10987, USA.
Song
Lun
L
Zhang
Dongyun
D
Wei
Lixin
L
Huang
Chuanshu
C
D000818:Animals; D002461:Cell Line, Transformed; D051546:Cyclooxygenase 2 / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D000078404:Epidermal Cells; D004817:Epidermis / Q000187:drug effects*; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D006801:Humans; D051379:Mice; D018345:Mice, Knockout; D050778:NFATC Transcription Factors / Q000172:deficiency*; D052247:Nitric Oxide Synthase Type II / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D015533:Transcriptional Activation / Q000187:drug effects
D004791:Enzyme Inhibitors; D050778:NFATC Transcription Factors; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D052247:Nitric Oxide Synthase Type II; D051546:Cyclooxygenase 2; D013755:Tetradecanoylphorbol Acetate