Ouyang Weiming, Hu Yu, Li Jingxia, Ding Min, Lu Yongju, Zhang Dongyun, Yan Yan, Song Lun, Qu Qingshan, Desai Dhimant, Amin Shantu, Huang Chuanshu
Nelson Institute of Environmental Medicine, New York University School of Medicine, 57 Old Forge Road, Tuxedo, NY 10987, USA.
Carcinogenesis. 2007 Oct;28(10):2218-26. doi: 10.1093/carcin/bgm115. Epub 2007 May 23.
Nuclear factor of activated T cell (NFAT)-3 is a member of the transcription factor NFAT family, which has been demonstrated to be responsible for the up-regulation of the pro-inflammatory cytokine tumor necrosis factor (TNF) in the immune system. Our most recent studies have also shown that TNF is able to induce cell transformation in mouse epidermal Cl41 cells by induction of cyclooxygenase-2 (COX-2) expression. To provide direct evidence for NFAT3 in the environmental carcinogen-caused carcinogenic effect, (+/-)-benzo[a]pyrene-7,8-diol-9,10-epoxide (B[a]PDE), an ultimate environmental carcinogen metabolized from benzo[a]pyrene, was utilized. We found that exposure of Cl41 cells to B[a]PDE was able to induce cell transformation in Cl41 cells, while specific knock-down of NFAT3 resulted in the dramatic inhibition of this cell transformation. The tumorigenicity of B[a]PDE-caused transformed cells was confirmed in nude mice, whereas the tumor formation of B[a]PDE-treated NFAT3 small interference RNA (siRNA) knock-down cells was significantly reduced. Further studies showed that the role of NFAT3 in B[a]PDE-caused cell transformation was mediated by up-regulation of its downstream targeted gene TNF. This conclusion was based on the findings that inhibition of NFAT3 activation by either FK506 or NFAT3 siRNA dramatically down-regulated the TNF induction upon B[a]PDE exposure, and that knock-down of TNF by its specific siRNA also led to abrogation of B[a]PDE-induced cell transformation in Cl41 cells and their tumorigenicity in nude mice. Collectively, these results provide direct evidence for the important role of NFAT3 activation in B[a]PDE-induced cell transformation by up-regulation of TNF expression in mouse epidermal Cl41 cells, further suggesting that B[a]PDE may exert its tumor promotion effect on skin carcinogenesis, at least partially, by inducing TNF expression.
活化T细胞核因子（NFAT）-3是转录因子NFAT家族的成员，已被证明在免疫系统中负责促炎细胞因子肿瘤坏死因子（TNF）的上调。我们最近的研究还表明，TNF能够通过诱导环氧合酶-2（COX-2）表达在小鼠表皮Cl41细胞中诱导细胞转化。为了提供NFAT3在环境致癌物致癌作用中的直接证据，使用了从苯并[a]芘代谢而来的最终环境致癌物（±）-苯并[a]芘-7,8-二醇-9,10-环氧化物（B[a]PDE）。我们发现，Cl41细胞暴露于B[a]PDE能够诱导Cl41细胞发生细胞转化，而NFAT3的特异性敲低导致这种细胞转化受到显著抑制。B[a]PDE诱导的转化细胞在裸鼠中的致瘤性得到证实，而B[a]PDE处理的NFAT3小干扰RNA（siRNA）敲低细胞的肿瘤形成明显减少。进一步的研究表明，NFAT3在B[a]PDE诱导的细胞转化中的作用是通过上调其下游靶基因TNF介导的。这一结论基于以下发现：FK506或NFAT3 siRNA对NFAT3激活的抑制显著下调了B[a]PDE暴露后的TNF诱导，并且其特异性siRNA敲低TNF也导致Cl41细胞中B[a]PDE诱导的细胞转化及其在裸鼠中的致瘤性被消除。总的来说，这些结果为NFAT3激活通过上调小鼠表皮Cl41细胞中TNF表达在B[a]PDE诱导的细胞转化中的重要作用提供了直接证据，进一步表明B[a]PDE可能至少部分地通过诱导TNF表达对皮肤癌发生发挥肿瘤促进作用。
