Zhang Dongyun, Li Jingxia, Song Lun, Ouyang Weiming, Gao Jimin, Huang Chuanshu
Nelson Institute of Environmental Medicine, New York University School of Medicine, Tuxedo, NY 10987, USA.
Mol Cancer Res. 2008 Jan;6(1):165-74. doi: 10.1158/1541-7786.MCR-07-0181.
Cyclooxygenase-2 (COX-2) is reported to be one of the early-response gene products induced by 12-O-tetradecanoylphorbol-13-acetate (TPA). However, the relevance of COX-2 in TPA-induced cell transformation and the underlying mechanisms remains to be explored. Initially, we verified COX-2 induction after TPA treatment in mouse embryonic fibroblasts (MEF) and mouse epidermal cells Cl 41. More importantly, introduction of COX-2 small interfering RNA in MEFs or Cl 41 cells suppressed the cell transformation caused by TPA treatment. This inhibition could be reversed by overexpression of human full-length COX-2, indicating that COX-2 is at least one of the critical molecules involved in TPA-induced cell transformation. We further showed that TPA-promoted cell cycle progression was partially suppressed by COX-2 small interfering RNA, indicating that COX-2 also participated in TPA-associated cell cycle progression. Investigation of the upstream signaling pathways revealed that c-Jun-NH(2)-kinase 1 (JNK1), but not JNK2, played important roles in COX-2 induction, because knockout of JNK1 gene rather than JNK2 gene markedly impaired COX-2 induction. Furthermore, inhibition of c-Jun/activator protein 1 pathway or JNKs/c-Jun pathway by overexpression of dominant negative mutants of c-Jun, or MKK4 and MKK7 together, resulted in impairment of COX-2 induction, suggesting that JNK1/c-Jun/activator protein 1 pathway is involved in TPA-associated COX-2 induction. In contrast, IKK/p65 nuclear factor-kappaB pathway was not implicated because knockout of IKKalpha, IKKbeta, or p65 gene did not affect COX-2 induction although nuclear factor-kappaB was activated by TPA. In addition, the TPA-promoted cell cycle progression was found impaired in JNK1-deficient, but not in JNK2-deficient, MEFs. Our results show that JNK1-associated COX-2 induction is implicated in TPA-associated cell transformation and cell cycle progression.
据报道，环氧合酶-2（COX-2）是由12-O-十四烷酰佛波醇-13-乙酸酯（TPA）诱导产生的早期反应基因产物之一。然而，COX-2在TPA诱导的细胞转化中的相关性及其潜在机制仍有待探索。首先，我们在小鼠胚胎成纤维细胞（MEF）和小鼠表皮细胞Cl 41中验证了TPA处理后COX-2的诱导情况。更重要的是，在MEF或Cl 41细胞中引入COX-2小干扰RNA可抑制TPA处理引起的细胞转化。这种抑制作用可通过人全长COX-2的过表达来逆转，表明COX-2至少是参与TPA诱导细胞转化的关键分子之一。我们进一步表明，COX-2小干扰RNA可部分抑制TPA促进的细胞周期进程，表明COX-2也参与了TPA相关的细胞周期进程。对上游信号通路的研究表明，c-Jun氨基末端激酶1（JNK1）而非JNK2在COX-2诱导中起重要作用，因为JNK1基因敲除而非JNK2基因敲除显著损害了COX-2的诱导。此外，通过过表达c-Jun的显性负突变体或同时过表达MKK4和MKK7来抑制c-Jun/激活蛋白1途径或JNKs/c-Jun途径，会导致COX-2诱导受损，提示JNK1/c-Jun/激活蛋白1途径参与了TPA相关的COX-2诱导。相比之下，IKK/p65核因子-κB途径未涉及，因为尽管TPA激活了核因子-κB，但敲除IKKα、IKKβ或p65基因并不影响COX-2的诱导。此外，在JNK1缺陷的MEF中发现TPA促进的细胞周期进程受损，但在JNK2缺陷的MEF中未受损。我们的结果表明，JNK1相关的COX-2诱导与TPA相关的细胞转化和细胞周期进程有关。
