A JNK1/AP-1-dependent, COX-2 induction is implicated in 12-O-tetradecanoylphorbol-13-acetate-induced cell transformation through regulating cell cycle progression.
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.
Zhang
Dongyun
D
Nelson Institute of Environmental Medicine, New York University School of Medicine, Tuxedo, NY 10987, USA.
Li
Jingxia
J
Song
Lun
L
Ouyang
Weiming
W
Gao
Jimin
J
Huang
Chuanshu
C
D000818:Animals; D002453:Cell Cycle / Q000187:drug effects*; D002471:Cell Transformation, Neoplastic / Q000187:drug effects*; D051546:Cyclooxygenase 2 / Q000096:biosynthesis*; D004790:Enzyme Induction / Q000187:drug effects; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects / Q000201:enzymology; D006801:Humans; D051550:I-kappa B Kinase / Q000378:metabolism; D051379:Mice; D048055:Mitogen-Activated Protein Kinase 8 / Q000378:metabolism*; D048056:Mitogen-Activated Protein Kinase 9 / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D018808:Transcription Factor AP-1 / Q000378:metabolism*; D051996:Transcription Factor RelA / Q000378:metabolism
D018808:Transcription Factor AP-1; D051996:Transcription Factor RelA; D051546:Cyclooxygenase 2; D048056:Mitogen-Activated Protein Kinase 9; D051550:I-kappa B Kinase; D048055:Mitogen-Activated Protein Kinase 8; D013755:Tetradecanoylphorbol Acetate