ABSTRACT
The DEAD-box RNA helicases p68 (DDX5) and p72 (DDX17) have been shown to act as transcriptional co-activators for a diverse range of transcription factors, including oestrogen receptor-alpha (ERalpha). Here, we show that, although both proteins interact with and co-activate ERalpha in reporter gene assays, small interfering RNA-mediated knockdown of p72, but not p68, results in a significant inhibition of oestrogen-dependent transcription of endogenous ERalpha-responsive genes and oestrogen-dependent growth of MCF-7 and ZR75-1 breast cancer cells. Furthermore, immunohistochemical staining of ERalpha-positive primary breast cancers for p68 and p72 indicate that p72 expression is associated with an increased period of relapse-free and overall survival (P=0.006 and 0.016, respectively), as well as being inversely associated with Her2 expression (P=0.008). Conversely, p68 shows no association with relapse-free period, or overall survival, but it is associated with an increased expression of Her2 (P=0.001), AIB-1 (P<0.001) and higher tumour grade (P=0.044). Our data thus highlight a crucial role for p72 in ERalpha co-activation and oestrogen-dependent cell growth and provide evidence in support of distinct but important roles for both p68 and p72 in regulating ERalpha activity in breast cancer.
Subject(s)
Breast Neoplasms/pathology , Cell Proliferation , DEAD-box RNA Helicases/physiology , Estrogen Receptor alpha/physiology , Estrogens/pharmacology , Transcription, Genetic , Animals , Breast Neoplasms/genetics , Breast Neoplasms/metabolism , COS Cells , Cell Proliferation/drug effects , Cell Survival/drug effects , Cell Survival/genetics , Chlorocebus aethiops , DEAD-box RNA Helicases/metabolism , Estrogen Receptor alpha/genetics , Estrogen Receptor alpha/metabolism , Estrogens/metabolism , Female , Gene Expression Regulation, Neoplastic , Humans , Nuclear Receptor Coactivator 1/metabolism , Nuclear Receptor Coactivator 1/physiology , Protein Binding , Transcription, Genetic/drug effects , Transcription, Genetic/genetics , Transcriptional Activation , Tumor Cells, CulturedABSTRACT
RATIONALE: Acute lung injury (ALI) is a disease process that is characterized by diffuse inflammation in the lung parenchyma. Recent studies demonstrated that cyclooxygenase-2 (COX-2) induced at the late phase of inflammation aids in the resolution of inflammation by generating 15-deoxy-delta(12,14)-prostaglandin J2 (15d-PGJ2). Transcription factor Nrf2 is activated by electrophiles and exerts antiinflammatory effects by inducing the gene expression of antioxidant and detoxification enzymes. OBJECTIVES: Because 15d-PGJ2 is an endogenous electrophile, we hypothesized that it protects against ALI by activating Nrf2. METHODS: To test this hypothesis, we generated a reversible ALI model by intratracheal injection of carrageenin, an inducer of acute inflammation, whose stimulation has been known to induce COX-2. MAIN RESULTS: We found that ALI induced by carrageenin was markedly exacerbated in Nrf2-knockout mice, compared with wild-type mice. Analysis of bronchoalveolar lavage fluids also revealed that the magnitude and the duration of acute inflammation, indicated by albumin concentration and the number of neutrophils, were significantly enhanced in Nrf2-knockout mice. Treatment of wild-type mice with NS-398, a selective COX-2 inhibitor, significantly exacerbated ALI to the level of Nrf2-knockout mice. In the lungs of NS-398-treated wild-type mice, both the accumulation of 15d-PGJ2 and the induction of Nrf2 target antioxidant genes were significantly attenuated. Exogenous administration of 15d-PGJ2 reversed the exacerbating effects of NS-398 with the induction of antioxidant genes. CONCLUSIONS: These results demonstrated in vivo that 15d-PGJ2 plays a protective role against ALI by exploiting the Nrf2-mediated transcriptional pathway.
