TCEAL7, a putative tumor suppressor gene, negatively regulates NF-kappaB pathway

Oncogene. 2010 Mar 4;29(9):1362-73. doi: 10.1038/onc.2009.431. Epub 2009 Dec 7.

Abstract

We have previously shown that a frequently downregulated gene, transcription elongation factor A-like 7 (TCEAL7), promoted anchorage-independent growth and modulated Myc activity in ovarian surface epithelial cells immortalized with temperature-sensitive large T antigen and human telomerase reverse transcriptase (OSEtsT/hTERT). Analysis of protein/DNA array showed that TCEAL7 downregulation resulted in an approximately twofold increase in nuclear factor (NF)-kappaB binding to its target DNA sequence. In this study we showed that short hairpin RNA (shRNA)-mediated downregulation of TCEAL7 in two different immortalized OSE cells showed higher NF-kappaB activity, as determined using reporter and gel-shift assays. Transient transfection of TCEAL7 inhibited the activation of NF-kappaB in TCEAL7-downregulated clones, IOSE-523 and in other ovarian cancer cell lines (OVCAR8, SKOV3ip and DOV13), suggesting that TCEAL7 negatively regulates NF-kappaB pathway. Consistent with this observation, TCEAL7-downregulated clones showed higher levels of NF-kappaB targets, such as pro-proliferative (cyclin-D1 and cMyc), pro-angiogenic (interleukin (IL)-6, IL-8 and vascular endothelial growth factor (VEGF)), inflammatory (intercellular adhesion molecule 1 (ICAM-1) and cyclooxygenase-2 (Cox-2)) and anti-apoptotic (B-cell lymphoma-extra large (Bcl-xl)) genes when compared with vector controls. Inhibition of NF-kappaB by IkappaB kinase (IKK) inhibitor (BMS 345541) attenuated cell survival and proliferation of TCEAL-knockdown clones. Although TCEAL7 inhibited p65 transcriptional activity, it did not modulate the cytoplasmic signaling of the NF-kappaB pathway, by itself or by tumor necrosis factor-alpha (TNF-alpha). Chromatin immunoprecipitation (ChIP) assays revealed increased recruitment of p65 and p300 to the promoters of IL-8 and IL-6 in TCEAL7-downregulated clones. Collectively, these results indicate a novel role for TCEAL7 in the negative regulation of NF-kappaB signaling at the basal level by modulating transcriptional activity of NF-kappaB on its target gene promoters, potentially providing a novel mechanism by which NF-kappaB activity may be deregulated in ovarian cancer cells.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Line, Tumor
  • Cyclooxygenase 2 / genetics
  • Cyclooxygenase 2 / metabolism
  • Down-Regulation
  • Female
  • Gene Expression Regulation, Neoplastic
  • Genes, Tumor Suppressor / physiology*
  • Humans
  • I-kappa B Proteins / pharmacology*
  • NF-KappaB Inhibitor alpha
  • NF-kappa B / antagonists & inhibitors
  • NF-kappa B / genetics
  • NF-kappa B / metabolism*
  • Nuclear Proteins / genetics
  • Nuclear Proteins / metabolism*
  • Ovarian Neoplasms / metabolism
  • Ovarian Neoplasms / pathology*
  • Transcription Factors / physiology
  • Tumor Necrosis Factor-alpha / genetics
  • Tumor Necrosis Factor-alpha / metabolism*

Substances

  • I-kappa B Proteins
  • NF-kappa B
  • NFKBIA protein, human
  • Nuclear Proteins
  • TCEAL7 protein, human
  • Transcription Factors
  • Tumor Necrosis Factor-alpha
  • NF-KappaB Inhibitor alpha
  • Cyclooxygenase 2
  • PTGS2 protein, human