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

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)-kappa B 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-kappa B activity, as determined using reporter and gel-shift assays. Transient transfection of TCEAL7 inhibited the activation of NF-kappa B in TCEAL7-downregulated clones, IOSE-523 and in other ovarian cancer cell lines (OVCAR8, SKOV3ip and DOV13), suggesting that TCEAL7 negatively regulates NF-kappa B pathway. Consistent with this observation, TCEAL7-downregulated clones showed higher levels of NF-kappa B 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 antiapoptotic (B-cell lymphoma-extra large (Bcl-xl)) genes when compared with vector controls. Inhibition of NF-kappa B by I kappa B 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-kappa B 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-kappa B signaling at the basal level by modulating transcriptional activity of NF-kappa B on its target gene promoters, potentially providing a novel mechanism by which NF-kappa B activity may be deregulated in ovarian cancer cells. Oncogene (2010) 29, 1362-1373; doi:10.1038/onc.2009.431; published online 7 December 2009