Molecular mechanisms of constitutive and inducible NF-kappaB activation in oesophageal adenocarcinoma

Abstract

Background Nuclear factor-kappaB (NF-κB) regulates the expression of a large number of genes involved in the immune and inflammatory response. NF-κB is constitutively activated in oesophageal tumour tissues and induced in oesophageal cells by bile and acid. The aim of the present study was to define the mechanisms underlying NF-κB activation in oesophageal adenocarcinoma. Patients and methods Fresh biopsy specimens were obtained from 20 patients with oesophageal adenocarcinoma. The activation of NF-κB in oesophageal tumour specimens and oesophageal SKGT-4 cells was assessed by gel mobility shift and Western blotting. Phosphorylation of protein kinase B (AKT/PKB), Ikappa kinase-alpha/beta (IKK-α/β) and extracellular signal-regulated kinase 1/2 (ERK1/2) was examined by Western blotting. High content analysis was used to quantify NF-κB translocation in oesophageal cells. Results Oesophageal tumour tissues had higher levels of NF-κB. Increased levels of phosphorylated AKT and IKK-α/β and ERK1/2 were detected in tumour tissues compared with normal oesophageal mucosa. Exposure of SKGT-4 cells to deoxycholic acid (DCA) or acid resulted in NF-κB activation and phosphorylation of AKT, IKK-α/β and ERK1/2. Specific inhibitors for phosphoinositide 3-kinase; PI3K (LY294002 and worhmannin) and ERK1/2 inhibitors (PD98059 and U0126) suppressed DCA- and acid-induced NF-κB activation. The proteasome inhibitor MG-132 and the antioxidants vitamin C and pyrrolidine dithiocarbamate (PDTC) also inhibited NF-κB activation. Conclusions Our data demonstrate a major role for PI3K/AKT-IKK-α/β-ERK1/2 signalling pathway in NF-κB activation in oesophageal adenocarcinoma. These results suggest that NF-κB may be a prognostic marker for oesophageal adenocarcinoma, and modulating of NF-κB may uncover new therapeutic strategies.