Inducible nuclear factor-kappaB activation contributes to chemotherapy resistance in gastric cancer

BACKGROUND: Activation of nuclear factor-kappaB (NF-kappaB) inhibits chemotherapy-induced apoptosis in some cancer cell lines. Inhibition of NF-kappaB by adenoviral delivery of an IkappaBalpha superrepressor (Ad.IkappaBalpha-SR) should potentiate 5-fluorouracil (5-FU) and irinotecan chemotherapy in gastric cancer cells. STUDY DESIGN: NCI-N87 and AGS human gastric cancer cells were studied. Chemotherapy-induced NF-kappaB activation was assessed using a luciferase reporter assay. Inhibition of NF-kappaB was assessed by luciferase reporter assay and by electrophoretic mobility shift assay. Cells were pretreated for 1 hour with Ad.IkappaBalpha (25 MOI) and incubated with 5-FU or the active metabolite of irinotecan (SN-38). Cell growth was assessed by cell proliferation assay and induction of apoptosis was determined by flow cytometry and caspase 3/7 assay. RESULTS: 5-FU and SN-38 significantly induced NF-kappaB activation as measured by luciferase reporter assay (p < 0.001). Ad.IkappaBalpha-SR treatment inhibited NF-kappaB binding as demonstrated by electrophoretic mobility shift assay and by luciferase reporter assay. In AGS cells, pretreatment with Ad.IkappaBalpha-SR followed by 5-FU (0.005 mmol/L) or SN-38 (10 ng/mL) led to increased growth inhibition of 13% and 59%, respectively (p < 0.001). Similarly, growth inhibition in NCI cells was significantly increased by pretreatment with Ad.IkappaBalpha followed by 5-FU (0.001 mmol/L) or SN-38 (0.5 ng/mL) (p < 0.001). In both cell lines, Ad.IkappaBalpha-SR enhanced apoptosis by both flow cytometry and caspase 3/7 assay as compared with chemotherapy alone. CONCLUSIONS: NF-kappaB is activated in human gastric cancer in response to chemotherapy and may result in inducible chemoresistance. Inhibition of NF-kappaB by Ad.IkappaBalpha-SR enhances the antitumor effects of chemotherapy and has potential as a novel antineoplastic strategy.