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.


METHODS
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.
Department of Surgery, University of Florida College of Medicine, Gainesville, FL 32610, USA.
E Ramsay
ER
Camp
Jing
J
Li
Douglas J
DJ
Minnich
Adam
A
Brank
Lyle L
LL
Moldawer
Sally L D
SL
MacKay
Steven N
SN
Hochwald
D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects; D002166:Camptothecin / Q000031:analogs & derivatives* / Q000494:pharmacology; D002455:Cell Division / Q000187:drug effects; D045744:Cell Line, Tumor; D019008:Drug Resistance, Neoplasm / Q000502:physiology*; D005472:Fluorouracil / Q000494:pharmacology; D006801:Humans; D000077146:Irinotecan; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000378:metabolism*; D013274:Stomach Neoplasms / Q000188:drug therapy*
D000964:Antimetabolites, Antineoplastic; D000972:Antineoplastic Agents, Phytogenic; D016328:NF-kappa B; D000077146:Irinotecan; D005472:Fluorouracil; D002166:Camptothecin