NADPH oxidase overexpression in human colon cancers and rat colon tumors induced by 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP).
NADPH oxidase/dual-oxidase (Nox/Duox) family members have been implicated in nuclear factor kappa-B (NFκB)-mediated inflammation and inflammation-associated pathologies. We sought to examine, for the first time, the role of Nox/Duox and NFκB in rats treated with the cooked meat heterocyclic amine carcinogen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP). In the PhIP-induced colon tumors obtained after 1 year, Nox1, Nox4, NFκB-p50 and NFκB-p65 were all highly overexpressed compared with their levels in adjacent normal-looking colonic mucosa. Nox1 and Nox4 mRNA and protein levels also were markedly elevated in a panel of primary human colon cancers, compared with their matched controls. In HT29 human colon cancer cells, Nox1 knockdown induced G1 cell cycle arrest, whereas in Caco-2 cells there was a strong apoptotic response, with increased levels of cleaved caspase-3, -6, -7 and poly(ADP-ribose)polymerase. Nox1 knockdown blocked lipopolysaccharide-induced phosphorylation of IκB kinase, inhibited the nuclear translocation of NFκB (p50 and p65) proteins, and attenuated NFκB DNA binding activity. There was a corresponding reduction in the expression of downstream NFκB targets, such as MYC, CCND1 and IL1β. The results provide the first evidence for a role of Nox1, Nox4 and NFκB in PhIP-induced colon carcinogenesis, including during the early stages before tumor onset. Collectively, the findings from this investigation and others suggest that further work is warranted on the role of Nox/Duox family members and NFκB in colon cancer development.
Wang
Rong
R
Linus Pauling Institute, Oregon State University, Corvallis, Oregon 97331, USA.
Dashwood
Wan-Mohaiza
WM
Nian
Hui
H
Löhr
Christiane V
CV
Fischer
Kay A
KA
Tsuchiya
Naoto
N
Nakagama
Hitoshi
H
Ashktorab
Hassan
H
Dashwood
Roderick H
RH
D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D017209:Apoptosis; D015153:Blotting, Western; D002273:Carcinogens / Q000633:toxicity; D016022:Case-Control Studies; D002453:Cell Cycle; D049109:Cell Proliferation; D003110:Colonic Neoplasms / Q000139:chemically induced / Q000201:enzymology* / Q000235:genetics; D005260:Female; D006801:Humans; D007093:Imidazoles / Q000633:toxicity; D007124:Immunoenzyme Techniques; D008297:Male; D008875:Middle Aged; D019255:NADPH Oxidases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D052002:NF-kappa B p50 Subunit / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation; D012333:RNA, Messenger / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics; D051381:Rats; D011916:Rats, Inbred F344; D020133:Reverse Transcriptase Polymerase Chain Reaction; D051996:Transcription Factor RelA / Q000235:genetics / Q000378:metabolism
D002273:Carcinogens; D007093:Imidazoles; D052002:NF-kappa B p50 Subunit; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D051996:Transcription Factor RelA; C049584:2-amino-1-methyl-6-phenylimidazo(4,5-b)pyridine; D019255:NADPH Oxidases