Nonsteroidal anti-inflammatory drug-activated gene-1 over expression in transgenic mice suppresses intestinal neoplasia.
OBJECTIVE
The nonsteroidal anti-inflammatory drug-activated gene (NAG-1) was identified as a proapoptotic, antitumorigenic protein in vitro, induced by many antitumorigenic and chemopreventive drugs including cyclooxygenase inhibitors. However, its antitumorigenic activity has not been elucidated in vivo.


METHODS
Transgenic mice were generated that ubiquitously overexpress human NAG-1 under the control of a chicken beta-actin promoter (CAG). The NAG-1 transgenic mice (NAG-(Tg+)) were characterized, and then the antitumorigenic activity was evaluated with 2 colorectal carcinogenesis models: chemical induction with azoxymethane and genetic induction using the Apc(Min+) mutation.


RESULTS
NAG-(Tg+) showed no apparent phenotype other than a reduction in body weight, particularly in males. To examine whether NAG-1 expression would suppress intestinal tumorigenesis, the NAG-(Tg+) mice were treated with the colorectal carcinogen azoxymethane. NAG-(Tg+) mice developed 50% fewer aberrant crypt foci and no tumors, in comparison with nontransgenic littermates. This result demonstrates that expression of this human protein in vivo can suppress chemically induced carcinogenesis in the colon. The NAG-(Tg+) mice were also crossed with Apc(Min+) mice to determine the effect of the transgene on intestinal polyp formation. NAG-(Tg+) mice heterozygous for the Apc(Min+) mutation had a significantly reduced polyp load (60%) compared with nontransgenic Apc(Min+) littermates.


CONCLUSIONS
Our results support NAG-1 as an important regulator of intestinal adenoma growth in vivo and suggest that NAG-1 may act as a tumor suppressor gene.
Baek
Seung Joon
SJ
Department of Pathobiology, College of Veterinary Medicine, University of Tennessee, Knoxville, Tennessee, USA.
Okazaki
Ryuji
R
Lee
Seong-Ho
SH
Martinez
Jeanelle
J
Kim
Jong-Sik
JS
Yamaguchi
Kiyoshi
K
Mishina
Yuji
Y
Martin
David W
DW
Shoieb
Ahmed
A
McEntee
Michael F
MF
Eling
Thomas E
TE
D000818:Animals; D016207:Cytokines / Q000235:genetics / Q000502:physiology*; D005260:Female; D017491:Genes, APC; D016147:Genes, Tumor Suppressor; D055436:Growth Differentiation Factor 15; D006801:Humans; D007414:Intestinal Neoplasms / Q000517:prevention & control*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009154:Mutation; D010641:Phenotype
D016207:Cytokines; C526140:GDF15 protein, human; C526141:Gdf15 protein, mouse; D055436:Growth Differentiation Factor 15