Colon
tumors develop more frequently in male than in female. Nuclear factor erythroid 2-related factor 2 (Nrf2) plays differential roles in the stage of
tumorigenesis. The purpose of this study was to investigate the role of Nrf2 on
colitis-associated
tumorigenesis using Nrf2 knockout (KO) female mice.
Azoxymethane (AOM) and
dextran sulfate sodium (DSS)-treated wild-type (WT) and Nrf2 KO female mice were sacrificed at week 2 and 16 after AOM injection. Severity of
colitis,
tumor incidence, and levels of inflammatory mediators were evaluated in AOM/DSS-treated WT and Nrf2 KO mice. Furthermore, qRT-PCR, Western blot abnalysis, and ELISA were performed in colon tissues. At week 2, AOM/DSS-induced colon tissue damages were significantly greater in Nrf2 KO than in WT mice. At week 16,
tumor numbers (> 2 mm size) were significantly lower in both the proximal and distal colon in Nrf2 KO compared to WT. The overall incidences of
adenoma/
cancer of the proximal colon and submucosal invasive
cancer of the distal colon were reduced by Nrf2 KO. The
mRNA and
protein expression levels of NF-κB-related mediators (i.e., iNOS and COX-2) and Nrf2-related
antioxidants (i.e.,
heme oxygenase-1 and
glutamate-cysteine ligase catalytic subunit) were significantly lower in the Nrf2 KO than in WT mice. Interestingly, the
protein level of
15-hydroxyprostaglandin dehydrogenase (15-PGDH) was higher in AOM/DSS-treated Nrf2 KO than in WT mice. Our results support the oncogenic effect of Nrf2 in the later stage of
carcinogenesis and upregulation of
tumor suppressor
15-PGDH might contribute to the repression of
colitis-associated
tumorigenesis in Nrf2 KO female mice.