NF-κB signalling is an important factor in the development of
inflammation-associated
cancers. Mouse models of Helicobacter-induced
gastric cancer and
colitis-associated colorectal cancer have demonstrated that classical NF-κB signalling is an important regulator of these processes. In the stomach, it has also been demonstrated that signalling involving specific NF-κB
proteins, including NF-κB1/p50, NF-κB2/p52, and c-Rel, differentially regulate the development of gastric pre-
neoplasia. To investigate the effect of NF-κB subunit loss on
colitis-associated
carcinogenesis, we administered
azoxymethane followed by pulsed
dextran sodium sulphate to C57BL/6, Nfkb1(-/-), Nfkb2(-/-), and c-Rel(-/-) mice. Animals lacking the c-Rel subunit were more susceptible to
colitis-associated cancer than wild-type mice, developing 3.5 times more
colonic polyps per animal than wild-type mice. Nfkb2(-/-) mice were resistant to
colitis-associated cancer, developing fewer
polyps per colon than wild-type mice (median 1 compared to 4). To investigate the mechanisms underlying these trends,
azoxymethane and
dextran sodium sulphate were administered separately to mice of each genotype. Nfkb2(-/-) mice developed fewer clinical signs of
colitis and exhibited less severe
colitis and an attenuated
cytokine response compared with all other groups following DSS administration.
Azoxymethane administration did not fully suppress colonic epithelial mitosis in c-Rel(-/-) mice and less colonic epithelial apoptosis was also observed in this genotype compared to wild-type counterparts. These observations demonstrate different functions of specific NF-κB subunits in this model of
colitis-associated
carcinogenesis. NF-κB2/p52 is necessary for the development of
colitis, whilst c-Rel-mediated signalling regulates colonic epithelial cell turnover following DNA damage.