Cysteinyl leukotriene receptor 1 facilitates tumorigenesis in a mouse model of colitis-associated colon cancer

Cysteinyl leukotriene receptor 1 (CysLT(1)R) has been shown to be up-regulated in the adenocarcinomas of colorectal cancer patients, which is associated with a poor prognosis. In a spontaneous model of colon cancer, CysLT(1)R disruption was associated with a reduced tumor burden in double-mutant female mice (Apc(Min/+/)Cysltr1(−/−)) compared to Apc(Min/+) littermates. In the current study, we utilized a genetic approach to investigate the effect of CysLT(1)R in the induced azoxymethane/dextran sulfate sodium (AOM/DSS) model of colitis-associated colon cancer. We found that AOM/DSS female mice with a global disruption of the Cysltr1 gene (Cysltr1(−/−)) had a higher relative body weight, a more normal weight/length colon ratio and smaller-sized colonic polyps compared to AOM/DSS wild-type counterparts. The Cysltr1(−/−) colonic polyps exhibited low-grade dysplasia, while wild-type polyps had an adenoma-like phenotype. The Cysltr1(−/−) colonic polyps exhibited significant decreases in nuclear β-catenin and COX-2 protein expression, while the normal crypts surrounding the polyps exhibited increased Mucin 2 expression. Furthermore, Cysltr1(−/−) mice exhibited an overall reduction in inflammation, with a significant decrease in proinflammatory cytokines, polyp 5-LOX expression and infiltration of CD45 leukocytes and F4/80 macrophages. In conclusion, the present genetic approach in an AOM/DSS model further supports an important role for CysLT(1)R in colon tumorigenesis.