Il18-deficient mice exhibit enhanced expression of mitogenic/inflammatory cytokines and STAT-3 phosphorylation after AOM/DSS treatment. Cohorts of 8–10 WT and Il18^−/− mice per group were injected i.v. with AOM on day 0, followed by 3 d of DSS administration in drinking water. Thereafter, colons were resected, RNA was extracted, and RT-PCR was performed using specific primers for the indicated genes. The gene expression was normalized to Gapdh levels, and the expression of each gene relative to untreated WT mice is depicted (A). Tissue sections were stained for pSTAT3. Photomicrographs of representative sections from the respective groups are shown at 200× magnification. Protein extracts were analyzed by Western blotting for COX-2, STAT3, and pSTAT3 expression. Gapdh was used as a control (C). Quantification of colonic epithelial cell proliferation and apoptosis was performed in tissue sections stained with Ki67 or ApopTag antibodies. The number of proliferating cells per crypt and the number of apoptotic cells/field are shown. The data shown in A–D correspond to a representative experiment out of two performed. Data represent means ± SE. *, P < 0.05; **, P < 0.01.