Fig. 2. Footprints of inflammation in azoxymethane (AOM)-initiated and dextran sulfate sodium (DSS)-promoted colitis-associated carcinogenesis. Mice given a single intraperitoneal dose of AOM (10 mg/kg) followed by exposure to 2% DSS in drinking developed colon tumors. (A) Mast cells were identified by tryptase immunostaining and counted. A statistically significant (***P < 0.001) increase of mast cells was noted in tumor tissues of the AOM plus DSS treated group (× 400 magnification). (B) Tissue levels of TNF-α. *Significantly different from the value of the control group (P < 0.05). (C, D) Expression of representative tissue matrix metalloproteinases (MMPs). The expression of MMPs was measured by reverse transcription-PCR. (D) The catalytic activity of MMPs was assessed by the Gelatin zymography as described in Materials and Methods. (E-G) Serum levels of interleukin (IL)-6, TNF-α, and nitric oxide (NO). Significantly higher levels of IL-6, TNF-α, and NO were noted in AOM + DSS group, suggesting inflammation contributed to colitic cancer. The experimental details are described in the Materials and Methods. GAPDH, glyceraldehyde-3-phosphate dehydrogenase; MW, molecular weight.

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