FIG 2.

Colonization with B. fragilis protects mice against development of colon cancer. (A) Schematic overview of the azoxymethane (AOM)/dextran sulfate sodium (DSS)-induced colorectal cancer model. C57BL/6J (B6) mice were treated orally with PBS (control), B. fragilis, or B. fragilis ΔPSA three times a week starting a week prior to AOM injection until the end of the experiment (8 mice per group). After an initial AOM intraperitoneal injection (10 mg/kg), 3% DSS was administered via the drinking water for 6 days followed by administration of regular drinking water. The mice underwent a second DSS treatment cycle with 3% DSS-treated water on day 25 for 6 days and a third cycle with 1.5% DSS-treated water on day 55 for 4 to 6 days. The mice were sacrificed on day 81 post-AOM injection. (B) Percent weight change in the indicated groups during DSS treatment. (C) Number of tumors in the distal colon (left) and the sum of tumor size (right) in the indicated groups on day 81 of AOM-DSS treatment. (D) Scores of hyperplasia (left) and dysplasia (right) from longitudinal sections of distal colon of the indicated groups on day 81 of AOM-DSS treatment. Data are representative of results from at least two experiments. Statistical significance was calculated using unpaired Student's t tests and nonparametric Mann-Whitney tests. *, P < 0.05 (in all panels).