Figure 6.

Lack of AhR increases the response to DEN-induced liver tumors. AhR+/+ and AhR−/− male mice were treated with the carcinogen DEN twice at 4 and 5 weeks of age. (a) Kaplan-Meier survival curve for a 1 year period since treatment. Surviving mice were killed at the end of the experiment. (b) Liver tumors were recovered from mice and classified in three ranges of sizes corresponding to <2 mm³, >1 cm³ and those of more than ¾ of the liver. (c) Livers from DEN-treated AhR+/+ and AhR−/− mice were weighted and the results represented as percentage with respect to the average liver weight of untreated wild type and AhR-null mice. (d) Representative mild lesion (left) and grown liver tumor (right) from DEN-treated AhR+/+ mice are shown. Hematoxylin-eosin stained sections from the corresponding tumors are shown below. Arrowheads indicate liver lesions in AhR+/+ livers. (e) Representative fully-grown liver carcinomas from DEN-treated AhR−/− mice. Hematoxylin-eosin stained sections from the corresponding tumors are shown below. A total of 30 AhR+/+ and 30 AhR−/− mice were used. A set of 10 control mice for each genotype were also analyzed. Data are shown as mean ± SD. **p < 0.01. Bar: 100 μm.