12–14-d-old pups were injected with a single dose of 5 mg/kg DEN. At the indicated times, male mice were killed and livers were examined for tumors. Macroscopic HCCs were confirmed by hematoxylin and eosin analysis, as described in Materials and methods. Tumor development was significantly different in Socs3 h-KO mice as determined by a log-rank test, with a p-value of 0.0027.