Background:  Chronic ethanol consumption increases the risk of hepatic cirrhosis and hepatocellular carcinoma (HCC). While sex differences exist in susceptibility to ethanol‐induced liver damage/HCC development, little is known about the effects of ethanol on tumor progression.

Methods:  Neonatal male and female mice were initiated with a single dose of diethylnitrosamine (DEN). Sixteen or 40 weeks later, animals were placed on a 10/20% (v/v) ethanol–drinking water (EtOH‐DW; alternate days) regime for 8 weeks. At study end, liver tissue and serum were analyzed for liver pathology/function and cytokine expression.

Results:  DEN reproducibly induced hepatic foci/tumors in male and female mice. Ethanol diminished hepatic function and increased liver damage, but ethanol alone did not induce hepatic foci/HCC formation. In DEN‐initiated EtOH‐DW animals, ethanol significantly increased tumor incidence and burden, but only in male mice. Male and female mice (±DEN) demonstrated comparable blood alcohol content at necropsy, yet increased hepatic damage and diminished hepatic function/antioxidant capacity were significantly greater in males. Analysis of liver mRNA for Th1, Th2, or T‐regulatory factors demonstrated significantly elevated SMAD3 in male compared to female mice in response to EtOH, DEN initiation, and DEN + EtOH‐DW.

Conclusions:  These data demonstrate male mice are more susceptible to HCC incidence and progression in the setting of chronic ethanol feeding than females. Differences in markers of hepatic immune response in male mice suggest that increased TGFβ‐SMAD3 signaling may enhance promotion in this model of HCC progression, effects modulated by chronic ethanol feeding.