Alcohol and liver cancer: tumors can arise through different routes

Alcohol and liver cancer are connected by more than the well-established increase in cancer risk associated with drinking. In mouse experiments, alcohol changed the route by which liver tumors developed: which cells they came from, which metabolic programs they adopted, and how accessible they were to the immune system.

The liver is not a uniform collection of identical cells. Hepatocytes occupying different parts of a liver lobule perform different jobs. Cells nearer the portal vein are more involved in amino-acid metabolism and glucose production, while those closer to the central vein specialize in functions that include processing foreign compounds. This division of labor is known as liver zonation.

The Nature Communications study compared three complementary mouse models of hepatocellular carcinoma associated with metabolic dysfunction-associated steatohepatitis, or MASH; alcohol-related liver disease; and the combined metabolic and alcohol-related condition known as MetALD. The researchers used genetic lineage tracing together with gene-expression, metabolomic and immune profiling to reconstruct how the tumors formed.

When a liver cell changes its identity

A particularly informative group of MASH tumors had activated β-catenin, a signaling protein involved both in cell growth and in maintaining normal liver zonation.

One might expect these tumors to originate in the liver zone where β-catenin programs are normally strongest. Lineage tracing instead pointed to a different route. Most arose from periportal and midlobular hepatocytes and subsequently acquired features characteristic of cells closer to the central vein.

In one lineage-tracing experiment, 96% of 61 tumor nodules examined in five mice carried the label of their periportal or midlobular origin. The transformation therefore involved more than uncontrolled proliferation: the cells also changed their metabolic identity.

This shift was accompanied by activation of a pathway linking metabolism to immune suppression. The enzyme IDO1 promotes conversion of the amino acid tryptophan into kynurenine. Kynurenine can then activate the AhR receptor, which controls the expression of multiple genes. In these MASH tumors, the IDO1–kynurenine–AhR pathway contributed to a tumor state that was difficult for immune cells to control.

That is consistent with a broader feature of β-catenin-active hepatocellular carcinoma: such tumors can develop an immune-excluded microenvironment in which effective T-cell attack is restricted.

Ethanol changed the route

Adding ethanol to metabolic liver disease did not simply intensify the same tumor-forming process.

Ethanol disrupted perivenous metabolic and xenobiotic programs and destabilized signaling involving β-catenin and AhR. The resulting tumors became more heterogeneous. Alongside hepatocyte-derived cancers, the researchers detected tumors linked to biliary cells and liver progenitor cells.

The origin of β-catenin-positive tumors also changed. Whereas most such tumors in the MASH model traced back to periportal or midlobular hepatocytes, about 90% of the examined tumors in the MetALD model no longer carried that lineage label.

At the same time, kynurenine–AhR-associated immune suppression was reduced and the immune microenvironment shifted. MetALD tumors contained greater infiltration by CD4+ and CD8+ T cells and fewer of some myeloid populations capable of suppressing antitumor immunity.

The difference became particularly clear when the researchers blocked PD-1, one of the inhibitory pathways that can restrain T-cell activity. MASH tumors showed little response in this model. In MetALD mice, however, anti-PD-1 treatment reduced average tumor volume by about 73.5%, while the number of tumors fell from roughly 16 to 5 per animal.

The researchers also tested the mechanism from another direction. Pharmacological inhibition of AhR or hepatocyte-specific deletion of β-catenin reduced MASH-HCC burden and restored sensitivity to PD-1 blockade.

The same diagnosis can hide different biology

The study illustrates why a shared diagnostic label does not necessarily imply a shared biological route to cancer. Hepatocellular carcinomas can emerge from different cellular states and develop different immune environments depending on the chronic liver injury in which they arise.

One interpretation must be explicitly avoided. The findings do not suggest that alcohol is beneficial for cancer immunotherapy. Ethanol is a carcinogenic and hepatotoxic exposure. In the experiments it increased steatosis, cellular senescence and tissue remodeling while opening additional routes to tumor development.

The study is also primarily preclinical. The causal experiments were performed in mice, and several central comparisons involved only five animals per group. The anti-PD-1 sensitivity observed in the MetALD model therefore cannot be assumed to occur in patients with metabolic and alcohol-related liver disease.

The broader conclusion is more important: the cause of chronic liver injury may influence not only whether cancer develops, but also which cellular program gives rise to it and how the resulting tumor interacts with the immune system. For future precision treatment, the biological history of the diseased liver may therefore matter alongside the mutations found inside the cancer itself.