Background: Obesity and pro-inflammatory alterations of the gut microbiome are risk factors for gastrointestinal (GI) cancers, including liver cancer (HCC). Dysregulated TGF-β signaling through Smad3 and βII-Spectrin and loss of CEACAM1 activity are implicated in fatty liver disease. CEACAM1 expression is significantly decreased in the liver of patients with Metabolic dysfunction-associated steatohepatitis (MASH). In contrast, in hepatocellular carcinoma (HCC), high CEACAM1 βII-Spectrin levels are associated with invasion, metastasis, and poor prognosis. Liver-specific βII-Spectrin knockout (LSKO) blocks MASH and HCC (Sci Transl Med 2021; 13:624). We hypothesize that TGF-β signaling and βII-spectrin modulate CEACAM1 in MASH and HCC.
Methods: Wild type and liver-specific βII-Spectrin (Sptbn1) knockout (LSKO) mice fed a high-fat diet (HFD) or Western diet (WD) were analyzed for Ceacam1 expression, changes in immune cell population, liver inflammation, and cancer. We used Alphafold and molecular modeling to identify the CEACAM1 and SPTBN1 interaction sites, followed by functional studies.
Results: Single-cell sequencing analysis of MASH mice liver revealed that Ceacam1 expression is significantly decreased in hepatocytes. Interestingly, low MASH-associated CEACAM1 levels were restored to normal in tissues from liver-specific βII-Spectrin knockout (LSKO) mice. Transcriptomic and multiplex imaging analysis suggested that proinflammatory TGF-β signaling is activated and infiltration of CD11b⁺ cells is increased in the MASH liver. These phenotypes were blocked in LSKO mice and siRNA-knockdown of βII-spectrin blocked diet-induced obesity, fibrosis, lipid accumulation, tissue damage, and cancer susceptibility. Structural analysis of CECAM1 and βII-Spectrin revealed critical residues involved in the interaction. We identified that CEACAM1 interacts with the Smad3 adaptor, βII-spectrin, in a TGF-β dependent manner.
Conclusion: These data suggest that βII-Spectrin regulates CEACAM1 expression in the liver and that it may be a potential target for therapeutic intervention to treat MASH and prevent progression to HCC.

Xin Wang

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