The liver immune milieu balances immune activation against pathogens with tolerance toward microbiota and food-derived antigens. However, this inherent tolerogenicity can impair effective anti-tumor immunity. Hepatocellular carcinoma (HCC) is a leading cause of cancer-related mortality worldwide, with most patients ineligible for surgery and resistant to immunotherapy. A prerequisite for efficient anti-tumor immunity is antigen presentation to T cells. Conventional dendritic cells (cDCs), particularly mature/activated cDCs (mDCs), can migrate to lymph nodes, cross-present tumor antigens, and secrete immune-stimulatory signals that orchestrate cytotoxic responses. However, the role of mDCs in HCC immunity remains poorly understood.

To evaluate the proficiency of mDCs in antigen cross-presentation, we performed in vitro assays using bone marrow-derived dendritic cells loaded with tumor-derived material from OVA-expressing cells. We compared mDCs with other cDC subsets by assessing their ability to process and present tumor antigens to OT-I T cells. In vivo, we utilized a murine HCC line (Hep53.4) implanted subcutaneously (s.c.) to study mDC function in tumor growth and antigen trafficking to the draining lymph node. To further investigate the role of mDCs in HCC, we employed two gene-targeted mouse models: one enabling mDC tracking (mDC-RED) and another allowing their inducible depletion (mDC-DTR). Two-photon microscopy was used to examine mDC localization in liver tumors. Additionally, we established autochthonous HCC models induced either by carcinogen exposure or genetic manipulation. The impact of different oncogenic drivers on the tumor immune landscape was analyzed using flow cytometry and scRNAseq.

We observed that mDCs exhibit superior CD8⁺ T cell activation capacity compared to other cDC subsets in vitro. In the Hep53.4 s.c model, we demonstrated that migratory DCs are the only subset capable of trafficking tumor-derived material to the tumor-draining lymph node. In an orthotopic Hep53.4 model, we observed that while mDCs accumulate near the tumor, they are actively excluded from the tumor mass. Similarly, in chemically induced HCC, mDC abundance is reduced, yet they remain the primary source of immune-stimulatory cytokines within the tumor microenvironment. In β-catenin-driven HCC, we observed a profound reduction in mDC interactions with other immune cells, along with their complete exclusion from the tumor mass.

Our findings highlight a potential role for mDCs in orchestrating effective anti-tumor immune responses. However, their abundance and function appear to be shaped by the tumor microenvironment. Ongoing studies are aimed at further dissecting the mechanisms that regulate cDC activation, migration, and antigen presentation in HCC.