Tumor-Infiltrating mregDCs Restrain Anti-Tumor Immunity in Early Relapse HCC

Emerging evidence highlights the tumor microenvironment's (TME) role in hepatocellular carcinoma (HCC), yet how tumor-infiltrating myeloid cells drive relapse is unclear. Using full-length single-cell RNA sequencing (scRNA-seq) on samples from primary and early-relapse HCC patients, we identified a dendritic cell subset DC3, which in relapsed tumor exhibited features of mature DCs enriched in immunoregulatory molecules (mregDCs). Mechanistically, mregDCs recruit dysfunctional CD161⁺CD8⁺ T cells, which secrete TNF-α, thereby activating the non-canonical NF-κB pathway to promote the differentiation of mature DCs into mregDCs via tumor necrosis factor receptor 2 (TNFR2). Our results from in vivo mouse models demonstrated that dual blockade of TNFR2 and PD-L1 reduced tumor burden more effectively than anti-PD-L1 monotherapy in mregDC-rich HCC. We also found strong interactions between mregDCs and FCN1+ monocytes, a myeloid-derived suppressor cell (MDSC)-like population. Our study characterizes an mregDC-mediated immunosuppressive network in relapse HCC, nominating TNFR2 as a therapeutic target for myeloid-focused HCC immunotherapy.