Background and aims: Cancer relapse is one of the major causes of mortality in patients after curative resection of primary tumors. Furthermore, significant proportion of patients with recurrent tumor lack of effective treatments, thus novel therapeutic strategies are urgently needed. Although there have been several single-cell studies of primary tumor, functional roles and mechanism of tumor-infiltrating immune cells, especially those of myeloid cells in tumor relapse have remained to be elucidated.

Methods: We analyzed the RNA profile of 16498 cells from 12 primary and 6 early-relapse HCC cases. Digital pathology, multiplex immunofluorescent staining and digital spatial profiling (DSP) of paired primary and relapsed tumors from 41 HCC patients were also performed as our validation set. The molecular mechanisms associated with DCs was further tested through ex vivo and in vivo experiments.

Results: We performed single-cell clustering and visualized 3 DC clusters (cDC1, cDC2, and DC3). Compared with the other two subsets, the enrichment of DC3 in relapsed HCC was correlated with a higher second recurrence rate. Deeper inspections of the signature genes indicated this subset as ‘mregDC’, a DC subset enriched in maturation and regulatory molecules. Our results demonstrated that mregDC recruited CD161+CD8+ T cells that had an innate-like, low-cytotoxic, and low-clonal-expansion phenotype. CD161+CD8+ T cells secreted large amounts of TNF to activate non-canonical NF-κB pathway via tumor necrosis factor receptor 2 (TNFR2) and promoted the differentiation of immature DC into mregDC. This positive feedback loop between mregDC and CD161+CD8+ T cells shaped a dysfunctional anti-tumor immunity, facilitating cancer relapse in HCC. In vivo assay further indicated that therapy combining anti-TNFR2 and PD-L1 antibodies significantly inhibited HCC tumor growth via impeding the infiltration of mregDC compared with anti-PD-L1 monotherapy. We also found mregDC recruited FCN1+ monocyte, a MDSC-like cell population to create an immunosuppressive niche of relapsed HCC.

Conclusions: We identified this population of mregDC with immunomodulatory function in recurrent HCC and demonstrated the role of these special DCs in shaping the immunosuppressive microenvironment of recurrent tumors. Our study suggests that mregDC may be a new target for the treatment of recurrent HCC in the future.

Citation Format: Zefan Zhang, Jian Zhou, Jia Fan, Yu Zhong, Liang Wu, Yunfan Sun. Tumor-infiltrating mregDC restrains anti-tumor immunity to promote cancer relapse in HCC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6871.