Intratumoral stem-like CCR4+ regulatory T cells orchestrate the immunosuppressive microenvironment in hepatocellular carcinoma

Regulatory T (Treg) cell depletion has been reported to increase antitumor immunity. However, severe autoimmunity can occur following systemic Treg cell loss, which could be avoided if selectively depleting tumor-infiltrated Treg cells. Here, we identified CCR4+ Treg cells as the predominant type of Treg cells recruited in the hepatitis B-associated hepatocellular carcinoma (HCC), correlating with drug resistance and viral load titres. Particularly, CCR4+ Tregs were characterized as specific cytokine-driving self-renewal and PD-1+ TCF1+ stem-like properties that mediated resource immunosuppression and immune escape in tumor microenvironment. Substantial chromatin remodeling between intratumoral and induced Tregs by applying technology of ATAC-seq suggested a long-term chromatin reprogramming accounted for CCR4+ Tregs to acquire an enhanced immune suppressive functionality. To block the chemotaxis of CCR4+ Treg cells, we developed a N-terminus of CCR4 recombinant protein (N-CCR4-Fc) as a neutralizing pseudo-receptor that effectively binding to its ligand CCL22. Treatments of CCR4 antagonist or N-CCR4-Fc achieved to block intratumoral Treg accumulation, overcome sorafenib resistance, sensitize PD-1 checkpoint blockage therapy, thus prolonged the survival of mice from tumor-loaden death. Our data suggested that CCR4 could be a potential precision target for enhancing the antitumor immunity by specifically inhibiting tumor-infiltrated Treg pool maintenance, indicating a new strategy for immunotherapy complementing the first/second-line agent against Hepatitis B -associated HCC.