Immunosuppression developed by cancer cells remains a leading cause of treating failure of immunotherapies. This study aimed to explore the function of human endogenous retrovirus-H long terminal repeat-associating 2 (HHLA2), an immune checkpoint molecule from the B7 family, in the immune escape in hepatocellular carcinoma (HCC). Mouse models with primary HCC or with xenograft tumors were established. The portion of tumor-associated macrophages (TAMs) and the level of PD-L1 in the tumor tissues were examined. THP-1 cells were treated with PMA to obtain a macrophage-like phenotype. The PMA-treated THP-1 cells were co-cultured with the HCC cells in Transwell chambers to examine the function of HHLA2 in chemotactic migration and polarization of macrophages. HHLA2 expression was correlated with infiltration of immune cells, especially macrophages, and was linked to poor prognosis of patients with HCC. HHLA2 knockdown reduced incidence rate of primary HCC in mice. It also reduced tumor metastasis, the portion of M2 macrophages, and the expression of PD-L1 in primary and xenograft tumors. In vitro, HHLA2 upregulation increased expression of PD-L1 in HCC cells indirectly by inducing M2 polarization and chemotactic migration of macrophages. Interferon gamma (IFNG) enhanced expression of interferon regulatory factor 1 (IFR1) in HCC cells, and IFR1 bound to the promoter region of HHLA2 to activate HHLA2 expression. This study suggested that the IFNG/IFR1/HHLA2 axis in HCC induces M2 polarization and chemotactic migration of macrophages, which leads to immune escape and development of HCC.

癌细胞产生的免疫抑制仍然是免疫疗法治疗失败的主要原因。本研究旨在探讨来自 B7 家族的免疫检查点分子人内源性逆转录病毒-H 长末端重复相关 2 (HHLA2) 在肝细胞癌 (HCC) 免疫逃逸中的功能。建立了具有原发性 HCC 或异种移植肿瘤的小鼠模型。检查肿瘤相关巨噬细胞（TAM）的部分和肿瘤组织中PD-L1的水平。用 PMA 处理 THP-1 细胞以获得巨噬细胞样表型。PMA 处理的 THP-1 细胞与 Transwell 室中的 HCC 细胞共培养，以检查 HHLA2 在趋化迁移和巨噬细胞极化中的功能。HHLA2 表达与免疫细胞的浸润有关，尤其是巨噬细胞，并且与 HCC 患者的不良预后有关。HHLA2 敲低降低了小鼠原发性 HCC 的发病率。它还减少了原发性和异种移植肿瘤中的肿瘤转移、M2 巨噬细胞的部分以及 PD-L1 的表达。在体外，HHLA2上调通过诱导M2极化和巨噬细胞趋化迁移间接增加了HCC细胞中PD-L1的表达。干扰素 γ (IFNG) 增强了 HCC 细胞中干扰素调节因子 1 (IFR1) 的表达，并且 IFR1 与 HHLA2 的启动子区域结合以激活 HHLA2 表达。本研究提示HCC中的IFNG/IFR1​​/HHLA2轴诱导巨噬细胞的M2极化和趋化迁移，从而导致免疫逃逸和HCC的发展。