Department of Laboratory Medicine, Tianjin Hospital, Tianjin, 300211, China.
Department of Pathology, The Fourth Hospital of Hebei Medical University, Shijiazhuang, Hebei, 050011, China.
J Transl Med. 2024 Mar 12;22(1):272. doi: 10.1186/s12967-024-05069-y.
In HBV-associated HCC, T cells often exhibit a state of functional exhaustion, which prevents the immune response from rejecting the tumor and allows HCC to progress. Moreover, polymerase-specific T cells exhibit more severe T-cell exhaustion compared to core-specific T cells. However, whether HBV DNA polymerase drives HBV-specific CD8 T cell exhaustion in HBV-related HCC remains unclear.
We constructed a Huh7 cell line stably expressing HA-HBV-DNA-Pol and applied co-culture systems to clarify its effect on immune cell function. We also examined how HBV-DNA-Pol modulated PD-L1 expression in HCC cells. In addition, HBV-DNA-Pol transgenic mice were used to elucidate the underlying mechanism of HBV-DNA-Pol/PD-L1 axis-induced T cell exhaustion.
Biochemical analysis showed that Huh7 cells overexpressing HBV-DNA-Pol inhibited the proliferation, activation, and cytokine secretion of Jurkat cells and that this effect was dependent on their direct contact. A similar inhibitory effect was observed in an HCC mouse model. PD-L1 was brought to our attention during screening. Our results showed that the overexpression of HBV-DNA-Pol upregulated PD-L1 mRNA and protein expression. PD-L1 antibody blockade reversed the inhibitory effect of Huh7 cells overexpressing HBV-DNA-Pol on Jurkat cells. Mechanistically, HBV-DNA-Pol interacts with PARP1, thereby inhibiting the nuclear translocation of PARP1 and further upregulating PD-L1 expression.
Our findings suggest that HBV-DNA-Pol can act as a regulator of PD-L1 in HCC, thereby directing anti-cancer immune evasion, which further provides a new idea for the clinical treatment of liver cancer.
在 HBV 相关 HCC 中，T 细胞通常表现出功能衰竭状态，这阻止了免疫反应排斥肿瘤，使 HCC 得以进展。此外，与核心特异性 T 细胞相比，聚合酶特异性 T 细胞表现出更严重的 T 细胞衰竭。然而，HBV DNA 聚合酶是否在 HBV 相关 HCC 中驱动 HBV 特异性 CD8 T 细胞衰竭仍不清楚。
我们构建了稳定表达 HA-HBV-DNA-Pol 的 Huh7 细胞系，并应用共培养系统来阐明其对免疫细胞功能的影响。我们还研究了 HBV-DNA-Pol 如何调节 HCC 细胞中 PD-L1 的表达。此外，使用 HBV-DNA-Pol 转基因小鼠阐明 HBV-DNA-Pol/PD-L1 轴诱导 T 细胞衰竭的潜在机制。
生化分析表明，过表达 HBV-DNA-Pol 的 Huh7 细胞抑制 Jurkat 细胞的增殖、活化和细胞因子分泌，并且这种作用依赖于它们的直接接触。在 HCC 小鼠模型中观察到类似的抑制作用。在筛选过程中引起了我们对 PD-L1 的关注。我们的结果表明，HBV-DNA-Pol 的过表达上调了 PD-L1 mRNA 和蛋白表达。PD-L1 抗体阻断逆转了过表达 HBV-DNA-Pol 的 Huh7 细胞对 Jurkat 细胞的抑制作用。在机制上，HBV-DNA-Pol 与 PARP1 相互作用，从而抑制 PARP1 的核转位，进一步上调 PD-L1 表达。
我们的研究结果表明，HBV-DNA-Pol 可作为 HCC 中 PD-L1 的调节剂，从而指导抗肿瘤免疫逃逸，这为肝癌的临床治疗提供了新的思路。
