Background & Aims: Portal vein tumor thrombus (PVTT) worsens the prognosis of hepatocellular carcinoma by increasing intrahepatic dissemination and inducing portal vein hypertension. However, the immune characteristics of PVTT remain unclear. Therefore, this study aims to explore the immune microenvironment in PVTT. Approach & Results: Time-of-flight mass cytometry (CyTOF) revealed that macrophages and monocytes were the dominant immune cell type in PVTT, with a higher proportion than in primary tumor (PT) and blood (54.1% vs. 26.3% and 9.1%, p<0.05). The differentially enriched clustering of inhibitory and regulatory immune cells in PVTT indicated an immune-suppressive environment. According to the single-cell RNA sequencing (scRNA-seq), TAM-C5AR1 was characterized by leukocyte chemotaxis and was the most common subpopulation in PVTT (36.7%). Multiple immunofluorescence staining showed that the C5aR+ TAM/Mφ were enriched in PVTT compared to both PT and liver, and positively correlated with C5a (r=0.559, p<0.001). Notably, THP-1 (monocyte cell line) was recruited by CSQT2 (PVTT cell line) and exhibited up-regulation of CD163, CD206, and PD-L1 upon stimulation. C5aR antagonist could reverse this. C5aR+ TAMs could also inhibit Granzyme B in CD8+ T cells. High infiltration of C5aR+ TAMs in PVTT correlated with poor differentiation (p<0.009), and was a risk factor for overall survival (p=0.003) and for re-formation of PVTT after resection (p=0.007). Conclusions: TAMs, especially C5aR+ TAMs, were enriched in PVTT. C5aR+ TAMs contribute to the development of PVTT and poor prognosis by reshaping the immunosuppressive environment.

中文翻译：

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单细胞分辨率下肝细胞癌静脉癌栓的不同免疫微环境


背景和目标：门静脉癌栓（PVTT）通过增加肝内扩散并诱导门静脉高压，使肝细胞癌的预后恶化。然而，PVTT 的免疫特性仍不清楚。因此，本研究旨在探索 PVTT 中的免疫微环境。方法和结果：飞行时间质谱流式细胞术（CyTOF）显示，巨噬细胞和单核细胞是PVTT中的主要免疫细胞类型，比例高于原发肿瘤（PT）和血液中的比例（54.1%对26.3%和9.1%，p<0.05）。PVTT 中抑制性和调节性免疫细胞的差异富集聚集表明免疫抑制环境。根据单细胞 RNA 测序 （scRNA-seq），TAM-C5AR1 以白细胞趋化性为特征，是 PVTT 中最常见的亚群 （36.7%）。多重免疫荧光染色显示，与 PT 和肝脏相比，PVTT 中 C5aR+ TAM/Mφ 富集，与 C5a 呈正相关 （r=0.559，p<0.001）。值得注意的是，THP-1 （单核细胞系） 被 CSQT2 （PVTT 细胞系） 募集，并在刺激后表现出 CD163 、 CD206 和 PD-L1 的上调。C5aR 拮抗剂可以逆转这种情况。C5aR+ TAMs 还可以抑制 CD8+ T 细胞中的颗粒酶 B。PVTT 中 C5aR+ TAMs 的高浸润与分化不良相关 （p<0.009），是总生存期 （p=0.003） 和切除后 PVTT 重组 （p=0.007） 的危险因素。结论： TAMs，尤其是 C5aR+ TAMs，在 PVTT 中富集。C5aR+ TAMs 通过重塑免疫抑制环境，促进 PVTT 的发生和不良预后。