Single-cell dissection of the multicellular ecosystem and molecular feature sunderlying microvascular invasion in hepatocellular carcinoma
Microvascular invasion (MVI) is a significant pathological feature of hepatocellular carcinoma (HCC) associated with poor outcomes, early recurrence, and intrahepatic metastasis in post-surgical resection and transplant patients. However, the tumor microenvironment (TME) and transcriptional programs underlying MVI remain poorly understood. In this study, we conducted single-cell RNA sequencing of 46,789 individual cells from 10 samples of MVI+ (MVI present) and MVI- (MVI absent) HCC patients, providing a comprehensive single-cell atlas of MVI. Single-cell dissection of the multicellular ecosystem revealed the emergence or expansion of cycling T cells, LAMP3+ dendritic cells, TREM2+ macrophages, myofibroblasts, and tumor-promoting arterial i endothelial cells within the MVI+ TME. MVI+ malignant cells are characterized by high proliferation rates and the ability to evade immune detection through the upregulation of non-classical MHC class I molecules. In contrast, MVI-malignant cells exhibit an inflammatory milieu.  Furthermore, we identified the CCL16/CCR1 interaction between TREM2+ macrophages and malignant cells as a contributing factor in MVI formation and tumor progression. Notably, we identified a unique multicellular module that plays the dominant role in shaping the immunosuppressive microenvironment of MVI and correlates with poor prognosis. In summary, these findings enhance our understanding of the underlying cellular and molecular mechanisms driving MVI and provide valuable insights for improving clinical diagnosis and developing more effective treatment strategies. Overall design: Ten independent surgical resected specimens were collected from five HCC patients (3 MVI present patients and 2 MVI absent patients), including 5 HCC tissues and 5 adjacent non-tumor tissues for single-cell RNA sequencing . Inclusion criteria for patients comprised the absence of apparent metastases, a singular tumor of dimensions between 3 and 5 cm, and no prior therapeutic intervention.