Stress-responsive MAIT cells are associated with immunosuppressive microenvironment and microvascular invasion in hepatocellular carcinoma

Microvascular invasion (MVI) is a predominant risk factor for postoperative recurrence in hepatocellular carcinoma (HCC). Although the tumor microenvironment (TME) governs invasive behaviors, the mechanisms by which tumor-intrinsic and microenvironmental stressors associate with T cell dysfunction in the context of MVI remain poorly defined. This study aimed to investigate the association between stress-responsive T cells and MVI progression and to identify potential immunotherapeutic targets for preventing vascular dissemination. We performed single-cell RNA sequencing on MVI-positive (MVI + ) and MVI-negative (MVI − ) hepatocellular carcinoma (HCC) specimens to interrogate the phenotypic landscape of stress-responsive T cells. By integrating multi-source bulk and single-cell transcriptomic datasets with spatial transcriptomics, we delineated the distinct stress-responsive phenotype of mucosal-associated invariant T (MAIT) cells. Findings were validated using flow cytometry, multiplex immunohistochemistry, and in vitro functional assays. Orthotopic liver cancer models were established to assess the association between the CCL20–CCR6 axis and MVI in vivo. Pharmacological interventions using CCR6-specific antagonists or Acetyl-6-formylpterin were evaluated for their efficacy in reducing MVI formation. We identified a distinct stress-responsive MAIT (MAIT_SR) cell subset that correlated strongly with MVI presence. MAIT_SR cells exhibited elevated heat shock protein expression but diminished cytotoxicity, with pathway enrichment in hypoxia, glycolysis, and NF-κB signaling. Notably, MAIT_SR cells were a dominant cellular source of CCL20. In vivo, CCL20 administration was associated with increased MVI progression, whereas pharmacological blockade of CCR6 or treatment with Acetyl-6-formylpterin effectively reduced MVI formation. Mechanistically, MAIT_SR cells localized to peritumoral regions, recruiting CD4 + T cells via the CCL20–CCR6 axis and driving their differentiation into regulatory T cells through TGF-β1 secretion. We identified a novel association between the MAIT_SR–CCL20/TGF-β1–CD4 + T cell axis and MVI in HCC. These findings support a link between stress signaling and the peritumoral immunosuppressive niche, and suggest that CCR6 antagonism and Acetyl-6-formylpterin may represent actionable therapeutic strategies to mitigate microvascular invasion and improve postoperative outcomes in HCC.