Hepatic Arterial Bland Embolization Increases Th17 Cell Infiltration in a Syngeneic Rat Model of Hepatocellular Carcinoma

Purpose To determine the tumor immune cell landscape after transcatheter arterial bland embolization (TAE) in a clinically relevant rat hepatocellular carcinoma (HCC) model. Materials and Methods Buffalo rats ( n = 21) bearing syngeneic McArdle RH-7777 rat hepatoma cells implanted into the left hepatic lobe underwent TAE using 70–150 µm beads ( n = 9) or hepatic artery saline infusion ( n = 12). HCC nodules, peritumoral margin, adjacent non-cancerous liver, and splenic parenchyma were collected and disaggregated to generate single-cell suspensions for immunological characterization 14 d after treatment. Changes in tumor-infiltrating immune subsets including CD4 T cells (Th17 and Treg), CD8 cytotoxic T cells (IFNγ), and neutrophils were evaluated by multiparameter flow cytometry. Migration and colony formation assays were performed to examine the effect of IL-17, a signature cytokine of Th17 cells, on McArdle RH-7777 hepatoma cells under conditions simulating post-embolization environment (i.e., hypoxia and nutrient privation). Statistical significance was determined by the Student unpaired t test or one-way ANOVA. Results TAE induces increased infiltration of Th17 cells in liver tumors when compared with controls 14 d after treatment (0.29 ± 0.01 vs. 0.19 ± 0.02; p = 0.02). A similar pattern was observed in the spleen (1.41 ± 0.13 vs. 0.57 ± 0.08; p 0.05). In vitro post-embolization assays demonstrated that IL-17 reduces McA-RH7777 cell migration at 24–48 h ( p = 0.003 and p = 0.002, respectively). Conclusion Transcatheter hepatic arterial bland embolization induces local and systemic increased infiltration of Th17 cells and expression of their signature cytokine IL-17. In a simulated post-embolization environment, IL-17 significantly reduced McA-RH7777 cell migration.