Strong CD8⁺ T-cell responses against tumor-associated antigens prolong the recurrence-free interval after tumor treatment in patients with hepatocellular carcinoma

Aim We investigated whether tumor-specific CD8⁺ T-cell responses affect tumor-free survival as well as the relationship between CD8⁺ T-cell responses against tumor-associated antigens (TAAs) and the clinical course after tumor treatment in patients with hepatocellular carcinoma (HCC). Methods Twenty patients with HCC that were treated by radiofrequency ablation or trans-catheter chemo-embolization (TACE) and in whom HCC was undetectable by ultrasonography, CT, and/or MRI 1 month after treatment were enrolled in the study. Before and after treatment for HCC, analyses of TAA (glypican-3, NY-ESO-1, and MAGE-1)-specific CD8⁺ T-cell responses were evaluated with an interferon-γ enzyme-linked immunospot (ELISpot) assay using peripheral CD8⁺ T-cells, monocytes, and 104 types of 20-mer synthetic peptide overlapping by 10 residues and spanning the entirety of the 3 TAAs. Results Sixteen out of 20 patients (80%) showed a positive response (≥10 TAA-specific cells/10⁵ CD8⁺ T-cells) before or after treatment. When we performed univariate analysis of prognostic factors for the tumor-free period in the 20 patients, platelet count, prothrombin time, and the number of TAA-specific CD8⁺ T-cells after treatment were significant factors (P = 0.027, 0.030, and 0.004, respectively). In multivariate analysis, the magnitude of the TAA-specific CD8⁺ T-cell response (≥40 TAA-specific cells/10⁵ CD8⁺ T-cells) was the only significant prognostic factor for a prolonged tumor-free interval (hazard ratio 0.342, P = 0.022). Conclusions Our results suggest that strong TAA-specific CD8⁺ T-cell responses suppress the recurrence of HCC. Immunotherapy to induce TAA-specific cytotoxic T lymphocytes by means such as the use of peptide vaccines should be considered for clinical application in patients with HCC after local therapy.