Radiofrequency thermal ablation (RFA) destroys tumoral tissue generating a local necrosis followed by marked inflammatory response with a dense T-cell infiltrate. In this study, we tested whether hepatocellular carcinoma thermal ablation can induce or enhance T-cell responses specific for hepatocellular carcinoma-associated antigens. Peripheral blood mononuclear cells derived from 20 patients with hepatocellular carcinoma were stimulated before and a month after RFA treatment with autologous hepatocellular carcinoma-derived protein lysates obtained before and immediately after RFA treatment. The effect of thermal ablation on memory T-cell responses to recall antigens [tetanus toxoid, protein purified derivative (PPD), Escherichia coli] was also assessed. T-cell reactivity was analyzed in an IFN-; enzymelinked immunospot assay and by intracellular IFN-; staining. Treatment was followed by a significant increase of patients responsive either to tumor antigens derived from both the untreated hepatocellular carcinoma tissue (P < 0.05) and the necrotic tumor (P < 0.01) and by a higher frequency of circulating tumor-specific T cells. T-cell responses to recall antigens were also significantly augmented. Phenotypic analysis of circulating T and natural killer cells showed an increased expression of activation and cytotoxic surface markers. However, tumor-specific T-cell responses were not associated with protection from hepatocellular carcinoma relapse. Evidence of tumor immune escape was provided in one patient by the evidence that a new nodule of hepatocellular carcinoma recurrence was not recognized by T cells obtained at the time of RFA. In conclusion, RFA treatment generates the local conditions for activating the tumorspecific T-cell response. Although this effect is not sufficient for controlling hepatocellular carcinoma, it may represent the basis for the development of an adjuvant immunotherapy in patients undergoing RFA for primary and secondary liver

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The definition of the risk of hepatocellular carcinoma (HCC) recurrence after resection represents a central issue to improve the clinical management of patients. In this study we examined the prognostic relevance of infiltrating immune cell subsets in the tumor (TIL) and in nontumorous (NT) liver (LIL), and the expression of immune-related and lineage-specific mRNAs in HCC and NT liver derived from 42 patients. The phenotype of infiltrating cells was analyzed by flow cytometry, and mRNA expression in liver tissue was examined by real-time reverse transcription (RT)-PCR. The tumor immune microenvironment was enriched in inhibitory and dysfunctional cell subsets. Enrichment in CD4+ T-cells and in particular CD4 and CD8+ memory subsets within TIL was predictive of better overall survival (OS) and time to recurrence (TTR). Increased programmed death ligand 1 (PDL1) mRNA content and higher prevalence of invariant NKT (iNKT) cells were associated with shorter OS and TTR, respectively. By combined evaluation of infiltrating cell subsets along with mRNA profiling of immune and tumor related genes, we identified the intratumoral frequency of memory T-cells and iNKT-cells as well as PDL1 expression as the best predictors of clinical outcome. HCC infiltrate is characterized by the expression of molecules with negative regulatory function that may favor tumor recurrence and poor survival.

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Radiofrequency thermal ablation represents an effective treatment for hepatocellular carcinoma (HCC) and it can also exert an "adjuvant" effect on spontaneous antitumor T-cell responses, as suggested by human and animal studies. The adjuvant effect is thought to depend on the huge amount of necrotic tumor antigen made available to the immune system by HCC thermal ablation. In addition, radiofrequency thermal ablation may result in the release of local stimuli responsible for activation and maturation of antigen-presenting cells (APCs). To test this hypothesis, we studied APC maturation and function in 19 patients undergoing thermal ablation for HCC. Patients' monocytes induced to differentiate with granulocyte macrophage colony-stimulating factor (GM-CSF), or GM-CSF plus IL-4, were cocultured in vitro with tumor debris generated by radiofrequency thermal ablation. Expression of costimulatory molecules, lymphnode homing chemokine receptor, antigen presentation, and cytokine secretion were enhanced by incubation with HCC treated tissue as compared with untreated HCC and nontumor liver tissue. Moreover, HCC-specific T-cell responses could be induced by monocytes activated with GM-CSF and incubated with thermally ablated HCC tissue. HCC thermal ablation can create an antigenic source along with stimuli appropriate for maturation of APCs to induce HCC-specific T-cell responses. These results contribute to explain at least in part the adjuvant effect of HCC thermal ablation and suggest a novel strategy to induce maturation of APCs and their loading with HCC antigens for active immunotherapy protocols aimed at reducing HCC recurrence after thermal ablation.