Eishiro Mizukoshi

UNLABELLED: Recent evidence suggests that hepatocellular carcinoma (HCC) is organized by a subset of cells with stem cell features (cancer stem cells; CSCs). CSCs are considered a pivotal target for the eradication of cancer, and liver CSCs have been identified by the use of various stem cell markers. However, little information is known about the expression patterns and characteristics of marker-positive CSCs, hampering the development of personalized CSC-targeted therapy. Here, we show that CSC markers EpCAM and CD90 are independently expressed in liver cancer. In primary HCC, EpCAM+ and CD90+ cells resided distinctively, and gene-expression analysis of sorted cells suggested that EpCAM+ cells had features of epithelial cells, whereas CD90+ cells had those of vascular endothelial cells. Clinicopathological analysis indicated that the presence of EpCAM+ cells was associated with poorly differentiated morphology and high serum alpha-fetoprotein (AFP), whereas the presence of CD90+ cells was associated with a high incidence of distant organ metastasis. Serial xenotransplantation of EpCAM+ /CD90+ cells from primary HCCs in immune-deficient mice revealed rapid growth of EpCAM+ cells in the subcutaneous lesion and a highly metastatic capacity of CD90+ cells in the lung. In cell lines, CD90+ cells showed abundant expression of c-Kit and in vitro chemosensitivity to imatinib mesylate. Furthermore, CD90+ cells enhanced the motility of EpCAM+ cells when cocultured in vitro through the activation of transforming growth factor beta (TGF-β) signaling, whereas imatinib mesylate suppressed TGFB1 expression in CD90+ cells as well as CD90+ cell-induced motility of EpCAM+ cells. CONCLUSION: Our data suggest the discrete nature and potential interaction of EpCAM+ and CD90+ CSCs with specific gene-expression patterns and chemosensitivity to molecular targeted therapy. The presence of distinct CSCs may determine the clinical outcome of HCC.

UNLABELLED: Radiofrequency ablation (RFA) is one of the treatments for hepatocellular carcinoma (HCC) and is known to enhance host immune response. However, the epitopes to which enhanced immune responses occur, the impact on patient prognosis, and the functions and phenotype of T cells induced are still unclear. To address these issues, we analyzed immune responses before and after RFA in 69 HCC patients using 11 tumor-associated antigen (TAA)-derived peptides that we identified to be appropriate to analyze HCC-specific immune responses. The immune responses were analyzed using enzyme-linked immunospot (ELISPOT) assay and tetramer assays using peripheral blood mononuclear cells. An increase in the number of TAA-specific T cells detected by interferon-γ ELISPOT assays occurred in 62.3% of patients after RFA. The antigens and their epitope to which enhanced T cell responses occur were diverse, and some of them were newly induced. The number of TAA-specific T cells after RFA was associated with the prevention of HCC recurrence, and it was clarified to be predictive of HCC recurrence after RFA by univariate and multivariate analyses. The number of TAA-specific T cells after RFA was inversely correlated with the frequency of CD14+ HLA-DR(-/low) myeloid-derived suppressor cells (MDSCs). The modification of T cell phenotype was observed after RFA. The number of TAA-specific T cells at 24 weeks after RFA was decreased. CONCLUSION: Although RFA can enhance various TAA-specific T cell responses and the T cells induced contribute to the HCC recurrence-free survival of patients, besides immunosuppression by MDSCs, the memory phenotype and lifetime of TAA-specific T cells are not sufficient to prevent HCC recurrence completely. Additional treatments by vaccine or immunomodulatory drugs might be useful to improve the immunological effect of RFA.