The interaction between T cell immunoglobulin- and mucin-domain-containing molecule (Tim-3) expressed on T helper 1 (Th1) cells, and its ligand, galectin-9, negatively regulates Th1-mediated immune responses. However, it is poorly understood if and how the Tim-3/galectin-9 signaling pathway is involved in immune escape in patients with hepatocellular carcinoma (HCC). Here we studied the expression, function, and regulation of the Tim-3/galectin-9 pathway in patients with hepatitis B virus (HBV)-associated HCC. We detected different levels of galectin-9 expression on antigen-presenting cell (APC) subsets including Kupffer cells (KCs), myeloid dendritic cells (DCs), and plasmacytoid DCs in HCC. The highest galectin-9 expression was on KCs in HCC islets, not in the adjacent tissues. Furthermore, Tim-3 expression was increased on CD4(+) and CD8(+) T cells in HCC as compared to the adjacent tissues, and Tim-3(+) T cells were replicative senescent and expressed surface and genetic markers for senescence. Interestingly, tumor-infiltrating T-cell-derived interferon (IFN)-γ stimulated the expression of galectin-9 on APCs in the HCC microenvironment. Immunofluorescence staining revealed a colocalization of Tim-3(+) T cells and galectin-9(+) KCs in HCC. Functional studies demonstrated that blockade of the Tim-3/galectin-9 signaling pathway importantly increased the functionality of tumor-infiltrating Tim-3(+) T cells as shown by increased T-cell proliferation and effector cytokine production. Finally, we show that the numbers of Tim-3(+) tumor-infiltrating cells were negatively associated with patient survival.
Conclusion: Our work demonstrates that the Tim-3/galectin-9 signaling pathway mediates T-cell senescence in HBV-associated HCC. The data suggest that this pathway could be an immunotherapeutic target in patients with HBV-associated HCC.
Copyright © 2012 American Association for the Study of Liver Diseases.