ABSTRACT
Inhibiting the cytotoxic T-lymphocyte-associated protein-4 (CTLA-4)-mediated immune checkpoint system using an anti-CTLA-4 antibody (Ab) can suppress the growth of various cancers, but the detailed mechanisms are unclear. In this study, we established a monoclonal hepatocellular carcinoma cell line (Hepa1-6 #12) and analyzed the mechanisms associated with anti-CTLA-4 Ab treatment. Depletion of CD4+ T cells, but not CD8+ T cells, prevented anti-CTLA-4 Ab-mediated anti-tumor effects, suggesting dependence on CD4+ T cells. Anti-CTLA-4 Ab treatment resulted in recruitment of interferon-gamma (IFN-g)-producing CD4+ T cells, called T-helper 1 (Th1), into tumors, and neutralization of IFN-g abrogated the anti-tumor effects. Moreover, tumor growth suppression did not require major histocompatibility complex (MHC)-I or MHC-II expression on cancer cells. In vitro studies showed that IFN-g can induce cell cycle arrest and apoptosis in tumor cells. Taken together, these data demonstrate that anti-CTLA-4 Ab can exert its anti-tumor effects through Th1-mediated cell cycle arrest and apoptosis.
Subject(s)
Apoptosis , CTLA-4 Antigen , Carcinoma, Hepatocellular , Cell Cycle Checkpoints , Interferon-gamma , Liver Neoplasms , Th1 Cells , Carcinoma, Hepatocellular/drug therapy , Carcinoma, Hepatocellular/pathology , Carcinoma, Hepatocellular/metabolism , Apoptosis/drug effects , Animals , Th1 Cells/immunology , Th1 Cells/drug effects , CTLA-4 Antigen/antagonists & inhibitors , CTLA-4 Antigen/metabolism , Liver Neoplasms/drug therapy , Liver Neoplasms/pathology , Liver Neoplasms/metabolism , Cell Cycle Checkpoints/drug effects , Mice , Cell Line, Tumor , Interferon-gamma/metabolism , Humans , Mice, Inbred C57BL , Cell Proliferation/drug effects , Antibodies, Monoclonal/pharmacology , Antibodies, Monoclonal/therapeutic useABSTRACT
The ex vivo production of platelets depleted of human leukocyte antigen class I (HLA-I) could serve as a universal measure to overcome platelet transfusion refractoriness caused by HLA-I incompatibility. Here, we developed human induced pluripotent cell-derived HLA-I-deficient platelets (HLA-KO iPLATs) in a clinically applicable imMKCL system by genetic manipulation and assessed their immunogenic properties including natural killer (NK) cells, which reject HLA-I downregulated cells. HLA-KO iPLATs were deficient for all HLA-I but did not elicit a cytotoxic response by NK cells in vitro and showed circulation equal to wild-type iPLATs upon transfusion in our newly established Hu-NK-MSTRG mice reconstituted with human NK cells. Additionally, HLA-KO iPLATs successfully circulated in an alloimmune platelet transfusion refractoriness model of Hu-NK-MISTRG mice. Mechanistically, the lack of NK cell-activating ligands on platelets may be responsible for evading the NK cell response. This study revealed the unique non-immunogenic property of platelets and provides a proof of concept for the clinical application of HLA-KO iPLATs.