• Molecules and Cells
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• v.45 no.8
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• pp.513-521
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• 2022

Cytotoxic T lymphocyte antigen-4 (CTLA-4) is an immune checkpoint molecule that is mainly expressed on activated T cells and regulatory T (Treg) cells that inhibits T-cell activation and regulates immune homeostasis. Due to the crucial functions of CTLA-4 in T-cell biology, CTLA-4-targeted immunotherapies have been developed for autoimmune disease as well as cancers. CTLA-4 is known to compete with CD28 to interact with B7, but some studies have revealed that its downstream signaling is independent of its ligand interaction. As a signaling domain of CTLA-4, the tyrosine motif plays a role in inhibiting T-cell activation. Recently, the lysine motif has been shown to be required for the function of Treg cells, emphasizing the importance of CTLA-4 signaling. In this review, we summarize the current understanding of CTLA-4 biology and molecular signaling events and discuss strategies to target CTLA-4 signaling for immune modulation and disease therapy.

• Journal of Microbiology and Biotechnology
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• v.22 no.8
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• pp.1066-1076
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• 2012

Previous observations demonstrated that various immunosuppressive agents and their combination therapies can increase allograft survival rates. However, these treatments may have serious side effects and cannot substantially improve or prolong graft survival in acute graft-versus-host disease (GVHD). To improve the therapeutic potency of divalent immunoadhesins, we have constructed and produced several tetravalent forms of immunoadhesins comprising each of cytotoxic T-lymphocyte-associated antigen-4 (CTLA4), CD2, and lymphocyte activation gene-3 (LAG3). Flow cytometric and T cell proliferation analyses displayed that tetravalent immunoadhesins have a higher binding affinity and more potent efficacy than divalent immunoadhesins. Although all tetravalent immunoadhesins possess better efficacies, tetravalent forms of CTLA4-Ig and LAG3-Ig revealed higher inhibitory effects on T cell proliferation than tetravalent forms of TNFR2-Ig and CD2-Ig. In vitro mixed lymphocytes reaction (MLR) showed that combined treatment with tetravalent CTLA4-Ig and tetravalent LAG3-Ig was highly effective for inhibiting T cell proliferation in both human and murine allogeneic stimulation. In addition, both single tetravalent-form and combination treatments can prevent the lethality of murine acute GVHD. The results of this study demonstrated that co-blockade of the major histocompatibility complex class (MHC)II:T cell receptor (TCR) and CD28:B7 pathways by using tetravalent human LAG3-Ig and CTLA4-Ig synergistically prevented murine acute GVHD.

• IMMUNE NETWORK
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• v.5 no.3
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• pp.172-178
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• 2005

Background: Carcinoembryonic antigen (CEA) is well-known soluble tumor marker frequently detectable in peripheral blood of carcinoma patients and considered as good target for antigen-specific immunotherapy. However, it is known that the induction of immune response to CEA is very difficult because CEA is a self-antigen expressed in fetal cells and weakly expressed in normal colorectal epithelial cells. To enhance anti-tumor immunity specific for CEA, recombinant CEA protein was modified using listeriolysin O (LLO) for endosomal lysis and trans activator of transcription (Tat) domain for transducing extracellular proteins into cytoplasm. Methods: After immunization using dendritic cells pulsed with Tat-CEA, both Tat-CEA and LLO, and both Tat-CEA and Tat-LLO, antibody titer to CEA and LLO, cytotoxic T lymphocyte activity and the frequency of IFN-${\gamma}$ producing T lymphocytes were measured. Results: Immunization using DC pulsed with both Tat-CEA and Tat-LLO protein showed the increasement of production of CEA-specific antibody in serum, cytotoxic T lymphocyte activity, the frequency of IFN-${\gamma}$ secreting T cells, compared with DC pulsed with both Tat-CEA and LLO. Furthermore the ratio of CD8+T cell to $CD4^+$ cell among CEA-specific T cells was increased in group pulsed with both Tat-CEA and Tat-LLO. Conclusion: These results suggested that DC vaccine using Tat-LLO could be used for the development of effective immunotherapy for the treatment of tumor.

• Radiation Oncology Journal
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• v.34 no.4
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• pp.250-259
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• 2016

Immune checkpoint blockades including monoclonal antibodies (mAbs) of cytotoxic T-lymphocyte antigen-4 (CTLA-4), programmed death-1 (PD-1), and programmed death-ligand 1 (PD-L1) have been emerged as a promising anticancer therapy. Several immune checkpoint blockades have been approved by US Food and Drug Administration (FDA), and have shown notable success in clinical trials for patients with advanced melanoma and non-small cell lung cancer. Radiotherapy is a promising combination partner of immune checkpoint blockades due to its potent pro-immune effect. This review will cover the current issue and the future perspectives for combined with radiotherapy and immune checkpoint blockades based upon the available preclinical and clinical data.

• Asian Pacific Journal of Cancer Prevention
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• v.17 no.3
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• pp.905-910
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• 2016

Breast cancer is one of the major threats to female health, and its incidence is rapidly increasing in many countries. Currently, breast cancer is treated with surgery, followed by chemotherapy or radiation therapy, or both. However, a substantial proportion of breast cancer patients might have a risk for local relapse that leads to recurrence of their disease and/or metastatic breast cancer. Therefore searching for new and potential strategies for breast cancer treatment remains necessary. Immunotherapy is an attractive and promising approach that can exploit the ability of the immune system to identify and destroy tumors and thus prevent recurrence and metastatic lesions. The most promising and attractive approach of immunotherapeutic research in cancer is the blockade of immune checkpoints. In this review, we discuss the potential of certain inhibitors of immune checkpoints, such as antibodies targeting cytotoxic T-lymphocyte antigen 4 (CTLA-4), programmed death 1 (PD-1) and lymphocyte activation gene-3 (LAG-3), in breast cancer therapeutics. Immune checkpoint inhibitors may represent future standards of care for breast cancer as monotherapy or combined with standard therapies.

• Korean Journal of Microbiology
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• v.49 no.3
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• pp.221-227
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• 2013

Human immunodeficiency virus (HIV), hepatitis B virus (HBV), and hepatitis C virus (HCV) cause viral infections that lead to chronic diseases. When they invade human body, virus specific T cells play an important role in antiviral effector functions including killing virus-infected cells and helping B cells to produce specific antibodies against viral proteins. The antiviral activity of T cells is usually affected by immune-regulatory factors that express on surface of T cells. Recently, many researchers have investigated the relationship between effector functions of virus specific T cells and characteristics of immune regulatory factors (e.g., CD28, CD25, CD45RO, FoxP3, PD-1, CTLA-4). In particular, Immune inhibitory molecules such as forkhead box P3 (FoxP3), programmed death-1 (PD-1), and cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) are associated with T-cell dysfunction. They are shown to be up-regulated in chronic viral diseases such as hepatitis B, hepatitis C or human immunodeficiency virus infection. Therefore, the positive correlation between viral persistence and expression of immune regulatory factors (FoxP3, PD-1, and CTLA-4) has been suggested. In this review, the roles of immune regulatory factors FoxP3, PD-1, and CTLA-4 were discussed in chronic viral diseases such as HIV, HBV, or HCV.

• Asian-Australasian Journal of Animal Sciences
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• v.22 no.1
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• pp.20-25
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• 2009

Xenotransplantation of pig organs into humans is a potential solution for the shortage of donor organs for transplantation. However, multiple immune barriers preclude its clinical application. In particular, the initial type of rejection in xenotransplantation is an acute cellular rejection by host $CD8^+$ cytotoxic T lymphocyte (CTL) cells that react to donor major histocompatibility complex (MHC) class I. The human cytomegalovirus (HCMV) glycoprotein Unique Short (US) 2 specifically targets MHC class I heavy chains to relocate them from the endoplasmic reticulum (ER) membrane to the cytosol, where they are degraded by the proteasome. In this study we transfected the US2 gene into minipig fetal fibroblasts and established four US2 clonal cell lines. The integration of US2 into transgenic fetal cells was confirmed using PCR and Southern blot assay. The reduction of Swine Leukocyte Antigen (SLA)-I by US2 was also detected using Flow cytometry assay (FACS). The FACS analysis of the US2 clonal cell lines demonstrated a substantial reduction in SLA-I surface expression. The level (44% to 76%) of SLA-I expression in US2 clonal cell lines was decreased relative to the control. In cytotoxicity assay the rate of $CD8^+$ T cell-mediated cytotoxicity was significantly reduced to 23.8${\pm}$15.1% compared to the control (59.8${\pm}$8.4%, p<0.05). In conclusion, US2 can directly protect against $CD8^+$-mediated cell lysis. These results indicate that the expression of US2 in pig cells may provide a new approach to overcome the CTL-mediated immune rejection in xenotransplantation.

• Asian Pacific Journal of Cancer Prevention
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• v.16 no.2
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• pp.571-578
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• 2015

Prostate cancer is the most common cancer in men. In this study, we investigated immune responses of cytotoxic T lymphocytes (CTLs) against TRAMP-C2 prostate cancer cells after activation by dendritic cells (DCs) loaded with TRAMP-C2 freeze-thaw antigen and/or PEP-3 peptide in vitro. Bone marrow-derived DC from the bone marrow of the C57BL/6 were induced to mature by using the cytokine of rhGM-CSF and rhIL-4, and loaded with either the freeze-thaw antigen or PEP-3 peptide or both of them. Maturation of DCs was detected by flow cytometry. The killing efficiency of the CTLs on TRAMP-C2 cells were detected by flow cytometry, CCK8, colony formation, transwell migration, and wound-healing assay. The levels of the IFN-${\gamma}$, TNF-${\beta}$ and IL-12 were measured by enzyme-linked immunosorbent assay (ELISA). Compared with the unloaded DCs, the loaded DCs had significantly increased expression of several phenotypes related to DC maturation. CTLs activated by DCs loaded with freeze-thaw antigen and PEP-3 peptide had more evident cytotoxicity against TRAMP-C2 cells in vitro. The secretion levels of IFN-${\gamma}$, TNF-${\beta}$ and IL-12, secreted by DCs loaded with antigen and PEP-3 and interaction with T cells, were higher than in the other groups. Our results suggest that the CTLs activated by DCs loaded with TRAMP-C2 freeze-thaw antigen and PEP-3 peptide exert a remarkable killing efficiency against TRAMP-C2 cells in vitro.

• Asian Pacific Journal of Cancer Prevention
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• v.17 no.8
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• pp.3785-3791
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• 2016

Background: Previous studies have assessed the association between the Cytotoxic T-lymphocyte Antigen-4(CTLA-4) polymorphism with the risk of malignant bone tumor, but the conclusions were inconsistent. We aimed to clarify association of cytotoxic T-lymphocyte antigen-4 polymorphisms with malignant bone tumors risk by performing a meta-analysis. Materials and Methods: The databases including PubMed, EMBase databases and the Cochrane Library were searched to identify the eligible studies prior to January 30 2016. Odds ratio (OR) with 95% confidence interval (95%CI) were used to estimate the strengths of the association between the CTLA-4 polymorphism and the malignant bone tumor risks. The meta-analysis was performed by STATA 12.0. Results: Four individual studies with a total of 1003 cases with malignant bone tumor and 1162 controls were included in our meta-analysis. The results of meta-analysis on those data demonstrated that CTLA-4 +49G>A polymorphism was associated with the risk of Ewing's sarcoma and osteosarcoma strongly (A vs. G: OR=1.36, 95%CI:1.20-1.54, p=0.000; AA+AG vs. GG: OR=1.35, 95%CI:1.14-1.61, p=0.001; AA vs. GG: OR=2.24, 95%CI:1.67-2.99, p=0.000; AA vs. AG+GG: OR=2.00, 95%CI:1.53-2.62, p=0.000), but CTLA-4 -318C/T polymorphism was not associated with the risk of malignant bone tumor (C vs. T: OR=0.76, 95%CI:0.76-1.08, p= 0.262; CC+CT vs. TT: OR=0.70, 95%CI:0.41-1.20, p= 0.198; CC vs. TT: OR=0.69, 95%CI:0.40-1.19, p= 0.183; CC vs. CT+TT: OR=0.92, 95%CI:0.75-1.13, p= 0.419). Subgroup analysis showed that there are significantly positive correlations between CTLA-4 +49G>A polymorphism and increased risks of malignant bone tumors in large size of sample (A vs. G: OR=1.347, 95%CI: 1.172,1.548, p=0.000; AA vs. GG: OR=2.228, 95%CI: 1.608,3.085, p=0.000), Ewing's Sarcoma or Osteosarcoma (A vs. G: OR=1.361, 95%CI: 1.201,1.540, p=0.000; AA vs. GG: OR=2.236, 95%CI: 1.674,2.986, p=0.000), and PCR-RFLP or Sequencing(A vs. G: OR=1.361, 95%CI: 1.201,1.540, p=0.000; AA vs. GG: OR=2.236, 95%CI: 1.674,2.986, p=0.000), but CTLA-4 -318C/T polymorphism was not associated with the risk of malignant bone tumors in diagnosis, genotype method, and sample size (all p>0.05). Conclusions: CTLA-4 +49A/G variant was associated with an increased risk of developing the malignant bone tumors, such as Ewing's sarcoma and osteosarcoma. However, it failed to show the association between CTLA-4 -318C/T polymorphism and the risk of malignant bone tumors. Future large-scale studies remain to be done to confirm our conclusions.

• IMMUNE NETWORK
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• v.2 no.1
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• pp.35-40
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• 2002

Background: CTLA-4 (Cytotoxic T Lymphocyte associated Antigen 4, CD152) has been known as a homologue of CD28, an accessory molecule providing a key costimulatory signal for successful antigen-driven activations of T lymphocyte. Most of biochemical and cell biological characteristics of the CD152 protein remain unknown while those of CD28 have been characterized in detail. Methods: In this study CD152 expression in both $CD4^+$ and $CD8^+$ PBLs was studied by using flow cytometry. And intracellular CD152 multiprotein complex was purified and used for generating antibodies recognizing proteins composing of intracellular CTLA-4 multi protein complex. Results: Level of surface expression of this molecule was peaked at 2 days of PHA stimulation in flow cytometric analysis. 40~45% of PHA blast cells were $CD152^+$ in both of two subsets at this stage and the level of expression were equivalent in both two subsets. Contrary to this surface expression, intracellular expression was peaked at day 3 and it was preferentially induced in $CD8^+$ cells and about 60% of $CD8^+$ cells were $CD152^+$ at this stage. High molecular weight (>350 kD) intacellular CD152 protein complex purified by using preparative electrophoresis were immunized into rabbits and then 3 different anti-P34PC4, anti-P34PC7 and anti-P34PC8 antibodies were obtained. Using these 3 antibodies two unknown antigens associated with intracellular CD152 multiprotein complex were found and their molecular weights were 54 kD and 75 kD, respectively. Among these, the former was present as 110 kD homodimer in non-reducing condition. Conclusion: It seemed that 34 kD intracellular CD152 molecule forms high molecular weight multiprotein complex at least with 2 proteins of 75 kD monomer and 110 kD homodimer.