CTLA-4 promotes lymphoma progression through tumor stem cell enrichment and immunosuppression.

Recently, systemic administration of a human monoclonal antibody directed against cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) expressed on circulating T cells in patients with chronic lymphocytic leukaemia (CLL) has been considered. Also, CLL cells have been shown to express CTLA-4, increased levels of which in the leukaemic compartment are a predictor of good clinical outcome. Since both CLL and Treg microenvironment cells can be targeted by the CTLA-4 blocking antibody in this immunotherapy approach, the investigation of the functional effect of CTLA-4 blockade on CLL cells might be of potential clinical relevance. The main aim of this study was to examine the effect of CTLA-4 blockade on proliferation activity and apoptosis of CLL cells in patients with low and high CTLA-4 expression. We found that in the high CTLA-4-expressing CLL group, CTLA-4 blockade on the CLL cell surface resulted in a significant increase in the median percentages of Ki67+ cells and a tendency to decrease in the proportion of apoptotic cells. In contrast, in the low CTLA-4 expressors, CTLA-4 blockade did not affect the proliferation activity or the frequency of apoptosis. This study reports for the first time the different effect of CTLA-4 blockade on CLL cells in CLL patients depending on the levels of CTLA-4 expression. CTLA-4 blockade seems to induce pro-survival signals in leukaemic cells from CLL patients exhibiting high CTLA-4 expression, suggesting that an immunotherapy approach based on the systemic use of monoclonal anti-CTLA-4 antibodies could be an unfavourable strategy for some CLL patients.

Cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) is an immune checkpoint expressed in regulatory T (Treg) cells and activated T lymphocytes. Despite its potential as a treatment strategy for melanoma, CTLA-4 inhibition has limited efficacy. Using data from The Cancer Genome Atlas (TCGA) melanoma database and another dataset, we found that decreased CTLA4 mRNA was associated with a poorer prognosis in metastatic melanoma. To investigate further, we measured blood CTLA4 mRNA in 273 whole-blood samples from an Australian cohort and found that it was lower in metastatic melanoma than in healthy controls and associated with worse patient survival. We confirmed these findings using Cox proportional hazards model analysis and another cohort from the US. Fractionated blood analysis revealed that Treg cells were responsible for the downregulated CTLA4 in metastatic melanoma patients, which was confirmed by further analysis of published data showing downregulated CTLA-4 surface protein expression in Treg cells of metastatic melanoma compared to healthy donors. Mechanistically, we found that secretomes from human metastatic melanoma cells downregulate CTLA4 mRNA at the post-transcriptional level through miR-155 while upregulating FOXP3 expression in human Treg cells. Functionally, we demonstrated that CTLA4 expression inhibits the proliferation and suppressive function of human Treg cells. Finally, miR-155 was found to be upregulated in Treg cells from metastatic melanoma patients compared to healthy donors. Our study provides new insights into the underlying mechanisms of reduced CTLA4 expression observed in melanoma patients, demonstrating that post-transcriptional silencing of CTLA4 by miRNA-155 in Treg cells may play a critical role. Since CTLA-4 expression is downregulated in non-responder melanoma patients to anti-PD-1 immunotherapy, targeting miRNA-155 or other factors involved in regulating CTLA4 expression in Treg cells without affecting T cells could be a potential strategy to improve the efficacy of immunotherapy in melanoma. Further research is needed to understand the molecular mechanisms regulating CTLA4 expression in Treg cells and identify potential therapeutic targets for enhancing immune-based therapies.

Genetic variation in ICOS regulates mRNA levels of ICOS and splicing isoforms of CTLA4

Recent evidence has pointed out that the cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) expression is a poor prognosis factor. However, the implications of CTLA-4 expression on circulating inflammatory mediators are unclear for breast cancer. Tumor biopsies and blood samples were collected from 117 breast cancer patients. Oxidative stress parameters were evaluated in plasma samples by measuring the lipoperoxidation profile and nitric oxide metabolites (NOx). Interleukins 12 (IL-12) and 4 (IL-4) were assessed by ELISA. CTLA-4 expression was determined by immunofluorescence assessed by its labeling in tumor-infiltrating leukocytes (TILs) or breast tumors. Correlations between CTLA-4 expression in breast tumors with TCD4/TCD8 infiltrating lymphocyte and inflammation-related genes were performed using data from TIMER 2.0/TCGA databases (n = 2160). CTLA-4 expression in TILs significantly correlated to triple-negative breast tumors. Patients carrying CTLA-4-positive tumors exhibited lower plasmatic NOx levels, and those expressing CTLA-4 in TILs had reduced levels of IL-12 in plasma. No changes in either IL-4 or lipid peroxidation profiles were detected concerning any CTLA4 status. Compared to the Luminal A ones, oxidative stress parameters and cytokines were observed in patients bearing triple-negative tumors. CTLA-4 expression in all breast cancer subtypes positively correlated to TCD4/TCD8 lymphocyte infiltrates, as well as to the pro-inflammatory genes IL12A, IL4, NFKB1, NFKB2, NOS1, NOS2, and NOS3. CTLA-4 expression in both tumor and TILs can affect the systemic inflammatory status of breast cancer patients, especially antitumor molecules such as IL-12 and NOx that correlate to more aggressive disease.

The new quest in CTLA-4 insufficiency: How to immune modulate effectively?

Objective: To investigate the survival and death risk factors of mesothelioma cases stratified by the expression levels of CD8 and cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) , providing new clue to evaluate disease progression and clinical outcome. Methods: This was a retrospective case report, which included 47 clinically and pathologically confirmed mesothelioma cases on November 2016. Their clinical and pathological information, asbestos exposure history and survival data were collected. Infiltrated lymphocyte, 5-methylcytosine (5-mC) , CTLA-4, CD8 and Ki-67 antigen were detected using hematoxylin-eosin staining and immunohistochemistry. Survival time and death risk factors of mesothelioma patients with different CD8 and CTLA-4 protein expression characteristics were analyzed. And analyze the influence of Ki-67 expression on the survival of patients with different CD8 and CTLA-4 protein and gene expression characteristics. Results: Among the 47 cases, 63.8% (30/47) had low/medium level of infiltrated lymphocyte. The immunohistochemistry scores of CTLA-4, CD8, 5-mC and Ki-67 were 92.97 (54.95, 120.65) , 72.41 (36.62, 89.82) , 11.09 (3.40, 52.89) and 5.88 (2.41, 11.48) , respectively. Patients with CD8(high) CTLA-4(high) had higher 5-mC level than those with CD8(high) CTLA-4(low) (P<0.01) . The median survival time of 27 cases was 0.83±0.29 year. The median survival times of those with CD8(high) CTLA-4(high) and CD8(high) CTLA-4(low) were 0.58±0.51 year and 0.83±0.30 year, respectively (P=0.521) . The immunohistochemistry score of Ki-67 ≥5.88 was an independent death risk factor for patients with CD8(high) CTLA-4(low) (HR=8.40, P=0.01) . Under different CD8 and CTLA-4 protein expression characteristics, in the patients with CD8(high) CTLA-4(low), the median survival times of those with high and low Ki-67 expression were 0.57±0.11 years and 2.31±0.46 years, respectively (P<0.01) . Under different CD8 and CTLA-4 mRNA expression characteristics, in the patients with CD8(high) CTLA-4(low), the median survival times of those with high and low Ki-67 mRNA expression were 1.20±0.36 years and 3.38±0.43 years, respectively (P=0.018) . Conclusion: Mesothelioma case with high CD8 but low CTLA-4 content might coexist DNA hypomethylation. In the presence of high Ki-67 expression, their survival time appears to be shortened with increased death risk.

Background and ObjectivesMyasthenia gravis (MG) is an autoimmune disease associated with comorbid thymoma in 10%–15% of cases. Cytotoxic T lymphocyte–associated antigen 4 (CTLA4) expressed by T cells downregulates T-cell–mediated immune response. Polymorphisms in the CTLA4 gene have been associated with the development of MG. In this context, we aimed to determine whether CTLA4 expression in the thymoma differs between patients with and without MG and whether CTLA4 gene polymorphisms are associated with these differences.MethodsThis is a retrospective study of all patients, with and without MG, surgically treated at our institution for thymoma between January 2010 and December 2020. Ten samples were obtained from normal thymuses as controls. The number of CTLA4-positive cells in paraffin-embedded thymoma samples was determined by immunohistochemistry. The presence of follicular-center and regulatory T-cell lymphocytes was determined by immunohistochemistry (B-cell lymphoma [BCL]-6 expression) and double immunofluorescence–based staining of CD4-FOXP3, respectively. We evaluated the association between thymic expression of CTLA4 and the development of MG. We also determined the association between CTLA4 expression and various clinical and prognostic characteristics of MG. We sequenced the CTLA4 gene and evaluated possible associations between CTLA4 polymorphisms and thymic CTLA4 expression. Finally, we assessed the potential association between these polymorphisms and the risk of MG.ResultsForty-one patients with thymoma were included. Of them, 23 had comorbid MG (56.1%). On average, patients with MG had fewer CTLA4-positive cells in the thymoma than non-MG patients: 69.3 cells/mm2 (95% CIs: 39.6–99.1) vs 674.4 (276.0–1,024.0) cells/mm2; p = 0.001 and vs controls (200.74 [57.9–343.6] cells/mm2; p = 0.02). No between-group differences (MG vs non-MG) were observed in the number of cells positive for BCL6 or CD4-FOXP3. CTLA4 expression was not associated with differences in MG outcome or treatment refractoriness. Two polymorphisms were detected in the CTLA4 gene, rs231770 (n = 30 patients) and rs231775 (n = 17). MG was present in a similar proportion of patients for all genotypes. However, a nonsignificant trend toward a lower CTLA4-positive cell count was observed among carriers of the rs231775 polymorphism vs noncarriers: 77.9 cells/mm2 (95% CI: −51.5 to 207.5) vs 343.3 cells/mm2 (95% CI: 126.2–560.4).DiscussionReduced CTLA4 expression in thymoma may predispose to a higher risk of developing MG.

Objective To investigate the effect of high mobility group box-1 protein (HMGBI)on the expression of cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) in regulatory T cells (Treg)and its potential receptor mechanism in mice.Methods CD4+ CD25+ Tregs isolated from the spleens of C3H/HeN [ Toll-like receptor 4 (TLR4) wild type ] mice by magnetic beads were seeded on 96-well cell culture plates coated with 1 mg/L anti-CD3 and soluble CD28.By treatment with or without anti-mouse TLR4 antibody,the time-and dose-dependent responses between HMGBI stimulation and CTLA-4 expres-sion on CD4+ CD25+ Tregs were studied.Results Compared to normal controls, the expression of CTLA-4 on CD4+ CD25+ Tregs stimulated by 0.1 mg/L HMGBI was significantly down-regulated at 24,48,and 72 h (47.56±5.49,35.83±4.96, and 31.94±4.65, respectively) (all P<0.01), especially at 48 and 72 h.Meanwhile, markedly decreased expression of CTLA-4 was found CD4+ CD25+ Tregs treated with HMGB1 at various concentrations (0.01,0.1 and 1 mg/L) for 48 h (58.87±6.70,33.34±4.00 and 29.90±4.30, respectively, all P<0.01).After pretreatment with TLR4 antibody, however, the CTLA-4 expression on CD4+ CD25+ Tregs was significantly enhanced by HMGB1 (0.1 Mg/L) stimulation at 24,48 and 72H(90.39±8.80,93.13±4.80 and 80.and 80.29±4.31,respectively,P<0.05 or P,0.01).After treatment with different doses of HMGB1 for 48 h,the CTLA-4 expression on CD4+CD25+Tregs was much higher in 0.1 mg/L HMGB1 group(94.98±6.35)than in mormal controls(P<0.01).Conclusion With HMGB1 stimulation,TLR4 can markedly down-regulate CTLA-a expression levels on CD4+CD25+Tregs,thereby influencing the immunlolgical activity of Tregs. Key words: High mobility group box 1 protein; Toll like reecreptor; Regulatory T cells

Cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) targeted therapy by anti-CTLA-4 monoclonal antibody (mAb) is highly effective in cancer patients. However, it is extremely expensive and potentially produces autoimmune-related adverse effects. Therefore, the development of a method to evaluate CTLA-4 expression prior to CTLA-4-targeted therapy is expected to open doors to evidence-based and cost-efficient medical care and to avoid adverse effects brought about by ineffective therapy. In this study, we aimed to develop a molecular imaging probe for CTLA-4 visualization in tumor. First, we examined CTLA-4 expression in normal colon tissues, cultured CT26 cells, and CT26 tumor tissues from tumor-bearing BALB/c mice and BALB/c nude mice by reverse transcription polymerase chain reaction (RT-PCR) analysis and confirmed whether CTLA-4 is strongly expressed in CT26 tumor tissues. Second, we newly synthesized 64Cu-1,4,7,10-tetraazacyclododecane-N,N′,N″,N‴-tetraacetic acid-anti-mouse CTLA-4 mAb (64Cu-DOTA-anti-CTLA-4 mAb) and evaluated its usefulness in positron emission tomography (PET) and ex-vivo biodistribution analysis in CT26-bearing BALB/c mice. High CTLA-4 expression was confirmed in the CT26 tumor tissues of tumor-bearing BALB/c mice. However, CTLA-4 expression was extremely low in the cultured CT26 cells and the CT26 tumor tissues of tumor-bearing BALB/c nude mice. The results suggested that T cells were responsible for the high CTLA-4 expression. Furthermore, 64Cu-DOTA-anti-CTLA-4 mAb displayed significantly high accumulation in the CT26 tumor, thereby realizing non-invasive CTLA-4 visualization in the tumor. Together, the results indicate that 64Cu-DOTA-anti-CTLA-4 mAb would be useful for the evaluation of CTLA-4 expression in tumor.

Increased cAMP-PKA signaling pathway activation is involved in up-regulation of CTLA-4 expression in CD4+ T cells in acute SIVmac239-infected Chinese rhesus macaques

T Cells from Chronic Lymphocytic Leukemia (CLL) Patients Display Dysregulated Expression of Immune Checkpoint Molecules and Activation Markers Mainly Restricted to CD4+ Cells and Correlated with Disease Activity

Intrahepatic cholangiocarcinoma (ICC) is highly invasive and carries high mortality due to limited therapeutic strategies. In other solid tumors, immune checkpoint inhibitors (ICIs) target cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) and programmed death 1 (PD1), and the PD1 ligand PD-L1 has revolutionized treatment and improved outcomes. However, the relationship and clinical significance of CTLA-4 and PD-L1 expression in ICC remains to be addressed. Deciphering CTLA-4 and PD-L1 interactions in ICC enable targeted therapy for this disease. In this study, immunohistochemistry (IHC) was used to detect and quantify CTLA-4, forkhead box protein P3 (FOXP3), and PD-L1 in samples from 290 patients with ICC. The prognostic capabilities of CTLA-4, FOXP3, and PD-L1 expression in ICC were investigated with the Kaplan–Meier method. Independent risk factors related to ICC survival and recurrence were assessed by the Cox proportional hazards models. Here, we identified that CTLA-4+ lymphocyte density was elevated in ICC tumors compared with peritumoral hepatic tissues (P <.001), and patients with a high density of CTLA-4+ tumor-infiltrating lymphocytes (TILsCTLA-4 High) showed a reduced overall survival (OS) rate and increased cumulative recurrence rate compared with patients with TILsCTLA-4 Low (P <.001 and P = .024, respectively). Similarly, patients with high FOXP3+ TILs (TILsFOXP3 High) had poorer prognoses than patients with low FOXP3+ TILs (P = .021, P = .034, respectively), and the density of CTLA-4+ TILs was positively correlated with FOXP3+ TILs (Pearson r = .31, P <.001). Furthermore, patients with high PD-L1 expression in tumors (TumorPD-L1 High) and/or TILsCTLA-4 High presented worse OS and a higher recurrence rate than patients with TILsCTLA-4 LowTumorPD-L1 Low. Moreover, multiple tumors, lymph node metastasis, and high TumorPD-L1/TILsCTLA-4 were independent risk factors of cumulative recurrence and OS for patients after ICC tumor resection. Furthermore, among ICC patients, those with hepatolithiasis had a higher expression of CTLA-4 and worse OS compared with patients with HBV infection or undefined risk factors (P = .018). In conclusion, CTLA-4 is increased in TILs in ICC and has an expression profile distinct from PD1/PD-L1. TumorPD-L1/TILsCTLA-4 is a predictive factor of OS and ICC recurrence, suggesting that combined therapy targeting PD1/PD-L1 and CTLA-4 may be useful in treating patients with ICC.

Cytokine-induced killer (CIK) cells are in vitro-expanded cells harboring potent toxicity against tumor cells. Recently, it was identified that the cytotoxicity and proliferation of CIK cells are restricted by a prolonged CIK cell culture period. Cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) serves a negative role in T cell activation and proliferation. This study aims to determine whether CTLA-4 expression is associated with the inhibition of CIK cells. CIK cells were generated from peripheral blood mononuclear cells (PBMCs), and CTLA-4 shRNA (shCTLA-4) lentivirus was applied to knockdown CTLA-4 expression in CIK cells. The proliferation of CIK cells was evaluated following shCTLA-4 lentiviral transduction, and the cytotoxicity of CIK cells was investigated using the CytoTox 96 Non-Radioactive Cytotoxicity assay. The expression of CTLA-4 in CIK cells was significantly increased, compared with that in PBMCs. The shCTLA-4 lentivirus efficiently knocked down the expression of CTLA-4 in CIK cells. The shCTLA-4 lentivirus transduction of CIK cells promoted the proliferation of CIK cells in vitro (3.18±0.19-fold vs. 2.42±0.29-fold). Furthermore, the cytotoxicity of shCTLA-4 lentivirus-transduced CIK cells was significantly improved when compared with that of control shRNA lentivirus-transduced CIK cells (54.5±2.13% vs. 30.5±1.67%). Thus, the suppression of CTLA-4 expression increases cytotoxicity and ex vivo expansion of CIK cells, which indicates a clinical significance for CTLA-4 blockade in CIK cell therapy.

Background/AimsThe immunoregulatory molecules programmed death 1 (PD-1) and cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) are associated with the dysfunction of antiviral effector T-cells, which leads to T-cell exhaustion and persistent viral infection in patients with chronic hepatitis C and chronic hepatitis B. Little is known about the role of PD-1 and CTLA-4 in patients with symptomatic acute hepatitis A (AHA).MethodsPeripheral blood mononuclear cells were isolated from seven patients with AHA and from six patients with nonviral acute toxic hepatitis (ATH) during the symptomatic and convalescent phases of the respective diseases; five healthy subjects acted as controls. The expression of PD-1 and CTLA-4 on T-cells was measured by flow cytometry.ResultsPD-1 and CTLA-4 expression during the symptomatic phase was significantly higher in the T-cells of AHA patients than in those of ATH patients or healthy controls (PD-1: 18.3% vs 3.7% vs 1.6%, respectively, p<0.05; CTLA-4: 23.5% vs 6.1% vs 5.9%, respectively, p<0.05). The levels of both molecules decreased dramatically during the convalescent phase of AHA, whereas a similar pattern was not seen in ATH.ConclusionsOur findings are consistent with a viral-protective effect of PD-1 and CTLA-4 as inhibitory molecules that suppress cytotoxic T-cells and thereby prevent the destruction of virus-infected hepatocytes in AHA.

Objective To analyze the expressions of cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) in the peripheral blood of patients with active tuberculosis (ATB) or latent tuberculosis infection (LTBI), and to evaluate its diagnostic value in differentiation of ATB and LTBI. Methods Forty-eight patients including 18 ATB cases and 30 LTBI cases were continuously enrolled from Wuxi No.5 People′s Hospital and Huashan Hospital affiliated to Fudan University from January 2011 to March 2013. Flow cytometry was applied to detect the CTLA-4 expression in CD4+ CD25+ FoxP3+ T cells in the peripheral blood of the 48 subjects. CTLA-4 levels were compared using non-parametric Mann-Whitney U test. Results The median percentage of CTLA-4+ Treg in CD4+ CD25+ Foxp3+ Treg cells of ATB patients was 18.95% (quantile range: 13.86%, 27.73%), and that in LTBI patients was 6.67% (quantile range: 5.74%, 9.59%), which was statistically significant (U=18.0, P<0. 01). Receiver operating curve (ROC) based on the CTLA-4 expression indicated that the area under the curve was 0.96, with the optimum cut-off value of 13.25%. Thus, the sensitivity and specificity for the diagnosis of ATB were 86.7% and 94.4%, respectively. Conclusion CTLA-4 has highly sensitivity and specificity for the differential diagnosis of ATB and LTBI whose interferon-gamma releasing assays are all positive, which may also provide meaningful clue for the study of pathogenesis of ATB. Key words: CTLA-4; Active tuberculosis; Latent tuberculosis infection; Differential diagnosis