Decitabine Treatment of Glioma-Initiating Cells Enhances Immune Recognition and Killing

Epigenetic Induction of Cancer-Testis Antigens and Endogenous Retroviruses at Single-Cell Level Enhances Immune Recognition and Response in Glioma

Glioblastoma (GBM) is the most common malignant primary brain tumor and remains incurable. Previous work has shown that systemic administration of Decitabine (DAC) induces sufficient expression of cancer-testis antigens (CTA) in GBM for targeting by adoptive T-cell therapy in vivo. However, the mechanisms by which DAC enhances immunogenicity in GBM remain to be elucidated. Using New York esophageal squamous cell carcinoma 1 (NY-ESO-1) as a representative inducible CTA, we demonstrate in patient tissue, immortalized glioma cells, and primary patient-derived gliomaspheres that basal CTA expression is restricted by promoter hypermethylation in gliomas. DAC treatment of glioma cells specifically inhibits DNA methylation silencing to render NY-ESO-1 and other CTA into inducible tumor antigens at single-cell resolution. Functionally, NY-ESO-1 T-cell receptor-engineered effector cell targeting of DAC-induced antigen in primary glioma cells promotes specific and polyfunctional T-cell cytokine profiles. In addition to induction of CTA, DAC concomitantly reactivates tumor-intrinsic human endogenous retroviruses, interferon response signatures, and MHC-I. Overall, we demonstrate that DAC induces targetable tumor antigen and enhances T-cell functionality against GBM, ultimately contributing to the improvement of targeted immune therapies in glioma.

SIGNIFICANCE

This study dissects the tumor-intrinsic epigenetic and transcriptional mechanisms underlying enhanced T-cell functionality targeting decitabine-induced cancer-testis antigens in glioma. Our findings demonstrate concomitant induction of tumor antigens, reactivation of human endogenous retroviruses, and stimulation of interferon signaling as a mechanistic rationale to epigenetically prime human gliomas to immunotherapeutic targeting.

Understanding and therapeutically exploiting cGAS/STING signaling in glioblastoma

Since the discovery that cGAS/STING recognizes endogenous DNA released from dying cancer cells and induces type I interferon and antitumor T cell responses, efforts to understand and therapeutically target the STING pathway in cancer have ensued. Relative to other cancer types, the glioma immune microenvironment harbors few infiltrating T cells, but abundant tumor-associated myeloid cells, possibly explaining disappointing responses to immune checkpoint blockade therapies in cohorts of patients with glioblastoma. Notably, unlike most extracranial tumors, STING expression is absent in the malignant compartment of gliomas, likely due to methylation of the STING promoter. Nonetheless, several preclinical studies suggest that inducing cGAS/STING signaling in the glioma immune microenvironment could be therapeutically beneficial, and cGAS/STING signaling has been shown to mediate inflammatory and antitumor effects of other modalities either in use or being developed for glioblastoma therapy, including radiation, tumor-treating fields, and oncolytic virotherapy. In this Review, we discuss cGAS/STING signaling in gliomas, its implications for glioma immunobiology, compartment-specific roles for STING signaling in influencing immune surveillance, and efforts to target STING signaling - either directly or indirectly - for antiglioma therapy.

Epigenetically modified AP-2α by DNA methyltransferase facilitates glioma immune evasion by upregulating PD-L1 expression

Programmed death-ligand 1 (PD-L1) ensures that tumor cells escape T-cell-mediated tumor immune surveillance. However, gliomas are characteristic of the low immune response and high-resistance therapy, it is necessary to understand molecular regulatory mechanisms in glioblastoma, especially the limited regulation of PD-L1 expression. Herein, we show that low expression of AP-2α is correlated with high expression of PD-L1 in high-grade glioma tissues. AP-2α binds directly to the promoter of the CD274 gene, not only inhibits the transcriptional activity of PD-L1 but enhances endocytosis and degradation of PD-L1 proteins. Overexpression of AP-2α in gliomas enhances CD8+ T cell-mediated proliferation, effector cytokine secretion, and cytotoxicity in vitro. Tfap2a could increase the cytotoxic effect of Cd8+ T cells in CT26, B16F10, and GL261 tumor-immune models, improve anti-tumor immunity, and promote the efficacy of anti-PD-1 therapy. Finally, the EZH2/H3K27Me3/DNMT1 complex mediates the methylation modification of AP-2α gene and maintains low expression of AP-2α in gliomas. 5-Aza-dC (Decitabine) treatment combines with anti-PD-1 immunotherapy to efficiently suppress the progression of GL261 gliomas. Overall, these data support a mechanism of epigenetic modification of AP-2α that contributes to tumor immune evasion, and reactivation of AP-2α synergizes with anti-PD-1 antibodies to increase antitumor efficacy, which may be a broadly applicable strategy in solid tumors.

Treatment with decitabine induces the expression of stemness markers, PD-L1 and NY-ESO-1 in colorectal cancer: potential for combined chemoimmunotherapy

BACKGROUND

The mechanism of tumor immune escape and progression in colorectal cancer (CRC) is widely investigated in-vitro to help understand and identify agents that might play a crucial role in response to treatment and improve the overall survival of CRC patients. Several mechanisms of immune escape and tumor progression, including expression of stemness markers, inactivation of immunoregulatory genes by methylation, and epigenetic silencing, have been reported in CRC, indicating the potential of demethylating agents as anti-cancer drugs. Of these, a chemotherapeutic demethylating agent, Decitabine (DAC), has been reported to induce a dual effect on both DNA demethylation and histone changes leading to an increased expression of target biomarkers, thus making it an attractive anti-tumorigenic drug.

METHODS

We compared the effect of DAC in primary 1076 Col and metastatic 1872 Col cell lines isolated and generated from patients' tumor tissues. Both cell lines were treated with DAC, and the expression of the NY-ESO-1 cancer-testis antigen, the PD-L1 immunoinhibitory marker, and the CD44, Nanog, KLF-4, CD133, MSI-1 stemness markers were analyzed using different molecular and immunological assays.

RESULTS

DAC treatment significantly upregulated stemness markers in both primary 1076 Col and meta-static 1872 Col cell lines, although a lower effect occurred on the latter: CD44 (7.85 fold; ***p = 0.0001 vs. (4.19 fold; *p = 0.0120), Nanog (4.1 fold; ***p < 0.0001 vs.1.69 fold; ***p = 0.0008), KLF-4 (4.33 fold; ***p < 0.0001 vs.2.48 fold; ***p = 0.0005), CD133 (16.77 fold; ***p = 0.0003 vs.6.36 fold; *p = 0.0166), and MSI-1 (2.33 fold; ***p = 0.0003 vs.2.3 fold; ***p = 0.0004), respectively. Interestingly, in the metastatic 1872 Col cells treated with DAC, the expression of both PD-L1 and NY-ESO-1 was increased tenfold (*p = 0.0128) and fivefold (***p < 0.0001), respectively.

CONCLUSIONS

We conclude that the upregulation of both stemness and immune checkpoint markers by DAC treatment on CRC cells might represent a mechanism of immune evasion. In addition, induction of NY-ESO-1 may represent an immuno-therapeutic option in metastatic CRC patients. Finally, the combination of DAC and anti-PD-1/anti-PD-L1 antibodies treatment should represent a potential therapeutic intervention for this group of patients.

Mapping of DNA methylation-sensitive cellular processes in gingival and periodontal ligament fibroblasts in the context of periodontal tissue homeostasis

Interactions between gingival fibroblasts (GFs) and oral pathogens contribute to the chronicity of inflammation in periodontitis. Epigenetic changes in DNA methylation are involved in periodontitis pathogenesis, and recent studies indicate that DNA methyltransferase (DNMT) inhibitors may protect against epithelial barrier disruption and bone resorption. To assess the impact of DNMT inhibition on GFs, cells were cultured with decitabine (5-aza-2'-deoxycytidine, DAC) for 12 days to induce DNA hypomethylation. We observed several potentially detrimental effects of DAC on GF biological functions. First, extended treatment with DAC reduced GF proliferation and induced necrotic cell death. Second, DAC amplified Porphyromonas gingivalis- and cytokine-induced expression and secretion of the chemokine CCL20 and several matrix metalloproteinases (MMPs), including MMP1, MMP9, and MMP13. Similar pro-inflammatory effects of DAC were observed in periodontal ligament fibroblasts. Third, DAC upregulated intercellular adhesion molecule-1 (ICAM-1), which was associated with increased P. gingivalis adherence to GFs and may contribute to bacterial dissemination. Finally, analysis of DAC-induced genes identified by RNA sequencing revealed increased expression of CCL20, CCL5, CCL8, CCL13, TNF, IL1A, IL18, IL33, and CSF3, and showed that the most affected processes were related to immune and inflammatory responses. In contrast, the genes downregulated by DAC were associated with extracellular matrix and collagen fibril organization. Our observations demonstrate that studies of DNMT inhibitors provide important insights into the role of DNA methylation in cells involved in periodontitis pathogenesis. However, the therapeutic potential of hypomethylating agents in periodontal disease may be limited due to their cytotoxic effects on fibroblast populations and stimulation of pro-inflammatory pathways.

Combination of single-cell and bulk RNA seq reveals the immune infiltration landscape and targeted therapeutic drugs in spinal cord injury

Background

In secondary spinal cord injury (SCI), the immune microenvironment of the injured spinal cord plays an important role in spinal regeneration. Among the immune microenvironment components, macrophages/microglia play a dual role of pro-inflammation and anti-inflammation in the subacute stage of SCI. Therefore, discovering the immune hub genes and targeted therapeutic drugs of macrophages/microglia after SCI has crucial implications in neuroregeneration. This study aimed to identify immune hub genes and targeted therapeutic drugs for the subacute phase of SCI.

Methods

Bulk RNA sequencing (bulk-RNA seq) datasets (GSE5296 and GSE47681) and single-cell RNA sequencing (scRNA-seq) dataset (GSE189070) were obtained from the Gene Expression Omnibus database. In the bulk RNA-seq, the R package 'limma,' 'WGCNA,' and 'CIBERSORT' were used to jointly screen key immune genes. Subsequently, the R package 'Seurat' and the R package 'celldex' were used to divide and annotate the cell clusters, respectively. After using the Autodock software to dock immune hub genes and drugs that may be combined, the effectiveness of the drug was verified using an in vivo experiment with the T9 SCI mouse model.

Results

In the bulk-RNA seq, B2m, Itgb5, and Vav1 were identified as immune hub genes. Ten cell clusters were identified in scRNA-seq, and B2m and Itgb5 were mainly located in the microglia, while Vav1 was mainly located in macrophages. Molecular docking results showed that the proteins corresponding to these immune genes could accurately bind to decitabine. In decitabine-treated mice, the pro-inflammatory factor (TNF-α, IL-1β) levels were decreased while anti-inflammatory factor (IL-4, IL-10) levels were increased at 2 weeks post-SCI, and macrophages/microglia transformed from M1 to M2. At 6 weeks post-SCI, the neurological function score and electromyography of the decitabine treatment group were also improved.

Conclusion

In the subacute phase of SCI, B2m, Itgb5, and Vav1 in macrophages/microglia may be key therapeutic targets to promote nerve regeneration. In addition, low-dose decitabine may promote spinal cord regeneration by regulating the polarization state of macrophages/microglia.

Decitabine increases neoantigen and cancer testis antigen expression to enhance T-cell-mediated toxicity against glioblastoma

BACKGROUND

Glioblastoma (GBM) is the most common and malignant primary brain tumor in adults. Despite maximal treatment, median survival remains dismal at 14-24 months. Immunotherapies, such as checkpoint inhibition, have revolutionized management of some cancers but have little benefit for GBM patients. This is, in part, due to the low mutational and neoantigen burden in this immunogenically "cold" tumor.

METHODS

U87MG and patient-derived cell lines were treated with 5-aza-2'-deoxycytidine (DAC) and underwent whole-exome and transcriptome sequencing. Cell lines were then subjected to cellular assays with neoantigen and cancer testis antigen (CTA) specific T cells.

RESULTS

We demonstrate that DAC increases neoantigen and CTA mRNA expression through DNA hypomethylation. This results in increased neoantigen presentation by MHC class I in tumor cells, leading to increased neoantigen- and CTA-specific T-cell activation and killing of DAC-treated cancer cells. In addition, we show that patients have endogenous cancer-specific T cells in both tumor and blood, which show increased tumor-specific activation in the presence of DAC-treated cells.

CONCLUSIONS

Our work shows that DAC increases GBM immunogenicity and consequent susceptibility to T-cell responses in vitro. Our results support a potential use of DAC as a sensitizing agent for immunotherapy.

Exploring glioblastoma stem cell heterogeneity: Immune microenvironment modulation and therapeutic opportunities

Despite its growing use in cancer treatment, immunotherapy has been virtually ineffective in clinical trials for gliomas. The inherently cold tumor immune microenvironment (TIME) in gliomas, characterized by a high ratio of pro-tumor to anti-tumor immune cell infiltrates, acts as a seemingly insurmountable barrier to immunotherapy. Glioma stem cells (GSCs) within these tumors are key contributors to this cold TIME, often functioning indirectly through activation and recruitment of pro-tumor immune cell types. Furthermore, drivers of GSC plasticity and heterogeneity (e.g., reprogramming transcription factors, epigenetic modifications) are associated with induction of immunosuppressive cell states. Recent studies have identified GSC-intrinsic mechanisms, including functional mimicry of immune suppressive cell types, as key determinants of anti-tumor immune escape. In this review, we cover recent advancements in our understanding of GSC-intrinsic mechanisms that modulate GSC-TIME interactions and discuss cutting-edge techniques and bioinformatics platforms available to study immune modulation at high cellular resolution with exploration of both malignant (i.e., GSC) and non-malignant (i.e., immune) cell fractions. Finally, we provide insight into the therapeutic opportunities for targeting immunomodulatory GSC-intrinsic mechanisms to potentiate immunotherapy response in gliomas.

Epigenetic Drugs and Their Immune Modulating Potential in Cancers

Epigenetic drugs are used for the clinical treatment of hematologic malignancies; however, their therapeutic potential in solid tumors is still under investigation. Current evidence suggests that epigenetic drugs may lead to antitumor immunity by increasing antigen presentation and may enhance the therapeutic effect of immune checkpoint inhibitors. Here, we highlight their impact on the tumor epigenome and discuss the recent evidence that epigenetic agents may optimize the immune microenvironment and promote antiviral response.

Synergistic regulation of methylation and SP1 on MAGE-D4 transcription in glioma

BACKGROUND

The family of MAGE genes is well known due to the majority of MAGE genes expressing specifically in tumor tissues while restrictedly in normal tissues. MAGE-D4 is one of the MAGE family and considered as a promising target for glioma immunotherapy because of its overexpression in glioma and restricted expression in normal tissues. Whereas the mechanism of MAGE-D4 heterogeneous expression in glioma has not yet been elucidated. In this study, the transcriptional regulation mechanism of MAGE-D4 in glioma is focused from the perspectives of promoter methylation and SP1.

METHODS

Dual-luciferase reporter assay was performed to identify the core promoter of MAGE-D4 gene. Mass spectrometry was applied to quantify the methylation status of MAGE-D4 promoter in 50 glioma and 9 normal brain tissues. The influence of methylation and SP1 on MAGE-D4 transcriptional activity was evaluated by dual-luciferase reporter assay, qRT-PCR, western blot and ChIP-qPCR. Decitabine, an epigenetic drug, was used to treat the glioma cells. Then the treated cells were evaluated the influence of demethylation on SP1 binding to MAGE-D4 promoter.

RESULTS

The -358 to +172 bp region was identified as the core promoter of MAGE-D4 gene which demonstrated hypomethylated and negative correlation between methylation level and MAGE-D4 mRNA expression in glioma tissues. For single CpG unit analysis, 8 CpG units (CpG unit 1, 2, 3, 4, 5, 6, 9 and 12) in MAGE-D4 core promoter showed hypomethylated in glioma and the methylation level of CpG unit 6 was positively associated with the prognosis of glioma patients. Furthermore, the methylation level of CpG unit 1 and 6 was negative negatively correlated with MAGE-D4 mRNA expression. Then, the results demonstrated that the promoter activity of MAGE-D4 was decreased by methylation in glioma cell lines. In addition, SP1 can binds directly to the MAGE-D4 promoter leading to up-regulation of MAGE-D4 mRNA through activation of its promoter. Finally, demethylation of MAGE-D4 promoter could benefit the SP1 binding and resulting co-activation of MAGE-D4 promoter by demethylation and SP1 in glioma cell lines.

CONCLUSION

These findings indicate that the synergies of promoter hypomethylation and SP1 up-regulated MAGE-D4 transcription in glioma, which implies a potential approach to resolve the heterogeneous expression of MAGE-D4 in order to establish foundation for the MAGE-D4 based glioma therapy.

Immunocompetent Mouse Models in the Search for Effective Immunotherapy in Glioblastoma

Glioblastoma (GBM) is the most aggressive intrinsic brain tumor in adults. Despite maximal therapy consisting of surgery and radio/chemotherapy, GBM remains largely incurable with a median survival of less than 15 months. GBM has a strong immunosuppressive nature with a multitude of tumor and microenvironment (TME) derived factors that prohibit an effective immune response. To date, all clinical trials failed to provide lasting clinical efficacy, despite the relatively high success rates of preclinical studies to show effectivity of immunotherapy. Various factors may explain this discrepancy, including the inability of a single mouse model to fully recapitulate the complexity and heterogeneity of GBM. It is therefore critical to understand the features and limitations of each model, which should probably be combined to grab the full spectrum of the disease. In this review, we summarize the available knowledge concerning immune composition, stem cell characteristics and response to standard-of-care and immunotherapeutics for the most commonly available immunocompetent mouse models of GBM.

The Brain Microenvironment Induces DNMT1 Suppression and Indolence of Metastatic Cancer Cells

Brain metastasis is an ineffective process, and many cancer cells enter into an indolent state following extravasation in the brain. Single cell RNA sequencing of melanoma brain metastases reveals that non-proliferating brain metastatic melanoma cells exhibit a pattern of gene expression associated with inhibition of DNA methyltransferase 1 (DNMT1). The brain microenvironment, specifically the combination of reactive astrocytes and mechanically soft surroundings, suppressed DNMT1 expression in various cancer types and caused cell cycle delay. Somewhat unexpectedly, we find that DNMT1 suppression not only induces cell cycle delay but also activates pro-survival signals in brain metastatic cancer cells, including L1CAM and CRYAB. Our results demonstrate that transcriptional changes triggered by DNMT1 suppression is a key step for cancer cells to survive in the brain microenvironment and that they also restrict cancer cell proliferation. The dual consequences of DNMT1 suppression can explain the persistence of indolent cancer cells in the brain microenvironment.

Prognostic value of indoleamine 2,3 dioxygenase in patients with higher-risk myelodysplastic syndromes treated with azacytidine

Hypomethylating agents (HMAs) are widely used in patients with higher-risk myelodysplastic syndromes (MDS) not eligible for stem cell transplantation; however, the response rate is <50%. Reliable predictors of response are still missing, and it is a major challenge to develop new treatment strategies. One current approach is the combination of azacytidine (AZA) with checkpoint inhibitors; however, the potential benefit of targeting the immunomodulator indoleamine-2,3-dioxygenase (IDO-1) has not yet been evaluated. We observed moderate to strong IDO-1 expression in 37% of patients with high-risk MDS. IDO-1 positivity was predictive of treatment failure and shorter overall survival. Moreover, IDO-1 positivity correlated inversely with the number of infiltrating CD8⁺ T cells, and IDO-1+ patients failed to show an increase in CD8⁺ T cells under AZA treatment. In vitro experiments confirmed tryptophan catabolism and depletion of CD8⁺ T cells in IDO-1+ MDS, suggesting that IDO-1 expression induces an immunosuppressive microenvironment in MDS, thereby leading to treatment failure under AZA treatment. In conclusion, IDO-1 is expressed in more than one-third of patients with higher-risk MDS, and is predictive of treatment failure and shorter overall survival. Therefore, IDO-1 is emerging as a promising predictor and therapeutic target, especially for combination therapies with HMAs or checkpoint inhibitors.

Epigenetic Reprogramming for Targeting IDH-Mutant Malignant Gliomas

Targeting the epigenome has been considered a compelling treatment modality for several cancers, including gliomas. Nearly 80% of the lower-grade gliomas and secondary glioblastomas harbor recurrent mutations in isocitrate dehydrogenase (IDH). Mutant IDH generates high levels of 2-hydroxyglutarate (2-HG) that inhibit various components of the epigenetic machinery, including histone and DNA demethylases. The encouraging results from current epigenetic therapies in hematological malignancies have reinvigorated the interest in solid tumors and gliomas, both preclinically and clinically. Here, we summarize the recent advancements in epigenetic therapy for lower-grade gliomas and discuss the challenges associated with current treatment options. A particular focus is placed on therapeutic mechanisms underlying favorable outcome with epigenetic-based drugs in basic and translational research of gliomas. This review also highlights emerging bridges to combination treatment with respect to epigenetic drugs. Given that epigenetic therapies, particularly DNA methylation inhibitors, increase tumor immunogenicity and antitumor immune responses, appropriate drug combinations with immune checkpoint inhibitors may lead to improvement of treatment effectiveness of immunotherapy, ultimately leading to tumor cell eradication.

Epigenetic downregulation of STAT6 increases HIF-1α expression via mTOR/S6K/S6, leading to enhanced hypoxic viability of glioma cells

Multifunctional signal transducer and activator of transcription (STAT) proteins play important roles in cancer. Here, we have shown that STAT6 is epigenetically silenced in some cases of malignant glioblastoma, which facilitates cancer cell survival in a hypoxic microenvironment. This downregulation results from hypermethylation of CpG islands within the STAT6 promoter by DNA methyltransferases. STAT6 interacts with Rheb under hypoxia and inhibits mTOR/S6K/S6 signaling, in turn, inducing increased HIF-1α translation. STAT6 silencing and consequent tumor-promoting effects are additionally observed in glioma stem-like cells (GSC). Despite recent advances in cancer treatment, survival rates have shown little improvement. This is particularly true in the case of glioma, where multimodal treatment and precision medicine is needed. Our study supports the application of epigenetic restoration of STAT6 with the aid of DNA methyltransferase inhibitors, such as 5-aza-2-deoxycytidine, for treatment of STAT6-silenced gliomas.

Efficacy of azacitidine is independent of molecular and clinical characteristics - an analysis of 128 patients with myelodysplastic syndromes or acute myeloid leukemia and a review of the literature

Azacitidine is the first drug to demonstrate a survival benefit for patients with MDS. However, only half of patients respond and almost all patients eventually relapse. Limited and conflicting data are available on predictive factors influencing response. We analyzed 128 patients from two institutions with MDS or AML treated with azacitidine to identify prognostic indicators. Genetic mutations in ASXL1, RUNX1, DNMT3A, IDH1, IDH2, TET2, TP53, NRAS, KRAS, FLT3, KMT2A-PTD, EZH2, SF3B1, and SRSF2 were assessed by next-generation sequencing. With a median follow up of 5.6 years median survival was 1.3 years with a response rate of 49%. The only variable with significant influence on response was del(20q). All 6 patients responded (p = 0.012) but survival was not improved. No other clinical, cytogenetic or molecular marker for response or survival was identified. Interestingly, patients from poor-risk groups as high-risk cytogenetics (55%), t-MDS/AML (54%), TP53 mutated (48%) or relapsed after chemotherapy (60%) showed a high response rate. Factors associated with shorter survival were low platelets, AML vs. MDS, therapy-related disease, TP53 and KMT2A-PTD. In multivariate analysis anemia, platelets, FLT3-ITD, and therapy-related disease remained in the model. Poor-risk factors such as del(7q)/-7, complex karyotype, ASXL1, RUNX1, EZH2, and TP53 did not show an independent impact. Thus, no clear biomarker for response and survival can be identified. Although a number of publications on predictive markers for response to AZA exist, results are inconsistent and improved response rates did not translate to improved survival. Here, we provide a comprehensive overview comparing the studies published to date.

Decitabine Inhibits Gamma Delta T Cell Cytotoxicity by Promoting KIR2DL2/3 Expression

Gamma delta (γδ) T cells, which possess potent cytotoxicity against a wide range of cancer cells, have become a potential avenue for adoptive immunotherapy. Decitabine (DAC) has been reported to enhance the immunogenicity of tumor cells, thereby reinstating endogenous immune recognition and tumor lysis. However, DAC has also been demonstrated to have direct effects on immune cells. In this study, we report that DAC inhibits γδ T cell proliferation. In addition, DAC increases the number of KIR2DL2/3-positive γδ T cells, which are less cytotoxic than the KIR2DL2/3-negative γδ T cells. We found that DAC upregulated KIR2DL2/3 expression in KIR2DL2/3-negative γδ T cells by inhibiting KIR2DL2/3 promoter methylation, which enhances the binding of KIR2DL2/3 promoter to Sp-1 and activates KIR2DL2/3 gene expression. Our data demonstrated that DAC can inhibit the function of human γδ T cells at both cellular and molecular levels, which confirms and extrapolates the results of previous studies showing that DAC can negatively regulate the function of NK cells and αβ T cells of the immune system.

Nerve/glial antigen (NG) 2 is a crucial regulator of intercellular adhesion molecule (ICAM)-1 expression

The proteoglycan nerve/glial antigen (NG) 2 is expressed on multiple cell types and mediates cell proliferation and migration. However, little is known about its function in gene regulation. In this study, we demonstrate that in pericytes and glioblastoma cells intercellular adhesion molecule (ICAM)-1, an essential protein for leukocyte adhesion and transmigration, underlies a NG2-dependent expression. As shown by flow cytometry, Western blot analysis and quantitative real-time polymerase chain reaction (qRT-PCR), silencing of NG2 in human placenta-derived pericytes increased the expression of ICAM-1. Pathway analyses revealed that this is mediated by extracellular-regulated-kinases (ERK) 1/2 signaling. Moreover, leukocyte adhesion to NG2 siRNA-treated pericytes was significantly enhanced when compared to scrambled (scr) siRNA-treated control cells. In vivo, we detected increased ICAM-1 protein levels in the retina of mice lacking NG2 expression. To exclude that this novel mechanism is pericyte-specific, we additionally analyzed the expression of ICAM-1 in dependency of NG2 in two glioblastoma cell lines. We found that A1207 and M059K cells exhibit an inverse expression pattern of NG2 and ICAM-1. Finally, downregulation of NG2 in A1207 cells significantly increased ICAM-1 expression. Taken together, these findings indicate that NG2 may represent a promising target for the modulation of ICAM-1-mediated immune responses.