Suppression Of Dendritic Cells Research Articles

Mechanism of TLR4-Mediated Anti-Inflammatory Response Induced by Exopolysaccharide from the Probiotic Bacillus subtilis.

Intestinal inflammatory diseases affect millions of people worldwide, and one class of drugs showing promise toward treatment of several inflammatory diseases is probiotics. Numerous studies have been performed using probiotics to prevent and treat intestinal inflammatory diseases. Most of these studies used intact bacteria, and neither the active molecule nor the molecular mechanisms by which they affect immune responses are known. We have shown that the probiotic Bacillus subtilis is anti-inflammatory and can protect mice from acute colitis induced by the enteric pathogen Citrobacter rodentium. We identified and purified the active molecule, exopolysaccharide (EPS), and showed that it protects mice from C. rodentium-induced colitis by inducing anti-inflammatory M2 macrophages or inhibitory dendritic cells (DCs), both of which inhibit excessive T cell responses. We showed previously that EPS affects macrophages and DCs in a TLR4-dependent manner, and in the current study we asked how EPS induces these anti-inflammatory cells and how they function to inhibit T cells. By investigating the signaling downstream of TLR4 that leads to acquisition of inhibitory properties of macrophages and DCs, we found that EPS induces expression of the inhibitory molecule IDO in bone marrow-derived DCs, and that inhibition of T cell proliferation by IDO-expressing bone marrow-derived DCs utilizes the kynurenine/aryl hydrocarbon receptor circuit. Furthermore, unlike LPS, EPS does not induce inflammatory cytokines upon injection invivo, directly demonstrating different outcomes induced by two different TLR4 agonists.

Dendritic cell therapy augments antitumor immunity triggered by CDK4/6 inhibition and immune checkpoint blockade by unleashing systemic CD4 T-cell responses

BackgroundCyclin-dependent kinase 4/6 inhibitors (CDK4/6i) combined with endocrine therapy are a mainstay treatment for hormone receptor-positive breast cancer. While their principal mechanism is inhibition of cancer cell proliferation, preclinical and...

New Frontiers in Diagnosis and Prevention of Acute Kidney Injury (AKI): The Role of Dendritic Cells and Innovative High-Throughput Techniques

Kidney diseases, including acute kidney injury (AKI) and chronic kidney disease (CKD), represent a general, public health urgency, causing a heavy burden to global health care systems. Moreover, AKI is a frequent complication of hospitalization, and it is associated with short-term morbidity and mortality rate greater than 50%, as a result of its relationship with other severe complications. Furthermore, multiple pathophysiologic processes are involved in AKI, such as cellular death, apoptosis, mesenchymal transition, cellular infiltration, inflammation, cytokines release, coagulation, and complement activation. Since increasing evidence highlighted the central role of the immune system in AKI pathophysiology, several efforts have been made to delineate the link between this disease and the different population of immune cells. This narrative review aims to describe the role played by dendritic cells (DCs) in AKI, with a special focus on recent findings suggesting DCs suppression as a promising strategy to prevent AKI negative side effects and ameliorate renal injury and dysfunction. Furthermore, we briefly summarize the main characteristics of innovative high-throughput techniques, including as genomics, transcriptomics, proteomics, and metabolomics in the context of AKI.

Dendritic cell immunotherapy with miR-155 enriched tumor-derived exosome suppressed cancer growth and induced antitumor immune responses in murine model of colorectal cancer induced by CT26 cell line

Nowadays, various strategies are considered to prime Dendritic cells (DCs) with tumor antigens. The tumor cell-derived exosomes are recognized as one of the most efficient strategies for achieving this purpose. In this regard, MicroRNA 155 (miR-155) is employed as one of the most prominent miRNAs, which play substantial roles in DCs maturation and IL-12 production. This study investigates the tumor growth suppression and antitumor effects of DCs primed with miR-155-enriched exosome on the BALB/c murine model of colorectal cancer induced by CT-26 cell lines.Therefore, a holistic framework is proposed for the analysis procedure. In the first stage, miRNA-155 was electroporated into texosomes. In the second stage, bonemarrow-derived DCs were treated with miRNA-155 enriched texosomes. Then, antitumor properties of manipulated DC have been evaluated in the BALB/c mice model of colorectal cancer. After DC immunotherapy, several features have been assessed for each animal, including survival, body weight, tumor volume/size, histopathology, and serum cytokine levels. Also, flow cytometric evaluation has been performed for the spleen and the tumor tissue T-cell subsets.The findings demonstrated that the primed DCs could significantly increase IL-12p70 and IFN-γ in serum and accelerate the differentiation, proliferation, and cytotoxicity effects on the Th and CTL cells. Also, the treatment also increased the infiltration of Th and CTL cells into the tumor microenvironment while decreasing Tregs. This situation causes tumor growth control, and survival improvement.Therefore, DC immunotherapywith miR-155-enriched texosomes can be employed as a the desired approach for inducing antitumor immune responses, controlling tumor growth, and improving survival in mice with colorectal cancer. However, it is essential to perform more investigations to confirm the clinical application of this approach in humans and other types of tumors.

Targeting cancer-associated fibroblast-secreted WNT2 restores dendritic cell-mediated antitumour immunity

ObjectiveSolid tumours respond poorly to immune checkpoint inhibitor (ICI) therapies. One major therapeutic obstacle is the immunosuppressive tumour microenvironment (TME). Cancer-associated fibroblasts (CAFs) are a key component of the TME...

Abstract PR07: Quiescent cancer cells form immunotherapy resistant reservoirs by forming an immune suppressive niche

Abstract Immunotherapy is a promising treatment for Triple-Negative Breast Cancer (TNBC), but patients recur, arising the need to understand mechanisms of resistance. We discovered that in primary breast cancer, tumor cells that survive T-cell attack while still expressing the targeted antigen are in a quiescent state. Quiescent Cancer Cells (QCCs) are found clustering together forming intra-tumor cold regions with reduced immune infiltration. QCCs display superior tumorigenic capacity and higher expression of stemness genes than their proliferative counterparts. We adapted single-cell-RNA-sequencing with precise spatial resolution to profile infiltrating cells inside and outside the QCC niches. This transcriptomic analysis revealed hypoxia-induced programs and identified more exhausted T-cells, tumor-protective fibroblasts, and suppressive dendritic cells inside clusters of QCCs. This uncovered differential phenotypes in infiltrating cells based on their specific intra-tumor location and their proximity to functionally disntinct sub-populations of tumor cells. Thus, QCCs constitute immunotherapy-resistant reservoirs by orchestrating a local hypoxic immune-suppressive milieu that alters fibroblasts and dendritic cells leading to T cell dysfunction. Eliminating QCCs holds the promise to counteract resistance to immunotherapy and prevent disease recurrence in TNBC. This abstract is also being presented as Poster P007. Citation Format: Judith Agudo. Quiescent cancer cells form immunotherapy resistant reservoirs by forming an immune suppressive niche [abstract]. In: Abstracts: AACR Virtual Special Conference: Tumor Immunology and Immunotherapy; 2021 Oct 5-6. Philadelphia (PA): AACR; Cancer Immunol Res 2022;10(1 Suppl):Abstract nr PR07.

The influence of harvest method on dendritic cell function and clinical outcomes in a randomized trial of a dendritic cell vaccine to prevent recurrences in high-risk melanoma.

9548 Background: A randomized, double-blind, placebo-controlled phase IIb trial of the tumor lysate, particle loaded, dendritic cell (TLPLDC) vaccine was conducted to prevent recurrence in patients (pts) with resected stage III/IV melanoma. Two methods for dendritic cell (DC) harvest were used for vaccine production, including no pretreatment or pretreatment with granulocyte-colony stimulating factor (G-CSF) in an attempt to reduce blood draw volumes. This analysis investigates differences in clinical outcomes and RNA gene expression between these DC harvest methods for TLPLDC vaccine creation. Methods: The TLPLDC vaccine is created by loading autologous tumor lysate into yeast cell wall particles (YCWPs) and exposing them to phagocytosis by DCs. By investigator/pt choice, pts had 120mL of blood drawn for DC harvest, or pts received 300μg of G-CSF for pre-DC mobilization and a 50-70 mL blood draw 24-48 hours later. Total vaccine production time was 72 hrs. Pts were randomized 2:1 to receive TLPLDC or placebo (DCs exposed to empty YCWPs). 1-1.5 x10^6 cells/dose were injected intradermally at 0, 1, 2, 6, 12, and 18 months. Differences in disease free survival (DFS) and overall survival (OS) were evaluated by Kaplan Meier analysis between pts who did not receive pretreatment (TLPLDC), pts who did receive pretreatment with G-CSF (TLPLDC+G), and pts receiving placebo. RNA-seq analysis was performed on the total RNA of pts’ prepared TLPLDC vaccines to assess gene expression. Relative RNA expression (RRE) was compared between TLPLDC and TLPLDC+G. Results: As previously reported, 144 pts were randomized: 103 received TLPLDC (46 TLPLDC, 57 TLPLDC+G) and 41 received placebo. There were no significant clinicopathologic or treatment differences between the three treatment arms. Survival was significantly improved in TLPLDC compared to TLPLDC+G or placebo, including 36-month OS (92.9% vs 62.8% vs 72.3% respectively, p = 0.022) and DFS (51.8% vs 23.4% vs 27.1%, p = 0.027). When compared to TLPLDC+G (n = 3) vaccine, RNA-seq from TLPLDC vaccine (n = 3) showed upregulation of genes associated with DC maturation, including HLA-DMB (RRE: 3.60), IFIT1 (3.38), CD27 (3.26), IFI44L (3.24), MX1 (2.96), HLA-DQA1 (2.67), HLA-DRA (2.40), CD49D (2.34) and CD74 (2.09), while downregulated genes were associated with DC suppression or immaturity including SERPINA1 (RRE:7.8), TLR2 (6.65), CCR1 (5.11), IL10 (4.19), CD93 (3.84) and CD14 (3.25). Conclusions: Pts receiving TLPLDC vaccine had significantly improved OS and DFS, while outcomes remained similar between those who received TLPLDC+G vs placebo. Pts who did not receive G-CSF had higher expression of genes linked to DC maturation and antigen processing and presentation, likely explaining the improvement in clinical efficacy. A phase III trial to further assess the TLPLDC vaccine to prevent recurrence is planned. Clinical trial information: NCT02301611.

HESC-derived immune suppressive dendritic cells induce immune tolerance of parental hESC-derived allografts.

BackgroundWith their inherent capability of unlimited self-renewal and unique potential to differentiate into functional cells of the three germ layers, human embryonic stem cells (hESCs) hold great potential in regenerative medicine. A major challenge in the application of hESC-based cell therapy is the allogeneic immune rejection of hESC-derived allografts.MethodsWe derived dendritic cell-like cells (DCLs) from wild type and CTLA4-Ig/PD-L1 knock-in hESCs, denoted WT DCLs and CP DCLs. The expression of DC-related genes and surface molecules was evaluated, as well as their DCL capacity to stimulate allogeneic T cells and induce regulatory T (Treg) cells in vitro. Using an immune system humanized mouse model, we investigated whether the adoptive transfer of CP DCLs can induce long-term immune tolerance of parental hESC-derived smooth muscle and cardiomyocyte allografts.FindingsCP DCLs can maintain immune suppressive properties after robust inflammatory stimulation and induce Treg cells. While CP DCLs survive transiently in vivo, they induce long-term immune tolerance of parental hESC-derived allografts.InterpretationThis strategy does not cause systemic immune suppression but induces immune tolerance specific for DCL-specific HLAs, and thus it presents a safe and effective approach to induce immune tolerance of allografts derived from any clinically approved hESC line.FundingNSFC, leading talents of Guangdong Province Program (No. 00201516), Key R&D Program of Guangdong Province (2019B020235003), Science and Technology Innovation Committee of Shenzhen Municipality (JCYJ20180504170301309), National High-tech R&D Program (863 Program No. 2015AA020310), Shenzhen “Sanming” Project of Medicine (SZSM201602102), Development and Reform Commission of Shenzhen Municipality (S2016004730009), CIRM (DISC2–10559).

CCL21 and Dendritic Cell Suppression in Paediatric B Cell Acute Lymphoblastic Leukaemia

Despite the accumulation of genetic mutations likely to generate antigenic neoepitopes, acute lymphoblastic leukaemia (ALL) cells are poor at eliciting anti-tumour immune responses. Similarly to dendritic cells (DCs), B cells have antigen presenting capacity. In B cell ALL (B-ALL), blast expression of co-stimulatory molecules is down regulated whilst endogenous (tumour) antigens are presented through MHC class I and II[1], thus mimicking the DC peripheral tolerance mechanism. This leads to antigen specific anergy in naïve T cells capable of recognising the malignant cells and an anti-tumour immune response is not mounted. A robust DC response, presenting tumour antigens alongside co-stimulation, should be sufficient to overcome this since no intrinsic T cell defect exists in these patients. However, several studies have reported deficiencies in DC number and function in patients with B-ALL. Maecker et al. demonstrated that paediatric patients with B-ALL have significantly reduced blood DC counts at diagnosis, a reduction not attributable to disease induced bone marrow hypoplasia since blood DC numbers do not correlate with granulocyte or monocyte numbers or haemoglobin[2]. Mami et al. identified that CD34+ peripheral blood mononuclear cells from patients with B-ALL at diagnosis are ineffective at generating functional DCs in vitro suggesting that B-ALL cells, or leukaemia derived factors, may contribute to a block in DC development[3]. In this study, we monitored DCs and plasma cytokines in paediatric patients with B-ALL at diagnosis and throughout remission induction chemotherapy, in peripheral blood (PB) and the bone marrow (BM) tumour microenvironment, to identify on treatment changes in DCs and DC regulatory cytokines. 17 paediatric patients diagnosed with precursor B cell ALL were enrolled in this study. Matched PB and BM aspirate samples were collected at time points co-ordinating with treatment protocol (diagnosis, and induction days 8 and/or 15 and 29). Mononuclear cells and plasma samples were obtained by density gradient centrifugation. DCs were identified by flow cytometry (based on expression of HLA-DR(+), lack of B, T, NK and monocyte markers (CD3-, CD19-, CD56-, CD14-)). Plasma cytokines were analysed by Luminex multi-plex immunoassay. Our study confirmed that blood DCs are low in paediatric patients with B-ALL at diagnosis and that this scenario is mirrored in the BM tumour microenvironment. PB and BM DCs remained low through days 8 and 15 of induction remission chemotherapy however, we identified day 29 of induction chemotherapy as a key time point in the re-establishment of BM DCs, when a significant increase was recorded compared to both earlier time points and day 29 PB samples. Concordantly, high levels of two homeostatic chemokines were recorded in PB and BM plasma samples at diagnosis, CCL19 and CCL21. While CCL19 expression remained consistent throughout induction chemotherapy, CCL21 declined rapidly and was not detectable in any PB or BM day 29 plasma sample, coinciding with the rapid reduction of blasts that occurs during induction therapy. The re-emergence of DCs in the bone marrow and other lymphoid organs may represent the first stages in re-establishment of effective anti-tumour immunosurveillance and contribute to the cure of B-ALL. With overall survival rates greater than 90% it is clear that effective immunosurveillance, capable of maintaining a state of heath post-treatment, is re-established in most patients. When and how this occurs in the treatment process is not yet understood. However, CCL21 may play an important role in mediating immune tolerance to B-ALL, since mouse studies have demonstrated its ability to protect tumours from immune rejection[4]. Here, the re-establishment of BM DCs occurred concordantly to the reduction of CCL21 in the BM tumour microenvironment suggesting that over-expression of CCL21 may contribute to DC suppression in paediatric B-ALL patients. [1] Cardoso et al. (1996) Blood 88(1), 41-48; [2] Meaker et al. (2006) Leukemia 20(4), 645-649; [3] Mami et al. (2004) Br. J. Heamatol. 126(1), 77-80; [4] Sheilds et al. (2010) Science 328, 749-752. Disclosures No relevant conflicts of interest to declare.

Current state of organ transplant tolerance.

Immunological tolerance has long been considered the 'holy grail' of organ transplantation. Although tolerance has been an active area of research for 70 years, its clinical application has only been possible in the last two decades and widespread use remains an, as yet, unattained goal. Recent advances in the understanding of immune regulation have identified many new approaches to tolerance induction and several clinical trials are currently aimed at bringing this treatment to more patients. Mixed chimerism remains the most successful approach to tolerance induction. However, many treatments, including adoptive transfer of regulatory T cells, regulatory B cells, and immune suppressive dendritic cells and myeloid derived suppressor cells have shown great promise in preclinical models. Recent clinical studies have found that both kidney and liver operational tolerance are achievable in the appropriate settings. Furthermore, combining multiple tolerance approaches has shown potential to produce durable and safer tolerance. Tolerance to protect kidney and liver allografts has become a valuable therapy in the correct circumstances. Through further clinical trials and an improved understanding of immune regulatory components, tolerance is poised to have a significant impact on transplantation in the years to come.

Constitutively active GSK3β as a means to bolster dendritic cell functionality in the face of tumour-mediated immune suppression

ABSTRACTIn patients with cancer, the functionality of Dendritic Cells (DC) is hampered by high levels of tumor-derived suppressive cytokines, which interfere with DC development and maturation. Poor DC development can limit the efficacy of immune checkpoint blockade and in vivo vaccination approaches. Interference in intracellular signaling cascades downstream from the receptors of major tumor-associated suppressive cytokines like IL-10 and IL-6, might improve DC development and activation, and thus enhance immunotherapy efficacy. We performed exploratory functional screens on arrays consisting of >1000 human kinase peptide substrates to identify pathways involved in DC development and its inhibition by IL-10 or IL-6. The resulting alterations in phosphorylation of the kinome substrate profile pointed to glycogen-synthase kinase-3β (GSK3β) as a pivotal kinase in both DC development and suppression. GSK3β inhibition blocked human DC differentiation in vitro, which was accompanied by decreased levels of IL-12p70 secretion, and a reduced capacity for T cell priming. More importantly, adenoviral transduction of monocytes with a constitutively active form of GSK3β induced resistance to the suppressive effects of IL-10 and melanoma-derived supernatants alike, resulting in improved DC development, accompanied by up-regulation of co-stimulatory markers, an increase in CD83 expression levels in mature DC, and diminished release of IL-10. Moreover, adenovirus-mediated intratumoral manipulation of this pathway in an in vivo melanoma model resulted in DC activation and recruitment, and in improved immune surveillance and tumor control. We propose the induction of constitutive GSK3β activity as a novel therapeutic means to bolster DC functionality in the tumor microenvironment.

Increased Akt-Driven Glycolysis Is the Basis for the Higher Potency of CD137L-DCs.

CD137 ligand-induced dendritic cells (CD137L-DCs) are a new type of dendritic cells (DCs) that induce strong cytotoxic T cell responses. Investigating the metabolic activity as a potential contributing factor for their potency, we find a significantly higher rate of glycolysis in CD137L-DCs than in granulocyte macrophage colony-stimulating factor (GM-CSF) and interleukin 4 induced monocyte-derived DCs (moDCs). Using unbiased screening, Akt-mTORC1 activity was found to be significantly higher throughout the differentiation and maturation of CD137L-DCs than that of moDCs. Furthermore, this higher activity of the Akt-mTORC1 pathway is responsible for the significantly higher glycolysis rate in CD137L-DCs than in moDCs. Inhibition of Akt during maturation or inhibition of glycolysis during and after maturation resulted in suppression of inflammatory DCs, with mature CD137L-DCs being the most affected ones. mTORC1, instead, was indispensable for the differentiation of both CD137L-DCs and moDCs. In contrast to its role in supporting lipid synthesis in murine bone marrow-derived DCs (BMDCs), the higher glycolysis rate in CD137L-DCs does not lead to a higher lipid content but rather to an accumulation of succinate and serine. These data demonstrate that the increased Akt-driven glycolysis underlies the higher activity of CD137L-DCs.

Dendritic Cells and CD8 T Cell Immunity in Tumor Microenvironment.

Dendritic cells (DCs) play a central role in the regulation of the balance between CD8 T cell immunity vs. tolerance to tumor antigens. Cross-priming, a process which DCs activate CD8 T cells by cross-presenting exogenous antigens, plays a critical role in generating anti-tumor CD8 T cell immunity. However, there are compelling evidences now that the tumor microenvironment (TME)-mediated suppression and modulation of tumor-infiltrated DCs (TIDCs) impair their function in initiating potent anti-tumor immunity and even promote tumor progression. Thus, DC-mediated cross-presentation of tumor antigens in tumor-bearing hosts often induces T cell tolerance instead of immunity. As tumor-induced immunosuppression remains one of the major hurdles for cancer immunotherapy, understanding how DCs regulate anti-tumor CD8 T cell immunity in particular within TME has been under intensive investigation. Recent reports on the Batf3-dependent type 1 conventional DCs (cDC1s) in anti-tumor immunity have greatly advanced our understanding on the interplay of DCs and CD8 T cells in the TME, highlighted by the critical role of CD103+ cDC1s in the cross-priming of tumor antigen-specific CD8 T cells. In this review, we will discuss recent advances in anti-tumor CD8 T cell cross-priming by CD103+ cDC1s in TME, and share perspective on future directions including therapeutic applications and memory CD8 T cell responses.

Abstract B75: Loss of cross-presentation by tissue resident DC1 in lung adenocarcinomas is an early event that correlates to exhaustion of endogenous antitumor CD8+ T cell responses

Abstract Recent studies highlighted the essential role of tissue-resident dendritic cells (DCs) for T cells priming and immune checkpoint therapy, however the mechanism leading to DCs suppression during tumor growth are still poorly understood. Here we have isolated CD103 (DC1) and Cd11b (DC2) from orthotopic Kras/Trp53 adenocarcinomas to study their function and gene expression profiles. At early stages of tumor progression (day 14-21) DC1 effectively cross-presented tumor antigens acquired in vivo and this was paralleled by the presence of IFN-γ; secreting tumor specific CD8+ T cells in the lung. Starting from day 28 post tumor inoculation, despite minor changes in tumor burden, DC1 were no longer able to cross present tumor associated antigens and CD8+ T cell responses were concomitantly shut-off. DC1 isolated from tumor bearing lungs and fed with antigen ex-vivo confirmed a selective loss in cross-presentation. In parallel, DC2 skewed their cytokine profile and acquired a Th17 promoting phenotype mediated by high production of IL-23. In order to identify factors causing the sudden loss in DC1 activity we analyzed gene expression profiles in total lung tissues. At day 21 we observed a peak in T cell attracting chemokines together with expression of inhibitory pathways. This signature was dramatically modified at day 28, with a decrease in T cell associated genes and an increase in neutrophils related transcripts. Gene expression profiles in de-activated DC1 showed modulation of transcripts related to innate activation and antigen processing. In summary, this study identifies a narrow temporal window during which tissue resident DCs lose the ability to cross-present tumor associated antigens. Loss of DC1 function is accompanied by cell-intrinsic changes in gene expression, cell extrinsic changes in the tumor microenvironment and loss of activity in endogenous CD8+ T antitumor responses. Citation Format: Nicoletta Caronni, Francesca Simoncello, Karla Cervantes-Luevano, Licio Collavin, Federica Benvenuti. Loss of cross-presentation by tissue resident DC1 in lung adenocarcinomas is an early event that correlates to exhaustion of endogenous antitumor CD8+ T cell responses [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2017 Oct 1-4; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2018;6(9 Suppl):Abstract nr B75.

Downregulation of Membrane Trafficking Proteins and Lactate Conditioning Determine Loss of Dendritic Cell Function in Lung Cancer.

Restoring antigen presentation for efficient and durable activation of tumor-specific CD8+ T-cell responses is pivotal to immunotherapy, yet the mechanisms that cause subversion of dendritic cell (DC) functions are not entirely understood, limiting the development of targeted approaches. In this study, we show that bona fide DCs resident in lung tumor tissues or DCs exposed to factors derived from whole lung tumors become refractory to endosomal and cytosolic sensor stimulation and fail to secrete IL12 and IFNI. Tumor-conditioned DC exhibited downregulation of the SNARE VAMP3, a regulator of endosomes trafficking critical for cross-presentation of tumor antigens and DC-mediated tumor rejection. Dissection of cell-extrinsic suppressive pathways identified lactic acid in the tumor microenvironment as sufficient to inhibit type-I IFN downstream of TLR3 and STING. DC conditioning by lactate also impacted adaptive function, accelerating antigen degradation and impairing cross-presentation. Importantly, DCs conditioned by lactate failed to prime antitumor responses in vivo These findings provide a new mechanistic viewpoint to the concept of DC suppression and hold potential for future therapeutic approaches.Significance: These findings provide insight into the cell-intrinsic and cell-extrinsic mechanisms that cause loss of presentation of tumor-specific antigens in lung cancer tissues. Cancer Res; 78(7); 1685-99. ©2018 AACR.

Low-frequency ultrasound-induced VEGF suppression and synergy with dendritic cell-mediated anti-tumor immunity in murine prostate cancer cells in vitro

High tumor vascular endothelial growth factor (VEGF) levels are associated with poor treatment outcomes in prostate cancer (PCa), and immune deficiency in the PCa microenvironment, especially suppression of dendritic cell (DC) proliferation, has been confirmed. In this study, we (1) investigated whether VEGF participates in DC suppression in murine PCa cells (RM-1), (2) down-regulated VEGF expression using low-frequency ultrasound and microbubbles (UM), and (3) further explored any synergistic effect on immunological activation. DCs from the bone marrow of BALB/c mice were stimulated by the addition of cytokines (granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-4 (IL-4)), and we analyzed their proliferation status via flow cytometric recognition of the surface antigen markers CD11c and CD83. The results demonstrated that co-culture with RM-1 cells markedly inhibited expression of the general marker CD11c and the mature marker CD83; UM weakened this inhibition by down-regulating VEGF expression. T lymphocytes were extracted from murine spleens, and CD4 and CD8a were identified as the biomarkers of activated cells participating in the anti-tumor immune response. When DCs, T lymphocytes and RM-1 cells were co-cultured, cell migration and invasion assays and cytoactive detection showed that UM could not only directly suppress PCa cell evolution but also promote activation of anti-tumor immunocytes in the VEGF-inhibited microenvironment.

CTLA-4 positive breast cancer cells suppress dendritic cells maturation and function.

Cytotoxic T lymphocyte-associated antigen 4 (CTLA-4), a potent immunoregulatory molecule, can down-regulate T-cell activation and inhibit anti-tumor immune response. This study showed that LPS-stimulated human dendritic cells (DCs) decreased the expression of HLA-DR, CD83 and costimulatory molecules (CD40, CD80 and CD86) following coculturing with CTLA-4+ breast cancer cells. Moreover, the suppressed DCs further inhibited proliferation of allogeneic CD4+/CD8+ T-cells, differentiation of Th1 and function of cytotoxic lymphocytes (CTLs). However, CTLA-4 blockade in breast cancer cells could recover DC maturation and cytokine production, elevate antigen-presenting function of DCs, reverse Th1/CTLs response and cytokine secretion. Subsequent study demonstrated that the activation of extracellular-signal regulated kinase and signal transducer and activator of transcription 3 of DCs caused by CTLA-4+ breast cancer cells were the predominant mechanism of DC suppression. In addition, CTLA-4 blockade treatment also directly inhibited proliferation and induced apoptosis of CTLA-4+ breast cancer cells. Collectively, CTLA-4 was expressed and functional on human breast cancer cells through influencing maturation and function of DCs in vitro, and CTLA-4 blockage not only recovered the antigen-presenting function of DCs and T-cells activation but also suppressed the biological activity of breast cancer cells themselves. This study highlights the clinical application of CTLA-4 blockade therapy in breast cancer.

Genome-Wide STAT3 Binding Analysis after Histone Deacetylase Inhibition Reveals Novel Target Genes in Dendritic Cells

STAT3 is a master transcriptional regulator that plays an important role in the induction of both immune activation and immune tolerance in dendritic cells (DCs). The transcriptional targets of STAT3 in promoting DC activation are becoming increasingly understood; however, the mechanisms underpinning its role in causing DC suppression remain largely unknown. To determine the functional gene targets of STAT3, we compared the genome-wide binding of STAT3 using ChIP sequencing coupled with gene expression microarrays to determine STAT3-dependent gene regulation in DCs after histone deacetylase (HDAC) inhibition. HDAC inhibition boosted the ability of STAT3 to bind to distinct DNA targets and regulate gene expression. Among the top 500 STAT3 binding sites, the frequency of canonical motifs was significantly higher than that of noncanonical motifs. Functional analysis revealed that after treatment with an HDAC inhibitor, the upregulated STAT3 target genes were those that were primarily the negative regulators of proinflammatory cytokines and those in the IL-10 signaling pathway. The downregulated STAT3-dependent targets were those involved in immune effector processes and antigen processing/presentation. The expression and functional relevance of these genes were validated. Specifically, functional studies confirmed that the upregulation of IL-10Ra by STAT3 contributed to the suppressive function of DCs following HDAC inhibition.

Small-molecule inhibitor sorafenib regulates immunoreactions by inducing survival and differentiation of bone marrow cells.

Sorafenib has been used for the treatment of liver cancer. However, its clinical impact on human immunity system remains poorly known. Our previous study has shown that sorafenib modulates immunosuppressive cell populations in murine liver cancer models. Here, we continue to report that low doses of sorafenib promotes the survival of murine bone marrow cells (BMCs) in a dose-dependent manner by up-regulating the anti-apoptotic protein survivin. Sorafenib induces differentiation of BMCs into suppressive dendritic cells that inhibit autologous T-cell proliferation and stimulate CD4(+) T cells to express increased IL-1β, IL-2, IL-4, IL-10, IFN-γ and TNF-α, and reduced levels of IL-6 and CD25, which indicates that sorafenib-induced dendritic cells represent a distinct cellular subset with unique properties. Taken together, our findings suggest that in addition to its anticancer effects, sorafenib has an immunoregulatory property that is apparent at low doses.

PD-1 inhibition results in reduced dendritic cell (DC) activation of HIV-1-specific de novo CTL and enhancement of DC-induced CTL memory recall responses

Abstract Combination strategies consisting of DC vaccines and suppression of immunoregulatory pathways such as PD-1 blockade have been advocated to elicit optimal CTL responses in chronic diseases including cancer and HIV infection. We have shown that inactivated HIV-1 virus loaded, high IL-12 producing, mature, type-1 polarized DC (DC1) can activate CTL from naïve CD8+ T cell precursors that more effectively kill HIV-1-infected cells than CTL derived from memory CD8+ T cells. Here we tested DC1 transfected with an adenoviral (Ad) vector encoding anti-PD-1 antibody (DC.αPD1) enhancement of both primary as well as memory CTL responses to HIV-1. Ad-αPD1-transduced DC1 (DC.αPD1) secreted high levels of functional anti-PD1 Ab without affecting their phenotype or IL-12p70-producing capacity. We next compared HIV Gag peptide epitope-loaded DC.αPD1 to DC1 that were transfected with an empty vector for their ability to activate either purified, autologous naïve or memory HIV-1-specific CD8+ T cells from chronic HIV-1-infected participants of the Multicenter AIDS Cohort Study. When compared to the control DC1, antigen-loaded DC.αPD1 enhanced the overall magnitude of HIV-1-specific CTL responses induced, as determined by the expansion of HIV-1-peptide responsive CD107a and IFNγ expressing T cells. In contrast, the overall number HIV-1 antigen-reactive CTL derived from the naïve CD8+ T cell fraction sharply decreased when using the DC.αPD1-based approach. These results suggest previously unrecognized, opposing roles of the inhibitory receptor PD-1 in DC1-induced primary versus memory recall CD8+ T cell responses to HIV-1.