Saponin-based adjuvants enhance antigen cross-presentation in human CD11c+ CD1c+ CD5- CD163+ conventional type 2 dendritic cells.

BACKGROUND: Adjuvants are key for effective vaccination against cancer and chronic infectious diseases. Saponin-based adjuvants (SBAs) are unique among adjuvants in their ability to induce robust cell-mediated immune responses in addition to antibody responses. Recent preclinical studies revealed that SBAs induced cross-presentation and lipid bodies in otherwise poorly cross-presenting CD11b+ murine dendritic cells (DCs). METHOD: Here, we investigated the response of human DC subsets to SBAs with RNA sequencing and pathway analyses, lipid body induction visualized by laser scanning microscopy, antigen translocation to the cytosol, and antigen cross-presentation to CD8+ T cells. RESULTS: RNA sequencing of SBA-treated conventional type 1 DC (cDC1) and type 2 DC (cDC2) subsets uncovered that SBAs upregulated lipid-related pathways in CD11c+ CD1c+ cDC2s, especially in the CD5- CD163+ CD14+ cDC2 subset. Moreover, SBAs induced lipid bodies and enhanced endosomal antigen translocation into the cytosol in this particular cDC2 subset. Finally, SBAs enhanced cross-presentation only in cDC2s, which requires the CD163+ CD14+ cDC2 subset. CONCLUSIONS: These data thus identify the CD163+ CD14+ cDC2 subset as the main SBA-responsive DC subset in humans and imply new strategies to optimize the application of saponin-based adjuvants in a potent cancer vaccine.

DC-SCRIPT affects mammary organoids branching morphogenesis by modulating the FGFR1-pERK signaling axis.

Loss of expression of the transcription regulator DC-SCRIPT (Zfp366) is a prominent prognostic event in estrogen receptor-positive breast cancer patients. Studying the inherent link between breast morphogenesis and tumorigenesis, we recently reported that DC-SCRIPT affects normal mammary branching morphogenesis and mammary epithelium homeostasis. Here we investigated the molecular mechanism involved in DC-SCRIPT mediated regulation of FGF2 induced mammary branching morphogenesis in a 3D organoid culture system. Our data show that the delayed mammary organoid branching observed in DC-SCRIPT-/- organoids cannot be compensated for by increasing FGF2 levels. Interestingly, FGFR1, the dominant FGF2 receptor, was expressed at a significantly lower level in basal epithelial cells of DC-SCRIPT deficient organoids relative to wildtype organoids. A potential link between DC-SCRIPT and FGFR1 was further supported by the predicted locations of the DC-SCRIPT DNA binding motif at the Fgfr1 gene. Moreover, ERK1/2 phosphorylation downstream of the FGFR1 pathway was decreased in basal epithelial cells of DC-SCRIPT deficient organoids. Altogether, this study shows a relationship between DC-SCRIPT and FGFR1 related pERK signaling in modulating the branching morphogenesis of mammary organoids in vitro.

DC-SCRIPT deficiency delays mouse mammary gland development and branching morphogenesis.

Mammary glands are unique organs in which major adaptive changes occur in morphogenesis and development after birth. Breast cancer is the most common cancer and a major cause of mortality in females worldwide. We have previously identified the loss of expression of the transcription regulator DC-SCRIPT (Zfp366) as a prominent prognostic event in estrogen receptor positive breast cancer patients. DC-SCRIPT affects multiple transcriptional events in breast cancer cells, including estrogen and progesterone receptor-mediated transcription, and promotes CDKN2B-related cell cycle arrest. As loss of DC-SCRIPT expression appears an early event in breast cancer development, we here investigated the role of DC-SCRIPT in mammary gland development using wild-type and DC-SCRIPT knockout mice. Mice lacking DC-SCRIPT exhibited severe breeding problems and showed significant growth delay relative to littermate wild-type mice. Subsequent analysis revealed that DC-SCRIPT was expressed in mouse mammary epithelium and that DC-SCRIPT deficiency delayed mammary gland morphogenesis in vivo. Finally, analysis of 3D mammary gland organoid cultures confirmed that loss of DC-SCRIPT dramatically delayed mammary organoid branching in vitro. The study shows for the first time that DC-SCRIPT deficiency delays mammary gland morphogenesis in vivo and in vitro. These data define DC-SCRIPT as a novel modulator of mammary gland development.

Dendritic Cells Actively Limit Interleukin-10 Production Under Inflammatory Conditions via DC-SCRIPT and Dual-Specificity Phosphatase 4.

Dendritic cell (DC)-based immunotherapy makes use of the DC's ability to direct the adaptive immune response toward activation or inhibition. DCs perform this immune orchestration in part by secretion of selected cytokines. The most potent anti-inflammatory cytokine interleukin-10 (IL-10) is under tight regulation, as it needs to be predominantly expressed during the resolution phase of the immune response. Currently it is not clear whether there is active suppression of IL-10 by DCs at the initial pro-inflammatory stage of the immune response. Previously, knockdown of the DC-specific transcription factor DC-SCRIPT has been demonstrated to mediate an extensive increase in IL-10 production upon encounter with pro-inflammatory immune stimuli. Here, we explored how DC-SCRIPT contributes to IL-10 suppression under pro-inflammatory conditions by applying chromatin immunoprecipitation sequencing analysis of DC-SCRIPT and the epigenetic marks H3K4me3 and H3K27ac in human DCs. The data showed binding of DC-SCRIPT to a GA-rich motif at H3K27ac-marked genomic enhancers that associated with genes encoding MAPK dual-specificity phosphatases (DUSPs). Functional studies revealed that upon knockdown of DC-SCRIPT, human DCs express much less DUSP4 and exhibit increased phosphorylation of the three major MAPKs (ERK, JNK, and p38). Enhanced ERK signaling in DC-SCRIPT-knockdown-DCs led to higher production of IL-10, which was reverted by rescuing DUSP4 expression. Finally, DC-SCRIPT-knockdown-DCs induced less IFN-γ and increased IL-10 production in naïve T cells, indicative for a more anti-inflammatory phenotype. In conclusion, we have delineated a new mechanism by which DC-SCRIPT allows DCs to limit IL-10 production under inflammatory conditions and potentiate pro-inflammatory Th1 responses. These insights may be exploited to improve DC-based immunotherapies.

Anti-GD2 mAb and Vorinostat synergize in the treatment of neuroblastoma.

Neuroblastoma (NBL) is a childhood malignancy of the sympathetic nervous system. For high-risk NBL patients, the mortality rate is still over 50%, despite intensive multimodal treatment. Anti-GD2 monoclonal antibody (mAB) in combination with systemic cytokine immunotherapy has shown clinical efficacy in high-risk NBL patients. Targeted therapy using histone deacetylase inhibitors (HDACi) is currently being explored in cancer treatment and already shows promising results. Using our recently developed transplantable TH-MYCN NBL model, we here report that the HDAC inhibitor Vorinostat synergizes with anti-GD2 mAb therapy in reducing NBL tumor growth. Further mechanistic studies uncovered multiple mechanisms for the observed synergy, including Vorinostat-induced specific NBL cell death and upregulation of the tumor antigen GD2 on the cell surface of surviving NBL cells. Moreover, Vorinostat created a permissive tumor microenvironment (TME) for tumor-directed mAb therapy by increasing macrophage effector cells expressing high levels of Fc-receptors (FcR) and decreasing the number and function of myeloid-derived suppressor cells (MDSC). Collectively, these data imply further testing of other epigenetic modulators with immunotherapy and provide a strong basis for clinical testing of anti-GD2 plus Vorinostat combination therapy in NBL patients.

DC-SCRIPT Regulates IL-10 Production in Human Dendritic Cells by Modulating NF-κBp65 Activation.

The balance between tolerance and immunity is important for the outcome of an infection or cancer, and dendritic cells (DCs) are key regulators of this balance. DC-specific transcript (DC-SCRIPT) is a protein expressed by DCs and has been demonstrated to suppress both TLR-mediated expression of IL-10 and glucocorticoid receptor-mediated transcription of glucocorticoid-induced leucine zipper (GILZ). Because GILZ is known to promote IL-10 production, we investigated whether these two processes are linked. Dual-knockdown and inhibition experiments demonstrated that neither GILZ nor glucocorticoid receptor play a role in TLR-induced IL-10 production after DC-SCRIPT knockdown. The NF-κB pathway is another route involved in IL-10 production after DC activation. Strikingly, inhibition of NF-κB led to a decreased TLR-mediated IL-10 production in DC-SCRIPT knockdown DCs. Moreover, DC-SCRIPT knockdown DCs showed enhanced phosphorylation, acetylation, and IL10 enhancer binding of the NF-κB subunit p65. These data demonstrate that besides nuclear receptor regulation, DC-SCRIPT also modulates activation of NF-κBp65 after TLR activation in human DCs.

DC-SCRIPT is a novel regulator of the tumor suppressor gene CDKN2B and induces cell cycle arrest in ERα-positive breast cancer cells.

Breast cancer is one of the most common causes of cancer-related deaths in women. The estrogen receptor (ERα) is well known for having growth promoting effects in breast cancer. Recently, we have identified DC-SCRIPT (ZNF366) as a co-suppressor of ERα and as a strong and independent prognostic marker in ESR1 (ERα gene)-positive breast cancer patients. In this study, we further investigated the molecular mechanism on how DC-SCRIPT inhibits breast cancer cell growth. DC-SCRIPT mRNA levels from 190 primary ESR1-positive breast tumors were related to global gene expression, followed by gene ontology and pathway analysis. The effect of DC-SCRIPT on breast cancer cell growth and cell cycle arrest was investigated using novel DC-SCRIPT-inducible MCF7 breast cancer cell lines. Genome-wide expression profiling of DC-SCRIPT-expressing MCF7 cells was performed to investigate the effect of DC-SCRIPT on cell cycle-related gene expression. Findings were validated by real-time PCR in a cohort of 1,132 ESR1-positive breast cancer patients. In the primary ESR1-positive breast tumors, DC-SCRIPT expression negatively correlated with several cell cycle gene ontologies and pathways. DC-SCRIPT expression strongly reduced breast cancer cell growth in vitro, breast tumor growth in vivo, and induced cell cycle arrest. In addition, in the presence of DC-SCRIPT, multiple cell cycles related genes were differentially expressed including the tumor suppressor gene CDKN2B. Moreover, in 1,132 primary ESR1-positive breast tumors, DC-SCRIPT expression also correlated with CDKN2B expression. Collectively, these data show that DC-SCRIPT acts as a novel regulator of CDKN2B and induces cell cycle arrest in ESR1-positive breast cancer cells.

Vitamin D controls murine and human plasmacytoid dendritic cell function.

Topical application of the vitamin D (VitD) analog calcipotriol is a highly effective standard treatment modality of psoriatic skin lesions. However, the immune modulatory effects of the treatment are incompletely understood. VitD is well known to induce tolerogenic responses in conventional dendritic cells (cDCs). Plasmacytoid DCs (pDCs) comprise a specialized, naturally occurring DC subset known to be important in autoimmune diseases including psoriasis. pDCs from the blood rapidly infiltrate psoriatic skin and are key to the initiation of the immune-mediated pathogenesis of the disease. We now demonstrate that pDCs express various proteins of the VitD receptor (VDR) pathway, including the VitD-metabolizing enzymes Cyp27B1 and Cyp24A1, and that VDR is transcriptionally active in pDCs. Moreover, VitD impairs the capacity of murine and human pDCs to induce T-cell proliferation and secretion of the T-helper 1 cytokine IFNγ. The inhibitory effect of VitD is dependent on the expression of the VDR in the DCs. This study demonstrates that VitD signaling can act as a natural inhibitory mechanism on both cDCs and pDCs, which may instigate the development of VitD-based therapeutic applications for psoriasis and other inflammatory skin diseases.

Nuclear receptor expression patterns in murine plasmacytoid and conventional dendritic cells.

Dendritic cells (DC) play a central role in the immune system. They can either induce immunity or promote tolerance. The DC family is generally comprised of two functionally distinct DC subsets. Conventional dendritic cells (cDC) are the classical antigen presenting cells; plasmacytoid dendritic cells (pDC) are the main producers of type I interferons thereby serving innate immunity. Upon activation DCs are able to present antigen and stimulate T cells. The immune modulatory functions of DCs largely depend on the recognition of soluble cues. Besides pathogen derived cues, recent data indicate that the tissue micro-environment, i.e. of the gut and skin affects cDC function. Many of these micro-environmental factors are ligands for the nuclear receptor (NR) family of transcription regulators known to affect immunity and tolerance. Whether pDC function is also influenced by tissue derived cues, like hormones, vitamins and metabolic products, is largely unknown. Here, we investigated the NR expression profile of murine pDCs and cDCs. We assessed the mRNA levels of 19 NRs of in vitro derived as well as ex vivo isolated DCs from four different lymphoid tissues. We observed that cDCs and pDCs expressed the same repertoire of NRs. Expression levels, however, differed between the two subsets, especially upon maturation of DCs. These data imply that NR ligands do impact pDC function and that their activity might be regulated in a DC-specific manner.

Analysis of genes regulated by the transcription factor LUMAN identifies ApoA4 as a target gene in dendritic cells.

Dendritic cells (DCs) are professional antigen presenting cells of the immune system that play a crucial role in initiating immune responses and maintaining self tolerance. Better understanding of the molecular basis of DC immunobiology is required to improve DC-based immunotherapies. We previously described the interaction of transcription factor LUMAN (also known as CREB3 or LZIP) with the DC-specific transmembrane protein DC-STAMP in DCs. Target genes of LUMAN and its role in DCs are currently unknown. In this study we set out to identify genes regulated by LUMAN in DCs using microarray analysis. Expression of a constitutively active form of LUMAN in mouse DC cell line D2SC/1 identified Apolipoprotein A4 (ApoA4) as its target gene. Subsequent validation experiments, bioinformatics-based promoter analysis, and silencing studies confirmed that ApoA4 is a true target gene of LUMAN in bone marrow-derived DCs (BMDCs).

DC-STAMP interacts with ER-resident transcription factor LUMAN which becomes activated during DC maturation.

Dendritic cells (DCs) are the professional antigen-presenting cells (APC) which efficiently prime the immune response or induce tolerance. We recently identified Dendritic Cell Specific TrAnsMembrane Protein (DC-STAMP), a novel 470 amino acid protein preferentially expressed by dendritic cells. Previously we demonstrated that DC-STAMP re-localizes towards the Golgi upon DC maturation. To identify proteins that interact with DC-STAMP, a yeast-2-hybrid analysis was performed. Here, we report a physically interacting partner of DC-STAMP in the endoplasmic reticulum (ER), called LUMAN (also known as CREB3 or LZIP). LUMAN was previously described as an ER-resident transcription factor with unknown function. It is activated in a process called regulated intramembrane proteolysis (RIP), which involves translocation to the Golgi and subsequent proteolytic cleavage. The proteolytically activated form of the protein then translocates to the nucleus. Our data indicate that DC-STAMP plays an important role in the modulation of LUMAN activation. Moreover, we demonstrate that LUMAN is endogenously expressed by DC and becomes activated by RIP upon DC maturation induced by various different stimuli. These data define LUMAN/DC-STAMP as a novel regulatory circuit in DC.

Molecular characterization of the murine homologue of the DC-derived protein DC-SCRIPT.

Dendritic cell-specific transcript (DC-SCRIPT) is a putative DC zinc (Zn) finger-type transcription factor described recently in humans. Here, we illustrate that DC-SCRIPT is highly conserved in evolution and report the initial characterization of the murine ortholog of DC-SCRIPT, which is also preferentially expressed in DC as shown by real-time quantitative polymerase chain reaction, and its distribution resembles that of its human counterpart. Studies undertaken in human embryonic kidney 293 cells depict its nuclear localization and reveal that the Zn finger domain of the protein is mainly responsible for nuclear import. The human and the mouse genes are located in syntenic chromosomal regions and exhibit a similar genomic organization with numerous common transcription factor-binding sites in their promoter region, including sites for many factors implicated in haematopoiesis and DC biology, such as Gfi, GATA-1, Spi-B, and c-Rel. Taken together, these data show that DC-SCRIPT is well-conserved in evolution and that the mouse homologue is more than 80% homologous to the human protein. Therefore, mouse models can be used to elucidate the function of this novel DC marker.

Identification and characterization of DC-SCRIPT, a novel dendritic cell-expressed member of the zinc finger family of transcriptional regulators.

Dendritic cells (DC) compose a heterogeneous population of cells that hold a leading role in initiating and directing immune responses. Although their function in recognizing, capturing, and presenting Ags is well defined, the molecular mechanisms that control their differentiation and immune functions are still largely unknown. In this study, we report the isolation and characterization of DC-SCRIPT, a novel protein encoded by an 8-kb mRNA that is preferentially expressed in DC. DC-SCRIPT is expressed in multiple DC subsets in vivo, including myeloid DC, plasmacytoid DC, and Langerhans cells. At the protein level, DC-SCRIPT consists of a proline-rich region, 11 C2H2-type zinc fingers, and an acidic region. Localization studies reveal that DC-SCRIPT resides in the nucleus and that nuclear localization is critically dependent on the zinc fingers. The protein displays no transcriptional activation properties according to assorted transactivation assays, but interacts with the corepressor C-terminal binding protein 1. Taken together, our results show that we have isolated a novel DC marker that could be involved in transcriptional repression. In contrast to other DC molecules, DC-SCRIPT identifies all DC subsets tested to date.

The dendritic cell-derived protein DC-STAMP is highly conserved and localizes to the endoplasmic reticulum.

Recently, we described the molecular identification of dendritic cell-specific TrAnsMembrane protein (DC-STAMP), a multimembrane-spanning protein preferentially expressed by human DC (hDC). In this report, we describe the identification and expression profile of the murine homologue of DC-STAMP (mDC-STAMP) as well as the characterization of the DC-STAMP protein. The results demonstrate that mDC-STAMP is over 90% homologous to hDC-STAMP and is also preferentially expressed by DC in vitro and ex vivo. mDC-STAMP expression is enhanced by interleukin-4 and down-regulated upon DC maturation. Analysis of differently tagged DC-STAMP proteins further demonstrates that hDC-STAMP and mDC-STAMP are glycosylated and primarily localize to an intracellular compartment. Applying confocal microscopy and electron microscopy, we demonstrate that hDC-STAMP localizes to the endoplasmic reticulum (ER) in human embryonic kidney 293 cells as well as hDC transduced with an adenovirus encoding hDC-STAMP-green fluorescent protein fusion protein. These data imply that DC-STAMP may exert its effect in the ER.