Activation of dendritic cells by targeted DNA: a potential addition to the armamentarium for anti-cancer immunotherapy.

In the past decade, remarkable progress has been made in immunotherapy against cancer. Specifically, the introduction of immune checkpoint inhibitors has revolutionized the field. However, many patients are unable to benefit significantly from this treatment option. One of the major reasons for this is most likely the absence of an adequate tumor-specific T cell response in these patients. A way to circumvent this problem might be to combine immune checkpoint inhibitor treatment with new strategies to activate tumor-specific T cells. One such strategy could be to activate and mature dendritic cells in situ. Dendritic cells carry an array of external and internal pattern recognition receptors that induce cell activation and maturation when interacting with their corresponding damage-associated or pathogen-associated molecular patterns (DAMPs or PAMPs). Targeting such molecular patterns directly to dendritic cells might be a way to evoke stronger immune responses. Here, we review our recent findings using antibody-targeted DNA. We summarize the results from our experiments showing that dendritic cells can be actively targeted in vivo through the αXß2 integrin subunit CD11c, and that DNA delivered through this receptor in vitro leads to maturation of dendritic cells via the cytosolic cGAS/STING DNA-sensing pathway.

Interleukin 20 protein locates to distinct mononuclear cells in psoriatic skin.

We previously demonstrated that mRNA for the pro-inflammatory cytokine interleukin 20 (IL-20) is expressed in suprapapillary keratinocytes of lesional psoriatic skin (LS). Here, we describe the distribution of IL-20 protein and the identity of the IL-20-positive cells in LS. We found that the main part of IL-20 immunoreactivity is present in mononuclear cells of the dermal papillae, and that the IL-20-positive cells located in the papillae were langerin+, CD1a+, CD4+ and CD303+. These cells might be immature dendritic cell. In situ hybridization for IL-20 mRNA on non-LS, ex vivo stimulated with IL-1ß revealed a colocalization between IL-20 mRNA and the keratinocyte marker CK14. No IL-20 mRNA was detected in the dermal mononuclear cells. Our results suggest that IL-20 is produced by keratinocytes, released into the epidermis and then possibly taken up by papillary mononuclear cells. Our study supports that IL-20 is involved in the pathogenesis of psoriasis.

Oral vitamin D3 supplementation reduces monocyte-derived dendritic cell maturation and cytokine production in Crohn's disease patients.

BACKGROUND: Low serum vitamin D levels may provoke or aggravate Crohn's disease (CrD). Vitamin D3 is a well-known immune modulator that affects immune functions in vitro and may prevent CrD flares. Dendritic cells (DC) are key mediators of vitamin D3 effects. In this study, we describe changes in monocyte-derived DC (mo-DC) maturation marker expression and cytokine production following 26 weeks of oral vitamin D3 supplementation in CrD patients. METHODS: Ten CrD patients who had increased serum 25-hydroxy vitamin D levels after oral vitamin D3 and calcium treatment and ten seasonally matched placebo-treated patients were selected for this study. Mo-DC were generated before and after the 26 weeks and induced to mature upon lipopolysaccharide (LPS) stimulation. Maturation marker expression and cytokine production were analysed. Mo-DC function was analysed in a mixed leucocyte reaction (MLR). RESULTS: Compared with baseline values, LPS-matured mo-DC exhibited reduced expression of CD80 and reduced production of the cytokines IL-10, IL-1ß, and IL-6 following 26 weeks of oral vitamin D3 supplementation. Mo-DC performance in an allogeneic MLR was unchanged after vitamin D3 supplementation. Treatment with the placebo did not affect maturation markers, cytokine production, or the MLR. CONCLUSIONS: Vitamin D3 treatment in CrD patients led to hypo-responsive LPS-stimulated mo-DC. This finding indicates that vitamin D3 levels have an impact on the monocytic precursors of mo-DC in vivo and may explain the positive effects of vitamin D3 supplementation on CrD patients. Alternatively, CrD patients with high serum vitamin D3 levels may represent a subgroup with low disease activity.

Novel nucleotide-packaging vaccine delivers antigen and poly(I:C) to dendritic cells and generate a potent antibody response in vivo.

An issue with many current vaccines is the dependency on broadly inflammatory adjuvants, such as aluminum hydroxide or aluminum salts that affect many immune- and non-immune cells. These adjuvants are not necessarily activating all antigen-presenting cells (APCs) that take up the antigen and most likely they also activate APCs with no antigen uptake, as well as many non-immune cells. Conjugation of antigen and adjuvant would enable the use of smaller amounts of adjuvant and avoid unnecessary tissue damage and activation of bystander cells. It would ensure that all APCs that take up the antigen would also become activated and avoid that immature and non-activated APCs present the antigen to T cells without a co-stimulatory signal, leading to tolerogenesis. We have developed a novel vaccine that co-deliver antigen and a nucleotide adjuvant to the same APC and lead to a strong activation response in dendritic cells and macrophages. The vaccine is constructed as a fusion-protein with an antigen fused to the DNA/RNA-binding domain from the Hc2 protein from Chlamydia trachomatis. We have found that the fusion protein is able to package polyinosinic:polycytidylic acid (poly(I:C)) or dsDNA into small particles. These particles were taken up by macrophages and dendritic cells and led to strong activation and maturation of these cells. Immunization of mice with the fusion protein packaged poly(I:C) led to a stronger antibody response compared to immunization with a combination of poly(I:C) and antigen without the Hc2 DNA/RNA-binding domain.

Cholesterol-binding motifs in STING that control endoplasmic reticulum retention mediate anti-tumoral activity of cholesterol-lowering compounds.

The cGAS-STING pathway plays a crucial role in anti-tumoral responses by activating inflammation and reprogramming the tumour microenvironment. Upon activation, STING traffics from the endoplasmic reticulum (ER) to Golgi, allowing signalling complex assembly and induction of interferon and inflammatory cytokines. Here we report that cGAMP stimulation leads to a transient decline in ER cholesterol levels, mediated by Sterol O-Acyltransferase 1-dependent cholesterol esterification. This facilitates ER membrane curvature and STING trafficking to Golgi. Notably, we identify two cholesterol-binding motifs in STING and confirm their contribution to ER-retention of STING. Consequently, depletion of intracellular cholesterol levels enhances STING pathway activation upon cGAMP stimulation. In a preclinical tumour model, intratumorally administered cholesterol depletion therapy potentiated STING-dependent anti-tumoral responses, which, in combination with anti-PD-1 antibodies, promoted tumour remission. Collectively, we demonstrate that ER cholesterol sets a threshold for STING signalling through cholesterol-binding motifs in STING and we propose that this could be exploited for cancer immunotherapy.

25-Hydroxy vitamin D3 modulates dendritic cell phenotype and function in Crohn's disease.

BACKGROUND: In Crohn's disease (CrD), vitamin D may help to balance an exaggerated immune response and thereby improve the disease course. The immunomodulating effects depend on the activation of 25-hydroxy vitamin D3 (25-D3), into 1,25-dihydroxy vitamin D3 (1,25-D3). This activation has previously been shown to take place in dendritic cells (DC) from healthy individuals. We hypothesised that DC from CrD patients are able to regulate and control inflammatory responses through 25-D3 activation. METHODS: During differentiation, monocyte-derived DC from 20 CrD patients were cultured with either 25-D3 or 1,25-D3 and matured with lipopolysaccharide (LPS). We examined DC surface marker expression, cytokine production, and the ability to induce cell proliferation in an allogeneic mixed leukocyte reaction. RESULTS: Following stimulation with LPS, DC exposed to either 25-D3 or 1,25-D3 exhibited lower expression levels of CD80, CD83, CD86, and HLA-DR and diminished TNF-α production compared with DC cultured with LPS alone. In contrast, CD14 expression and IL-6 production were higher following 25-D3 or 1,25-D3 treatment. Compared with LPS alone, both forms of vitamin D3 reduced the ability of DC to activate lymphocytes. CONCLUSIONS: Following stimulation with 25-D3, DC from CrD patients displayed a reduced response to LPS with a diminished capability to activate T cells compared with DC stimulated with LPS alone. These data indicate that intrinsic activation of 25-D3 occurs in DC from CrD patients and show that 25-D3 can modulate DC function in CrD. Our data suggest that vitamin D deficiency may contribute to the uncontrolled inflammatory process seen in CrD.

Boron nanoparticles inhibit tumour growth by boron neutron capture therapy in the murine B16-OVA model.

BACKGROUND: Boron neutron capture therapy usually relies on soluble, rather than particulate, boron compounds. This study evaluated the use of a novel boron nanoparticle for boron neutron capture therapy. MATERIALS AND METHODS: Two hundred and fifty thousand B16-OVA tumour cells, pre-incubated with boron nanoparticles for 12 hours, were injected subcutaneously into C57BL/6J mice. The tumour sites were exposed to different doses of neutron radiation one, four, or eight days after tumour cell inoculation. RESULTS: When the tumour site was irradiated with thermal neutrons one day after injection, tumour growth was delayed and the treated mice survived longer than untreated controls (median survival time 20 days (N = 8) compared with 10 days (N = 7) for untreated mice). CONCLUSION: Boron nanoparticles significantly delay the growth of an aggressive B16-OVA tumour in vivo by boron neutron capture therapy.

CD11c-targeted Delivery of DNA to Dendritic Cells Leads to cGAS- and STING-dependent Maturation.

Immunotherapeutic activation of tumor-specific T cells has proven to be an interesting approach in anticancer treatment. Particularly, anti-CTLA-4 and anti-PD-1/PD-L1 treatment looks promising, and conceivably, even better clinical results might be obtained if such treatment could be combined with boosting the existing tumor-specific T-cell response. One way to achieve this could be by increasing the level of maturation of dendritic cells locally and in the draining lymph nodes. When exposed to cancer cells, dendritic cells may spontaneously mature because of danger-associated molecular patterns derived from the tumor cells. Double-stranded DNA play a particularly important role in the activation of the dendritic cells, through engagement of intracellular DNA-sensors, and signaling through the adaptor protein STING. In the present study, we have investigated the maturational response of human monocyte-derived dendritic cells (moDC) and human monocytic THP-1 cells to targeted and untargeted DNA. We used an anti-CD11c antibody conjugated with double-stranded DNA to analyze the maturation status of human moDCs, as well as maturation using a cGAS KO and STING KO THP-1 cell maturation model. We found that dendritic cells can mature after exposure to cytoplasmic double-stranded DNA delivered through CD11c-mediated endocytosis. Moreover, we show that THP-1 cells matured using IL-4, GM-CSF, and ionomycin upregulate DC-maturation markers after CD11c-targeted delivery of double-stranded DNA. This upregulation is completely abrogated in cGAS KO and STING KO cells.

Interleukin 20 regulates dendritic cell migration and expression of co-stimulatory molecules.

BACKGROUND: Psoriasis is an inflammatory disease characterized by leukocyte skin infiltration. Interestingly, recent works suggest that the migration of dendritic cells (DCs) is abnormal in psoriatic skin. DCs have significant role in regulating the function of T lymphocytes, at least in part influenced by the local environment of cytokines. In psoriatic skin lesions the expression of IL-20 is highly up-regulated. It is unclear if this cytokine has any influence on DCs. METHODS: Here, we investigated the influence of IL-20 in monocyte-derived dendritic cell (MDDCs) in vitro. This work addressed IL-20 effects on DC maturation, receptor expression and signaling. By use of extra cellular matrix components mimicking the skin environment, we also studied the functional effects of IL-20 on the chemotactic migration of DCs. Based on the recent finding that CD18 integrin are shed during migration of myeloid leukocytes, the concentration of these adhesion molecules was measured in MDDCs culture supernatants post migration. RESULTS: Following stimulation with IL-20, immature human MDDCs enhanced the expression of the co-stimulatory molecule CD86, further enabling activation of the p38 MAPK, but not the STAT3, pathway. IL-20 increased the migration of MDDCs in a biphasic response narrowly controlled by the interleukin concentration. A concomitant change in the shedding of CD18 integrins suggested that these adhesion molecules play a role in the migration of the MDDCs through the extracellular matrix layer. CONCLUSION: Taken together, our findings points to a possible, yet subtle, role of IL-20 in DCs migration. The biphasic response suggests that the aberrant IL-20 expression in psoriasis impedes DC migration, which could be a part of the processes that precipitates the dysregulated inflammatory response associated with this disease.

Immunohistochemical characterisation of the local immune response in azoxymethane-induced colon tumours in the BDIX inbred rat strain.

The aim of the present study was to characterise the local immune response in a chemically induced colon tumour model in the rat. Elucidating the character of the immune reaction may contribute to optimizing immunotherapeutic regimens for colon carcinoma in this model. Colon cancer was induced by four weekly subcutaneous azoxymethane injections in inbred rats of the BDIX/OrlIco strain in two separate studies. Azoxymethane-induced tumours show many similarities to spontaneously occurring human colon carcinomas with respect to histopathological appearance. In our studies, the overall inflammatory reaction of the submucosa below the tumour was evaluated in haematoxylin-eosin-stained tissue sections. Phenotypic characterization of leukocyte infiltration in the tumour tissue was performed by immunohistochemical staining using antibodies detecting various leukocyte subsets, i.e. T cells, natural killer cells, macrophages/monocytes, and dendritic cells. The results showed that the azoxymethane-induced colon tumours were strongly infiltrated by macrophages. Furthermore, the tumours showed a moderate degree of infiltrating CD4-positive cells. Very few natural killer, CD8-positive T cells and dendritic cells (identified by the OX62 antibody) were seen in the tumour tissue. Virtually no CD25-positive cells were found. This immunohistochemical characterisation of the tumour-infiltrating immune response in this rat model could form the basis for studies aimed at developing new immunotherapeutic regimens for human colon cancer.

Cripto-1 expression in glioblastoma multiforme.

Human glioblastoma multiforme (GBM) is an aggressive cancer with a very poor prognosis. Cripto-1 (CR-1) has a key regulatory role in embryogenesis, while in adult tissue re-expression of CR-1 has been correlated to malignant progression in solid cancers of non-neuronal origin. As CR-1 expression has yet to be described in cerebral cancer and CR-1 is regulated by signaling pathways dysregulated in GBM, we aimed to investigate CR-1 in the context of expression in GBM. The study was performed using enzyme-linked immunosorbent assay (ELISA), Western blotting, polymerase chain reaction (PCR) and immunohistochemistry to analyze the blood and tissue from 28 GBM and 4 low-grade glioma patients. Within the patient cohort, we found high CR-1 protein levels in blood plasma to significantly correlate with a shorter overall survival. We identified CR-1 in different areas of GBM tissue, including perivascular tumor cells, and in endothelial cells. Collectively, our data suggest that CR-1 could be a prognostic biomarker for GBM with the potential of being a therapeutic target.

Targeted antiepidermal growth factor receptor (cetuximab) immunoliposomes enhance cellular uptake in vitro and exhibit increased accumulation in an intracranial model of glioblastoma multiforme.

Therapeutic advances do not circumvent the devastating fact that the survival rate in glioblastoma multiforme (GBM) is less than 5%. Nanoparticles consisting of liposome-based therapeutics are provided against a variety of cancer types including GBM, but available liposomal formulations are provided without targeting moieties, which increases the dosing demands to reach therapeutic concentrations with risks of side effects. We prepared PEGylated immunoliposomes (ILs) conjugated with anti-human epidermal growth factor receptor (EGFR) antibodies Cetuximab ( α -hEGFR-ILs). The affinity of the α -hEGFR-ILs for the EGF receptor was evaluated in vitro using U87 mg and U251 mg cells and in vivo using an intracranial U87 mg xenograft model. The xenograft model was additionally analyzed with respect to permeability to endogenous albumin, tumor size, and vascularization. The in vitro studies revealed significantly higher binding of α -hEGFR-ILs when compared with liposomes conjugated with isotypic nonimmune immunoglobulin. The uptake and internalization of the α -hEGFR-ILs by U87 mg cells were further confirmed by 3D deconvolution analyses. In vivo, the α -hEGFR-ILs accumulated to a higher extent inside the tumor when compared to nonimmune liposomes. The data show that α -hEGFR-ILs significantly enhance the uptake and accumulation of liposomes in this experimental model of GBM suggestive of improved specific nanoparticle-based delivery.

Human dendritic cell antigen presentation and chemotaxis are inhibited by intrinsic 25-hydroxy vitamin D activation.

The immunomodulatory effects of vitamin D have primarily been investigated using the biologically active form 1,25-dihydroxy vitamin D3 (1,25-D3). It was recently demonstrated that dendritic cells (DC) are able to convert the inactive 25-hydroxy vitamin D3 (25-D3) into the active form via 1 alpha-hydroxylase. In this study, we set out to examine the possible consequences of this conversion on adaptive immune functions. Human monocyte-derived DC were matured by lipopolysaccharide (LPS) in the presence or absence of 25-D3. Subsequently, the conversion of 25-D3 into 1,25-D3, and the effects on surface marker expression, cytokine production, antigen-presenting capacity and chemotaxis of the DC were examined. 25-D3 was clearly converted into 1,25-D3 in the DC cultures and the process was accompanied by a reduced expression of CD80 (p<0.01), CD83 (p<0.01), CD86 (p=0.02), and HLA-DR (p=0.02). Also, the levels of the pro-inflammatory cytokines tumour necrosis factor (TNF) alpha (p=0.02) and interleukin (IL) 12 (p<0.01) were reduced. Interestingly, however, the CD14 expression (p<0.01) and the production of IL-1 beta (p<0.01) and IL-6 (p<0.01) increased. Thus, 25-D3 affected the delicate interplay between anti- and pro-inflammatory cytokines produced by the DC. Concurrently, 25-D3 reduced DC capacity to induce proliferation of antigen-specific T cells and DC chemotaxis towards chemokine (CC) ligand 21. This indicates that 25-D3 has a regulating function following intrinsic 1 alpha-hydroxylation, a mechanism that potentially has an immunomodulatory effect in vivo.

T cell homing to tumors detected by 3D-coordinated positron emission tomography and magnetic resonance imaging.

A general hindrance to progress in adoptive cellular therapy is the lack of detailed knowledge of the fate of transferred cells in the body of the recipient. In this study, we present a novel technique for tracking of 124I-labeled cells in situ, which combines the high spatial resolution of magnetic resonance imaging with the high sensitivity and spatial accuracy of positron emission tomography. We have used this technique, together with determination of tissue radioactivity, flow cytometry, and microscopy, to characterize and quantitate the specific accumulation of transferred CD8+ T cells in tumor tissue in a mouse model. Transgenic CD8+ T cells, specific for the ovalbumin peptide SIINFEKL, were adoptively transferred to recipients carrying a subcutaneous tumor of the ovalbumin-expressing malignant melanoma cell line B16-OVA. The number of SIINFEKL-specific CD8+ cells in the tumor tissue was determined by flow cytometry each day for 8 consecutive days after adoptive transfer. From low levels 1 day after injection, their number gradually increased until day 5 when an average of 3.3x10(6) SIINFEKL-specific cells per gram tumor tissue was found. By applying the combined positron emission tomography/magnetic resonance imaging technique we were able to determine the position of the transferred, 124I-labeled SIINFEKL-specific T cells in 3 dimensions in recipient mice, and could demonstrate a highly significant accumulation of the 124I label in and around the subcutaneous B16-OVA tumors compared with normal tissue. Accumulation of 124I was significantly higher in B16-OVA than in B16 tumors not expressing the OVA antigen.

Tumour-associated macrophages are related to progression in patients with metastatic melanoma following interleukin-2 based immunotherapy.

The aim of the present study was to analyze whether leukocyte subsets in peripheral blood and tumour biopsies obtained before treatment were able to predict response or survival in patients with metastatic melanoma following Interleukin-2 (IL-2) based immunotherapy. Flow cytometry was performed on peripheral blood for CD4(+) T cells, CD8(+) T cells and CD56(+) natural killer (NK) cells. Immunohistochemical analyses were used to identify CD4(+) T cells, CD8(+) T cells, CD57(+) NK cells and CD64(+) (macrophages) cells in tumour biopsies. High numbers of tumour-associated CD64(+) macrophages in tumour biopsies were statistically significantly associated with poor response to treatment. Our data suggest that tumour-associated macrophages may correlate negatively with response, which may be of biological importance for IL-2 based immunotherapy of malignant melanoma.

Accumulation in tumor tissue of adoptively transferred T cells: A comparison between intravenous and intraperitoneal injection.

Accumulation of T cells at the tumor is essential in cancer immunotherapy based on adoptive transfer of tumor-specific T cells. To gain further insight into the accumulation process and to evaluate the effect of using different routes of cell transfer, we investigated the accumulation of ovalbumin-specific CD8+ T cells (OT-I) injected either intravenously (IV) or intraperitoneally (IP) into mice carrying a subcutaneous tumor of the ovalbumin-expressing melanoma cell line B16-OVA. Maximal accumulation of the adoptively transferred cells in tumor tissue was observed 5 days after injection, irrespective of the injection route. The route of injection affected neither the total number of adoptively transferred cells found in tumor tissue nor the kinetics of this accumulation. In the spleen, however, the accumulation of adoptively transferred cells was clearly dependent on the injection route. IP injections resulted in a large number of adoptively transferred cells in the spleen on all days analyzed. In comparison, IV injection resulted in significantly fewer adoptively transferred cells in the spleen, and this number decreased over time. The route of injection affected neither the activation status of the adoptively transferred T cells that accumulated at the tumor site, nor the ability of these cells to control tumor growth. Two cell populations, SIINFEKL-tetramer(Low)(Tet(Low))CD69+ CD25+ and Tet(high)CD69- CD25-, were present in tumor samples, whereas only Tet(High)CD69- CD25- cells accumulated in the spleen. In tumors, IV injection resulted in a higher fraction of adoptively transferred cells with an activated phenotype (Tet(Low)CD69+ CD25+) compared with IP injection.

Detection of circulating tumor lysate-reactive CD4+ T cells in melanoma patients.

PURPOSE: We wanted to study whether an allogeneic melanoma lysate would be a feasible stimulatory antigen source for detection of a peripheral CD4+ T-cell immune response in patients with medically untreated malignant melanoma. The lysate was produced from a melanoma cell line (FM3.29) which expresses high amounts of melanoma antigens. METHODS: Fresh peripheral blood was incubated with and without lysate for 6 h in the presence of anti-CD28/anti-CD49d MoAb (for costimulation). After flow cytometric estimation of the frequency of CD69+/IFN-gamma+ cells in the CD4+ population, the response to lysate was calculated as the difference between the number of activated IFN-gamma-producing CD4+ cells in the lysate-stimulated and the nonstimulated sample. RESULTS: An immune response to lysate was observed in blood samples from 11 of 15 patients (73%) with metastatic melanoma. A weak response was found in 1 of 4 patients radically operated for localized disease, whereas no responders were seen among 7 healthy donors. The fraction of circulating lysate-activated T cells ranged from 0.0037% to 0.080% of the CD4+ population. A negative result of the assay was found occasionally, especially in donors with high background levels of spontaneous IFN-gamma production, indicating an inhibitory effect of the lysate. CONCLUSIONS: This method for detection of a peripheral T-cell immune response in melanoma patients has several advantages for clinical use. The tumor lysate preparations may contain large numbers of stimulating antigens (known, as well as unknown) and are easily prepared and handled. Potentially, the assay might be useful as a diagnostic tool, a marker of residual or recurrent disease, a prognostic factor, or a predictor or monitor of the effect of antineoplastic therapy including immune-modulating therapy.