Dendritic cells dysfunction in tumour environment

A novel costimulatory molecule gene-modified leukemia cell-derived exosome enhances the anti-leukemia efficacy of DC vaccine in mouse models

OBJECTIVES

Leukemia cell-derived exosomes (LEXs), carrying leukemia cell-specific antigens, can serve as a source of antigen for dendritic cell (DC) vaccine loading. However, LEX-targeted DC-based vaccines have demonstrated limited antitumor immune effects in clinical trials, attributed to the low immunogenicity of LEXs and the scant levels of costimulatory molecules on DCs. The costimulatory molecules CD80 and CD86, which are crucial to DC function, play a significant role in enhancing immune efficacy. In this study, we explored the anti-leukemia immune response of costimulatory molecule gene-modified LEX-targeted DCs (LEX-8086) in vitro and in animal models.

METHODS

DCs were incubated with LEX-8086 to produce LEX-8086-targeted DCs (DCsLEX-8086). ELISA, cytotoxicity assays and flow cytometry utilized to assess the antitumor efficacy of DCsLEX8086 in vitro. Flow cytometry was used to evaluate the immunomodulatory function of DCsLEX8086 in animal models.

RESULTS

Our findings indicated that LEX-8086 enhanced the maturation and antigen-presenting ability of DCs. Immunization with DCsLEX8086 significantly activated CD8+ T cells and boosted the CTL response in vitro. More importantly, DCsLEX-8086 effectively suppressed tumor growth and exerted anti-leukemia effects in both prophylactic and therapeutic animal models. Furthermore, DCsLEX-8086 promoted the proportion of CD4+ T cells, CD8+ T cells and M1 macrophages in the tumor environments both prophylactically and therapeutically. Treatment with DCsLEX-8086 showed no significant difference in the levels of M2 macrophages but decreased the proportion of Tregs within the tumor bed during therapeutic experiments.

CONCLUSION

The results suggested that DCsLEX-8086 induces a more effective anti-leukemia immunity compared to DCsLEX-null in vivo and in vitro. DCsLEX-8086 might achieve antitumor effects by elevating the numbers of CD4+ T cells, CD8+ T cells, and M1 macrophages in tumors. Our findings indicate that DCsLEX-8086 could be leveraged to develop a new, highly effective vaccine for anti-leukemia immunity.

Engineered bacteria breach tumor physical barriers to enhance radio-immunotherapy

Radiotherapy widely applied for local tumor therapy in clinic has been recently reinvigorated by the discovery that radiotherapy could activate systematic antitumor immune response. Nonetheless, the endogenous radio-immune effect is still incapable of radical tumor elimination due to the prevention of immune cell infiltration by the physical barrier in tumor microenvironment (TME). Herein, an engineered Salmonella secreting nattokinase (VNPNKase) is developed to synergistically modulate the physical and immune characteristics of TME to enhance radio-immunotherapy of colon tumors. The facultative anaerobic VNPNKase enriches at the tumor site after systemic administration, continuously secreting abundant NKase to degrade fibronectin, dredge the extracellular matrix (ECM), and inactivate cancer-associated fibroblasts (CAFs). The VNPNKase- dredged TME facilitates the infiltration of CD103+ dendritic cells (DCs) and thus the presentation of tumor-associated antigens (TAAs) after radiotherapy, recruiting sufficient CD8+ T lymphocytes to specifically eradicate localized tumors. Moreover, the pre-treatment of VNPNKase before radiotherapy amplifies the abscopal effect and achieves a long-term immune memory effect, preventing the metastasis and recurrence of tumors. Our research suggests that this strategy using engineered bacteria to breach tumor physical barrier for promoting immune cell infiltration possesses great promise as a translational strategy to enhance the effectiveness of radio-immunotherapy in treating solid tumors.

Relation of Langerhans cell size to buccal carcinoma

Oral cancer decreases quality of life despite timely medical management. The carcinogens in tobacco products and their role in tumorigenesis are well documented. Langerhans cells (LCs) are a subset of antigen-presenting cells (APCs) that monitor the tumor microenvironment and engulf carcinogens and foreign bodies. We investigated the distribution and size of LCs and their relation to the mode of tobacco consumption and clinical outcome in patients with buccal carcinoma. We recruited patients with oral cancer who were scheduled for tumor excision and men with urethral stricture undergoing substitution urethroplasty using buccal mucosa. Normal and tumor-adjacent tissues were stained with CD1a antibody. The distribution and mean diameter of 100 LCs/patient were determined. We found significantly smaller LCs in patients who chewed only tobacco compared to those who consumed tobacco by other means. The size of LCs decreased significantly with progressive stages of malignant disease. We found that patients with larger LCs survived longer than those with smaller LCs during an average follow-up of 24 months. We suggest a relation between the size of LCs and clinical outcomes in patients with buccal carcinoma.

Application of Engineered Dendritic Cell Vaccines in Cancer Immunotherapy: Challenges and Opportunities

OPINION STATEMENT

The primary objective of this study is to evaluate the effectiveness of cancer vaccines containing genetically modified dendritic cells (DCs) in inducing transformational immune responses. This paper sheds considerable light on DCs' function in advancing treatment techniques. This objective is achieved by thoroughly analyzing the many facets of DCs and their strategic integration into cancer treatment. Due to their role as immune response regulators, DCs can potentially enhance cancer treatment strategies. DCs have the potential to revolutionize immunotherapy, as shown by a comprehensive analysis of their numerous characteristics. The review deftly transitions from examining the fundamentals of preclinical research to delving into the complexities of clinical implementation while acknowledging the inherent challenges in translating DC vaccine concepts into tangible progress. The analysis also emphasizes the potential synergistic outcomes that can be achieved by combining DC vaccines with established pharmaceuticals, thereby emphasizing the importance of employing a holistic approach to enhance treatment efficacy. Despite the existence of transformative opportunities, advancement is hindered by several obstacles. The exhaustive analysis of technical complexities, regulatory dynamics, and upcoming challenges provides valuable insights for overcoming obstacles requiring strategic navigation to incorporate DC vaccines successfully. This document provides a comprehensive analysis of the developments in DC-based immunotherapy, concentrating on its potential to transform cancer therapy radically.

Enhancing Immunogenicity in Metastatic Melanoma: Adjuvant Therapies to Promote the Anti-Tumor Immune Response

Advanced melanoma is an aggressive form of skin cancer characterized by low survival rates. Less than 50% of advanced melanoma patients respond to current therapies, and of those patients that do respond, many present with tumor recurrence due to resistance. The immunosuppressive tumor-immune microenvironment (TIME) remains a major obstacle in melanoma therapy. Adjuvant treatment modalities that enhance anti-tumor immune cell function are associated with improved patient response. One potential mechanism to stimulate the anti-tumor immune response is by inducing immunogenic cell death (ICD) in tumors. ICD leads to the release of damage-associated molecular patterns within the TIME, subsequently promoting antigen presentation and anti-tumor immunity. This review summarizes relevant concepts and mechanisms underlying ICD and introduces the potential of non-ablative low-intensity focused ultrasound (LOFU) as an immune-priming therapy that can be combined with ICD-inducing focal ablative therapies to promote an anti-melanoma immune response.

Bacterial outer membrane vesicle based versatile nanosystem boosts the efferocytosis blockade triggered tumor-specific immunity

Efferocytosis inhibition is emerging as an attractive strategy for antitumor immune therapy because of the subsequent leak of abundant immunogenic contents. However, the practical efficacy is seriously impeded by the immunosuppressive tumor microenvironments. Here, we construct a versatile nanosystem that can not only inhibit the efferocytosis but also boost the following antitumor immunity. MerTK inhibitor UNC2025 is loaded into the bacterial outer membrane vesicles (OMVs), which are then modified with maleimide (mU@OMVs). The prepared mU@OMVs effectively inhibits the efferocytosis by promoting the uptake while preventing the MerTK phosphorylation of tumor associated macrophages, and then captures the released antigens through forming universal thioether bonds. The obtained in situ vaccine effectively transfers to lymph nodes by virtue of the intrinsic features of OMVs, and then provokes intense immune responses that can efficiently prevent the growth, metastasis and recurrence of tumors in mice, providing a generalizable strategy for cancer immunotherapy.

Macrophages CD163+ and Factor XIIIa+ Provide a First-Line Defence against Proliferative Verrucous Leukoplakia Antigens

This study aimed to evaluate the density of the dendritic cells (DCs) and macrophages in oral leukoplakia (OL) and proliferative verrucous leukoplakia (PVL) by immunohistochemical analysis. We analysed paraffined tissue samples of PVL (n = 27), OL (n = 20), and inflammatory fibrous hyperplasia (n = 20) as the control group using the immunomarkers for DCs (CD1a, CD207, CD83, CD208 and CD123) and macrophages (CD68, CD163, FXIIIa and CD209). A quantitative analysis of positive cells in the epithelial and subepithelial areas was determined. Our results showed a reduction in CD208+ cells in the subepithelial area of the OL and PVL compared to the control. Additionally, we found a higher density of FXIIIa+ and CD163+ cells in the subepithelial area in PVL compared to the OL and control. Four-way MANOVA revealed a relationship between increased CD123+ cell density in the subepithelial area of “high-risk” samples regardless of disease. Macrophages provide the first line of defence against PVL antigens, suggesting a distinct pattern of innate immune system activation in PVL compared to OL, which may contribute to the complexity and the high rate of malignant transformation in the PVL.

The M2 macrophages infiltration of sebaceous tumors is linked to the aggressiveness of tumors but not to the mismatch repair pathway

PURPOSE

The immune microenvironment of sebaceous neoplasms (SNs) has been poorly explored, especially in benign lesions, and never correlated to the mismatch repair (MMR) status.

METHODS

We conducted an immuno-histological study to analyze the immune microenvironment of SNs. A tissue microarray was constructed including sebaceous adenomas (SAs), sebaceomas (Ss) and sebaceous carcinomas (SCs) to performed immuno-histological analysis of T cells, B cells, macrophages, dendritic cells, and expression of Programmed Death-1 (PD-1) and Programmed Death Ligand 1 (PD-L1). An automatized count was performed using the QuPath® software. Composition of the cellular microenvironment was compared to the aggressiveness, the MMR status, and to Muir-Torre syndrome (MTS).

RESULTS

We included 123 SNs (43 SAs, 19 Ss and 61 SCs) for which 71.5% had a dMMR phenotype. A higher infiltration of macrophages (CD68 +) of M2 phenotype (CD163 +) and dendritic cells (CD11c +) was noticed in SCs compared to benign SNs (SAs and Ss). Programmed cell death ligand-1 but not PD-1 was expressed by more immune cells in SCs compared to benign SNs. No difference in the immune cell composition regarding the MMR status, or to MTS was observed.

CONCLUSION

In SNs, M2 macrophages and dendritic cells infiltrates are associated with the progression and the malignant transformation of tumors. High PD-L1 expression in immune cells in SCs is an argument for the use of immunotherapy by anti-PD1 or PD-L1 in metastatic patients. The lack of correlation between the composition of immune cells in SNs and the MMR status emphasizes the singularity of SNs among MMR-associated malignancies.

Cutting-Edge CAR Engineering: Beyond T Cells

Chimeric antigen receptor (CAR)-T adoptive cell therapy is one of the most promising advanced therapies for the treatment of cancer, with unprecedented outcomes in haematological malignancies. However, it still lacks efficacy in solid tumours, possibly because engineered T cells become inactive within the immunosuppressive tumour microenvironment (TME). In the TME, cells of the myeloid lineage (M) are among the immunosuppressive cell types with the highest tumour infiltration rate. These cells interact with other immune cells, mediating immunosuppression and promoting angiogenesis. Recently, the development of CAR-M cell therapies has been put forward as a new candidate immunotherapy with good efficacy potential. This alternative CAR strategy may increase the efficacy, survival, persistence, and safety of CAR treatments in solid tumours. This remains a critical frontier in cancer research and opens up a new possibility for next-generation personalised medicine to overcome TME resistance. However, the exact mechanisms of action of CAR-M and their effect on the TME remain poorly understood. Here, we summarise the basic, translational, and clinical results of CAR-innate immune cells and CAR-M cell immunotherapies, from their engineering and mechanistic studies to preclinical and clinical development.

A therapeutic DC vaccine with maintained immunological activity exhibits robust anti-tumor efficacy

Dendritic cells (DCs) vaccines are a major focus of future anti-tumor immunotherapy for their pivotal role in eliciting reactive tumor-specific T-cell responses. Tumor cell-mediated DCs (TC-DC) activation and tumor antigen-mediated DCs (TA-DC) activation are two conventional modes of DC vaccine construction in clinical studies. The former physiologically mimicks the tumor identification and rejection, significantly contributing to DC-based immune recognition and migration towards the complexed tumor microenvironment (TME). However, as immunosuppressive molecules may exist in TME, these TC-DC are generally characterized with aberrant lipid accumulation and inositol-requiring kinase 1α (IRE1α)-X-box binding protein 1 (XBP1) hyperactivation, which is provoked by overwhelming oxidative stress and endoplasmic reticulum (ER) stress, resulting in TC-DC malfunction. Oppositely, without contacting immunosuppressive TME, TA-DC vaccines perform better in T-cell priming and lymph nodes (LNs) homing, but are relatively weak in TME infiltration and identification. Herein, we prepared a KIRA6-loaded α-Tocopherol nanoemulsion (KT-NE), which simultaneously ameliorated oxidative stress and ER stress in the dysfunctional lipid-laden TC-DC. The TC-DC treated by KT-NE could maintain immunological activity, simultaneously, exhibited satisfactory chemotaxis towards LNs and tumor sites in vivo, and effectively suppressed malignant progression by unleashing activated tumor-reactive T cells. This study generated a new DC-vaccine that owned puissant aptitude to identify complicated TME as well as robust immunological activity to boost T-cell initiation, which may provide some insights into the design and application of DC-vaccines for clinical application.

Triggering Receptors Expressed on Myeloid Cells 1 : Our New Partner in Human Oncology?

Inflammation is recognized as one of the hallmarks of cancer. Indeed, strong evidence indicates that chronic inflammation plays a major role in oncogenesis, promoting genome instability, epigenetic alterations, proliferation and dissemination of cancer cells. Mononuclear phagocytes (MPs) have been identified as key contributors of the inflammatory infiltrate in several solid human neoplasia, promoting angiogenesis and cancer progression. One of the most described amplifiers of MPs pro-inflammatory innate immune response is the triggering receptors expressed on myeloid cells 1 (TREM-1). Growing evidence suggests TREM-1 involvement in oncogenesis through cancer related inflammation and the surrounding tumor microenvironment. In human oncology, high levels of TREM-1 and/or its soluble form have been associated with poorer survival data in several solid malignancies, especially in hepatocellular carcinoma and lung cancer. TREM-1 should be considered as a potential biomarker in human oncology and could be used as a new therapeutic target of interest in human oncology (TREM-1 inhibitors, TREM-1 agonists). More clinical studies are urgently needed to confirm TREM-1 (and TREM family) roles in the prognosis and the treatment of human solid cancers.

Tim-3 adapter protein Bat3 acts as an endogenous regulator of tolerogenic dendritic cell function

Dendritic cells (DCs) sense environmental cues and adopt either an immune-stimulatory or regulatory phenotype, thereby fine-tuning immune responses. Identifying endogenous regulators that determine DC function can thus inform the development of therapeutic strategies for modulating the immune response in different disease contexts. Tim-3 plays an important role in regulating immune responses by inhibiting the activation status and the T cell priming ability of DC in the setting of cancer. Bat3 is an adaptor protein that binds to the tail of Tim-3; therefore, we studied its role in regulating the functional status of DCs. In murine models of autoimmunity (experimental autoimmune encephalomyelitis) and cancer (MC38-OVA-implanted tumor), lack of Bat3 expression in DCs alters the T cell compartment-it decreases TH1, TH17 and cytotoxic effector cells, increases regulatory T cells, and exhausted CD8+ tumor-infiltrating lymphocytes, resulting in the attenuation of autoimmunity and acceleration of tumor growth. We found that Bat3 expression levels were differentially regulated by activating versus inhibitory stimuli in DCs, indicating a role for Bat3 in the functional calibration of DC phenotypes. Mechanistically, loss of Bat3 in DCs led to hyperactive unfolded protein response and redirected acetyl-coenzyme A to increase cell intrinsic steroidogenesis. The enhanced steroidogenesis in Bat3-deficient DC suppressed T cell response in a paracrine manner. Our findings identified Bat3 as an endogenous regulator of DC function, which has implications for DC-based immunotherapies.

Systemic immune responses to irradiated tumours via the transport of antigens to the tumour periphery by injected flagellate bacteria

Because the tumour microenvironment is typically immunosuppressive, the release of tumour antigens mediated by radiotherapy or chemotherapy does not sufficiently activate immune responses. Here we show that, following radiotherapy, the intratumoural injection of a genetically attenuated strain of Salmonella coated with antigen-adsorbing cationic polymer nanoparticles caused the accumulation of tumour antigens at the tumour's periphery. This enhanced the crosstalk between the antigens and dendritic cells, and resulted in large increases in activated ovalbumin-specific dendritic cells in vitro and in systemic antitumour effects, and extended survival in multiple tumour models in mice, including a model of metastasis and recurrence. The antitumour effects were abrogated by the antibody-mediated depletion of CD8⁺ T cells, indicating that systemic tumour regression was caused by adaptive immune responses. Leveraging flagellate bacteria to transport tumour antigens to the periphery of tumours to potentiate the activation of dendritic cells may open up new strategies for in situ cancer vaccination.

Targeting Mononuclear Phagocyte Receptors in Cancer Immunotherapy: New Perspectives of the Triggering Receptor Expressed on Myeloid Cells (TREM-1)

Inflammatory cells are major players in the onset of cancer. The degree of inflammation and type of inflammatory cells in the tumor microenvironment (TME) are responsible for tilting the balance between tumor progression and regression. Cancer-related inflammation has also been shown to influence the efficacy of conventional therapy. Mononuclear phagocytes (MPs) represent a major component of the inflammatory circuit that promotes tumor progression. Despite their potential to activate immunosurveillance and exert anti-tumor responses, MPs are subverted by the tumor to support its growth, immune evasion, and spread. MP responses in the TME are dictated by a network of stimuli integrated through the cross-talk between activatory and inhibitory receptors. Alterations in receptor expression/signaling can create excessive inflammation and, when chronic, promote tumorigenesis. Research advances have led to the development of new therapeutic strategies aimed at receptor targeting to induce a tumor-infiltrating MP switch from a cancer-supportive toward an anti-tumor phenotype, demonstrating efficacy in different human cancers. This review provides an overview of the role of MP receptors in inflammation-mediated carcinogenesis and discusses the most recent updates regarding their targeting for immunotherapeutic purposes. We focus in particular on the TREM-1 receptor, a major amplifier of MP inflammatory responses, highlighting its relevance in the development and progression of several types of inflammation-associated malignancies and the promises of its inhibition for cancer immunotherapy.

Different methods of cell quantification can lead to different results: a comparison of digital methods using a pilot study of dendritic cells in HIV-positive patients

BACKGROUND

Although new digital pathology tools have improved the positive cell quantification, there is a heterogeneity of the quantification methods in the literature. The aim of this study was to evaluate and propose a novel dendritic cells quantification method in squamous cell carcinoma comparing it with a conventional quantification method.

MATERIAL AND METHODS

Twenty-six squamous cell carcinomas HIV-positive cases affecting the oropharynx, lips and oral cavity were selected. Immunohistochemistry for CD1a, CD83, and CD207 was performed. The immunohistochemical stains were evaluated by automated examination using a positive pixel count algorithm. A conventional quantification method (unspecific area method; UA) and a novel method (specific area method; SA) were performed obtaining the corresponding density of positive dendritic cells for the intratumoral and peritumoral regions. The Mann-Whitney U test was used to verify the influence of the quantification methods on the positive cell counting according to the evaluated regions. Data were subjected to the ANOVA and Student's t-test to verify the influence of the tumour location, stage, histological grade, and amount of inflammation on the dendritic cells density counting.

RESULTS

The cell quantification method affected the dendritic cells counting independently of the evaluated region (P-value <0.05). Significant differences between methods were also observed according to the tumour features evaluations.

CONCLUSIONS

The positive cell quantification method influences the dendritic cells density results. Unlike the conventional method (UA method), the novel SA method avoids non-target areas included in the hotspots improving the reliability and reproducibility of the density cell quantification.

The Effect of the Tumor Microenvironment and Tumor-Derived Metabolites on Dendritic Cell Function

Dendritic cells (DCs) have a critical effect on the outcome of adaptive immune responses against growing tumors. Recent studies on the metabolism on DCs provide new insights on the functioning of these critical controllers of innate and adaptive immunity. DCs within the tumor microenvironment (TME) often exist in an inactive state, which is thought to limit the adaptive immune response elicited by the growing tumor. Tumor-derived factors in the TME are known to suppress DC activation and result in functional alterations in DC phenotype. We are now beginning to appreciate that many of these factors can also induce changes in immune cell metabolism. In this review, we discuss the functional alternation of DC phenotype by tumor metabolites.

Strategies for developing and optimizing cancer vaccines

With the spotlight on cancer immunotherapy and the expanding use of immune checkpoint inhibitors, strategies to improve the response rate and duration of current cancer immunotherapeutics are highly sought. In that sense, investigators around the globe have been putting spurs on the development of effective cancer vaccines in humans after decades of efforts that led to limited clinical success. In more than three decades of research in pursuit of targeted and personalized immunotherapy, several platforms have been incorporated into the list of cancer vaccines from live viral or bacterial agents harboring antigens to synthetic peptides with the hope of stronger and durable immune responses that will tackle cancers better. Unlike adoptive cell therapy, cancer vaccines can take advantage of using a patient's entire immune system that can include more than engineered receptors or ligands in developing antigen-specific responses. Advances in molecular technology also secured the use of genetically modified genes or proteins of interest to enhance the chance of stronger immune responses. The formulation of vaccines to increase chances of immune recognition such as nanoparticles for peptide delivery is another area of great interest. Studies indicate that cancer vaccines alone may elicit tumor-specific cellular or humoral responses in immunologic assays and even regression or shrinkage of the cancer in select trials, but novel strategies, especially in combination with other cancer therapies, are under study and are likely to be critical to achieve and optimize reliable objective responses and survival benefit. In this review, cancer vaccine platforms with different approaches to deliver tumor antigens and boost immunity are discussed with the intention of summarizing what we know and what we need to improve in the clinical trial setting.

Aberrant Phenotype and Function of Dendritic Cells in Adult B Lineage Acute Lymphoblastic Leukemia

Dendritic cells (DCs) play a major role in regulating immune responses, but the aberrant phenotype and function of defective DCs in adult acute lymphoblastic leukemia (ALL) remain unclear. Here, B lineage ALL (B-ALL) patients were divided into groups according to different standards. By course of disease: newly diagnosed (ND), complete remission (CR), consolidation (CONS). By stratification: high risk (HR), standard risk (SR). By minimal residual disease (MRD): MRD positive(MRD+), MRD negative (MRD-). The proportion of plasmacytoid DC(pDC) and myeloid DC(mDC) were compared within these standards. The costimulatory molecule levels of pDC, mDC in ND and CR were measured and the function of peripheral blood monocyte-derived DC(MoDC)s were examined. We found proportions of pDC and mDC in ND were both lower compared to control group and gradually increased after CR. In HR and MRD+, the proportions were also lower compared to SR and MRD- at CR stage, respectively; but there were no difference between these comparisons when newly diagnosed. In ND, both CD80, CD86 levels in pDC, mDC were higher while the levels in activated MoDCs were lower when compared to control and CR group, respectively. The dextran uptake of MoDCs, T cell proliferation promoting ability, IL-12, BAFF, INF-α levels in supernatant and their mRNA relative expression in activated MoDCs in ND were also lower than those in control and CR group. So, DCs in B-ALL display suppressed status in phenotype and function，which would be gradually restored after effective chemotherapy. pDC and mDC could respond to patient condition, DCs proportion may be useful for monitoring disease progression.

The expression of MHC class II molecules on murine breast tumors delays T-cell exhaustion, expands the T-cell repertoire, and slows tumor growth

The expression of MHC class II molecules (MHCII) on tumor cells correlates with survival and responsiveness to immunotherapy. However, the mechanisms underlying these observations are poorly defined. Using a murine breast tumor line, we showed that MHCII-expressing tumors grew more slowly than controls and recruited more functional CD4⁺ and CD8⁺ T cells. In addition, MHCII-expressing tumors contained more TCR clonotypes expanded to a larger degree than control tumors. Functional CD8⁺ T cells in tumors depended on CD4⁺ T cells. However, both CD4⁺ and CD8⁺ T cells eventually became exhausted, even in MHCII-expressing tumors. Treatment with anti-CTLA4, but not anti-PD-1 or anti-TIM-3, promoted complete eradication of MHCII-expressing tumors. These results suggest tumor cell expression of MHCII facilitates the local activation of CD4⁺ T cells, indirectly helps the activation and expansion of CD8⁺ T cells, and, in combination with the appropriate checkpoint inhibitor, promotes tumor regression.

Diamonds in the Rough: Harnessing Tumor-Associated Myeloid Cells for Cancer Therapy

Therapeutic approaches that engage immune cells to treat cancer are becoming increasingly utilized in the clinics and demonstrated durable clinical benefit in several solid tumor types. Most of the current immunotherapies focus on manipulating T cells, however, the tumor microenvironment (TME) is abundantly infiltrated by a heterogeneous population of tumor-associated myeloid cells, including tumor-associated macrophages (TAMs), tumor-associated dendritic cells (TADCs), tumor-associated neutrophils (TANs), and myeloid-derived suppressor cells (MDSCs). Educated by signals perceived in the TME, these cells often acquire tumor-promoting properties ultimately favoring disease progression. Upon appropriate stimuli, myeloid cells can exhibit cytoxic, phagocytic, and antigen-presenting activities thereby bolstering antitumor immune responses. Thus, depletion, reprogramming or reactivation of myeloid cells to either directly eradicate malignant cells or promote antitumor T-cell responses is an emerging field of interest. In this review, we briefly discuss the tumor-promoting and tumor-suppressive roles of myeloid cells in the TME, and describe potential therapeutic strategies in preclinical and clinical development that aim to target them to further expand the range of current treatment options.

Plant-derived polysaccharides activate dendritic cell-based anti-cancer immunity

Today, cancers pose a major public health burden. Although a myriad of cancer treatments are available, only a few have achieved clinical efficacy. This is partly attributed to cancers capability to evade host immunity by converting dendritic cells (DCs) from potent stimulators to negative modulators of immunity. Dendritic cell-based immunotherapy attempts to resolve this problem by manipulating the functional characteristics of DCs. Plant-derived polysaccharides (PDPs) can stimulate the maturation of DCs conferring on them the capacity to present internalised tumorigenic antigens to naïve T cells and subsequently priming T cells to eliminate tumours. PDPs have been used as immune modulators and later as anti-cancer agents by Traditional Chinese Medicine practitioners for centuries. They are abundant in nature and form a large group of heterogeneous though structurally related macromolecules that exhibit diverse immunological properties. They can induce antigen pulsed DCs to acquire functional characteristics in vitro which can subsequently be re-introduced into cancer patients. They can also be used as adjuvants in DC-based vaccines or independently for their intrinsic anti-tumour activities. Clinically, some in vitro generated DCs have been shown to be both safe and immunogenic although their clinical application is limited in part by unsatisfactory functional maturation as well as impaired migration to draining lymph nodes where T cells reside. We review the relative potencies of individual PDPs to induce both phenotypic and functional maturation in DCs, their relative abilities to activate anti-cancer immunity, the possible mechanisms by which they act and also the challenges surrounding their clinical application.

Antitumor efficacy of the Runx2-dendritic cell vaccine in triple-negative breast cancer in vitro

Triple-negative breast cancer (TNBC) is a subtype of breast cancer with a poor prognosis and limited effective treatment. The rise in immunotherapeutic strategies prompted the establishment of a genetic vaccine against TNBC in vitro using a possible biological marker of TNBC. In the present study, different detection methods were used to evaluate the distribution and expression of runt-associated transcription factor 2 (Runx2) in various breast cancer cell lines. Following the development of the Runx2-dendritic cell (DC) vaccine using a lentivirus, the transfection efficacy was recorded. The T lymphocytes co-cultured with the vaccine were collected to assess the antitumor potency. Increased levels of Runx2 were expressed in breast cancer cells; however, different breast cancer cell lines expressed various levels of Runx2. Runx2 demonstrated particularly high expression in TNBC cells, compared with non-TNBC cells. A Runx2 lentivirus transfection system was successfully engineered, and Runx2 was transduced into dendritic cells whilst maintaining stable expression. The sustained and stable cytotoxic T cells induced in the transfected group had higher and more specific antitumor efficacy against TNBC, compared with the other cell lines. Runx2 may be a novel target for TNBC treatment. The Runx2-DC vaccine may induce specific and efficient antitumor effects in TNBC in vitro.

A decreased peritumoral CD1a+ cell number predicts a worse prognosis in oral squamous cell carcinoma

AIMS

Dendritic cells (DCs) are known to play a central role in the regulation of both innate and adaptive immunological responses, including antitumour immunity. The aim of this study was to evaluate the prognostic impact of intratumoral and peritumoral DCs in oral squamous cell carcinoma (OSCC) affecting the tongue and floor of the mouth.

METHODS AND RESULTS

Immunohistochemistry for CD1a and CD83 was performed in 53 patients with OSCC in the tongue and floor of the mouth. The markers were evaluated by automated examination in intratumoral and peritumoral compartments, and the results were expressed as density of cells/mm² . Correlations between these data and clinicopathological and survival outcomes were investigated. Depletion of peritumoral CD1a+ cells was associated with lymph node metastasis (P = 0.05), whereas depletion of peritumoral CD83+ cells was correlated with smoking history (P = 0.04), lymph node metastasis (P = 0.015), and extracapsular spread of lymph nodes (P = 0.018). Peritumoral CD1a+ was correlated with recurrence (P = 0.007) and overall survival (P = 0.03). The results of the survival analysis with the Cox proportional hazard model showed that depletion of peritumoral CD1a+ cells is an independent factor associated with overall survival and disease-free survival.

CONCLUSION

Our results suggest that depletion of peritumoral CD1a+ cells is a strong independent prognostic factor, predicting a higher recurrence rates and worse survival outcomes.

Dendritic cell-based immunotherapy

Immunotherapy using dendritic cell (DC)-based vaccination is an approved approach for harnessing the potential of a patient's own immune system to eliminate tumor cells in metastatic hormone-refractory cancer. Overall, although many DC vaccines have been tested in the clinic and proven to be immunogenic, and in some cases associated with clinical outcome, there remains no consensus on how to manufacture DC vaccines. In this review we will discuss what has been learned thus far about human DC biology from clinical studies, and how current approaches to apply DC vaccines in the clinic could be improved to enhance anti-tumor immunity.

The tumour microenvironment harbours ontogenically distinct dendritic cell populations with opposing effects on tumour immunity

Various steady state and inflamed tissues have been shown to contain a heterogeneous DC population consisting of developmentally distinct subsets, including cDC1s, cDC2s and monocyte-derived DCs, displaying differential functional specializations. The identification of functionally distinct tumour-associated DC (TADC) subpopulations could prove essential for the understanding of basic TADC biology and for envisaging targeted immunotherapies. We demonstrate that multiple mouse tumours as well as human tumours harbour ontogenically discrete TADC subsets. Monocyte-derived TADCs are prominent in tumour antigen uptake, but lack strong T-cell stimulatory capacity due to NO-mediated immunosuppression. Pre-cDC-derived TADCs have lymph node migratory potential, whereby cDC1s efficiently activate CD8⁺ T cells and cDC2s induce Th17 cells. Mice vaccinated with cDC2s displayed a reduced tumour growth accompanied by a reprogramming of pro-tumoural TAMs and a reduction of MDSCs, while cDC1 vaccination strongly induces anti-tumour CTLs. Our data might prove important for therapeutic interventions targeted at specific TADC subsets or their precursors.

Dendritic cells are antigen-presenting cells consisting of distinct subsets originating from different lineages. Here, the authors identify the subsets of dendritic cells populating the tumour tissue in both mice and humans and find they have opposing functions in regulating the anti-tumour immune response.

Role of abnormal Langerhans cells in oral epithelial dysplasia and oral squamous cell carcinoma: A pilot study

BACKGROUND

The oral epithelial dysplasia (OED) and oral squamous cell carcinoma (OSCC), although initiated by tobacco carcinogens, their progression is due to inability of Langerhans cells (LCs) to detect these abnormal cells and promote lymphocytes to destroy these cells. We assessed and quantified the tumor associated LCs and inflammation in OED and OSCC to understand their role.

MATERIALS AND METHODS

Fifty-five microscopic sections were assessed (27 OED and 28 OSCC). The LCs were detected using S-100 immunohistochemical marker. The number of tumor associated LCs were counted. The presence of abnormal appearing large cells and its relation to histopathologic grade and inflammation was assessed.

RESULTS

Significant increase in the LC count was observed in OSCC when compared to dysplasia. Large, abnormal appearing cells were observed in dysplasia and carcinomas however, these were more pronounced in moderate dysplasia and poorly-differentiated carcinomas. The presence of these abnormal appearing cells was associated with decrease in lymphocytic infiltrate.

CONCLUSION

The present study indicates more LC are recruited into the carcinoma. These accumulated nonfunctional LC in the tumor tissue are indicative of aggressive tumor with potential malignant transformation.

The multifaceted regulation and functions of PKM2 in tumor progression

Tumor cells undergo metabolic rewiring from oxidative phosphorylation towards aerobic glycolysis to maintain the increased anabolic requirements for cell proliferation. It is widely accepted that specific expression of the M2 type pyruvate kinase (PKM2) in tumor cells contributes to this aerobic glycolysis phenotype. To date, researchers have uncovered myriad forms of functional regulation for PKM2, which confers a growth advantage on the tumor cells to enable them to adapt to various microenvironmental signals. Here the richness of our understanding on the modulations and functions of PKM2 in tumor progression is reviewed, and some new insights into the paradoxical expression and functional differences of PKM2 in distinct cancer types are offered.

Low expression of dendritic cell-specific intercellular adhesion molecule-3-grabbing nonintegrin in non-Hodgkin lymphoma and a significant correlation with β2-microglobulin

Dendritic cell-specific intercellular adhesion molecule-3-grabbing nonintegrin (DC-SIGN), a member of the C-type lectin superfamily, has been reported to bind to various pathogens and several tumor cells and to participate in immunoregulation. It is still unclear whether there is a significant association between the level of DC-SIGN and non-Hodgkin lymphoma (NHL). To investigate the clinical diagnostic significance of DC-SIGN in NHL, we conducted a study with 52 NHL patients and 104 healthy individuals. Enzyme-linked immunosorbent assay and tissue microarray technology were utilized for the analysis. The serum sDC-SIGN levels in the NHL patients were significantly lower than those in the healthy controls (P=0.0019). A cutoff value of 1.499 µg/ml for sDC-SIGN predicted the presence of NHL with 78.85% sensitivity and 53.85% specificity [area under the curve (AUC)=0.6531, P=0.0019]. The serum sDC-SIGN levels in NHL patients were also significantly correlated with β2-microglobulin (P=0.0062). Moreover, tissue microarray analysis demonstrated that the expression of DC-SIGN in the lymph nodes or tissues of 96 NHL patients was significantly lower than that in 18 normal lymph nodes (P<0.0001). However, the expression of DC-SIGN in NHL displayed no significant correlation with the expression of CD20 or CD79a. In conclusion, DC-SIGN may be a promising biological molecule for clinical research on NHL, whereas the underlying roles need to be investigated in additional studies.

Influence of immunotherapy with autologous dendritic cells on innate and adaptive immune response in cancer

The objective of this study was to evaluate some of the mechanisms involved in the activation of the immune system in patients with advanced-stage cancer (n = 7) who received an autologous dendritic cell vaccine. We examined the immune response mediated by macrophages (CD14+), natural killer cells (CD56+), and B lymphocytes (CD19+) by flow cytometry and assessed the expression of Th1 (IFN-γ, TNF-α, IL-2, and IL-12), Th2 (IL-4), and Treg (TGF-β) cytokines by flow cytometry and an enzyme-linked immunosorbent assay. The CD14+ TNF-α+ population was significantly increased (P < 0.04) when patients received the vaccine; IL-2 expression in both NK cells and in B lymphocytes was increased after a transient initial increase showed a nearly significant decrease (P < 0.07 and P < 0.06 respectively), whereas the CD19+ and CD56+ populations did not show significant changes. Dendritic cell-based immunotherapy led to increased secretion of IFN-γ and IL-12 and reduced secretion of TGF-β. In conclusion, it is likely that the autologous dendritic cell vaccine stimulated the immune cells from the peripheral blood of patients with cancer and generally increased the production of Th1 cytokines, which are related to immunomodulatory responses against cancer.

Immunomodulatory monoclonal antibodies combined with peptide vaccination provide potent immunotherapy in an aggressive murine neuroblastoma model

PURPOSE

Neuroblastoma is one of the commonest extracranial tumors of childhood. The majority of patients present with metastatic disease for which outcome remains poor. Immunotherapy is an attractive therapeutic approach for this disease, and a number of neuroblastoma tumor antigens have been identified. Here, we examine the therapeutic potential of combining immunomodulatory monoclonal antibodies (mAb) with peptide vaccination in murine neuroblastoma models.

EXPERIMENTAL DESIGN

Neuroblastoma-bearing mice were treated with mAb targeting 4-1BB, CD40, and CTLA-4 alone, or in combination with a peptide derived from the tumor antigen survivin (GWEDPPNDI). Survivin-specific immune response and therapeutic efficacy were assessed.

RESULTS

In the Neuro2a model, treatment of established tumor with anti-4-1BB, anti-CD40, or anti-CTLA-4 mAb results in tumor regression and long-term survival in 40% to 60% of mice. This is dependent on natural killer (NK) and CD8(+) T cells and is associated with tumor CD8(+) lymphocyte infiltrate. Successful therapy is achieved only if mAb is given to mice once tumors are established, suggesting dependence on sufficient tumor to provide antigen. In the more aggressive AgN2a and NXS2 models, single-agent mAb therapy provides ineffective therapy. However, if mAb (anti-CTLA-4) is given in conjunction with survivin peptide vaccination, then 60% long-term survival is achieved. This is associated with the generation of survivin-specific T-cell immunity, which again is only shown in the presence of tumor antigen.

CONCLUSIONS

These data suggest that the combination of antigen and costimulatory mAb may provide effective immunotherapy against neuroblastoma and may be of particular use in the minimal residual disease setting.

Langerhans cells from human cutaneous squamous cell carcinoma induce strong type 1 immunity

Langerhans cells (LCs) are dendritic cells (DCs) localized to the epidermis. They should be the first antigen-presenting cells to encounter squamous cell carcinoma (SCC). The aim of this study was to investigate the ability of LCs isolated from human SCC to induce T-cell proliferation and polarization. We investigated the ability of LCs from SCC and peritumoral skin to induce T-cell proliferation and polarization. We also studied the effect of SCC supernatant on the ability of LCs from normal skin, in vitro-generated LCs, and DCs to activate and polarize T cells. LCs from SCC were stronger inducers of allogeneic CD4(+) and CD8(+) T-cell proliferation and IFN-γ production than LCs from peritumoral skin. We found that tumor supernatants (TSNs) were rich in immunosuppressive cytokines; despite this, allogeneic CD4(+) and CD8(+) T-cell proliferation and IFN-γ induction by LCs were augmented by TSN. Moreover, TSN facilitated IFN-γ induction by in vitro-generated LCs, but suppressed the ability of in vitro-generated DCs to expand allogeneic CD4(+) and CD8(+) T cells. We have demonstrated that LCs from SCC can induce type 1 immunity. TSN induces IFN-γ induction by in vitro-generated LCs. This contrasts greatly with prior studies showing that DCs from SCC cannot stimulate T cells. These data indicate that LCs may be superior to DCs for SCC immunotherapy and may provide a new rationale for harnessing LCs for the treatment of cancer patients.

Effect of siRNA-mediated downregulation of VEGF in Tca8113 cells on the activity of monocyte-derived dendritic cells

Vascular endothelial growth factor (VEGF) is a tumor angiogenesis factor that is important in immune regulation. In our previous study, we found that VEGF expression in the peripheral blood and neoplasm nest from patients with oral squamous cell carcinoma (OSCC) was positively correlated with the course of disease, while an inverse correlation between VEGF expression and dendritic cells (DCs) was identified in the peripheral blood. Therefore, in the present study, we investigated whether inhibition of human VEGF in the human tongue carcinoma cell line Tca8113 had effects on the activity of monocyte-derived DCs. We knocked down the expression of human VEGF in Tca8113 cells using the small interfering RNA (siRNA) technique. Tca8113 cells pre-transfected with siRNA targeting VEGF were co-cultured with monocyte‑derived immature and mature DCs. Cell proliferation was evaluated by a WST-8 assay. Cell apoptosis, cell cycle and cell phenotypes were determined by flow cytometry. The data revealed that downregulation of the human VEGF significantly inhibited the proliferation of Tca8113 cells and increased apoptosis. Inhibition of human VEGF arrested the cell cycle of Tca8113 cells at the G0/G1 phase. Our results showed that the co-culture of DCs with Tca8113 cells markedly inhibited the expression of the mature markers of DCs including HLA-DR, CD80, CD86, CD40 and CD1a, as well as the immature marker CD83, while inhibition of human VEGF in Tca8113 cells significantly reversed these effects. Therefore, human VEGF in Tca8113 cells may not only regulate the cell proliferation and apoptosis of oral squamous cell carcinoma cells, but may also inhibit DC maturation.

Mononuclear phagocyte heterogeneity in cancer: different subsets and activation states reaching out at the tumor site

Mononuclear phagocytes are amongst the most versatile cells of the body, contributing to tissue genesis and homeostasis and safeguarding the balance between pro- and anti-inflammatory reactions. Accordingly, these cells are notoriously heterogeneous, functioning in distinct differentiation forms (monocytes, MDSC, macrophages, DC) and adopting different activation states in response to a changing microenvironment. Accumulating evidence exists that mononuclear phagocytes contribute to all phases of the cancer process. These cells orchestrate the inflammatory events during de novo carcinogenesis, participate in tumor immunosurveillance, and contribute to the progression of established tumors. At the tumor site, cells such as tumor-associated macrophages (TAM) are confronted with different tumor microenvironments, leading to TAM subsets with specialized functions. A better refinement of the molecular and functional heterogeneity of tumor-associated mononuclear phagocytes might pave the way for novel cancer therapies that directly target these tumor-supporting cells.

Dendritic cell activation by glucan isolated from umbilicaria esculenta

Background

Lichen-derived glucans have been known to stimulate the functions of immune cells. However, immunostimulatory activity of glucan obtained from edible lichen, Umbilicaria esculenta, has not been reported. Thus we evaluated the phenotype and functional maturation of dendritic cells (DCs) following treatment of extracted glucan (PUE).

Methods

The phenotypic and functional maturation of PUE-treated DCs was assessed by flow cytometric analysis and cytokine production, respectively. PUE-treated DCs was also used for mixed leukocyte reaction to evaluate T cell-priming capacity. Finally we detected the activation of MAPK and NF-κB by immunoblot.

Results

Phenotypic maturation of DCs was shown by the elevated expressions of CD40, CD80, CD86, and MHC class I/II molecules. Functional activation of DCs was proved by increased cytokine production of IL-12, IL-1β, TNF-α, and IFN-α/β, decreased endocytosis, and enhanced proliferation of allogenic T cells. Polymyxin B, specific inhibitor of lipopolysaccharide (LPS), did not affect PUE activity, which suggested that PUE was free of LPS contamination. As a mechanism of action, PUE increased phosphorylation of ERK, JNK, and p38 MAPKs, and enhanced nuclear translocation of NF-κB p50/p65 in DCs.

Conclusion

These results indicate that PUE induced DC maturation via MAPK and NF-κB signaling pathways.

Dendritic cell-based vaccines for the therapy of experimental tumors

Dendritic cells (DCs) are believed to be the most potent antigen-presenting cells able to link the innate and adaptive immune systems. Many studies have focused on different immunotherapeutic approaches to applying DCs as tools to improve anticancer therapy. Although a number of investigations suggesting the benefit of DC-based vaccination during anticancer therapy have been reported, the general knowledge regarding the ultimate methods of DC-vaccine preparation is still unsatisfactory. In this article, the perspectives of DC-based anti-tumor immunotherapy and optimizing strategies of DC vaccination in humans in light of results obtained in mouse models are discussed.

Directing dendritic cell immunotherapy towards successful cancer treatment

The use of dendritic cells (DCs) for tumor immunotherapy represents a powerful approach for harnessing the patient's own immune system to eliminate tumor cells. However, suboptimal conditions for generating potent immunostimulatory DCs, as well as the induction of tolerance and suppression mediated by the tumors and its microenvironment have contributed to limited success. Combining DC vaccines with new approaches that enhance immunogenicity and overcome the regulatory mechanisms underlying peripheral tolerance may be the key to achieving effective and durable anti-tumor immune responses that translate to better clinical outcomes.

Induction of dendritic cell maturation by β-glucan isolated from Sparassis crispa

Sparassis crispa is a medicinal mushroom containing high 6-branched 1,3-β-D-glucan (sparan) content, which exhibits immune-mediated antitumor activity. In the present study, we investigated the stimulating effect of sparan on phenotypic and functional maturation of dendritic cells (DCs). Phenotypic maturation was confirmed by the elevated expressions of CD40, CD80, CD86, and MHC-I/II molecules. Functional activation was proved by increased cytokine production of IL-12, IL-1β, TNF-α, and IFN-α/β, enhanced IL-2 production and proliferation of allogenic T cells, and decreased endocytosis. The role of toll-like receptor 4 (TLR4) as a membrane receptor of sparan was proved by the impaired maturation of DCs generated from bone marrow cells of tlr4⁻/⁻ knock-out mice and TLR4-mutated C3H/HeJ mice, and by using anti-MD-2/TLR4 neutralizing antibody. Sparan increased phosphorylation of ERK, p38, and JNK, and enhanced nuclear translocation of NF-κB p50/p65 in DCs. These results indicate that sparan activates DCs via MAPK and NF-κB signaling pathways, which are signaling molecules downstream of TLR4.

Features of responding T cells in cancer and chronic infection

Ever since T cell exhaustion was initially characterized and thoroughly analyzed in the murine LCMV model, such a functional impairment has been validated in other chronic viral infections such as HIV, HCV, and HBV. In tumor immunology, it has always been postulated that tumor-reactive T cells could also become functionally exhausted owing to the high tumor-antigen load and accompanying inhibitory mechanisms. However, the empirical evidences for this hypothesis have not been as extensive as in chronic infection perhaps because much of the focus on T cell dysfunction in tumor immunology has been, and appropriately so, on breaking or bypassing immune tolerance and anergy to tumor/self antigens. On the basis of recent reports, it is becoming clear that T cell exhaustion also plays a crucial role in the impairment of antitumor immunity. In this review, we will comparatively evaluate the T cell responses in cancer and chronic infection, and the therapeutic strategies and interventions for both diseases.

Review of murine dendritic cells: types, location, and development

Dendritic cells (DCs) are key coordinators of the immune response, governing the choice between tolerance and immunity. DCs are professional antigen-presenting cells capable of presenting antigen on MHC molecules and priming CD4 and CD8 T-cell responses. They form a heterogeneous group of cells based on phenotype, location, and function. In this review, murine DCs will be discussed regarding their function with special emphasis on their tissue distribution. Recent findings on DC homeostasis during cancer progression will be presented. Finally, the developmental pathways leading to DC differentiation from their precursors will be summarized.

Antigen presentation by dendritic cells in tumors is disrupted by altered metabolism that involves pyruvate kinase M2 and its interaction with SOCS3

Dendritic cell (DC) function is negatively affected by tumors and tumor-derived factors, but little is known about the underlying mechanisms. Here, we show that intracellular SOCS3 in DCs binds to pyruvate kinase type M2 (M2-PK), which plays a critical role in ATP production through glycolysis. The interaction of SOCS3 with M2-PK reduced ATP production and impaired DC-based immunotherapy against tumors. Thus, SOCS3, which has been shown to be upregulated by tumor-derived factors, interacts with M2-PK to decrease ATP production, causing DC dysfunction. These dysfunctional DCs have a reduced ability to present antigens. Alteration of DC metabolism mediated by SOCS3 represents a novel mechanism for DC dysfunction in the tumor microenvironment.