Dendritic cells: making progress with tumour regression?

Metabolism of Dendritic Cells in Tumor Microenvironment: For Immunotherapy

Dendritic cells (DCs) are a type of an antigen-presenting cell which undertake a job on capturing antigens coming from pathogens or tumors and presenting to T cells for immune response. The metabolism of DCs controls its development, polarization, and maturation processes and provides energy support for its functions. However, the immune activity of DCs in tumor microenvironment (TME) is inhibited generally. Abnormal metabolism of tumor cells causes metabolic changes in TME, such as hyperglycolysis, lactate and lipid accumulation, acidification, tryptophan deprivation, which limit the function of DCs and lead to the occurrence of tumor immune escape. Combined metabolic regulation with immunotherapy can strengthen the ability of antigen-presentation and T cell activation of DCs, improve the existing anti-tumor therapy, and overcome the defects of DC-related therapies in the current stage, which has great potential in oncology therapy. Therefore, we reviewed the glucose, lipid, and amino acid metabolism of DCs, as well as the metabolic changes after being affected by TME. Together with the potential metabolic targets of DCs, possible anti-tumor therapeutic pathways were summarized.

Noncoding RNAs in Cancer Immunology

Cancer immunology is the study of interaction between cancer cells and immune system by the application of immunology principle and theory. With the recent approval of several new drugs targeting immune checkpoints in cancer, cancer immunology has become a very attractive field of research and is thought to be the new hope to conquer cancer. This chapter introduces the aberrant expression and function of noncoding RNAs, mainly microRNAs and long noncoding RNAs, in tumor-infiltrating immune cells, and their significance in tumor immunity. It also illustrates how noncoding RNAs are shuttled between tumor cells and immune cells in tumor microenvironments via exosomes or other microvesicles to modulate tumor immunity.

Optimizing dendritic cell-based immunotherapy for cancer

Dendritic cells (DCs) are the most powerful professional antigen-presenting cells and are unique in their capability to initiate, maintain and regulate the intensity of primary immune responses, including specific antitumor responses. Development of practical procedures to prepare sufficient numbers of functional human DCs in culture from the peripheral blood precursors, paved the way for clinical trials to evaluate various DC-based strategies in patients with malignant diseases. However, no definite conclusions regarding the clinical and even immunological efficacy of DC vaccination can be stated, despite the fact that 12 years have passed since the first clinical trial utilizing DCs in cancer patients. Many unanswered questions hamper the development of DC-based vaccines, including the source of DC preparation and protocols for DC generation, activation and loading with tumor antigens, source of tumor antigens, route of vaccine administration and methods of immunomonitoring. Fortunately, in spite of the many obstacles, DC vaccines continue to hold promise for cancer therapy.

Active immunotherapy using dendritic cells in the treatment of glioblastoma multiforme

OBJECTIVE

Glioblastoma multiforme, the most common malignant brain tumor still has a dismal prognosis with conventional treatment. Therefore, it is necessary to explore new and/or adjuvant treatment options to improve patient outcomes. Active immunotherapy is a new area of research that may be a successful treatment option. The focus is on vaccines that consist of antigen presenting cells (APCs) loaded with tumor antigen. We have conducted a systematic review of prospective studies, case reports and clinical trials. The goal of this study was to examine the efficacy and safety in terms of complications, median overall survival (OS), progression free survival (PFS) and quality of life.

METHODS

A PubMed search was performed to include all relevant studies that reported the characteristics, outcomes and complications of patients with GBM treated with active immunotherapy using dendritic cells. Reported parameters were immune response, radiological findings, median PFS and median OS. Complications were categorized based on association with the craniotomy or with the vaccine itself.

RESULTS

A total of 21 studies with 403 patients were included in our review. Vaccination with dendritic cells (DCs) loaded with autologous tumor cells resulted in increased median OS in patients with recurrent GBM (71.6-138.0 wks) as well as those newly diagnosed (65.0-230.4 wks) compared to average survival of 58.4 wks.

CONCLUSIONS

Active immunotherapy, specifically with autologous DCs loaded with autologous tumor cells, seems to have the potential of increasing median OS and prolonged tumor PFS with minimal complications. Larger clinical trials are needed to show the potential benefits of active immunotherapy.

Inhibition of dendritic cell migration by transforming growth factor-β1 increases tumor-draining lymph node metastasis

Background

Transforming growth factor (TGF)-β is known to be produced by progressor tumors and to immobilize dendritic cells (DCs) within those tumors. Moreover, although TGF-β1 has been shown to promote tumor progression, there is still no direct, in vivo evidence as to whether TGF-β1 is able to directly induce distant metastasis.

Methods

To address that issue and investigate the mechanism by which TGF-β1 suppresses DC activity, we subdermally inoculated mouse ears with squamous cell carcinoma cells stably expressing TGF-β1 or empty vector (mock).

Results

The numbers of DCs within lymph nodes draining the resultant TGF-β1-expressing tumors was significantly lower than within nodes draining tumors not expressing TGF-β1. We then injected fluorescently labeled bone marrow-derived dendritic cells into the tumors, and subsequent analysis confirmed that the tumors were the source of the DCs within the tumor-draining lymph nodes, and that there were significantly fewer immature DCs within the nodes draining TGF-β1-expressing tumors than within nodes draining tumors not expressing TGF-β1. In addition, 14 days after tumor cell inoculation, lymph node metastasis occurred more frequently in mice inoculated with TGF-β1 transfectants than in those inoculated with the mock transfectants.

Conclusions

These findings provide new evidence that tumor-derived TGF-β1 inhibits migration of DCs from tumors to their draining lymph nodes, and this immunosuppressive effect of TGF-β1 increases the likelihood of metastasis in the affected nodes.

Production of functional dendritic cells from menstrual blood--a new dendritic cell source for immune therapy

Dendritic cells (DCs) are the most professional antigen-presenting cells of the mammalian immune system. They are able to phagocytize, process antigen materials, and then present them to the surface of other cells including T lymphocytes in the immune system. These capabilities make DC therapy become a novel and promising immune-therapeutic approach for cancer treatment as well as for cancer vaccination. Many trials of DC therapy to treat cancers have been performed and have shown their application value. They involve harvesting monocytes or hematopoietic stem cells from a patient and processing them in the laboratory to produce DCs and then reintroduced into a patient in order to activate the immune system. DCs were successfully produced from peripheral, umbilical cord blood-derived monocytes or hematopoietic stem cells. In this research, we produced DCs from human menstrual blood-derived monocytes. Briefly, monocytes were isolated by FACS based on FSC vs. SSC plot from lysed menstrual blood. Obtained monocytes were induced into DCs by a two-step protocol. In the first step, monocytes were incubated in RPMI medium supplemented with 2% FBS, GM-CSF, and IL-4, followed by incubation in RPMI medium supplemented with α-TNF in the second step. Our data showed that induced monocytes had typical morphology of DCs, expressed HLA-DR, HLA-ABC, CD80 and CD86 markers, exhibited uptake of dextran-FITC, stimulated allogenic T cell proliferation, and released IL-12. These results demonstrated that menstrual blood can not only be a source of stromal stem cell but also DCs, which are a potential candidate for immune therapy.

Combination of all-trans retinoic acid and a human papillomavirus therapeutic vaccine suppresses the number and function of immature myeloid cells and enhances antitumor immunity

Despite advances in the development of human papillomavirus (HPV) prophylactic vaccines, little progress has been made in the field of therapeutic vaccines in recent years. In the present study, we found a significant accumulation of immature myeloid cells (ImC) in large TC-1 tumors and demonstrated that a HPV therapeutic vaccine restored antitumor immune responses with the correction of aberrant myeloid cell differentiation by all-trans retinoic acid (ATRA). Our study demonstrated that combining ATRA with vaccination not only decreased the number of Gr-1+ CD11b+ ImC, but for the first time also suppressed the function of Gr-1+ CD11b+ ImC with decreased expression of CD80. Furthermore, large numbers of CD11c+ CD80+, CD11c+ CD86+, and CD11c+ MHCII+ mature dendritic cells were recruited. The combination therapy generated significantly increased numbers of functional E7-specific T cells with elevated interferon- secretion and enhanced cytotoxic T-cell activity. These findings suggest potential clinical benefits for the combined use of ATRA and HPV therapeutic vaccines.

Dendritic cells in Barrett's esophagus and esophageal adenocarcinoma

BACKGROUND

Like other premalignant conditions that develop in the presence of chronic inflammation, the development and progression of Barrett's esophagus is associated with the development of an immune response, but how this immune response is regulated is poorly understood. A comprehensive literature search failed to find any report of the presence of dendritic cells in Barrett's intestinal metaplasia and esophageal adenocarcinoma and this prompted our study.

MATERIAL AND METHODS

We used immunohistochemical staining and electron microscopy to examine whether dendritic cells are present in Barrett's esophagus and esophageal adenocarcinoma. Immunohistochemical staining with CD83, a specific marker for dendritic cells, was performed on paraffin-embedded sections of Barrett's intestinal metaplasia (IM, n = 12), dysplasia (n = 11) and adenocarcinoma (n = 14).

RESULTS

CD83+ cells were identified in the lamina propria surrounding intestinal type glands in Barrett's IM, dysplasia, and cancer tissues. Computerized quantitative analysis showed that the numbers of dendritic cells were significantly higher in cancer tissues. Double immunostaining with CD83, CD20, and CD3, and electron microscopy demonstrated that dendritic cells are present in Barrett's esophagus and form clusters with T cells and B cells directly within the lamina propria.

CONCLUSIONS

These findings demonstrate that dendritic cells are present in Barrett's tissues, with a significant increase in density in adenocarcinoma compared to benign Barrett's esophagus. Dendritic cells may have a role in the pathogenesis and immunotherapy treatment of Barrett's esophagus and adenocarcinoma.

Recruitment of dendritic cells in human liver with metastases

Dendritic cells (DCs) play a key role in the generation of antitumor immune responses as the most potent professional antigen-presenting cells. In this study we examined the distribution of DCs subsets in selected areas of liver metastases and adjacent liver tissue of 74 patients with gastrointestinal cancers (14 gastric, 47 colon, and 13 rectal) using immunohistochemistry for the DCs markers S-100 protein, HLA-DR, CD1a, and CD83. S-100 protein-positive DCs were localized mainly in clusters in metastases and at the tumor border with the surrounding liver tissue, while HLA-DR-positive DCs were significantly more in number (P<0.0001) and were diffusely distributed in metastasis stroma and at the tumor border. S-100 protein-positive DCs with mature phenotype were presented around metastases and in the sinusoidal lumena, whereas S-100 protein-positive DCs with less mature phenotype based on their ultrastructure were scattered in the tumor stroma. CD1a- and CD83-positive DCs were observed predominantly in small groups or as single cells in the tumor stroma and in the invasive margin. The numbers of CD1a-positive DCs (immature) and CD83-positive DCs (mature) were comparable, but significantly lower than that of S-100 protein-positive (P<0.0001) and HLA-DR-positive cells (P<0.0001).We observed more S-100 protein-positive DCs and HLA-DR-expressing cells in the sinusoids and portal tracts of the liver tissue, surrounding metastases, than in control liver tissue. In conclusion, this study provides additional information on the functional subtypes and distribution of DCs infiltrating metastatic tissue and local liver environment in patients with liver metastases from gastrointestinal cancers.

Melanoma-infiltrating dendritic cells induce protective antitumor responses mediated by T cells

Dendritic cells are the most potent antigen-presenting cells inducing innate and adaptive immune response. Dendritic cells infiltrate melanomas, but their ability to induce host antitumor immunity remains obscure. In a previous study, we have observed that melanoma-infiltrating dendritic cells have the capacity to process antigens and migrate to lymph nodes to prime T lymphocytes. Here, we observed that melanoma-infiltrating dendritic cells extracted from melanoma without any additional manipulations were able to protect naive mice against a lethal challenge with the tumor. Remarkably, this was achieved with reinjection of 10(5) melanoma-infiltrating dendritic cells, a number that did not exceed the total number of melanoma-infiltrating dendritic cells recovered from one single tumor. Three observations indicate that protection was due to the natural loading of melanoma-infiltrating dendritic cells with tumor antigens. First, the protective effect was not observed with equivalent numbers of bone marrow-derived dendritic cells. Second, the protection induced was specific for the tumor from which the tumor-infiltrating dendritic cells were isolated. Third, depletion experiments indicate that both CD4+ and CD8+ T lymphocytes were required during the effector phase of the antitumor response. Hence, designing strategies aimed at rendering melanoma-infiltrating dendritic cells visible to host T cells may boost spontaneous antitumor immunity.

Tumor-derived factors impaired motility and immune functions of dendritic cells through derangement of biophysical characteristics and reorganization of cytoskeleton

The generation and progress of tumors are accompanied with a marked suppression of human immune system. To explore the mechanisms by which tumors escape from immune recognition, we studied the influences of tumor microenvironment on differentiation of dendritic cells (DCs), which play an important role in tumor immunology, by biophysical and immunological methods. It was found that the cytokines derived from tumors caused an increase in osmotic fragility and a decrease in membrane fluidity of DCs, disordering and elevated expression levels of cytoskeleton, and changes of the gene transcriptional levels and energy status of the cells. Moreover, IL-12 production and the expression levels of some surface-marker molecules were also suppressed. These changes led to impaired capabilities of antigen uptake, cell motility and naïve T cell activation; the abnormal biophysical characteristics of DCs may be one aspect of the immune escape mechanism of tumor. These results provide insights into the importance of the reconstruction of tumor microenvironment for immunotherapy based on the anti-cancer activities of DCs.

Transforming growth factor-beta1 immobilises dendritic cells within skin tumours and facilitates tumour escape from the immune system

Human skin tumours often regress spontaneously due to immune rejection. Murine skin tumours model this behaviour; some regress and others progress in syngeneic immunocompetent hosts. Previous studies have shown that progressor but not regressor skin tumours inhibit dendritic cell (DC) migration from the tumour to draining lymph nodes, and transforming growth factor-beta1 (TGF-beta1) has been identified as a responsible factor. To determine whether increased production of TGF-beta1 in the absence of other differences inhibits DC migration from the tumour and enables it to evade immune destruction, a murine regressor squamous cell carcinoma clone was transfected with the gene for TGF-beta1. This enhanced growth in vitro and in vivo, causing it to become a progressor. TGF-beta1 transfection reduced the number of infiltrating DCs by about 25%. Quantitation of CD11c+ E-cadherin+ (epidermally derived) DCs in lymph nodes determined that TGF-beta1 reduced the number of DCs that migrated from the tumour to undetectable levels. This was supported by showing that TGF-beta1 reduced DC migration from cultured tumour explants by greater than tenfold. TGF-beta1 transfection also reduced the number of infiltrating CD4 and CD8 T cells. Thus, TGF-beta1 production by skin tumours is sufficient to immobilise DCs within the tumour, preventing their migration to lymph nodes. This reduces the number of T cells that infiltrate the tumour, preventing regression. Thus, TGF-beta1 is a key regulator of whether skin tumours regress or progress.

The role of CD40-CD154 interaction in cell immunoregulation

CD40, a member of the nerve growth factor/tumor necrosis factor receptor superfamily, and its ligand, CD154, play essential roles in cell immune responses. The results of many studies have indicated that CD40-CD154 interaction can upregulate costimulatory molecules, activate antigen-presenting cells (APCs), influence T-cell priming and T-cell-mediated effector functions as well as participate in the pathogenic processing of chronic inflammatory diseases, such as autoimmune diabetes, graft rejection, atherosclerosis, and cancer. Ligation of CD40 on cancer cells was also found to produce a direct growth-inhibitory effect through cell cycle blockage and/or apoptosis with no overt side effects on normal cells and treatment with CD154 can heighten tumor rejection immune response as well. However, systemic treatment with CD154 has some potential risks. Therefore, searching for efficient and safe strategies of CD154-based cancer therapy has been a hot topic in human cancer research. This review focuses on the latest discovered functions of CD40-CD154 interaction in cell immune responses and on the new findings of CD154-based human cancer therapy.

On dendritic cell-based therapy for cancers

Dendritic cells (DCs), the most prevalent antigen-presenting cell in vivo, had been widely characterized in the last three decades. DCs are present in almost all tissues of the body and play cardinal roles in recognition of microbial agents, autoantigens, allergens and alloantigen. DCs process the microbial agents or their antigens and migrate to lymphoid tissues to present the antigenic peptide to lymphocytes. This leads to activation of antigen-specific lymphocytes. Initially, it was assumed that DCs are principally involved in the induction and maintenance of adaptive immune responses, but now it is evident that DCs also have important roles in innate immunity. These features make DCs very good candidates for therapy against various pathological conditions including malignancies. Initially, DC-based therapy was used in animal models of cancers. Data from these studies inspired considerable optimism and DC-based therapies was started in human cancers 8 years ago. In general, DC-based therapy has been found to be safe in patients with cancers, although few controlled trials have been conducted in this regard. Because, the fundamentals principles of human cancers and animal models of cancers are different, the therapeutic efficacy of the ongoing regime of DC-based therapy in cancer patients is not satisfactory. In this review, we covered the various aspects that should be considered for developing better regime of DC-based therapy for human cancers.

Cancer immunotherapy: the past, the present and the future

One of the most controversial issues in immunology for over a century has been whether an effective immune response can be elicited against malignant tumours. Whether the immunology community has believed cancer immunotherapy is feasible or impossible has been largely determined by the prevailing immunological paradigms at that time. In fact, during the last 110 years it is possible to trace at least five dramatic fluctuations in attitude towards cancer immunotherapy. It now appears, however, that overwhelming evidence is available to support the view that both the innate and adaptive immune responses can recognize and eliminate tumours. On the other hand, it remains to be seen if these immune responses can be harnessed to control cancer as, at the time of diagnosis, many tumours have already been immunoselected to be highly resistant to immune elimination. Based on these observations it is argued that immunotherapy approaches, other than the generation of tumour-specific cytotoxic T lymphocytes, must be explored. Alternative strategies include recruiting tumouricidal myeloid cells into tumours, generating antiangiogenic immune responses and directing innate immunity to hypoxia-induced ligands on tumour cells.