Trial watch: Dendritic cell-based interventions for cancer therapy

Immune Cells in Cancer Therapy and Drug Delivery

Recent studies indicate the critical role of tumour associated macrophages, tumour associated neutrophils, dendritic cells, T lymphocytes, and natural killer cells in tumourigenesis. These cells can have a significant impact on the tumour microenvironment via their production of cytokines and chemokines. Additionally, products secreted from all these cells have defined specific roles in regulating tumour cell proliferation, angiogenesis, and metastasis. They act in a protumour capacity in vivo as evidenced by the recent studies indicating that macrophages, T cells, and neutrophils may be manipulated to exhibit cytotoxic activity against tumours. Therefore therapy targeting these cells may be promising, or they may constitute drug or anticancer particles delivery systems to the tumours. Herein, we discussed all these possibilities that may be used in cancer treatment.

Intratumoral delivery of mTORC2-deficient dendritic cells inhibits B16 melanoma growth by promoting CD8(+) effector T cell responses

Dendritic cells (DC) play a pivotal role in the induction and regulation of immune responses. In cancer, DC-based vaccines have proven to be safe and to elicit protective and therapeutic immunological responses. Recently, we showed that specific mTORC2 (mechanistic target of rapamycin complex 2) deficiency in DC enhances their ability to promote Th1 and Th17 responses after LPS stimulation. In the present study, bone marrow-derived mTORC2-deficient (Rictor(-/-)) DC were evaluated as a therapeutic modality in the murine B16 melanoma model. Consistent with their pro-inflammatory profile (enhanced IL-12p70 production and low PD-L1 expression versus control DC), intratumoral (i.t.) injection of LPS-activated Rictor(-/-) DC slowed B16 melanoma growth markedly in WT C57BL/6 recipient mice. This antitumor effect was abrogated when Rictor(-/-) DC were injected i.t. into B16-bearing Rag(-/-) mice, and also after selective CD8(+) T cell depletion in wild-type hosts in vivo, indicating that CD8(+) T cells were the principal regulators of tumor growth after Rictor(-/-) DC injection. I.t. administration of Rictor(-/-) DC also reduced the frequency of myeloid-derived suppressor cells within tumors, and enhanced numbers of IFNγ(+) and granzyme-B(+) cytotoxic CD8(+) T cells both in the spleens and tumors of treated animals. These data suggest that selective inhibition of mTORC2 activity in activated DC augments their pro-inflammatory and T cell stimulatory profile, in association with their enhanced capacity to promote protective CD8(+) T cell responses in vivo, leading to slowed B16 melanoma progression. These novel findings may contribute to the design of more effective DC-based vaccines for cancer immunotherapy.

Antigen Selection for Enhanced Affinity T-Cell Receptor-Based Cancer Therapies

Evidence of adaptive immune responses in the prevention of cancer has been accumulating for decades. Spontaneous T-cell responses occur in multiple indications, bringing the study of de novo expressed cancer antigens to the fore and highlighting their potential as targets for cancer immunotherapy. Circumventing the immune-suppressive mechanisms that maintain tumor tolerance and driving an antitumor cytotoxic T-cell response in cancer patients may eradicate the tumor or block disease progression. Multiple strategies are being pursued to harness the cytotoxic potential of T cells clinically. Highly promising results are now emerging. The focus of this review is the target discovery process for cancer immune therapeutics based on affinity-matured T-cell receptors (TCRs). Target cancer antigens in the context of adoptive cell transfer technologies and soluble biologic agents are discussed. To appreciate the impact of TCR-based technology and understand the TCR discovery process, it is necessary to understand key differences between TCR-based therapy and other immunotherapy approaches. The review first summarizes key advances in the cancer immunotherapy field and then discusses the opportunities that TCR technology provides. The nature and breadth of molecular targets that are tractable to this approach are discussed, together with the challenges associated with finding them.

Antitumor dendritic cell-based vaccines: lessons from 20 years of clinical trials and future perspectives

Dendritic cells (DCs) are versatile elements of the immune system and are best known for their unparalleled ability to initiate and modulate adaptive immune responses. During the past few decades, DCs have been the subject of numerous studies seeking new immunotherapeutic strategies against cancer. Despite the initial enthusiasm, disappointing results from early studies raised some doubts regarding the true clinical value of these approaches. However, our expanding knowledge of DC immunobiology and the definition of the optimal characteristics for antitumor immune responses have allowed a more rational development of DC-based immunotherapies in recent years. Here, after a brief overview of DC immunobiology, we sought to systematize the knowledge provided by 20 years of clinical trials, with a special emphasis on the diversity of approaches used to manipulate DCs and their consequent impact on vaccine effectiveness. We also address how new therapeutic concepts, namely the combination of DC vaccines with other anticancer therapies, are being implemented and are leveraging clinical outcomes. Finally, optimization strategies, new insights, and future perspectives on the field are also highlighted.

ATMPs for Cancer Immunotherapy: A Regulatory Overview

This chapter discusses European regulatory requirements for development of advanced therapy medicinal products (ATMP) for cancer immunotherapy approaches, describing the framework for clinical trials and for marketing authorization.Regulatory critical issues and challenges for developing ATMP are also discussed, with focus on potency determination, long-term follow-up, comparability, and insertional mutagenesis issues. Some of the most critical features of GMP application to ATMP are also described.

Dendritic cells pulsed with tumor cells killed by high hydrostatic pressure induce strong immune responses and display therapeutic effects both in murine TC-1 and TRAMP-C2 tumors when combined with docetaxel chemotherapy

High hydrostatic pressure (HHP) has been shown to induce immunogenic cell death of cancer cells, facilitating their uptake by dendritic cells (DC) and subsequent presentation of tumor antigens. In the present study, we demonstrated immunogenicity of the HHP-treated tumor cells in mice. HHP was able to induce immunogenic cell death of both TC-1 and TRAMP-C2 tumor cells, representing murine models for human papilloma virus-associated tumors and prostate cancer, respectively. HHP-treated cells induced stronger immune responses in mice immunized with these tumor cells, documented by higher spleen cell cytotoxicity and increased IFNγ production as compared to irradiated tumor cells, accompanied by suppression of tumor growth in vivo in the case of TC-1 tumors, but not TRAMP-C2 tumors. Furthermore, HHP-treated cells were used for DC-based vaccine antigen pulsing. DC co-cultured with HHP-treated tumor cells and matured by a TLR 9 agonist exhibited higher cell surface expression of maturation markers and production of IL-12 and other cytokines, as compared to the DC pulsed with irradiated tumor cells. Immunization with DC cell-based vaccines pulsed with HHP-treated tumor cells induced high immune responses, detected by increased spleen cell cytotoxicity and elevated IFNγ production. The DC-based vaccine pulsed with HHP-treated tumor cells combined with docetaxel chemotherapy significantly inhibited growth of both TC-1 and TRAMP-C2 tumors. Our results indicate that DC-based vaccines pulsed with HHP-inactivated tumor cells can be a suitable tool for chemoimmunotherapy, particularly with regard to the findings that poorly immunogenic TRAMP-C2 tumors were susceptible to this treatment modality.

Antigenically Modified Human Pluripotent Stem Cells Generate Antigen-Presenting Dendritic Cells

Human pluripotent stem cells (hPSCs) provide a promising platform to produce dendritic cell (DC) vaccine. To streamline the production process, we investigated a unique antigen-loading strategy that suits this novel platform. Specifically, we stably modified hPSCs using tumour antigen genes in the form of a full-length tumour antigen gene or an artificial tumour antigen epitope-coding minigene. Such antigenically modified hPSCs were able to differentiate into tumour antigen-presenting DCs. Without conventional antigen-loading, DCs derived from the minigene-modified hPSCs were ready to prime a tumour antigen-specific T cell response and further expand these specific T cells in restimulation processes. These expanded tumour antigen-specific T cells were potent effectors with central memory or effector memory phenotype. Thus, we demonstrated that immunocompetent tumour antigen-loaded DCs can be directly generated from antigenically modified hPSCs. Using such strategy, we can completely eliminate the conventional antigen-loading step and significantly simplify the production of DC vaccine from hPSCs.

Umbilical cord blood-derived CD11c(+) dendritic cells could serve as an alternative allogeneic source of dendritic cells for cancer immunotherapy

Introduction

Allogenic dendritic cells (DCs) generated from healthy donors, who are complete or partially HLA-matched, have been used for clinical trials. One of the sources for allogenic DCs is umbilical cord blood (UCB) cells. However, as far as cord blood cells are concerned, looking at their naïve nature, there is a concern as to whether the DCs generated from them will have enough potential to elicit a proper T cell response. For this, we compared CD11c⁺ UCB-DCs/ Cytotoxic T lymphocytes (CTLs) with the conventional source, i.e. peripheral blood (PBL) monocyte DCs/CTLs, using various parameters.

Methods

CD11c⁺ DCs generated from the two sources were compared morphologically, phenotypically and functionally. Functional assays included antigen uptake, chemotactic migration and MLR (mixed lymphocyte reaction). The CTLs generated were examined for the activation markers, granzyme A & granzyme B, and IFN-γ secretion. MUC1 (STAPPVHNV) peptide-specific CTLs were quantified by Streptamer staining. In vitro CTL activity was assessed by their efficiency in killing MCF-7 cells. For in vivo CTL assay, a xenograft of MCF-7-luc-F5 cells in female NOD/SCID mice was employed. Regression of tumors in mice was monitored using an in vivo imaging system before and after ten days of CTL infusion. Statistical analysis of all the experiments between the two groups was evaluated by one-way ANOVA.

Results

The CD11c⁺ DCs from the two sources were morphologically and phenotypically similar. Their capacity to uptake antigen, migration towards CCL-19 and MLR activity were equivalent. UCB-CTLs had significantly higher levels of activation markers, number of MUC1 specific CTLs, IFN-γ secretion and IL-12p70/IL-10 ratio than that of PBL-CTLs. Hematoxylin and Eosin-stained tumor sections showed T cell infiltration, which was further confirmed by immunofluorescence staining. In vivo CTL activity was found to be similar with the two sources.

Conclusions

Our data demonstrate that CD11c⁺ UCB-DCs/CTLs are as potent as standard CD11c⁺ PBL-DC/CTLs and could therefore be used as an allogenic source for therapeutic purposes. The findings of this study could help in taking us one step closer towards the personalized therapy using DC based cancer vaccines.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-015-0160-8) contains supplementary material, which is available to authorized users.

Injectable cryogel-based whole-cell cancer vaccines

A biomaterial-based vaccination system that uses minimal extracorporeal manipulation could provide in situ enhancement of dendritic cell (DC) numbers, a physical space where DCs interface with transplanted tumour cells, and an immunogenic context. Here we encapsulate GM-CSF, serving as a DC enhancement factor, and CpG ODN, serving as a DC activating factor, into sponge-like macroporous cryogels. These cryogels are injected subcutaneously into mice to localize transplanted tumour cells and deliver immunomodulatory factors in a controlled spatio-temporal manner. These vaccines elicit local infiltrates composed of conventional and plasmacytoid DCs, with the subsequent induction of potent, durable and specific anti-tumour T-cell responses in a melanoma model. These cryogels can be delivered in a minimally invasive manner, bypass the need for genetic modification of transplanted cancer cells and provide sustained release of immunomodulators. Altogether, these findings indicate the potential for cryogels to serve as a platform for cancer cell vaccinations.

Generation of lentivirus-induced dendritic cells under GMP-compliant conditions for adaptive immune reconstitution against cytomegalovirus after stem cell transplantation

Background

Reactivation of latent viruses such as human cytomegalovirus (HCMV) after allogeneic hematopoietic stem cell transplantation (HSCT) results in high morbidity and mortality. Effective immunization against HCMV shortly after allo-HSCT is an unmet clinical need due to delayed adaptive T cell development. Donor-derived dendritic cells (DCs) have a critical participation in stimulation of naïve T cells and immune reconstitution, and therefore adoptive DC therapy could be used to protect patients after HSCT. However, previous methods for ex vivo generation of adoptive donor-derived DCs were complex and inconsistent, particularly regarding cell viability and potency after thawing. We have previously demonstrated in humanized mouse models of HSCT the proof-of-concept of a novel modality of lentivirus-induced DCs (“SmyleDCpp65”) that accelerated antigen-specific T cell development.

Methods

Here we demonstrate the feasibility of good manufacturing practices (GMP) for production of donor-derived DCs consisting of monocytes from peripheral blood transduced with an integrase-defective lentiviral vector (IDLV, co-expressing GM-CSF, IFN-α and the cytomegalovirus antigen pp65) that were cryopreserved and thawed.

Results

Upscaling and standardized production of one lot of IDLV and three lots of SmyleDCpp65 under GMP-compliant conditions were feasible. Analytical parameters for quality control of SmyleDCpp65 identity after thawing and potency after culture were defined. Cell recovery, uniformity, efficacy of gene transfer, purity and viability were high and consistent. SmyleDCpp65 showed only residual and polyclonal IDLV integration, unbiased to proto-oncogenic hot-spots. Stimulation of autologous T cells by GMP-grade SmyleDCpp65 was validated.

Conclusion

These results underscore further developments of this individualized donor-derived cell vaccine to accelerate immune reconstitution against HCMV after HSCT in clinical trials.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-015-0599-5) contains supplementary material, which is available to authorized users.

In vitro and in vivo imaging of initial B-T-cell interactions in the setting of B-cell based cancer immunotherapy

There has been a growing interest in the use of B cells for cancer vaccines, since they have yielded promising results in preclinical animal models. Contrary to dendritic cells (DCs), we know little about the migration behavior of B cells in vivo. Therefore, we investigated the interactions between CD40-activated B (CD40B) cells and cytotoxic T cells in vitro and the migration behavior of CD40B cells in vivo. Dynamic interactions of human antigen-presenting cells (APCs) and T cells were observed by time-lapse video microscopy. The migratory and chemoattractant potential of CD40B cells was analyzed in vitro and in vivo using flow cytometry, standard transwell migration assays, and imaging of fluorescently labeled murine CD40B cells. Murine CD40B cells show migratory features similar to human CD40B cells. They express important lymph node homing receptors which were functional and induced chemotaxis of T cells in vitro. Striking differences were observed with regard to interactions of human APCs with T cells. CD40B cells differ from DCs by displaying a rapid migratory pattern undergoing highly dynamic, short-lived and sequential interactions with T cells. In vivo, CD40B cells are home to the secondary lymphoid organs where they accumulate in the B cell zone before traveling to the B/T cell boundary. Moreover, intravenous (i.v.) administration of murine CD40B cells induced an antigen-specific cytotoxic T cell response. Taken together, this data show that CD40B cells home secondary lymphoid organs where they physically interact with T cells to induce antigen-specific T cell responses, thus underscoring their potential as cellular adjuvant for cancer immunotherapy.

Cancer immunotherapy in clinical practice -- the past, present, and future

Considerable progress has been made in the field of cancer immunotherapy in recent years. This has been made possible in large part by the identification of new immune-based cellular targets and the development of novel approaches aimed at stimulating the immune system. The role played by the immunosuppressive microenvironment in the development of tumors has been established. The success of checkpoint-inhibiting antibodies and cancer vaccines has marked the beginning of a new era in cancer treatment. This review highlights the clinically relevant principles of cancer immunology and various immunotherapeutic approaches that have either already entered mainstream oncologic practice or are currently in the process of being evaluated in clinical trials. Furthermore, the current barriers to the development of effective immunotherapies and the potential strategies of overcoming them are also discussed.

Dendritic cell-based vaccination in cancer: therapeutic implications emerging from murine models

Dendritic cells (DCs) play a pivotal role in the orchestration of immune responses, and are thus key targets in cancer vaccine design. Since the 2010 FDA approval of the first cancer DC-based vaccine (Sipuleucel-T), there has been a surge of interest in exploiting these cells as a therapeutic option for the treatment of tumors of diverse origin. In spite of the encouraging results obtained in the clinic, many elements of DC-based vaccination strategies need to be optimized. In this context, the use of experimental cancer models can help direct efforts toward an effective vaccine design. This paper reviews recent findings in murine models regarding the antitumoral mechanisms of DC-based vaccination, covering issues related to antigen sources, the use of adjuvants and maturing agents, and the role of DC subsets and their interaction in the initiation of antitumoral immune responses. The summary of such diverse aspects will highlight advantages and drawbacks in the use of murine models, and contribute to the design of successful DC-based translational approaches for cancer treatment.

Enhanced protective immunity derived from dendritic cells with phagocytosis of CD40 ligand transgene-engineered apoptotic tumor cells via increased dendritic cell maturation

AIMS AND BACKGROUND

Dendritic cells (DCs) play a pivotal role in regulating CD8+ cytotoxic T-lymphocyte (CTL) responses. Currently, DC vaccines have been used in experimental animal models and clinical trials for evaluation of antitumor immunity. However, their efficacy is limited, warranting the improvement of DC-based cancer vaccines. CD40 ligand (CD40L) stimulates DC activation and maturation via CD40-CD40L interaction. We demonstrated that DCs that had phagocytized apoptotic tumor cells induced antitumor immunity.

METHODS

We generated CD40L-expressing (EG7-CD40L) and the control (EG7-Null) EG7 tumor cells by transfection of EG7 tumor cells with CD40L-expressing adenoviral vector AdVCD40L and the control vector AdV(pLpA), respectively. We also generated DC vaccines (DC-EG7/CD40L and the control DC-EG7/Null) using DCs with phagocytosis of irradiated EG7-CD40L and EG7-Null tumor cells, and assessed their phenotype and immunogenicity by flow cytometry and animal studies in C57BL/6 mice.

RESULTS

We demonstrate that an irradiation of 9000-rad induced Annexin V-expressing cell apoptosis in most (~75%) tumor cells, and provide evidence for phagocytosis of apoptotic tumor cells by flow cytometry and confocal microscopy. The DC-EG7/CD40L cells showed higher expression of DC maturation markers (Ia(b), CD40, CD80, and CD86) and peptide/major histocompatibility complex I than the control DC-EG7/Null cells. In addition, DC-EG7/CD40L vaccine stimulates more efficient (0.97%) tumor-specific CTL responses than DC-EG7/Null cells (0.31%). Furthermore, 80% (4/5) of mice immunized with DC-EG7/CD40L vaccine become tumor-free after EG7 tumor cell challenge, whereas DC-EG7/Null vaccine only delays immunized mouse death.

CONCLUSIONS

Dendritic cells that have phagocytized CD40L-expressing apoptotic tumor cells appear to offer new strategies in DC cancer vaccines.

Trial Watch: Adoptive cell transfer for oncological indications

One particular paradigm of anticancer immunotherapy relies on the administration of (potentially) tumor-reactive immune effector cells. Generally, these cells are obtained from autologous peripheral blood lymphocytes (PBLs) ex vivo (in the context of appropriate expansion, activation and targeting protocols), and re-infused into lymphodepleted patients along with immunostimulatory agents. In spite of the consistent progress achieved throughout the past two decades in this field, no adoptive cell transfer (ACT)-based immunotherapeutic regimen is currently approved by regulatory agencies for use in cancer patients. Nonetheless, the interest of oncologists in ACT-based immunotherapy continues to increase. Accumulating clinical evidence indicates indeed that specific paradigms of ACT, such as the infusion of chimeric antigen receptor (CAR)-expressing autologous T cells, are associated with elevated rates of durable responses in patients affected by various neoplasms. In line with this notion, clinical trials investigating the safety and therapeutic activity of ACT in cancer patients are being initiated at an ever increasing pace. Here, we review recent preclinical and clinical advances in the development of ACT-based immunotherapy for oncological indications.

Trial watch: Naked and vectored DNA-based anticancer vaccines

One type of anticancer vaccine relies on the administration of DNA constructs encoding one or multiple tumor-associated antigens (TAAs). The ultimate objective of these preparations, which can be naked or vectored by non-pathogenic viruses, bacteria or yeast cells, is to drive the synthesis of TAAs in the context of an immunostimulatory milieu, resulting in the (re-)elicitation of a tumor-targeting immune response. In spite of encouraging preclinical results, the clinical efficacy of DNA-based vaccines employed as standalone immunotherapeutic interventions in cancer patients appears to be limited. Thus, efforts are currently being devoted to the development of combinatorial regimens that allow DNA-based anticancer vaccines to elicit clinically relevant immune responses. Here, we discuss recent advances in the preclinical and clinical development of this therapeutic paradigm.

The exosomes in tumor immunity

Exosomes are a kind of nanometric membrane vesicles and can be released by almost all kinds of cells, including cancer cells. As the important mediators in intercellular communications, exosomes mediate exchange of protein and genetic material derived from parental cells. Emerging evidences show that exosomes secreted by either host cells or cancer cells are involved in tumor initiation, growth, invasion and metastasis. Moreover, communications between immune cells and cancer cells via exosomes play dual roles in modulating tumor immunity. In this review, we focus on exosome-mediated immunosuppression via inhibition of antitumor responses elicited by immune cells (DCs, NK cells, CD4⁺ and CD8⁺ T cells, etc.) and induction of immunosuppressive or regulatory cell populations (MDSCs, Tregs and Bregs). Transfer of cytokines, microRNAs (miRNAs) and functional mRNAs by tumor-derived exosomes (TEXs) is crucial in the immune escape. Furthermore, exosomes secreted from several kinds of immune cells (DCs, CD4⁺ and CD8⁺ Tregs) also participate in immunosuppression. On the other hand, we summarize the current application of DC-derived and modified tumor-derived exosomes as tumor vaccines. The potential challenges about exosome-based vaccines for clinical application are also discussed.

Glioblastoma: molecular pathways, stem cells and therapeutic targets

Glioblastoma (GBM), a WHO-defined Grade IV astrocytoma, is the most common and aggressive CNS malignancy. Despite current treatment modalities, the survival time remains dismal. The main cause of mortality in patients with this disease is reoccurrence of the malignancy, which is attributed to treatment-resistant cancer stem cells within and surrounding the primary tumor. Inclusion of novel therapies, such as immuno- and DNA-based therapy, may provide better means of treating GBM. Furthermore, manipulation of recently discovered non-coding microRNAs, some of which regulate tumor growth through the development and maintenance of GBM stem cells, could provide new prospective therapies. Studies conducted by The Cancer Genome Atlas (TCGA) also demonstrate the role of molecular pathways, specifically the activated PI3K/AKT/mTOR pathway, in GBM tumorigenesis. Inhibition of the aforementioned pathway may provide a more direct and targeted method to GBM treatment. The combination of these treatment modalities may provide an innovative therapeutic approach for the management of GBM.

Type I IFN signaling on dendritic cells is required for NK cell-mediated anti-tumor immunity

NK cells play a vital role in innate anti-tumor immunity. Crosstalk between NK cells and dendritic cells (DCs) has come to the forefront in protection against tumors in the context of DC vaccines. We previously discovered that NK cell activation mediates the anti-tumor activity elicited by DC vaccines in response to melanoma tumor challenge in a murine lung metastasis model. In this study, we sought to explore the mechanism behind this NK-DC communication, specifically looking at the involvement of IL-15 and type I IFN signaling. Using DCs from IL-15(-/-) and IL-15Rα(-/-) mice, we found that the anti-tumor effect of the vaccine remained comparable with DCs from wild type mice. Moreover, DCs derived from IFN-α/βR(-/-) mice also maintained their anti-tumor effect. Interestingly, endogenous DCs were found to accumulate in the draining lymph nodes post-immunization and their depletion abolished the anti-tumor effect of the vaccine. Our findings suggest the important role that type I IFN signaling and endogenous DCs play in DC vaccine-mediated anti-tumor protection. Our data suggest that type I IFNs from vaccine DCs activate host DCs to provide NK cell-mediated anti-tumor immunity.

Dendritic cell-based vaccine efficacy: aiming for hot spots

Many approaches for cancer immunotherapy have targeted dendritic cells (DCs), directly or indirectly, for the induction of antitumor immune responses. DC-based vaccines have been developed using a wide variety of ex vivo DC culture conditions, antigen (Ag) source and loading strategies, maturation agents, and routes of vaccination. Adjuvants are used to activate innate immune cells at the vaccine injection site, to promote Ag transport to the draining lymph nodes (LNs) and to model adaptive immune responses. Despite years of effort, the effective induction of strong and durable antitumor T-cell responses in vaccinated patients remains a challenge. The study of vaccine interactions with other immune cells in the LNs and, more recently, in the injection site has opened new doors for understanding antitumor effector T-cell licensing and function. In this review, we will briefly discuss the relevant sites and up-to-date facts regarding possible targets for antitumor vaccine refinement. We will focus on the processes taking place at the injection site, adjuvant combinations and their role in DC-based vaccines, LN homing, and modeling vaccine-induced immune responses capable of controlling tumor growth and generating immune memory.

Dendritic cell-based vaccines: clinical applications in breast cancer

Recent evidence suggests that the immune system is involved in the carcinogenesis process and the antitumor immune responses impact the clinical outcome, thus emphasizing the concept of cancer immune surveillance. In this context, dendritic cells (DCs) seem to play a crucial role, as they are the most potent antigen-presenting cells (APCs) and are able to stimulate naive T lymphocytes and to generate memory T lymphocytes. Immunotherapy with DC-based vaccines is a very attractive approach to treat cancer, offering the potential for high tumor-specific cytotoxicity. Although breast cancer (BC) is traditionally considered a poorly immunogenic tumor, increasing numbers of both preclinical and clinical studies demonstrate that vaccination with DCs is capable of inducing an antitumor-specific response, while being well tolerated and safe. However, clinical objective responses are still disappointing and many reasons may explain the difficulty of developing effective DC-based therapies for BC. In this review, we discuss the characteristics of DCs, and the major clinical indications for DC-based immunotherapy in BC with related drawbacks.

Anti-CD27 Antibody Potentiates Antitumor Effect of Dendritic Cell-Based Vaccine in Prostate Cancer-Bearing Mice

In the current study, we investigated whether anti-CD27 monoclonal antibody can enhance the antitumor efficacy of a dendritic cell-based vaccine in prostate cancer-bearing mice. The overall therapeutic effect of a dendritic cell-based vaccine for prostate cancer remains moderate. A prostate cancer model was established by subcutaneous injection of RM-1 tumor cells into male C57BL/6 mice on day 0. After 4 days, tumor-bearing mice were treated with RM-1 tumor lysate-pulsed dendritic cells (i.e., dendritic cell-based vaccine), anti-CD27 monoclonal antibody, or a combination of RM-1 tumor lysate-pulsed dendritic cells with anti-CD27 monoclonal antibody. Mice were killed at 21 days after tumor cell implantation. Tumor size was measured for assessment of antitumor effect. Spleens were collected for analysis of antitumor immune responses. The antitumor immune responses were evaluated by measuring the proliferation and activity of T cells, which have the ability to kill tumor cells. The combination therapy with RM-1 tumor lysate-pulsed dendritic cells and anti-CD27 antibody significantly enhanced T-cell proliferation and activity, and significantly reduced tumor growth, compared with monotherapy with RM-1 tumor lysate-pulsed dendritic cells or anti-CD27 antibody. Our results suggest that combined treatment can strengthen antitumor efficacy by improving T-cell proliferation and activity.

Classification of current anticancer immunotherapies

During the past decades, anticancer immunotherapy has evolved from a promising therapeutic option to a robust clinical reality. Many immunotherapeutic regimens are now approved by the US Food and Drug Administration and the European Medicines Agency for use in cancer patients, and many others are being investigated as standalone therapeutic interventions or combined with conventional treatments in clinical studies. Immunotherapies may be subdivided into "passive" and "active" based on their ability to engage the host immune system against cancer. Since the anticancer activity of most passive immunotherapeutics (including tumor-targeting monoclonal antibodies) also relies on the host immune system, this classification does not properly reflect the complexity of the drug-host-tumor interaction. Alternatively, anticancer immunotherapeutics can be classified according to their antigen specificity. While some immunotherapies specifically target one (or a few) defined tumor-associated antigen(s), others operate in a relatively non-specific manner and boost natural or therapy-elicited anticancer immune responses of unknown and often broad specificity. Here, we propose a critical, integrated classification of anticancer immunotherapies and discuss the clinical relevance of these approaches.

Trial watch: Dendritic cell-based anticancer therapy

The use of patient-derived dendritic cells (DCs) as a means to elicit therapeutically relevant immune responses in cancer patients has been extensively investigated throughout the past decade. In this context, DCs are generally expanded, exposed to autologous tumor cell lysates or loaded with specific tumor-associated antigens (TAAs), and then reintroduced into patients, often in combination with one or more immunostimulatory agents. As an alternative, TAAs are targeted to DCs in vivo by means of monoclonal antibodies, carbohydrate moieties or viral vectors specific for DC receptors. All these approaches have been shown to (re)activate tumor-specific immune responses in mice, often mediating robust therapeutic effects. In 2010, the first DC-based preparation (sipuleucel-T, also known as Provenge®) has been approved by the US Food and Drug Administration (FDA) for use in humans. Reflecting the central position occupied by DCs in the regulation of immunological tolerance and adaptive immunity, the interest in harnessing them for the development of novel immunotherapeutic anticancer regimens remains high. Here, we summarize recent advances in the preclinical and clinical development of DC-based anticancer therapeutics.

Cancer immunotherapy and breaking immune tolerance: new approaches to an old challenge

Cancer immunotherapy has proven to be challenging as it depends on overcoming multiple mechanisms that mediate immune tolerance to self-antigens. A growing understanding of immune tolerance has been the foundation for new approaches to cancer immunotherapy. Adoptive transfer of immune effectors such as antitumor mAb and chimeric antigen receptor T cells bypasses many of the mechanisms involved in immune tolerance by allowing for expansion of tumor-specific effectors ex vivo. Vaccination with whole tumor cells, protein, peptide, or dendritic cells has proven challenging, yet may be more useful when combined with other cancer immunotherapeutic strategies. Immunomodulatory approaches to cancer immunotherapy include treatment with agents that enhance and maintain T-cell activation. Recent advances in the use of checkpoint blockade to block negative signals and to maintain the antitumor response are particularly exciting. With our growing knowledge of immune tolerance and ways to overcome it, combination treatments are being developed, tested, and have particular promise. One example is in situ immunization that is designed to break tolerance within the tumor microenvironment. Progress in all these areas is continuing based on clear evidence that cancer immunotherapy designed to overcome immune tolerance can be useful for a growing number of patients with cancer.

Trial watch: IDO inhibitors in cancer therapy

Indoleamine 2,3-dioxigenase 1 (IDO1) is the main enzyme that catalyzes the first, rate-limiting step of the so-called "kynurenine pathway", i.e., the metabolic cascade that converts the essential amino acid L-tryptophan (Trp) into L-kynurenine (Kyn). IDO1, which is expressed constitutively by some tissues and in an inducible manner by specific subsets of antigen-presenting cells, has been shown to play a role in the establishment and maintenance of peripheral tolerance. At least in part, this reflects the capacity of IDO1 to restrict the microenvironmental availability of Trp and to favor the accumulation of Kyn and some of its derivatives. Also, several neoplastic lesions express IDO1, providing them with a means to evade anticancer immunosurveillance. This consideration has driven the development of several IDO1 inhibitors, some of which (including 1-methyltryptophan) have nowadays entered clinical evaluation. In animal tumor models, the inhibition of IDO1 by chemical or genetic interventions is indeed associated with the (re)activation of therapeutically relevant anticancer immune responses. This said, several immunotherapeutic regimens exert robust clinical activity in spite of their ability to promote the expression of IDO1. Moreover, 1-methyltryptophan has recently been shown to exert IDO1-independent immunostimulatory effects. Here, we summarize the preclinical and clinical studies testing the antineoplastic activity of IDO1-targeting interventions.

Trial Watch: Radioimmunotherapy for oncological indications

During the past two decades, it has become increasingly clear that the antineoplastic effects of radiation therapy do not simply reflect the ability of X-, β- and γ-rays to damage transformed cells and directly cause their permanent proliferative arrest or demise, but also involve cancer cell-extrinsic mechanisms. Indeed, among other activities, radiotherapy has been shown to favor the establishment of tumor-specific immune responses that operate systemically, underpinning the so-called 'out-of-field' or 'abscopal' effect. Thus, ionizing rays appear to elicit immunogenic cell death, a functionally peculiar variant of apoptosis associated with the emission of a particularly immunostimulatory combination of damage-associated molecular patterns. In line with this notion, radiation therapy fosters, and thus exacerbates, the antineoplastic effects of various treatment modalities, including surgery, chemotherapy and various immunotherapeutic agents. Here, we summarize recent advances in the use of ionizing rays as a means to induce or potentiate therapeutically relevant anticancer immune responses. In addition, we present clinical trials initiated during the past 12 months to test the actual benefit of radioimmunotherapy in cancer patients.

Exogenous addition of arachidonic acid to the culture media enhances the functionality of dendritic cells for their possible use in cancer immunotherapy

The development of dendritic cell based vaccines is a promising approach in cancer immunotherapy. For their successful use in the clinics, the propagation and functionality of DCs is crucial. We earlier established a two-step method for the large scale generation of DCs from umbilical cord blood derived MNCs/CD34+ cells. This work aims at improving their functionality based on the following observations: in vitro generated DCs can be less efficient in migration and other functional activities due to lower eicosanoid levels. The production of eicosanoids from Arachidonic Acid (AA) can be hampered due to suppression of the enzyme phospholipase A2 by IL-4, an essential cytokine required for the differentiation of DCs. We hypothesized that exogenous addition of AA to the culture media during DC generation may result in DCs with improved functionality. DCs were generated with and without AA. The two DC sets were compared by phenotypic analysis, morphology and functional assays like antigen uptake, MLR, CTL assay and in vitro and in vivo migration. Though there were no differences between the two types of DCs in terms of morphology, phenotype and antigen uptake, AA⁺ DCs exhibited an enhanced in vitro and in vivo migration, T cell stimulatory capacity, CTL activity and significantly higher transcript levels of COX-2. AA⁺ DCs also show a favorable Th1 cytokine profile than AA^- DCs. Thus addition of AA to the culture media is skewing the DCs towards the secretion of more IL-12 and less of IL-10 along with the restoration of eicosanoids levels in a COX-2 mediated pathway thereby enhancing the functionality of these cells to be used as a potent cellular vaccine. Taken together, these findings will be helpful in the better contriving of DC based vaccines for cancer immunotherapy.

Trial watch: Cardiac glycosides and cancer therapy

Cardiac glycosides (CGs) are natural compounds sharing the ability to operate as potent inhibitors of the plasma membrane Na⁺/K⁺-ATPase, hence promoting—via an indirect mechanism—the intracellular accumulation of Ca²⁺ ions. In cardiomyocytes, increased intracellular Ca²⁺ concentrations exert prominent positive inotropic effects, that is, they increase myocardial contractility. Owing to this feature, two CGs, namely digoxin and digitoxin, have extensively been used in the past for the treatment of several cardiac conditions, including distinct types of arrhythmia as well as contractility disorders. Nowadays, digoxin is approved by the FDA and indicated for the treatment of congestive heart failure, atrial fibrillation and atrial flutter with rapid ventricular response, whereas the use of digitoxin has been discontinued in several Western countries. Recently, CGs have been suggested to exert potent antineoplastic effects, notably as they appear to increase the immunogenicity of dying cancer cells. In this Trial Watch, we summarize the mechanisms that underpin the unsuspected anticancer potential of CGs and discuss the progress of clinical studies that have evaluated/are evaluating the safety and efficacy of CGs for oncological indications.

Trial watch: Monoclonal antibodies in cancer therapy

During the past 20 years, dozens-if not hundreds-of monoclonal antibodies have been developed and characterized for their capacity to mediate antineoplastic effects, either as they activate/enhance tumor-specific immune responses, either as they interrupt cancer cell-intrinsic signal transduction cascades, either as they specifically delivery toxins to malignant cells or as they block the tumor-stroma interaction. Such an intense research effort has lead to the approval by FDA of no less than 14 distinct molecules for use in humans affected by hematological or solid malignancies. In the inaugural issue of OncoImmunology, we briefly described the scientific rationale behind the use of monoclonal antibodies in cancer therapy and discussed recent, ongoing clinical studies investigating the safety and efficacy of this approach in patients. Here, we summarize the latest developments in this exciting area of clinical research, focusing on high impact studies that have been published during the last 15 months and clinical trials launched in the same period to investigate the therapeutic profile of promising, yet hitherto investigational, monoclonal antibodies.

Trial watch: DNA vaccines for cancer therapy

The foundation of modern vaccinology dates back to the 1790s, when the English physician Edward Jenner uncovered the tremendous medical potential of prophylactic vaccination. Jenner’s work ignited a wave of nationwide vaccination campaigns abating the incidence of multiple life-threatening infectious diseases and culminating with the eradication of natural smallpox virus, which was definitively certified by the WHO in 1980. The possibility of using vaccines against cancer was first proposed at the end of the 19th century by Paul Ehrlich and William Coley. However, it was not until the 1990s that such a hypothesis began to be intensively investigated, following the realization that the immune system is not completely unresponsive to tumors and that neoplastic cells express immunogenic tumor-associated antigens (TAAs). Nowadays, anticancer vaccines are rapidly moving from the bench to the bedside, and a few prophylactic and therapeutic preparations have already been approved by FDA for use in humans. In this setting, one interesting approach is constituted by DNA vaccines, i.e., TAA-encoding circularized DNA constructs, often of bacterial origin, that are delivered to patients as such or by means of specific vectors, including (but not limited to) liposomal preparations, nanoparticles, bacteria and viruses. The administration of DNA vaccines is most often performed via the intramuscular or subcutaneous route and is expected to cause (1) the endogenous synthesis of the TAA by myocytes and/or resident antigen-presenting cells; (2) the presentation of TAA-derived peptides on the cell surface, in association with MHC class I molecules; and (3) the activation of potentially therapeutic tumor-specific immune responses. In this Trial Watch, we will summarize the results of recent clinical trials that have evaluated/are evaluating DNA vaccines as therapeutic interventions against cancer.

Trial watch: Chemotherapy with immunogenic cell death inducers

It is now clear that the immune system plays a critical role not only during oncogenesis and tumor progression, but also as established neoplastic lesions respond to therapy. Selected cytotoxic chemicals can indeed elicit immunogenic cell death, a functionally peculiar type of apoptosis that stimulates tumor-specific cognate immune responses. Such immunogenic chemotherapeutics include cyclophosphamide, doxorubicin and oxaliplatin (which are approved by FDA for the treatment of various hematological and solid malignancies), mitoxantrone (which is currently employed both as an anticancer agent and against multiple sclerosis) and patupilone (a microtubular poison in clinical development). One year ago, in the second issue of OncoImmunology, we discussed the scientific rationale behind immunogenic chemotherapy and reviewed the status of recent clinical trials investigating the off-label use of cyclophosphamide, doxorubicin, oxaliplatin and mitoxantrone in cancer patients. Here, we summarize the latest developments in this area of clinical research, covering both high-impact studies that have been published during the last 13 months and clinical trials that have been initiated in the same period to assess the antineoplastic profile of immunogenic chemotherapeutics.

Biodegradable microparticles loaded with doxorubicin and CpG ODN for in situ immunization against cancer

In situ immunization is based on the concept that it is possible to break immune tolerance by inducing tumor cell death in situ in a manner that provides antigen-presenting cells such as dendritic cells (DCs) with a wide selection of tumor antigens that can then be presented to the immune system and result in a therapeutic anticancer immune response. We designed a comprehensive approach to in situ immunization using poly(lactic-co-glycolic acid) (PLGA)-biodegradable microparticles (MPs) loaded with doxorubicin (Dox) and CpG oligodeoxynucleotides (CpG) that deliver Dox (chemotherapy) and CpG (immunotherapy) in a sustained-release fashion when injected intratumorally. Dox induces immunogenic tumor cell death while CpG enhances tumor antigen presentation by DCs. PLGA MPs allow their safe co-delivery while evading the vesicant action of Dox. In vitro, we show that Dox/CpG MPs can kill B and T lymphoma cells and are less toxic to DCs. In vivo, Dox/CpG MPs combined with antibody therapy to enhance and maintain the T cell response generated systemic immune responses that suppressed injected and distant tumors in a murine B lymphoma model, leading to tumor-free mice. The combination regimen was also effective at reducing T cell lymphoma and melanoma tumor burdens. In conclusion, Dox/CpG MPs represent an efficient and safe tool for in situ immunization that could provide a promising component of immunotherapy for patients with a variety of types of cancer.

A phase I clinical trial combining dendritic cell vaccination with adoptive T cell transfer in patients with stage IV melanoma

Adoptive transfer of in vitro-expanded tumor-infiltrating lymphocytes (TIL) has shown great clinical benefit in patients with malignant melanoma. TIL therapy itself has little side effects, but conditioning chemo- or radiotherapy and postinfusion interleukin 2 (IL-2) injections are associated with severe adverse advents. We reasoned that combining TIL infusion with dendritic cell (DC) vaccination could circumvent the need for conditioning and IL-2 support and thus represent a milder treatment approach. Eight patients with stage IV melanoma were enrolled in the MAT01 study, consisting of vaccination with autologous tumor-lysate-loaded DC, followed by TIL infusion. Six of eight patients were treated according to protocol, while one patient received only TIL and one only DC. Treatments were well tolerated with a single grade 3 adverse event. The small study size precludes analysis of clinical responses, though interestingly one patient showed a complete remission and two had stable disease. Analysis of the infusion products revealed that mature DC were generated in all cases. TIL after expansion were CD3+ T cells, dominated by effector memory CD8+ cytotoxic T cells. Analysis of the T cell receptor repertoire revealed presence of highly dominant clones in most infusion products, and many of these could be detected in the circulation for weeks after T cell transfer. Here, we report the first combination of DC vaccination and TIL infusion in malignant melanoma. This combined treatment was safe and feasible, though after evaluating both clinical and immunological parameters, we expect that administration of lymphodepleting chemotherapy and IL-2 will likely increase treatment efficacy.

mRNA-based dendritic cell vaccines

Cancer immunotherapy has been proposed as a powerful treatment modality. Active immunotherapy aspires to stimulate the patient's immune system, particularly T cells. These cells can recognize and kill cancer cells and can form an immunological memory. Dendritic cells (DCs) are the professional antigen-presenting cells of our immune system. They take up and process antigens to present them to T cells. Consequently, DCs have been investigated as a means to stimulate cancer-specific T-cell responses. An efficient strategy to program DCs is the use of mRNA, a well-defined and safe molecule that can be easily generated at high purity. Importantly, vaccines consisting of mRNA-modified DCs showed promising results in clinical trials. Therefore, we will introduce cancer immunotherapy and DCs and give a detailed overview on the application of mRNA to generate cancer-fighting DC vaccines.

Optimized dendritic cell-based immunotherapy for melanoma: the TriMix-formula

Since decades, the main goal of tumor immunologists has been to increase the capacity of the immune system to mediate tumor regression. In this regard, one of the major focuses of cancer immunotherapy has been the design of vaccines promoting strong tumor-specific cytotoxic T lymphocyte responses in cancer patients. Here, dendritic cells (DCs) play a pivotal role as they are regarded as nature's adjuvant and as such have become the natural agents for antigen delivery in order to finally elicit strong T cell responses (Villadangos and Schnorrer in Nat Rev Immunol 7:543-555, 2007; Melief in Immunity 29:372-383, 2008; Palucka and Banchereau in Nat Rev Cancer 12:265-277, 2012; Vacchelli et al. in Oncoimmunology 2:e25771, 2013; Galluzzi et al. in Oncoimmunology 1:1111-1134, 2012). Therefore, many investigators are actively pursuing the use of DCs as an efficient way of inducing anticancer immune responses. Nowadays, DCs can be generated at a large scale in closed systems, yielding sufficient numbers of cells for clinical application. In addition, with the identification of tumor-associated antigens, which are either selectively or preferentially expressed by tumors, a whole range of strategies using DCs for immunotherapy have been designed and tested in clinical studies. Despite the evidence that DCs loaded with tumor-associated antigens can elicit immune responses in vivo, clinical responses remained disappointingly low. Therefore, optimization of the cellular product and route of administration was urgently needed. Here, we review the path we have followed in the development of TriMixDC-MEL, a potent DC-based cellular therapy, discussing its development as well as further modifications and applications.

Lentivirus-Induced Dendritic Cells (iDC) for Immune-Regenerative Therapies in Cancer and Stem Cell Transplantation

Conventional dendritic cells (cDC) are ex vivo differentiated professional antigen presenting cells capable of potently stimulating naïve T cells and with vast potential for immunotherapeutic applications. The manufacture of clinical-grade cDC is relatively complex and requires several days for completion. Clinical trials showed poor trafficking of cDC from subcutaneous injection sites to lymph nodes (LN), where DC can optimally stimulate naïve lymphocytes for long-lasting memory responses. We demonstrated in mouse and human systems that a single overnight ex vivo lentiviral (LV) gene transfer into DC precursors for production of combination of cytokines and antigens was capable to induce autonomous self-differentiation of antigen-loaded DC in vitro and in vivo. These highly viable induced DC (iDC) effectively migrated from the injected skin to LN, where they effectively activated de novo antigen-specific effector memory T cells. Two iDC modalities were validated in relevant animal models and are now in clinical development: Self-differentiated Myeloid-derived Antigen-presenting-cells Reactive against Tumors co-expressing GM-CSF/IL-4/TRP2 for melanoma immunotherapy in the autologous setting (SmartDCtrp2), and Self-differentiated Myeloid-derived Lentivirus-induced against human cytomegalovirus as an allogeneic matched adoptive cell after stem cell transplantation (SmyleDCpp65). The lentiviral vector design and packaging methodology has “evolved” continuously in order to simplify and optimize function and biosafety of in vitro and in vivo genetic reprogramming of iDC. Here, we address the challenges seeking for new creations of genetically programmed iDC and integrase-defective LV vaccines for immune regeneration.

Trial Watch: Toll-like receptor agonists in oncological indications

Toll-like receptors (TLRs) are an evolutionarily conserved group of enzymatically inactive, single membrane-spanning proteins that recognize a wide panel of exogenous and endogenous danger signals. Besides constituting a crucial component of the innate immune response to bacterial and viral pathogens, TLRs appear to play a major role in anticancer immunosurveillance. In line with this notion, several natural and synthetic TLR ligands have been intensively investigated for their ability to boost tumor-targeting immune responses elicited by a variety of immunotherapeutic and chemotherapeutic interventions. Three of these agents are currently approved by the US Food and Drug Administration (FDA) or equivalent regulatory agencies for use in cancer patients: the so-called bacillus Calmette-Guérin, monophosphoryl lipid A, and imiquimod. However, the number of clinical trials testing the therapeutic potential of both FDA-approved and experimental TLR agonists in cancer patients is stably decreasing, suggesting that drug developers and oncologists are refocusing their interest on alternative immunostimulatory agents. Here, we summarize recent findings on the use of TLR agonists in cancer patients and discuss how the clinical evaluation of FDA-approved and experimental TLR ligands has evolved since the publication of our first Trial Watch dealing with this topic.

Immune response, safety, and survival and quality of life outcomes for advanced colorectal cancer patients treated with dendritic cell vaccine and cytokine-induced killer cell therapy

Purpose. To determine the immune response after dendritic cell (DC) vaccine and cytokine-induced killer cells (CIK) therapy and assess its associated toxicity, survival benefit, and changes in the quality of life (QOL) of advanced colorectal cancer (CRC) patients. Methods. We recruited 100 patients with unresectable CRC orrelapsed CRC after surgery who received DC vaccine and CIK cells (group immunotherapy, group I), and, as a control, 251 patients who had similar characteristics and underwent similar treatments, except for this immunotherapy (group nonimmunotherapy, group NI). After a follow-up period of 489.2 ± 160.4 days, overall survival (OS) of the two groups was compared using the Kaplan-Meier method. Results. In group I, 62% of patients developed a positive delayed type hypersensitivity response, and most patients showed an improvement in physical strength (75.2%), appetite (74.2%), sleeping (72.1%), and body weight (70.1%). Adverse events were fever (29.5%), insomnia (19.2%), anorexia (9.1%), sore joints (5.4%), and skin rash (1.0%). No toxicity was observed in patients treated with DC vaccine and CIK therapy. OS was significantly longer in group I than in group NI (P = 0.043). Conclusion. DC vaccine and CIK therapy were safe and could induce an immune response against CRC, thereby improving QOL and prolonging OS.

Therapeutic vaccines for cancer: an overview of clinical trials

The therapeutic potential of host-specific and tumour-specific immune responses is well recognized and, after many years, active immunotherapies directed at inducing or augmenting these responses are entering clinical practice. Antitumour immunization is a complex, multi-component task, and the optimal combinations of antigens, adjuvants, delivery vehicles and routes of administration are not yet identified. Active immunotherapy must also address the immunosuppressive and tolerogenic mechanisms deployed by tumours. This Review provides an overview of new results from clinical studies of therapeutic cancer vaccines directed against tumour-associated antigens and discusses their implications for the use of active immunotherapy.

Dasatinib enhances migration of monocyte-derived dendritic cells by reducing phosphorylation of inhibitory immune receptors Siglec-9 and Siglec-3

The SRC family of kinases (SFKs) is crucial to malignant growth, but also important for signaling in immune cells such as dendritic cells (DCs). These specialized antigen-presenting cells are essential for inducing and boosting specific T-cell responses against pathogens and malignancies. Targeted therapy with SFK inhibitors holds great promise as a direct anti-cancer treatment, but potentially also as an indirect treatment via immunomodulation. Here, we investigated whether the BCR-ABL/SRC inhibitor dasatinib would modulate the major effector functions of DCs, especially their migration, a prerequisite to interaction with lymphocytes in secondary lymphoid organs. We report for the first time that dasatinib more than doubled the number of mature human monocyte-derived DCs (moDCs) migrating toward a CCL19 gradient despite unchanged CCR7 expression when used for pretreatment. These effects were caused by dephosphorylation of SFKs, as confirmed by the specific SFK inhibitor SRC inhibitor 1, leading to dephosphorylation of the inhibitory immunoreceptors Siglec-9 and Siglec-3. The specific blocking of the latter also enhanced migration and underlined the importance of these SFK-dependent receptor systems for migration of moDCs. Dasatinib hampered the secretion of interleukin-12 by moDCs at clinically relevant concentrations. In contrast, endocytosis or boosting of cytomegalovirus-specific CD8(+) T-cell responses remained unaltered when applying dasatinib-pretreated moDCs, in line with minor effects on the expression of co-stimulatory molecules essential for DC-T cell interaction. The induction of enhanced migration of moDCs may potentially be useful in chemo-immunotherapeutic applications. Thus, the use of dasatinib or blocking Siglec antibodies as adjuvants in this setting to induce stronger immune responses is worthy of further study.

Metabolic control of dendritic cell activation and function: recent advances and clinical implications

Dendritic cells (DCs) are key regulators of both immunity and tolerance by controlling activation and polarization of effector T helper cell and regulatory T cell responses. Therefore, there is a major focus on developing approaches to manipulate DC function for immunotherapy. It is well known that changes in cellular activation are coupled to profound changes in cellular metabolism. Over the past decade there is a growing appreciation that these metabolic changes also underlie the capacity of immune cells to perform particular functions. This has led to the concept that the manipulation of cellular metabolism can be used to shape innate and adaptive immune responses. While most of our understanding in this area has been gained from studies with T cells and macrophages, evidence is emerging that the activation and function of DCs are also dictated by the type of metabolism these cells commit to. We here discuss these new insights and explore whether targeting of metabolic pathways in DCs could hold promise as a novel approach to manipulate the functional properties of DCs for clinical purposes.

CCL21 Cancer Immunotherapy

Cancer, a major health problem, affects 12 million people worldwide every year. With surgery and chemo-radiation the long term survival rate for the majority of cancer patients is dismal. Thus novel treatments are urgently needed. Immunotherapy, the harnessing of the immune system to destroy cancer cells is an attractive option with potential for long term anti-tumor benefit. Cytokines are biological response modifiers that stimulate anti-tumor immune responses. In this review, we discuss the anti-tumor efficacy of the chemotactic cytokine CCL21 and its pre-clinical and clinical application in cancer.

Trial Watch: Adoptive cell transfer for anticancer immunotherapy

The expression "adoptive cell transfer" (ACT) is commonly employed to indicate an immunotherapeutic regimen involving the isolation of autologous blood-borne or tumor-infiltrating lymphocytes, their selection/expansion/activation ex vivo, and their reinfusion into the patient, most often in the context of lymphodepleting pre-conditioning and in combination with immunostimulatory treatments. Optionally, the cellular material for ACT is genetically manipulated before expansion to (1) target specific tumor-associated antigens; (2) endogenously express immunostimulatory molecules; and/or (3) persist for long periods upon reinfusion. Consistent efforts have been dedicated at the amelioration of this immunotherapeutic regimen throughout the past decade, resulting in the establishment of ever more efficient and safer ACT protocols. Accordingly, the number of clinical trials testing ACT in oncological indications does not cease to increase. In this Trial Watch, we summarize recent developments in this exciting area of research, covering both high-impact studies that have been published during the last 12 months and clinical trials that have been launched in the same period to evaluate the safety and therapeutic potential of ACT in cancer patients.