Dendritic cell vaccines in cancer immunotherapy: from biology to translational medicine

HBV-associated hepatocellular carcinomas inhibit antitumor CD8+ T cell via the long noncoding RNA HDAC2-AS2

Hepatocellular carcinoma (HCC) is one of the most common malignancies worldwide. Extracellular vesicles (EV) are critical mediators of intercellular communication within the tumor microenvironment, and cancer-cell-secreted EVs often facilitate cancer progression. Here we show that in HBV-associated HCC, tumor-cell-derived EVs contain a TGFβ-inducible long noncoding RNA, termed HDAC2-AS2. EVs enriched with HDAC2-AS2 facilitate cancer progression by suppressing cytotoxicity of intra-tumor CD8+ T cells. Mechanistically, in activated cytotoxic CD8+ T cells, translocation of the transcription factor cyclin-dependent kinase 9 (CDK9), to the cytoplasm is critical for functional integrity. HDAC2-AS2 targets and blocks cytosolic CDK9, and this results in exhaustion of PD-1+CD8+ T cells and suppression of IFN-γ+CD8+ T cell cytotoxicity. Notably, we demonstrate that low CDK9 and high HDAC2-AS2 expressions are associated with poor survival of HCC, which can be rescued by anti-PD-1 therapy. These findings emphasize the significance of tumor-derived EVs in suppressing antitumor CD8+ T cell immunity to promote tumorigenesis, and highlight extracellular HDAC2-AS2 as a promising biomarker and therapeutic target for HCC.

Nanoparticle-based approaches to target the lymphatic system for antitumor treatment

Immunotherapies have been established as safe and efficient modalities for numerous tumor treatments. The lymphatic system, which is an important system, can modulate the immune system via a complex network, which includes lymph nodes, vessels, and lymphocytes. With the deepening understanding of tumor immunology, a plethora of immunotherapies, which include vaccines, photothermal therapy, and photodynamic therapy, have been established for antitumor treatments. However, the deleterious off-target effects and nonspecific targeting of therapeutic agents result in low efficacy of immunotherapy. Fortunately, nanoparticle-based approaches for targeting the lymphatic system afford a unique opportunity to manufacture drugs that can simultaneously tackle both aspects, thereby improving tumor treatments. Over the past decades, great strides have been made in the development of DC vaccines and nanomedicine as antitumor treatments in the field of lymphatic therapeutics and diagnosis. In this review, we summarize the current strategies through which nanoparticle technology has been designed to target the lymphatic system and describe applications of lymphatic imaging for the diagnosis and image-guided surgery of tumor metastasis. Moreover, improvements in the tumor specificity of nanovaccines and medicines, which have been realized through targeting or stimulating the lymphatic system, can provide amplified antitumor immune responses and reduce side effects, thereby promoting the paradigm of antitumor treatment into the clinic to benefit patients.

Epigenetically modulated FOXM1 suppresses dendritic cell maturation in pancreatic cancer and colon cancer

Forkhead box transcription factor M1 (FOXM1) is a proliferation‐associated transcription factor involved in tumorigenesis through transcriptional regulation of its target genes in various cells, including dendritic cells (DCs). Although previous work has shown that FOXM1 enhances DC maturation in response to house dust mite allergens, it is not known whether FOXM1 affects DC maturation in the context of tumor‐specific immunity. In this study, we examined the central role of FOXM1 in regulating bone marrow‐derived dendritic cell (BMDC) maturation phenotypes and function in pancreatic cancer and colon cancer. FOXM1 retarded maturation phenotypes of BMDCs, inhibited promotion of T‐cell proliferation, and decreased interleukin‐12 (IL‐12) p70 in tumor‐bearing mice (TBM). Notably, FOXM1 expression was epigenetically regulated by dimethylation on H3 lysine 79 (H3K79me2), a modification present in both tumor cells and BMDCs. Increased H3K79me2 enrichment was observed at the FOXM1 promoter in both BMDCs from TBM, and in BMDCs from wild‐type mice cultured with tumor‐conditioned medium that mimics the tumor microenvironment (TME). Furthermore, inhibition of the H3K79 methyltransferase DOT1L not only decreased enrichment of H3K79me2, but also downregulated expression of FOXM1 and partially reversed its immunosuppressive effects on BMDCs. Furthermore, we found that FOXM1 upregulated transcription of Wnt family number 5A (Wnt5a) in BMDCs in vitro; we also observed that exogenous Wnt5a expression abrogated BMDC maturation phenotypes by inhibiting FOXM1 and H3K79me2 modification. Therefore, our results reveal that upregulation of FOXM1 by H3K79me2 in pancreatic cancer and colon cancer significantly inhibits maturation phenotypes and function of BMDCs through the Wnt5a signaling pathway, and thus provide novel insights into FOXM1‐based antitumor immunotherapy.

Interactions Between Nanoparticles and Dendritic Cells: From the Perspective of Cancer Immunotherapy

Dendritic cells (DCs) are the primary antigen-presenting cells and play key roles in the orchestration of the innate and adaptive immune system. Targeting DCs by nanotechnology stands as a promising strategy for cancer immunotherapy. The physicochemical properties of nanoparticles (NPs) influence their interactions with DCs, thus altering the immune outcome of DCs by changing their functions in the processes of maturation, homing, antigen processing and antigen presentation. In this review, we summarize the recent progress in targeting DCs using NPs as a drug delivery carrier in cancer immunotherapy, the recognition of NPs by DCs, and the ways the physicochemical properties of NPs affect DCs' functions. Finally, the molecular pathways in DCs that are affected by NPs are also discussed.

Design and immunological evaluation of anti-CD205-tailored PLGA-based nanoparticulate cancer vaccine

The aim of this research was to develop a targeted antigen–adjuvant assembled delivery system that will enable dendritic cells (DCs) to efficiently mature to recognize antigens released from tumor cells. It is important to target the DCs with greater efficiency to prime T cell immune responses. In brief, model antigen, ovalbumin (OV), and monophosphoryl lipid A adjuvant were encapsulated within the nanoparticle (NP) by double emulsification solvent evaporation method. Targeted NPs were obtained through ligand incorporation via physical adsorption or chemical conjugation process. Intracellular uptake of the NPs and the maturation of DCs were evaluated with flow cytometry. Remarkably, the developed delivery system had suitable physicochemical properties, such as particle size, surface charge, OV encapsulation efficiency, biphasic OV release pattern, and safety profile. The ligand modified formulations had higher targeting efficiency than the non-tailored NPs. This was also evident when the targeted formulations expressed comparatively higher fold increase in surface activation markers such as CD40, CD86, and major histocompatibility complex class II molecules. The maturation of DCs was further confirmed through secretion of extracellular cytokines compared to control cells in the DC microenvironment. Physicochemical characterization of NPs was performed based on the polymer end groups, their viscosities, and ligand-NP bonding type. In conclusion, the DC stimulatory response was integrated to develop a relationship between the NP structure and desired immune response. Therefore, the present study narrates a comparative evaluation of some selected parameters to choose a suitable formulation useful for in vivo cancer immunotherapy.

Biophysical Properties and Motility of Human Mature Dendritic Cells Deteriorated by Vascular Endothelial Growth Factor through Cytoskeleton Remodeling

Dendritic cells (DCs), the most potent antigen-presenting cells, play a central role in the initiation, regulation, and maintenance of the immune responses. Vascular endothelial growth factor (VEGF) is one of the important cytokines in the tumor microenvironment (TME) and can inhibit the differentiation and functional maturation of DCs. To elucidate the potential mechanisms of DC dysfunction induced by VEGF, the effects of VEGF on the biophysical characteristics and motility of human mature DCs (mDCs) were investigated. The results showed that VEGF had a negative influence on the biophysical properties, including electrophoretic mobility, osmotic fragility, viscoelasticity, and transmigration. Further cytoskeleton structure analysis by confocal microscope and gene expression profile analyses by gene microarray and real-time PCR indicated that the abnormal remodeling of F-actin cytoskeleton may be the main reason for the deterioration of biophysical properties, motility, and stimulatory capability of VEGF-treated mDCs. This is significant for understanding the biological behavior of DCs and the immune escape mechanism of tumors. Simultaneously, the therapeutic efficacies may be improved by blocking the signaling pathway of VEGF in an appropriate manner before the deployment of DC-based vaccinations against tumors.

microRNA-155 deficiency impairs dendritic cell function in breast cancer

In antitumor immunity, dendritic cells (DCs) capture, process, and present tumor antigens to T cells, initiating a tumoricidal response. However, DCs are often dysfunctional due to their exposure to the tumor microenvironment (TME), leading to tumor escape from immune surveillance. Here, a vital role of microRNA-155 (miR-155) in regulating the function of DCs in breast cancer is reported. Host miR-155 deficiency enhanced breast cancer growth in mice, accompanied by reduced DCs in the tumors and draining lymph nodes. miR-155 deficiency in DCs impaired their maturation, migration ability, cytokine production, and the ability to activate T cells. We demonstrate that miR-155 regulates DC migration through epigenetic modulation of CCR7 expression. Moreover, IL-6 and IL-10, two cytokines abundant in the TME, are found to impair DC maturation by suppressing miR-155 expression. Furthermore, animal studies show that a lack of miR-155 diminishes the effectiveness of DC-based immunotherapy for breast cancer. In conclusion, these findings suggest that miR-155 is a master regulator of DC function in breast cancer, including maturation, cytokine secretion, migration toward lymph nodes, and activation of T-cells. These results suggest that boosting the expression of a single microRNA, miR-155, may significantly improve the efficacy of DC-based immunotherapies for breast cancer.

Magnetic Enrichment of Dendritic Cell Vaccine in Lymph Node with Fluorescent-Magnetic Nanoparticles Enhanced Cancer Immunotherapy

Dendritic cell (DC) migration to the lymph node is a key component of DC-based immunotherapy. However, the DC homing rate to the lymphoid tissues is poor, thus hindering the DC-mediated activation of antigen-specific T cells. Here, we developed a system using fluorescent magnetic nanoparticles (α-AP-fmNPs; loaded with antigen peptide, iron oxide nanoparticles, and indocyanine green) in combination with magnetic pull force (MPF) to successfully manipulate DC migration in vitro and in vivo. α-AP-fmNPs endowed DCs with MPF-responsiveness, antigen presentation, and simultaneous optical and magnetic resonance imaging detectability. We showed for the first time that α-AP-fmNP-loaded DCs were sensitive to MPF, and their migration efficiency could be dramatically improved both in vitro and in vivo through MPF treatment. Due to the enhanced migration of DCs, MPF treatment significantly augmented antitumor efficacy of the nanoparticle-loaded DCs. Therefore, we have developed a biocompatible approach with which to improve the homing efficiency of DCs and subsequent anti-tumor efficacy, and track their migration by multi-modality imaging, with great potential applications for DC-based cancer immunotherapy.

Dendritic cells serve as a "Trojan horse" for oncolytic adenovirus delivery in the treatment of mouse prostate cancer

AIM

Adenovirus-mediated gene therapy is a novel therapeutic approach for the treatment of cancer, in which replication of the virus itself is the anticancer method. However, the success of this novel therapy is limited due to inefficient delivery of the virus to the target sites. In this study, we used dendritic cells (DCs) as carriers for conditionally replicating adenoviruses (CRAds) in targeting prostate carcinoma (PCa).

METHODS

Four types of CRAds, including Ad-PC (without PCa-specific promoter and a recombinant human tumor necrosis factor, rmhTNF, sequence), Ad-PC-rmhTNF (without PCa-specific promoter), Ad-PPC-NCS (without an rmhTNF sequence) and Ad-PPC-rmhTNF, were constructed. The androgen-insensitive mouse PCa RM-1 cells were co-cultured with CRAd-loading DCs, and the viability of RM-1 cells was examined using MTT assay. The in vivo effects of CRAd-loading DCs on PCa were evaluated in RM-1 xenograft mouse model.

RESULTS

Two PCa-specific CRAds (Ad-PPC-NCS, Ad-PPC-rmhTNF) exhibited more potent suppression on the viability of RM-1 cells in vitro than the PCa-non-specific CRAds (Ad-PC, Ad-PC-rmhTNF). In PCa-bearing mice, intravenous injection of the PCa-specific CRAd-loading DCs significantly inhibited the growth of xenografted tumors, extended the survival time, and induced T-cell activation. Additionally, the rmhTNF-containing CRAds exhibited greater tumor killing ability than CRAds without rmhTNF.

CONCLUSION

DCs may be an effective vector for the delivery of CRAds in the treatment of PCa.

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.

Complete clinical responses to cancer therapy caused by multiple divergent approaches: a repeating theme lost in translation

Over 50 years of cancer therapy history reveals complete clinical responses (CRs) from remarkably divergent forms of therapies (eg, chemotherapy, radiotherapy, surgery, vaccines, autologous cell transfers, cytokines, monoclonal antibodies) for advanced solid malignancies occur with an approximately similar frequency of 5%–10%. This has remained frustratingly almost static. However, CRs usually underpin strong durable 5-year patient survival. How can this apparent paradox be explained? Over some 20 years, realization that (1) chronic inflammation is intricately associated with cancer, and (2) the immune system is delicately balanced between responsiveness and tolerance of cancer, provides a greatly significant insight into ways cancer might be more effectively treated. In this review, divergent aspects from the largely segmented literature and recent conferences are drawn together to provide observations revealing some emerging reasoning, in terms of “final common pathways” of cancer cell damage, immune stimulation, and auto-vaccination events, ultimately leading to cancer cell destruction. Created from this is a unifying overarching concept to explain why multiple approaches to cancer therapy can provide complete responses at almost equivalent rates. This “missing” aspect provides a reasoned explanation for what has, and is being, increasingly reported in the mainstream literature – that inflammatory and immune responses appear intricately associated with, if not causative of, complete responses induced by divergent forms of cancer therapy. Curiously, whether by chemotherapy, radiation, surgery, or other means, therapy-induced cell injury results, leaving inflammation and immune system stimulation as a final common denominator across all of these mechanisms of cancer therapy. This aspect has been somewhat obscured and has been “lost in translation” to date.