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

CD207+/langerin positive dendritic cells in invasive and in situ cutaneous malignant melanoma

INTRODUCTION

Dendritic cells are crucial for cutaneous immune response. Their role in melanoma progression is however a matter of controversy.

MATERIAL AND METHODS

The number of dendritic cells within epidermis and in peri- and intratumoral location was analyzed using CD207 immunostain in 17 cases of in situ and 25 case of invasive melanoma.

RESULTS

Average peritumoral CD207+ cells count was 22.88 for all cases, 17.94 for in situ lesions and 26.24 for invasive cases. Average epidermal CD207+ cells count was 164.47 for all cases, 183.00 for in situ lesions and 150.78 - for invasive cases. In case of invasive melanomas, peritumoral CD207+ cells count was positively correlated with Breslow stage (R = 0.59) mitotic activity within the tumor (R = 0.62). Invasive cases with regression showed higher intratumoral and epidermal CD207+ cells count than the ones without (275.00 vs. 95.32 and 173.20 vs. 148.35) but lower peritumoral CD207+ cells count (17.60 vs. 27.26). Invasive cases with ulceration showed higher intratumoral and peritumoral CD207+ cells count than the ones without ulceration (220.08 vs. 55.67 and 44.17 vs. 9.69).

CONCLUSIONS

CD207+ cells play a role in both progression and regression of melanoma but their exact role needs further studies.

Melanomas and Dysplastic Nevi Differ in Epidermal CD1c+ Dendritic Cell Count

Background. Dendritic cells could be involved in immune surveillance of highly immunogenic tumors such as melanoma. Their role in the progression melanocytic nevi to melanoma is however a matter of controversy. Methods. The number of dendritic cells within epidermis, in peritumoral zone, and within the lesion was counted on slides immunohistochemically stained for CD1a, CD1c, DC-LAMP, and DC-SIGN in 21 of dysplastic nevi, 27 in situ melanomas, and 21 invasive melanomas. Results. We found a significant difference in the density of intraepidermal CD1c+ cells between the examined lesions; the mean CD1c cell count was 7.00/mm² for invasive melanomas, 2.94 for in situ melanomas, and 13.35 for dysplastic nevi. The differences between dysplastic nevi and melanoma in situ as well as between dysplastic nevi and invasive melanoma were significant. There was no correlation in number of positively stained cells between epidermis and dermis. We did not observe any intraepidermal DC-LAMP+ cells neither in melanoma in situ nor in invasive melanoma as well as any intraepidermal DC-SIGN+ cells in dysplastic nevi. Conclusion. It was shown that the number of dendritic cells differs between dysplastic nevi, in situ melanomas, and invasive melanomas. This could eventually suggest their participation in the development of melanoma.

Irradiation enhances dendritic cell potential antitumor activity by inducing tumor cell expressing TNF-α

Dendritic cells (DCs)-based tumor vaccines have shown to be the promising methods for inducing therapeutic antitumor response. However, DCs alone rarely carry curative antitumor activity, and the immunosuppressive microenvironment may contribute to this defect of DC vaccinal function. Irradiation in combination with DCs has been shown to promote immune-mediated tumor destruction in preclinical studies. However, little is known about how irradiation alters the tumor microenvironment, and what host pathways modulate the activity of administrated DCs. In this study, BALB/c mice and the 4T1 breast cancer cell line were used in a tumor-bearing model. The tumor-bearing mice were irradiated locally up to 10 Gy for 3 consecutive days or a single dose of 30 Gy using a cesium source. Studies of dynamic change of the tumor microenvironment in irradiated versus untreated tumors revealed that there was no obvious change on IL-10, IL-6 and TGF-β expression or production, whereas increased TNF-α level within the first 2 weeks of irradiation. The increased TNF-α level is exactly right timing window for DCs injection, corresponding to the significant elevation of intratumoral CD8⁺ T infiltration and the regression of tumor size. With attention to scheduling, combination X-ray with DCs i.t. injection may offer a practical strategy to improve treatment outcomes.

Type I Interferons Modulate CD8+ T Cell Immunity to mRNA Vaccines

mRNA vaccines have emerged as potent tools to elicit antitumor T cell immunity. They are characterized by a strong induction of type I interferons (IFNs), potent inflammatory cytokines affecting T cell differentiation and survival. Recent reports have attributed opposing roles for type I IFNs in modulating CD8+ T cell immunity to mRNA vaccines, from profoundly stimulatory to strongly inhibitory. The mechanisms behind this duality are unclear. Disentangling the factors governing the beneficial or detrimental impact of type I IFNs on CD8+ T cell responses is vital to the design of mRNA vaccines of increased potency. In light of recent advancements regarding the complex role of type I IFNs in regulating CD8+ T cell immunity to infectious diseases, we posit that the dual outcome of type I IFNs on CD8+ T cell responses to mRNA vaccination is determined by the timing and intensity of type I IFN induction relative to T cell receptor (TCR) activation.

Adjuvant-Enhanced mRNA Vaccines

Recent advances in molecular biology have led to dramatic enhancement of the stability of in vitro transcribed (IVT) messenger RNA (mRNA) and improvement in its translational efficacy. Nowadays, mRNA-based vaccines represent a promising approach in the field of anticancer immunotherapy, gaining attention over the earlier-established bacteria-, virus-, or cell-based vaccination approaches. Here, we present the experimental procedures employed in our laboratory to induce anticancer immune responses in different murine tumor models using IVT mRNA encoding for immune activation signals and antigens of interest.

Electroporation of mRNA as Universal Technology Platform to Transfect a Variety of Primary Cells with Antigens and Functional Proteins

Electroporation (EP) of mRNA into human cells is a broadly applicable method to transiently express proteins of choice in a variety of different cell types. We have spent more than a decade to optimize and adapt this method, first for antigen-loading of dendritic cells (DCs), and subsequently for T cells, B cells, bulk PBMCs, and several cell lines. In this regard, antigens were introduced, processed, and presented in context of MHC class I and II. Next to that, functional proteins like adhesion receptors, T-cell receptors (TCRs), chimeric antigen receptors (CARs), constitutively active signal transducers, and others were successfully expressed. We have also established this protocol under full GMP compliance as part of a manufacturing license to produce mRNA-electroporated DCs for therapeutic vaccination in clinical trials. Therefore, we here want to share our universal mRNA electroporation protocol and the experience we have gathered with this method. The advantages of the transfection method presented here are: (1) easy adaptation to different cell types, (2) scalability from 10⁶ to approximately 10⁸ cells per shot, (3) high transfection efficiency (80-99 %), (4) homogenous protein expression, (5) GMP compliance if the EP is performed in a class A clean room, and (6) no transgene integration into the genome. The provided protocol involves: Opti-MEM® as EP medium, a square-wave pulse with 500 V, and 4 mm cuvettes. To adapt the protocol to differently sized cells, simply the pulse time is altered. Next to the basic protocol, we also provide an extensive list of hints and tricks, which in our opinion are of great value for everyone who intends to use this transfection technique.

Measuring the Adjuvant Activity of RNA Vaccines

mRNA has recently arisen as a promising new drug class with the potential to be applied to various therapeutic modalities, including protein replacement and vaccination against cancer and infectious diseases. Numerous approaches have been pursued to develop potent mRNA vaccines, many of them have proved to be successful and have already entered human clinical trials. RNA, especially in vitro transcribed, is extremely immunogenic as it induces innate immune responses through the activation of a variety of pattern recognition receptors. This feature of RNA is potentially beneficial for vaccine development, where antigen-encoding RNA might also function as an adjuvant to elicit potent antigen-specific T and B cell immune responses. Here, we describe the methods that can be used to evaluate the immunogenicity of RNA vaccines in vitro and in vivo.

Dendritic cell vaccines for melanoma: past, present and future

Administering dendritic cells (DC) loaded with tumor-associated antigens (TAA) ex vivo is a promising strategy for therapeutic vaccines in advanced melanoma. To date the induction of immune responses to specific TAA has been more impressive than clinical benefit because of TAA limitations, suboptimal DC and possibly immune-checkpoint inhibition. Various products, antigen-loading techniques, treatment schedules, routes of administration and adjunctive agents continue to be explored. Biologic heterogeneity suggests autologous tumor as the optimal TAA source to induce immune responses to the entire repertoire of unique patient-specific neoantigens. Many questions remain regarding the optimal preparation of DC and strategies for antigen loading. Effective DC vaccines should result in additive or synergistic effects when combined with checkpoint inhibitors.

Molecular and epigenetic features of melanomas and tumor immune microenvironment linked to durable remission to ipilimumab-based immunotherapy in metastatic patients

Background

Ipilimumab (Ipi) improves the survival of advanced melanoma patients with an incremental long-term benefit in 10–15 % of patients. A tumor signature that correlates with this survival benefit could help optimizing individualized treatment strategies.

Methods

Freshly frozen melanoma metastases were collected from patients treated with either Ipi alone (n: 7) or Ipi combined with a dendritic cell vaccine (TriMixDC-MEL) (n: 11). Samples were profiled by immunohistochemistry (IHC), whole transcriptome (RNA-seq) and methyl-DNA sequencing (MBD-seq).

Results

Patients were divided in two groups according to clinical evolution: durable benefit (DB; 5 patients) and no clinical benefit (NB; 13 patients). 20 metastases were profiled by IHC and 12 were profiled by RNA- and MBD-seq. 325 genes were identified as differentially expressed between DB and NB. Many of these genes reflected a humoral and cellular immune response. MBD-seq revealed differences between DB and NB patients in the methylation of genes linked to nervous system development and neuron differentiation. DB tumors were more infiltrated by CD8⁺ and PD-L1⁺ cells than NB tumors. B cells (CD20⁺) and macrophages (CD163⁺) co-localized with T cells. Focal loss of HLA class I and TAP-1 expression was observed in several NB samples.

Conclusion

Combined analyses of melanoma metastases with IHC, gene expression and methylation profiling can potentially identify durable responders to Ipi-based immunotherapy.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-016-0990-x) contains supplementary material, which is available to authorized users.

DNA is an efficient booster of dendritic cell-based vaccine

DC-based therapeutic vaccines as a promising strategy against chronic infections and cancer have been validated in several clinical trials. However, DC-based vaccines are complex and require many in vitro manipulations, which makes this a personalized and expensive therapeutic approach. In contrast, DNA-based vaccines have many practical advantages including simplicity, low cost of manufacturing and potent immunogenicity already proven in non-human primates and humans. In this study, we explored whether DC-based vaccines can be simplified by the addition of plasmid DNA as prime or boost to achieve robust CD8-mediated immune responses. We compared the cellular immunity induced in BALB/c and C57BL/6 mice by DC vaccines, loaded either with peptides or optimized SIV Env DNA, and plasmid DNA-based vaccines delivered by electroporation (EP). We found that mature DC loaded with peptides (P-mDC) induced the highest CD8(+) T cell responses in both strains of mice, but those responses were significantly higher in the C57BL/6 model. A heterologous prime-boost strategy (P-DC prime-DNA boost) induced CD8(+) T cell responses similar to those obtained by the P-DC vaccine. Importantly, this strategy elicited robust polyfunctional T cells as well as highest antigen-specific central memory CD8+ T cells in C57BL/6 mice, suggesting long-term memory responses. These results indicate that a DC-based vaccine in combination with DNA in a heterologous DC prime-DNA boost strategy has potential as a repeatedly administered vaccine.

MiR-26b inhibits melanoma cell proliferation and enhances apoptosis by suppressing TRAF5-mediated MAPK activation

Alterations in microRNA-26b (miR-26b) expression have been shown to participate in various malignant tumor developments. However, the possible function of miR-26b in human melanoma cells remains unclarified. In this study, quantitative polymerase chain reaction was used to explore the expression profiles of miR-26b in melanoma cells. The effect of miR-26b on cell viability was determined by using MTT assays and colony formation assay. The apoptosis levels were evaluated by using Annexin V/fluorescein isothiocyanate (FITC) apoptosis detection kit and the apoptosis cells were confirmed by Transmission Electron Microscopy (TEM). Luciferase reporter plasmids were constructed to confirm direct targeting. Our study found that the expression of miR-26b was downregulated in human melanoma specimens. Overexpression of miR-26b significantly increased the anti-proliferative effects and apoptosis in A375 and B16F10 melanoma cells. In addition, luciferase gene reporter assays confirmed that TRAF5 was a direct target gene of miR-26b and the anti-tumor effect of miR-26b in melanoma cells was significantly counteracted by treatment with TRAF5 overexpression. Furthermore, the molecular mechanisms underlying the tumor suppressor of miR-26b in malignant melanomas may be due to the dephosphorylation of MAPK pathway caused by the decrease in TRAF5 expression when miR-26b is up-regulated in melanoma cells. These findings indicate that miR-26b might influence TRAF5-MAPK signaling pathways to facilitate the malignant progression of melanoma cells.

Current status and perspectives of immune-based therapies for hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a frequent cancer with a high mortality. For early stage cancer there are potentially curative treatments including local ablation, resection and liver transplantation. However, for more advanced stage disease, there is no optimal treatment available. Even in the case of a "curative" treatment, recurrence or development of a new cancer in the precancerous liver is common. Thus, there is an urgent need for novel and effective (adjuvant) therapies to treat HCC and to prevent recurrence after local treatment in patients with HCC. The unique immune response in the liver favors tolerance, which remains a genuine challenge for conventional immunotherapy in patients with HCC. However, even in this "immunotolerant" organ, spontaneous immune responses against tumor antigens have been detected, although they are insufficient to achieve significant tumor death. Local ablation therapy leads to immunogenic tumor cell death by inducing the release of massive amounts of antigens, which enhances spontaneous immune response. New immune therapies such as dendritic cell vaccination and immune checkpoint inhibition are under investigation. Immunotherapy for cancer has made huge progress in the last few years and clinical trials examining the use of immunotherapy to treat hepatocellular carcinoma have shown some success. In this review, we discuss the current status of and offer some perspectives on immunotherapy for hepatocellular carcinoma, which could change disease progression in the near future.

mRNA Electroporation of Dendritic Cells with WT1, Survivin, and TriMix (a Mixture of caTLR4, CD40L, and CD70)

The immune system is a crucial player in the development of cancer. Once it is in imbalance and immunosuppressive mechanisms supporting tumor growth take over control, dendritic cell immunotherapy might offer a solution to restore the balance. There are several methods to manufacture dendritic cells but none of them has yet proven to be superior to others. In this chapter, we discuss the methodology using electroporation of mRNA encoding Wilms' tumor gene 1, survivin, and TriMix (mixture of caTLR4, CD40L, and CD70) to simultaneously load and mature dendritic cells.

Electroporated Antigen-Encoding mRNA Is Not a Danger Signal to Human Mature Monocyte-Derived Dendritic Cells

For therapeutic cancer vaccination, the adoptive transfer of mRNA-electroporated dendritic cells (DCs) is frequently performed, usually with monocyte-derived, cytokine-matured DCs (moDCs). However, DCs are rich in danger-sensing receptors which could recognize the exogenously delivered mRNA and induce DC activation, hence influencing the DCs' immunogenicity. Therefore, we examined whether electroporation of mRNA with a proper cap and a poly-A tail of at least 64 adenosines had any influence on cocktail-matured moDCs. We used 16 different RNAs, encoding tumor antigens (MelanA, NRAS, BRAF, GNAQ, GNA11, and WT1), and variants thereof. None of those RNAs induced changes in the expression of CD25, CD40, CD83, CD86, and CD70 or the secretion of the cytokines IL-8, IL-6, and TNFα of more than 1.5-fold compared to the control condition, while an mRNA encoding an NF-κB-activation protein as positive control induced massive secretion of the cytokines. To determine whether mRNA electroporation had any effect on the whole transcriptome of the DCs, we performed microarray analyses of DCs of 6 different donors. None of 60,000 probes was significantly different between mock-electroporated DCs and MelanA-transfected DCs. Hence, we conclude that no transcriptional programs were induced within cocktail-matured DCs by electroporation of single tumor-antigen-encoding mRNAs.

CD8 T-cell priming upon mRNA vaccination is restricted to bone-marrow-derived antigen-presenting cells and may involve antigen transfer from myocytes

Self-amplifying mRNAs (SAM(®) ) are a novel class of nucleic acid vaccines, delivered by a non-viral delivery system. They are effective at eliciting potent and protective immune responses and are being developed as a platform technology with potential to be used for a broad range of targets. However, their mechanism of action has not been fully elucidated. To date, no evidence of in vivo transduction of professional antigen-presenting cells (APCs) by SAM vector has been reported, while the antigen expression has been shown to occur mostly in the muscle fibres. Here we show that bone-marrow-derived APCs rather than muscle cells are responsible for induction of MHC class-I restricted CD8 T cells in vivo, but direct transfection of APCs by SAM vectors is not required. Based on all our in vivo and in vitro data we propose that upon SAM vaccination the antigen is expressed within muscle cells and then transferred to APCs, suggesting cross-priming as the prevalent mechanism for priming the CD8 T-cell response by SAM vaccines.

mRNA transcript therapy

mRNA is the central molecule of all forms of life. It is generally accepted that current life on Earth descended from an RNA world. mRNA, after its first therapeutic description in 1992, has recently come into increased focus as a method to deliver genetic information. The recent solution to the two main difficulties in using mRNA as a therapeutic, immune stimulation and potency, has provided the basis for a wide range of applications. While mRNA-based cancer immunotherapies have been in clinical trials for a few years, novel approaches; including, in vivo delivery of mRNA to replace or supplement proteins, mRNA-based generation of pluripotent stem cells, or genome engineering using mRNA-encoded meganucleases are beginning to be realized. This review presents the current state of mRNA drug technologies and potential applications, as well as discussing the challenges and prospects in mRNA development and drug discovery.

The ReNAissanCe of mRNA-based cancer therapy

About 25 years ago, mRNA became a tool of interest in anticancer vaccination approaches. However, due to its rapid degradation in situ, direct application of mRNA was confronted with considerable skepticism during its early use. Consequently, mRNA was for a long time mainly used for the ex vivo transfection of dendritic cells, professional antigen-presenting cells known to stimulate immunity. The interest in direct application of mRNA experienced a revival, as researchers became aware of the many advantages mRNA offers. Today, mRNA is considered to be an ideal vehicle for the induction of strong immune responses against cancer. The growing numbers of preclinical trials and as a consequence the increasing clinical application of mRNA as an off-the-shelf anticancer vaccine signifies a renaissance for transcript-based antitumor therapy. In this review, we highlight this renaissance using a timeline providing all milestones in the application of mRNA for anticancer vaccination.

RNA-based drugs and vaccines

RNA-based approaches have provided novel alternatives for modern drug discovery. The application of RNA as therapeutic agents has, until recently, been hampered by issues related to poor delivery and stability, but chemical modifications and new delivery approaches have increased progress. Moreover, the discovery of the importance of RNA in gene regulation and gene silencing has revealed new drug targets, especially related to treatment of cancer and other diseases. Recent engineering of small molecules designed from RNA sequences to target miRNAs opens up new possibilities in drug development. Furthermore, RNA-based vaccines have been engineered applying RNA virus vectors and non-viral delivery for vaccine development.

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.