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Background: Autologous monocyte-derived mRNA co-electroporated dendritic cells with mRNA encoding CD40 ligand (CD40L), CD70 and a constitutively activated TLR4 (caTLR4) (referred to as TriMixDC-MEL) have anti-tumor activity in advanced melanoma patients. We investigated the safety and activity of adjuvant TriMixDC-MEL in stage III/IV melanoma patients., Materials and Methods: Forty-one patients were randomly assigned to treatment with TriMixDC-MEL (n = 21) and standard follow-up (n = 20). "Cross-over" was allowed at the time of non-salvageable recurrence. The primary endpoint was the percentage of patients alive and disease-free at 1-year. For a subset of patients, (formalin-fixed paraffin-embedded), tumor tissue samples were available for mRNA expression profiling and PD-L1 immunohistochemical staining., Results: Baseline characteristics were well balanced. One-year after randomization, 71% of patients in the study arm were alive and free of disease compared to 35% in the control arm. After a median follow-up of 53 months (range 3-67), 23 patients experienced a non-salvageable melanoma recurrence (TriMixDC-Mel arm n = 9 and control arm n = 14).The median time to non-salvageable recurrence was superior in the TriMixDC-MEL arm (median 8 months (range 1-6) vs. not reached; log-rank p 0.044). TriMixDC-MEL-related adverse events (AE) consisted of transient local skin reactions, flu-like symptoms and post-infusion chills. No grade ≥ 3 AE's occurred. The mRNA expression profiling revealed four genes (STAT2, TPSAB1, CD9 and CSF2) as potential predictive biomarkers., Conclusion: TriMixDC-MEL id/iv as adjuvant therapy is tolerable and may improve the 1-year disease-free survival rate. Combination of optimized autologous monocyte-derived DC-formulations warrants further investigation in combination with currently approved adjuvant therapy options.

Purpose: Autologous monocyte-derived dendritic cells (DCs) electroporated with synthetic mRNA (TriMixDC-MEL) are immunogenic and have antitumor activity as a monotherapy in patients with pretreated advanced melanoma. Ipilimumab, an immunoglobulin G1 monoclonal antibody directed against the cytotoxic T-lymphocyte-associated protein 4 receptor that counteracts physiologic suppression of T-cell function, improves the overall survival of patients with advanced melanoma. This phase II study investigated the combination of TriMixDC-MEL and ipilimumab in patients with pretreated advanced melanoma., Patients and Methods: Thirty-nine patients were treated with TriMixDC-MEL (4 × 10(6) cells administered intradermally and 20 × 10(6) cells administered intravenously) plus ipilimumab (10 mg/kg every 3 weeks for a total of four administrations, followed by maintenance therapy every 12 weeks in patients who remained progression free). Six-month disease control rate according to the immune-related response criteria served as the primary end point., Results: The 6-month disease control rate was 51% (95% CI, 36% to 67%), and the overall tumor response rate was 38% (including eight complete and seven partial responses). Seven complete responses and one partial tumor response are ongoing after a median follow-up time of 36 months (range, 22 to 43 months). The most common treatment-related adverse events (all grades) consisted of local DC injection site skin reactions (100%), transient post-DC infusion chills (38%) and flu-like symptoms (84%), dermatitis (64%), hepatitis (13%), hypophysitis (15%), and diarrhea/colitis (15%). Grade 3 or 4 immune-related adverse events occurred in 36% of patients. There was no grade 5 adverse event., Conclusion: The combination of TriMixDC-MEL and ipilimumab is tolerable and results in an encouraging rate of highly durable tumor responses in patients with pretreated advanced melanoma., (© 2016 by American Society of Clinical Oncology.)

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.

Purpose: Melanoma patients with a high risk of recurrence may benefit from immunotherapy with mRNA-electroporated autologous monocyte-derived dendritic cells (DCs). Further benefit may be found in combining DC-therapy with interferon alfa-2b., Patients and Methods: The long-term clinical outcome of AJCC stage III/IV melanoma patients who had no evidence of disease at the time of treatment with autologous mRNA-electroporated DCs in a single-center pilot clinical trial was analyzed. Antigen loading was accomplished by co-electroporation of mRNA encoding a fusion protein between MAGE-A1, -A3, -C2, Tyrosinase, MelanA/MART-1, or gp100, and an HLA class II-targeting sequence. DCs were administered by 4-6 bi-weekly intradermal injections. IFN-α-2b (5 MIU TIW) was initiated either at recurrence (cohort 1), concomitant with DCs (cohorts 2 and 3), or following the fourth DC administration (cohort 4)., Results: Thirty melanoma patients were recruited between April 2006 and June 2009. DC-related adverse events included grade 2 local injection site reactions in all patients, grade 2 fever and flu-like symptoms in one patient, and skin depigmentation in seven patients. After a median follow-up of over 6 years, the median relapse-free survival is 22 months (95% CI 12-32 months). Twelve patients have died. The median overall survival has not been reached; the 2-year and 4-year survival rates are 93 and 70%, respectively., Conclusions: Adjuvant therapy following the resection of melanoma metastases with autologous mRNA-electroporated DCs, combined with interferon alfa-2b, is tolerable and results in encouraging long-term overall survival rates justifying further evaluation in a randomized clinical trial.

It is generally thought that dendritic cells (DCs) loaded with full-length tumor antigen could improve immunotherapy by stimulating broad T-cell responses and by allowing treatment irrespective of the patient's human leukocyte antigen (HLA) type. To investigate this, we determined the specificity of T cells from melanoma patients treated with DCs loaded with mRNA encoding a full-length tumor antigen fused to a signal peptide and an HLA class II sorting signal, allowing presentation in HLA class I and II. In delayed-type hypersensitive (DTH)-biopsies and blood, we found functional CD8(+) and CD4(+) T cells recognizing novel treatment-antigen-derived epitopes, presented by several HLA types. Additionally, we identified a CD8(+) response specific for the signal peptide incorporated to elicit presentation by HLA class II and a CD4(+) response specific for the fusion region of the signal peptide and one of the antigens. This demonstrates that the fusion proteins contain newly created immunogenic sequences and provides evidence that ex vivo-generated mRNA-modified DCs can induce effector CD8(+) and CD4(+) T cells from the naive T-cell repertoire of melanoma patients. Thus, this work provides definitive proof that DCs presenting the full antigenic spectrum of tumor antigens can induce T cells specific for novel epitopes and can be administered to patients irrespective of their HLA type.

The immunostimulatory capacity of dendritic cells is improved by co-electroporation with mRNA encoding CD40 ligand, constitutively active toll-like receptor 4, and CD70 (TriMix-DC). This pilot clinical trial evaluated the feasibility, safety, and immunogenicity of a therapeutic vaccination containing autologous TriMix-DC co-electroporated with mRNA encoding a human leukocyte antigen class II-targeting signal linked to 1 of 4 melanoma-associated antigens (MAGE-A3, MAGE-C2, tyrosinase, and gp100) in patients with advanced melanoma. Thirty-five American Joint Committee on Cancer stage III/IV melanoma patients received autologous TriMix-DC (4 administrations 2 weeks apart). Immune monitoring was performed by evaluating skin biopsies of delayed type IV hypersensitivity (DTH) reactions for presence of vaccinal antigen-specific DTH-infiltrating lymphocytes (DIL). Thereafter, patients could receive interferon-alpha-2b (IFN-α-2b) 5 MU subcutaneously 3 times weekly and additional TriMix-DC every 8 weeks. TriMix-DC-related adverse events comprised grade 2 local injection site reactions (all patients), and grade 2 fever and lethargy (2 patients). Vaccinal antigen-specific DIL were found in 0/6 patients tested at vaccine initiation and in 12/21 (57.1%) assessed after the fourth vaccine. A positive postvaccination DTH test correlated with IL-12p70 secretion capacity of TriMix-DC. No objective responses to TriMix-DC alone were seen according to RECIST. Twenty-nine patients received IFN-α-2b after the fourth vaccine without unexpected adverse events. During TriMix-DC/IFN-α-2b combination therapy, 1 partial response and 5 stable disease (disease control of >6 months with regression of metastases) were observed in 17 patients with evaluable disease at baseline. In conclusion, this study demonstrated that therapeutic vaccination with autologous TriMix-DC is feasible, safe, and immunogenic and can be combined with sequential IFN-α-2b.

Previous studies showed that stimulation of T cells derived from HIV-1-infected patients with autologous dendritic cells electroporated with mRNA encoding HIV antigens can induce antigen-specific T cell responses in vitro. Linking the antigen to an MHC class II-targeting sequence, such as dendritic cell lysosome-associated membrane protein (DC-LAMP), in the mRNA construct results in presentation of antigenic peptides in both MHC class I and class II molecules and therefore enhances the induced T cell responses. To analyze whether the lumenal domain of DC-LAMP is required for optimal induction of cellular immunity against HIV antigens, we compared fusion constructs with or without the lumenal domain of the DC-LAMP protein. A human codon-optimized consensus Gag sequence and a chimeric cDNA sequence encompassing Tat, Rev, and Nef codons (TaReNef ) were cloned into a vector containing the DC-LAMP sequence with or without its lumenal domain. The Gag protein lacking the DC-LAMP-derived sequence altogether elicited only weak T cell responses. DCs electroporated with Gag or TaReNef linked to DC-LAMP were able to elicit similar levels of antigen-specific CD4(+) and CD8(+) T cell responses for both Gag and TaReNef, irrespective of the addition of the DC-LAMP lumenal domain. These data show that DC-LAMP-mediated antigen targeting is absolutely required for optimal T cell stimulation, but that in our experimental setup, the lumenal part of DC-LAMP does not improve the overall induction of antigen-specific T cell responses.

Purpose: A critical factor determining the effectiveness of currently used dendritic cell (DC)-based vaccines is the DC activation or maturation status. We have recently shown that the T-cell stimulatory capacity of DCs pulsed with tumor-antigen-derived peptides can be considerably increased by activating the DCs through electroporation with mRNA encoding CD40 ligand, CD70, and a constitutively active Toll-like receptor 4 (TriMix DCs). Here, we investigate whether TriMix DCs can be coelectroporated with whole tumor-antigen-encoding mRNA., Experimental Design: The T-cell stimulatory capacity of TriMix DCs pulsed with the immunodominant MelanA-A2 peptide and that of TriMix DCs coelectroporated with MelanA mRNA were compared in vitro. TriMix DCs were also coelectroporated with mRNA encoding Mage-A3, Mage-C2, tyrosinase, or gp100. The capacity of these DCs to stimulate tumor-antigen-specific T cells in melanoma patients was investigated both in vitro before vaccination and after DC vaccination., Results: Like peptide-pulsed TriMix DCs, TriMix DCs coelectroporated with MelanA mRNA are very potent in inducing MelanA-specific CD8(+) T cells in vitro. These T cells have an activated phenotype, show cytolytic capacity, and produce inflammatory cytokines in response to specific stimulation. TriMix DCs coelectroporated with tyrosinase are able to stimulate tyrosinase-specific CD8(+) T cells in vitro from the blood of nonvaccinated melanoma patients. Furthermore, TriMix DCs coelectroporated with Mage-A3, Mage-C2, or tyrosinase are able to induce antigen-specific CD8(+) T cells through therapeutic DC vaccination., Conclusions: TriMix DCs coelectroporated with whole tumor-antigen mRNA stimulate antigen-specific T cells in vitro and induce antigen-specific T-cell responses in melanoma patients through vaccination. Therefore, they represent a promising new approach for antitumor immunotherapy.

Antigen-loaded dendritic cells (DCs) have been intensively investigated as potential cellular antitumor vaccines. Several recent reports have indicated that loading DCs with whole tumor derived mRNA or defined tumor-antigen-encoding mRNA represents an effective nonviral strategy to stimulate T cell responses both for in vitro and in vivo models. Here, we describe the electroporation method as a tool for introducing in vitro transcribed capped mRNA into human DCs for tumor vaccination. We use MART-1/Melan-A as a model tumor-associated antigen for the generation of a DC-based vaccine against melanoma cancer. In addition to efficient antigen loading, it is important to obtain a maximal number of potent antigen-presenting cells. Another prerequisite for the development of a DC-based cancer vaccine is to obtain mature DCs. In this chapter, we describe the basic techniques required for the successful genetic modification of DCs by using the mRNA electroporation method.