Dendritic Cell-based Cancer Vaccines Research Articles

Cellular Cancer Immunotherapy Development and Manufacturing in the Clinic.

The transfusion of naturally derived or modified cellular therapies, referred to as adoptive cell therapy (ACT), has demonstrated clinical efficacy in the treatment of hematologic malignancies and metastatic melanoma. In addition, cellular vaccination, such as dendritic cell-based cancer vaccines, continues to be actively explored. The manufacturing of these therapies presents a considerable challenge to expanding the use of ACT as a viable treatment modality, particularly at academic production facilities. Furthermore, the expanding commercial interest in ACT presents new opportunities as well as strategic challenges for the future vision of cellular manufacturing in academic centers. Current trends in the production of ACT at tertiary care centers and prospects for improved manufacturing practices that will foster further clinical benefit are reviewed herein.

Towards the next generation of cancer vaccines

During the past decade we have extensively explored dendritic cell based cancer vaccines. Dendritic cells (DC) isolated from a patient are loaded with tumor antigen and immune modulators to activate dendritic cells to optimize antigen presentation and T cell stimulation. We now know that this form of immunotherapy is safe and more recently we have also started to use natural DC circulating in the blood instead of monocyte derived DC. In particular myeloid DC and plasmacytoid DC are a powerful combination, now being tested in a phase III trial. Because with current DC based vaccinations a new vaccine must be generated for each patient, we have initiated studies to look for alternatives, where we either can target DC in vivo by nanoparticles, or even replace DC by the generation of ‘synthetic DC’. During my talk I will elaborate on these novel cancer vaccine developments and on the idea to design ‘synthetic lymph nodes’ for local cancer treatment.

Plasma-Activated Medium Potentiates the Immunogenicity of Tumor Cell Lysates for Dendritic Cell-Based Cancer Vaccines

Simple SummaryDendritic cells (DCs)-based anti-cancer vaccines displayed limited efficacy in clinical trials, mostly due to a lack of protocols for preparing immunogenic tumor antigens used in the vaccine. Here, a unique atmospheric pressure plasma jet was used to prepare a plasma-activated medium (PAM) which induced immunogenic cell death in tumor cells. This procedure increased the efficacy of tumor lysates in enhancing the immunogenicity of DCs according to their increased maturation, production of IL-12, and the capacity to induce cytotoxic CD8 T cells able to kill tumor cells. In contrast to the tumor lysates commonly used in DC vaccines, PAM-tumor lysates lacked the capacity to increase IL-10 production by DCs, and their potential to induce protumorogenic Th2 and regulatory T cells. Cumulatively, these results suggest that the novel method for preparing immunogenic tumor lysates with PAM could be suitable for improved DC-based immunotherapy of cancer patients.Autologous dendritic cells (DCs)-based vaccines are considered quite promising for cancer immunotherapy due to their exquisite potential to induce tumor antigen-specific cytotoxic T cells. However, a lack of efficient protocols for inducing immunogenic tumor antigens limits the efficacy of DC-based cancer vaccines. Here, we found that a plasma-activated medium (PAM) induces immunogenic cell death (ICD) in tumor cells but not in an immortalized L929 cell line or human peripheral blood mononuclear cells. PAM induced an accumulation of reactive oxygen species (ROS), autophagy, apoptosis, and necrosis in a concentration-dependent manner. The tumor lysates prepared after PAM treatment displayed increased immunogenicity in a model of human monocyte-derived DCs, compared to the lysates prepared by a standard freezing/thawing method. Mature DCs loaded with PAM lysates showed an increased maturation potential, as estimated by their increased expression of CD83, CD86, CD40, IL-12/IL-10 production, and attenuated PDL1 and ILT-4 expression, compared to the DCs treated with control tumor lysates. Moreover, in co-culture with allogeneic T cells, DCs loaded with PAM-lysates increased the proportion of cytotoxic IFN-γ+ granzyme A+ CD8+ T cells and IL-17A-producing T cells and preserved the Th1 response. In contrast, control tumor lysates-treated DCs increased the frequency of Th2 (CD4+IL-4+), CD4, and CD8 regulatory T cell subtypes, none of which was observed with DCs loaded with PAM-lysates. Cumulatively, these results suggest that the novel method for preparing immunogenic tumor lysates with PAM could be suitable for improved DC-based immunotherapy of cancer patients.

Methotrexate enhances antigen presentation and maturation of tumour antigen-loaded dendritic cells through NLRP3 inflammasome activation: a strategy for dendritic cell-based cancer vaccine.

Background:Dendritic cells (DCs) are antigen-presenting cells that play a pivotal role in adaptive cell-mediated immunity by priming and activating T cells against specific tumour and pathogenic antigens. Methotrexate (MTX), a folate derivative, functions as an immunoregulatory agent. However, the possible effect of MTX on tumour antigen-loaded DCs has not yet been investigated.Methods:We analysed the effect of MTX on the maturation and function of DCs along with tumour cell lysates (TCLs). Using bone marrow-derived DCs, we investigated the effect of MTX combined TCL-loaded DCs on T cells priming and proliferation. We also tested the anti-tumour immune effect on DCs when treated with MTX and/or TCL in vivo.Results:MTX combined with TCL not only enhanced DC maturation and stimulated cytokine release but also promoted CD8+ T cell activation and proliferation. The latter was associated with increased tumour antigen uptake and cross-presentation to T cells. Mechanistically, DC maturation and antigen presentation were partly modulated by NLRP3 inflammasome activation. Furthermore, immunisation of mice with MTX and TCL-pulsed DCs before a tumour challenge significantly delayed tumour onset and retarded its growth. This protective effect was due to priming of IFN-γ releasing CD8+ T cells and enhanced killing of tumour cells by cytotoxic T lymphocytes isolated from these immunised mice.Conclusion:MTX can function as a potent adjuvant in DC vaccines by increasing antigen presentation and T cell priming. Our findings provide a new strategy for the application of DC-based anti-tumour immunotherapy.

Towards a Systems Immunology Approach to Unravel Responses to Cancer Immunotherapy.

Immunotherapy, particularly immune checkpoint blockade and chimeric antigen receptor (CAR)-T cells, holds a great promise against cancer. These treatments have markedly improved survival in solid as well as in hematologic tumors previously considered incurable. However, durable responses occur in a fraction of patients, and existing biomarkers (e.g. PD-L1) have shown limited prediction power. This scenario highlights the need to dissect the complex interplay between immune and tumor cells to identify reliable biomarkers of response to be used for patients’ selection. In this context, systems immunology represents indeed the new frontier to address important clinical challenges in biomarker discovery. Through the integration of multiple layers of data obtained with several high-throughput approaches, systems immunology may give insights on the vast range of inter-individual differences and on the influences of genes and factors that cooperatively shape the individual immune response to a given treatment. In this Mini Review, we give an overview of the current high-throughput methodologies, including genomics, epigenomics, transcriptomics, metabolomics, proteomics, and multi-parametric phenotyping suitable for systems immunology as well as on the key steps of data integration and biological interpretation. Additionally, we review recent studies in which multi-omics technologies have been used to characterize mechanisms of response and to identify powerful biomarkers of response to checkpoint inhibitors, CAR-T cell therapy, dendritic cell-based and peptide-based cancer vaccines. We also highlight the need of favoring the collaboration of researchers with complementary expertise and of integrating multi-omics data into biological networks with the final goal of developing accurate markers of therapeutic response.

Generated SecPen_NY-ESO-1_ubiquitin-pulsed dendritic cell cancer vaccine elicits stronger and specific T cell immune responses

Dendritic cell-based cancer vaccines (DC vaccines) have been proved efficient and safe in immunotherapy of various cancers, including melanoma, ovarian and prostate cancer. However, the clinical responses were not always satisfied. Here we proposed a novel strategy to prepare DC vaccines. In the present study, a fusion protein SNU containing a secretin-penetratin (SecPen) peptide, NY-ESO-1 and ubiquitin was designed and expressed. To establish the DC vaccine (DC-SNU), the mouse bone marrow-derived DCs (BMDCs) were isolated, pulsed with SNU and maturated with cytokine cocktail. Then peripheral blood mononuclear cells (PBMCs) from C57BL/6 mice inoculated intraperitoneally with DC-SNU were separated and cocultured with MC38/MC38NY-ESO-1 tumor cells or DC vaccines. The results show that SNU was successfully expressed. This strategy made NY-ESO-1 entering cytoplasm of BMDCs more efficiently and degraded mainly by proteasome. As we expected, mature BMDCs expressed higher CD40, CD80 and CD86 than immature BMDCs. Thus, the PBMCs released more IFN-γ and TNF-α when stimulated with DC-SNU in vitro again. What's more, the PBMCs induced stronger and specific cytotoxicity towards MC38NY-ESO-1 tumor cells. Given the above, it demonstrated that DC-SNU loaded with SecPen and ubiquitin-fused NY-ESO-1 could elicit stronger and specific T cell immune responses. This strategy can be used as a platform for DC vaccine preparation and applied to various cancers treatment.

Rapid tumor vaccine using Toll-like receptor-activated ovarian cancer ascites monocytes.

BackgroundNovel therapeutic strategies in ovarian cancer (OC) are needed as the survival rate remains dismally low. Although dendritic cell-based cancer vaccines are effective in eliciting therapeutic responses, their complex and costly manufacturing process hampers their full clinical utility outside specialized clinics. Here, we describe a novel approach of generating a rapid and effective cancer vaccine using ascites-derived monocytes for treating OC.MethodsUsing the ID8 mouse ovarian tumor model and OC patient samples, we isolated ascites monocytes and evaluated them with flow cytometry, Luminex cytokine and chemokine array analysis, ex vivo cocultures with T cells, in vivo tumor challenge and T cell transfer experiments, RNA-sequencing and mass spectrometry.ResultsWe demonstrated the feasibility of isolating ascites monocytes and restoring their ability to function as bona fide antigen-presenting cells (APCs) with Toll-like receptor (TLR) 4 lipopolysaccharide and TLR9 CpG-oligonucleotides, and a blocking antibody to interleukin-10 receptor (IL-10R Ab) in the ID8 model. The ascites monocytes were laden with tumor antigens at a steady state in vivo. After a short 48 hours activation, they upregulated maturation markers (CD80, CD86 and MHC class I) and demonstrated strong ex vivo T cell stimulatory potential and effectively suppressed tumor and malignant ascites in vivo. They also induced protective long-term T cell memory responses. To evaluate the translational potential of this approach, we isolated ascites monocytes from stage III/IV chemotherapy-naïve OC patients. Similarly, the human ascites monocytes presented tumor-associated antigens (TAAs), including MUC1, ERBB2, mesothelin, MAGE, PRAME, GPC3, PMEL and TP53 at a steady state. After a 48-hour treatment with TLR4 and IL-10R Ab, they efficiently stimulated oligoclonal tumor-associated lymphocytes (TALs) with strong reactivity against TAAs. Importantly, the activated ascites monocytes retained their ability to activate TALs in the presence of ascitic fluid.ConclusionsAscites monocytes are naturally loaded with tumor antigen and can perform as potent APCs following short ex vivo activation. This novel ascites APC vaccine can be rapidly prepared in 48 hours with a straightforward and affordable manufacturing process, and would be an attractive therapeutic vaccine for OC.

An Anticancer Drug Cocktail of Three Kinase Inhibitors Improved Response to a Dendritic Cell-Based Cancer Vaccine.

Monocyte-derived dendritic cell (moDC)-based cancer therapies intended to elicit antitumor T-cell responses have limited efficacy in most clinical trials. However, potent and sustained antitumor activity in a limited number of patients highlights the therapeutic potential of moDCs. In vitro culture conditions used to generate moDCs can be inconsistent, and moDCs generated in vitro are less effective than natural DCs. On the basis of our study highlighting the ability for certain kinase inhibitors to enhance tumor antigenicity, we therefore screened kinase inhibitors for their ability to improve DC immunogenicity. We identified AKT inhibitor MK2206, DNA-PK inhibitor NU7441, and MEK inhibitor trametinib as the compounds most effective at modulating moDC immunogenicity. The combination of these drugs, referred to as MKNUTRA, enhanced moDC activity over treatment with individual drugs while exhibiting minimal toxicity. An evaluation of 335 activation and T-cell-suppressive surface proteins on moDCs revealed that MKNUTRA treatment more effectively matured cells and reduced the expression of tolerogenic proteins as compared with control moDCs. MKNUTRA treatment imparted to ICT107, a glioblastoma (GBM) DC-based vaccine that has completed phase II trials, an increased ability to stimulate patient-derived autologous CD8+ T cells against the brain tumor antigens IL13Rα2(345-354) and TRP2(180-188) In vivo, treating ICT107 with MKNUTRA, prior to injection into mice with an established GBM tumor, reduced tumor growth kinetics. This response was associated with an increased frequency of tumor-reactive lymphocytes within tumors and in peripheral tissues. These studies broaden the application of targeted anticancer drugs and highlight their ability to increase moDC immunogenicity.

Development of a lipoplex-type mRNA carrier composed of an ionizable lipid with a vitamin E scaffold and the KALA peptide for use as an ex vivo dendritic cell-based cancer vaccine

A dendritic cells (DCs)-based vaccine (DC-vaccine) system is an attractive technology for eliciting antigen-specific immune responses that can protect subjects from infectious diseases and for curing various types of cancers. For the insertion of a foreign antigen to DCs, the transfection of an antigen-coding mRNA to the cells is a promising approach. In order to introduce an antigen, a carrier for mRNA transfection is required, since the mRNA molecule per se is unstable in serum-containing medium. We previously reported on an ionizable lipid-like material with vitamin E-scaffolds (ssPalmE) as a material for a lipid nanoparticle (LNP)-based carrier for nucleic acids. In the present study, we report on the development of a lipoplex-type mRNA carrier for use as a DC-vaccine by using a combination of an ssPalmE-LNP and an α-helical cationic peptide “KALA” (ssPalmE-KALA). The transfection of mRNAs complexed with the ssPalmE-KALA achieved a significantly higher protein expression and the production of proinflammatory cytokines from murine bone marrow derived DCs (BMDCs) in comparison with a lipoplex that was prepared with an ssPalm with fatty acid-scaffolds (myristic acid; ssPalmM-KALA). A cellular uptake process and a pH-responsive membrane-destabilization activity cannot explain the preferred protein expression and immune-stimulation caused by the ssPalmE-KALA. Proteomic analyses suggest that transfection with the ssPalmM-KALA stimulates a down-regulatory pathway of translation, while the transfection with the ssPalmE-KALA does not stimulate it. In the vaccination with the BMDCs that were preliminarily transfected with an ovalbumin (OVA)-encoding mRNA elicited the induction OVA specific cytotoxic T-lymphocyte activity in vivo. In parallel, the vaccination induced significant prophylactic anti-tumor effects against a model tumor that stably expressed the OVA protein. Based on the above findings, the ssPalmE-KALA appears to be a potent ex vivo DCs-based RNA vaccine platform.

Tumor lysate-loaded Bacterial Ghosts as a tool for optimized production of therapeutic dendritic cell-based cancer vaccines

Cancer immunotherapy with dendritic cell (DC)-based vaccines has been used to treat various malignancies for more than two decades, however generally showed a limited clinical success. Among various factors responsible for their modest clinical activity is the lack of universally applied, standardized protocols for the generation of clinical-grade DC vaccines, capable of inducing effective anti-tumor immune responses. We investigated Bacterial Ghosts (BGs) – empty envelopes of Gram-negative bacteria – as a tool for optimized production of DC vaccines. BGs possess various intact cell surface structures, exhibiting strong adjuvant properties required for the induction of DC maturation, whereas their empty internal space can be easily filled with a source tumor antigens, e.g. tumor lysate. Hence BGs emerge as an excellent platform for both the induction of immunogenic DC maturation and loading with tumor antigens in a single-step procedure. We compared the phenotype, cytokine secretion profile, functional activity and ability to induce immunogenic T-cell responses in vitro of human monocyte-derived DCs generated using BG platform and DCs matured with widely used lipopolysaccharide (LPS) plus interferon-γ cocktail and loaded with tumor lysate. Both approaches induced DC maturation, however BG-based protocol was superior to LPS-based protocol in terms of the ability to induce DCs with a lower tolerogenic potential, resulting in a more robust CD8+ T cell activation and their functional activity as well as significantly lower induction of regulatory T cells. These superior parameters are attributed, at least in part, to the ability of BG-matured DCs to resist potential immunosuppressive and pro-tolerogenic activity of various tumor cell lysates, including melanoma, renal carcinoma and glioblastoma.

Dendritic Cell–Based Cancer Vaccines

Dendritic cells (DC) are specialized immune cells that play a critical role in promoting an immune response against Ags, which can include foreign pathogenic Ags and self-tumor Ags. DC are capable of boosting a memory T cell response but most importantly they are effective initiators of naive T cell responses. Many years of studies have focused on the use of DC vaccines against cancer to initiate and shape an antitumor-specific immune response and/or boost existing spontaneous antitumor T cell responses. In this study we give a brief overview of DC biology, function, and cellular subsets, and review the current status of the field of DC as cancer vaccines.

P3.07-008 Development of Immunomonitoring Assays for Dendritic Cell-Based Lung Cancer Immunotherapy

Allogeneic cancer cell lines might serve as a universal source of tumor antigens in the development of dendritic cell-based cancer vaccines. We showed that selected antigenic profile of lung cancer cell lines overlaps with antigenic profile of primary non/small cell lung cancer (NSCLC) tumors. However, it is unclear if T cells responses to all of these antigens can be detected in blood of NSCLC patients.

Development of oral cancer vaccine using recombinant Bifidobacterium displaying Wilms' tumor 1 protein.

Several types of vaccine-delivering tumor-associated antigens (TAAs) have been developed in basic and clinical research. Wilms' tumor 1 (WT1), identified as a gene responsible for pediatric renal neoplasm, is one of the most promising TAA for cancer immunotherapy. Peptide and dendritic cell-based WT1 cancer vaccines showed some therapeutic efficacy in clinical and pre-clinical studies but as yet no oral WT1 vaccine can be administrated in a simple and easy way. In the present study, we constructed a novel oral cancer vaccine using a recombinant Bifidobacterium longum displaying WT1 protein. B. longum 420 was orally administered into mice inoculated with WT1-expressing tumor cells for 4 weeks to examine anti-tumor effects. To analyze the WT1-specific cellular immune responses to oral B. longum 420, mice splenocytes were isolated and cytokine production and cytotoxic activities were determined. Oral administrations of B. longum 420 significantly inhibited WT1-expressing tumor growth and prolonged survival in mice. Immunohistochemical study and immunological assays revealed that B. longum 420 substantially induced tumor infiltration of CD4+T and CD8+T cells, systemic WT1-specific cytokine production, and cytotoxic activity mediated by WT1-epitope specific cytotoxic T lymphocytes, with no apparent adverse effects. Our novel oral cancer vaccine safely induced WT1-specific cellular immunity via activation of the gut mucosal immune system and achieved therapeutic efficacy with several practical advantages over existing non-oral vaccines.

Increased efficacy of a dendritic cell-based therapeutic cancer vaccine with adenosine receptor antagonist and CD73 inhibitor.

Dendritic cells are important in initiating immune responses; therefore, a range of dendritic cell-based approaches have been established to induce immune response against cancer cells. However, the presence of immunosuppressive mediators such as adenosine in the tumor microenvironment reduces the efficacy of dendritic cell-based cancer immunotherapy. In this study, we investigated whether blockade of the A2A adenosine receptor with a selective antagonist and a CD73 inhibitor may increase the efficacy of a dendritic cell-based cancer vaccine. According to the findings, this therapeutic combination reduced tumor growth, prolonged survival of tumor-bearing mice, and enhanced specific antitumor immune responses. Thus, we suggest that targeting cancer-derived adenosine improves the outcomes of dendritic cell-based cancer immunotherapy.

Dendritic cell vaccination in combination with docetaxel for patients with metastatic castration-resistant prostate cancer: A randomized phase II study

Background aimsWe investigated whether the addition of an autologous dendritic cell–based cancer vaccine (DCvac) induces an immune response in patients with metastatic castration-resistant prostate cancer treated with docetaxel. MethodsForty-three patients were randomized 1:1 to receive up to 10 cycles of docetaxel alone, 75 mg/m2 every 3 weeks or in combination with DCvac. Monocytes were harvested following a leukapheresis procedure, matured ex vivo and subsequently transfected with messenger RNA encoding multiple tumor-associated antigens (TAAs). DCvac was administered intradermally twice through treatment cycles 1–4 and once through treatment cycles 5–10. Immune cell composition and antigen-specific responses were analyzed using flow cytometry, ELISpot and delayed type hypersensitivity (DTH) tests. Toxicity was graded according to Common Terminology Criteria for Adverse Events version 3.0. Progression-free survival (PFS) and disease-specific survival (DSS) was calculated using the Kaplan-Meier method. ResultsProstate-specific antigen responses were similar in patients treated with docetaxel alone and combination therapy (58% versus 38%; P = 0.21). PFS and DSS were comparable: 5.5 versus 5.7 months (P = 0.62, log rank) and 21.9 versus 25.1 months (P = 0.60, log rank). Nine (50%) and 14 (78%) patients treated with docetaxel and DCvac had a TAA-specific or vaccine-specific immune response in the ELISpot and DTH analysis, respectively. Vaccine induced toxicity was limited to local reactions. Decline in myeloid-derived suppressor cells at the third treatment cycle was found to be an independent predictor of DSS. ConclusionsThe addition of DCvac was safe. Immune responses were detected in approximately half of the patients investigated.

Targeting the Immune Niche within the Bone Marrow Microenvironment: The Rise of Immunotherapy in Multiple Myeloma.

Multiple Myeloma (MM) cells inhibit the development of an effective anti- MM immune response via defects in T cell function, ineffective antigen presentation; reduced phagocytic capacity; natural killer and dendritic cell dysfunction; decreased responsiveness to IL-2 and defects in B cell immunity; upregulation of inhibitory pathways; and production of excessive proinflammatory cytokines. Moreover, immune cells including plasmacytoid dendritic cells and macrophages trigger tumor cell proliferation, survival, and drug resistance. The usefulness of immunotherapies in MM patients has first been supported by the identification of the graft-versus-myeloma effect in the context of allogeneic bone marrow (BM) transplantation. Subsequently, the inclusion of thalidomide and its derivatives, the Immunomodulatory Drugs (IMiDs) as well as of (immuno) proteasome inhibitors into MM regimens dramatically improved MM patients outcome during the last 15 years. Despite these unprecedented therapeutic advances MM remains an incurable disease. This article reviews novel immunotherapeutic approaches, which aim to restore the balance within the immunologic niche of the MM BM microenvironment. A systematic search was conducted of the Pubmed Medline, Embase, and Cochrane Library databases for primary articles, as well as of conference abstracts (e.g., of the American Society of Hematology, the American Society of Clinical Oncology, the American Association of Cancer Research, the European Hematology Association, and the Multiple Myeloma Workshop), practice guidelines, and registries of clinical trials. The inclusion of monoclonal antibodies, immune checkpoint inhibitors, chimeric antigen receptor-engineered (CAR) T cells, genetically engineered T cells, and vaccination, dendritic cellbased cancer vaccines in particular, into existing regimens is likely to significantly improve MM patient outcome in the near future. Given continuing efforts to target the immune niche within the bone marrow microenvironment we are confident that the rise of immunotherapies in MM will result in long-lasting responses in many of our patients within the next decade.

Combination strategies to enhance the potency of monocyte-derived dendritic cell-based cancer vaccines.

Dendritic cells (DCs) are potent inducers of adaptive immunity and their clinical use in cancer vaccine formulations remains an area of active translational and clinical investigation. Although cancer vaccines applied as monotherapies have had a modest history of clinical success, there is great enthusiasm for novel therapeutic strategies combining DC-based cancer vaccines with agents that 'normalize' immune function in the tumor microenvironment (TME). Broadly, these combination vaccines are designed to antagonize/remove immunosuppressive networks within the TME that serve to limit the antitumor action of vaccine-induced T cells and/or to condition the TME to facilitate the recruitment and optimal function and durability of vaccine-induced T cells. Such combination regimens are expected to dramatically enhance the clinical potency of DC-based cancer vaccine platforms.

Lung adenocarcinoma may be a more susceptive subtype to a dendritic cell-based cancer vaccine than other subtypes of non-small cell lung cancers: a multicenter retrospective analysis.

The J-SICT DC Vaccine Study Group provides dendritic cell (DC) vaccines for compassionate use under unified cell production and patient treatment regimens. We previously reported beneficial effects of DC vaccines on the overall survival of 62 patients with advanced non-small cell lung cancer (NSCLC) in a single-center analysis. Here, we extended analysis to 260 patients with NSCLC who were treated at six centers. Of the 337 patients who met the inclusion criteria, we analyzed 260 patients who received ≥5 peptide-pulsed DC vaccinations once every 2weeks. The mean survival time (MST) from diagnosis was 33.0months (95% confidence interval [CI]: 27.9-39.2), and that from time of first vaccination was 13.8months (95% CI 11.4-16.8). An erythema reaction at the injection site that was ≥30mm in diameter was correlated most strongly with overall survival from the first vaccine (≥30 vs. < 30mm: MST 20.4 vs. 8.8months, P<0.001). We reported a similar finding in our previous analysis of patients with advanced pancreatic cancer. Interestingly, although such findings were common between patients with adenocarcinoma and those with other subtypes, the former group experienced significantly prolonged overall survival and a higher response rate for erythema (56.3 vs. 37.3%, respectively, P=0.014). This is the first multicenter study that suggests a possible clinical benefit of DC vaccines for patients with advanced NSCLC, especially those with adenocarcinoma. These findings suggest a specific potential responder population for DC vaccines and warrant further investigation in well-controlled prospective randomized trials.

Abstract 2310: With a little help from CD4 T cells in adoptive T-cell transfer

Abstract Adoptive transfer of genetically engineered T cells offers great opportunities in cancer immunotherapy, however until recently, HLA-Class II-restricted TCRs have been largely ignored. We have identified and cloned HLA class II-restricted CD4+ T cells isolated from patients vaccinated with long peptides derived from antigens such as hTERT, survivin and frameshift mutated TGFβRII. Several of these cancer patients demonstrated outstanding clinical responses to peptide- or dendritic cell based cancer vaccines with &amp;gt;10-year survival. In these patients strong T-cell responses against peptides other than those used for vaccination were detected, suggesting epitope spreading. Responses against certain peptides associated with clinical benefit were identified and CD4+ T-cell clones recognizing such peptides were isolated. In depth studies of their specificities lead to the selection of HLA-DR and -DQ restricted T-cells having high functional avidity for the HLA-peptide complexes. We studied tumor cell and/or protein recognition and found one telomerase-specific CD4+ T-cell clone recognizing a melanoma cell line with the corresponding HLA allele. The TCR sequences of the interesting clones were identified. The ribosome skipping 2A sequence technique was used to express these TCRs in an mRNA expression vector or retrovirus. When expanded T cells were electroporated with these TCRs, both redirected CD8+ and CD4+ T cells produced TNF-α, IFN-γ and the degranulation marker (CD107a) following co-incubation with specific peptide-loaded targets. We have demonstrated that choosing highly functional CD4+ T-cell clones specific for tumor-associated or -specific antigens from patients with clinical responses after immunotherapy treatment is a successful method for identifying highly functional HLA class II restricted TCRs for adoptive T-cell transfer. The use of HLA class II-restricted TCRs may be of therapeutic value both in haematopoietic malignancies and in melanoma where tumor cells often express HLA class II. In addition, combining the redirection of T cells with both HLA class I- and class II-restricted TCRs may provide a more powerful therapeutic effect in adoptive T cell therapy. Citation Format: Else M. Inderberg, Sébastien Wälchli, Marit R. Myhre, Kari Lislerud, Gunnar Kvalheim, Gustav Gaudernack. With a little help from CD4 T cells in adoptive T-cell transfer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2310.

PD-L1 peptide co-stimulation increases immunogenicity of a dendritic cell-based cancer vaccine

ABSTRACTWe recently described naturally occurring PD-L1-specific T cells that recognize PD-L1-expressing immune cells as well as malignant cells. In the present study, we investigated whether the immunogenicity of a dendritic cell (DC)-based vaccine could be influenced by co-stimulation with a known PD-L1-derived epitope. We incubated a PD-L1-derived peptide epitope (19 amino acids long) or a control peptide (an irrelevant HIV epitope) with peripheral blood mononuclear cells from patients with malignant melanoma who had received a DC-based vaccine. We observed a significantly higher number of T cells that reacted to the vaccine in cultures that had been co-stimulated with the PD-L1 peptide epitope compared to cultures incubated with control peptide. Next, we characterized a novel PD-L1-derived epitope (23 amino acids long) and found that co-stimulation with both PD-L1 epitopes boosted the immune response elicited by the DC vaccine even further. Consequently, we observed a significant increase in the number of vaccine-reacting T cells in vitro. In conclusion, activation of PD-L1-specific T cells may directly modulate immunogenicity of DC vaccines. Addition of PD-L1 epitopes may thus be an easily applicable and attractive option to augment the effectiveness of cancer vaccines and other immunotherapeutic agents.