Antigen-specific Cytotoxic T Lymphocytes Research Articles

Renal cell carcinoma drug and cell therapy: today and tomorrow

Today, considerable progress in the renal cell carcinoma (RCC) treatment has been made due to development of targeted and immunotherapeutic approaches to the RCC treatment, especially in metastasising carcinoma. In the early stages of RCC, it is possible to use partial or total surgical nephrectomy, but in metastases development, the range of efficient treatment methods is dramatically limited. Appearance of targeted drugs like PD-1 and CTLA-4 receptors and their ligands’ inhibitors in clinical practice has significantly increased the total survival rate of patients with renal cell carcinoma. Emergence of adoptive cell therapy has opened new possibilities and prospects in RCC treatment. Previously activated in vitro cells are used there, which provides antineoplastic activity. For example, it could be antigen-specific cytotoxic T-lymphocytes (CTL), lymphokine-activated natural killers (LAK-NK-cells) and tumour-infiltrating lymphocytes (TILs). In this review, the authors specified the main molecular markers, associated with RCC; and signalling pathways (VEGFR- and EGFR-signalling pathway), which directly take part in carcinogenesis. The paper also looks at clinically applicable targeted immune drugs and the principle of their effect on tumorous cells. Besides, modern clinical studies of cell drugs have been considered. At the moment, there are a number of variants of targeted and immune drugs for the metastatic RCC treatment. Patients have no opportunity to use all the available agents because of their cost and toxicity level. For the most efficient treatment of patients with diagnosed metastatic RCC, it is necessarily to carry out risk stratification and prognostic factors for the response to treatment.

Quantitative T-cell repertoire analysis of peripheral blood mononuclear cells from lung cancer patients following long-term cancer peptide vaccination.

Therapeutic cancer peptide vaccination is an immunotherapy designed to elicit cytotoxic T-lymphocyte (CTL) responses in patients. A number of therapeutic vaccination trials have been performed, nevertheless there are only a few reports that have analyzed the T-cell receptors (TCRs) expressed on tumor antigen-specific CTLs. Here, we use next-generation sequencing (NGS) to analyze TCRs of vaccine-induced CTL clones and the TCR repertoire of bulk T cells in peripheral blood mononuclear cells (PBMCs) from two lung cancer patients over the course of long-term vaccine therapy. In both patients, vaccination with two epitope peptides derived from cancer/testis antigens (upregulated lung cancer 10 (URLC10) and cell division associated 1 (CDCA1)) induced specific CTLs expressing various TCRs. All URLC10-specific CTL clones tested showed Ca2+ influx, IFN-γ production, and cytotoxicity when co-cultured with URLC10-pulsed tumor cells. Moreover, in CTL clones that were not stained with the URLC10/MHC-multimer, the CD3 ζ chain was not phosphorylated. NGS of the TCR repertoire of bulk PBMCs demonstrated that the frequency of vaccine peptide-specific CTL clones was near the minimum detectable threshold level. These results demonstrate that vaccination induces antigen-specific CTLs expressing various TCRs at different time points in cancer patients, and that some CTL clones are maintained in PBMCs during long-term treatment, including some with TCRs that do not bind peptide/MHC-multimer.

Histone deacetylase (HDAC) inhibitor ACY241 enhances anti-tumor activities of antigen-specific central memory cytotoxic T lymphocytes against multiple myeloma and solid tumors.

Histone deacetylases (HDAC) are therapeutic targets in multiple cancers. ACY241, an HDAC6 selective inhibitor, has shown anti-multiple myeloma (MM) activity in combination with immunomodulatory drugs and proteasome inhibitors. Here we show ACY241 significantly reduces the frequency of CD138+ MM cells, CD4+CD25+FoxP3+ regulatory T cells, and HLA-DRLow/-CD11b+CD33+ myeloid-derived suppressor cells; and decreases expression of PD1/PD-L1 on CD8+ T cells and of immune checkpoints in bone marrow cells from myeloma patients. ACY241 increased B7 (CD80, CD86) and MHC (Class I, Class II) expression on tumor and dendritic cells. We further evaluated the effect of ACY241 on antigen-specific cytotoxic T lymphocytes (CTL) generated with heteroclitic XBP1unspliced184-192 (YISPWILAV) and XBP1spliced367-375 (YLFPQLISV) peptides. ACY241 induces co-stimulatory (CD28, 41BB, CD40L, OX40) and activation (CD38) molecule expression in a dose- and time-dependent manner, and anti-tumor activities, evidenced by increased perforin/CD107a expression, IFN-γ/IL-2/TNF-α production, and antigen-specific central memory CTL. These effects of ACY241 on antigen-specific memory T cells were associated with activation of downstream AKT/mTOR/p65 pathways and upregulation of transcription regulators including Bcl-6, Eomes, HIF-1 and T-bet. These studies therefore demonstrate mechanisms whereby ACY241 augments immune response, providing the rationale for its use, alone and in combination, to restore host anti-tumor immunity and improve patient outcome.

Injectable, Tough Alginate Cryogels as Cancer Vaccines.

A covalently crosslinked methacrylated (MA)-alginate cryogel vaccine has been previously shown to generate a potent response against murine melanoma, but is not mechanically robust and requires a large 16G needle for delivery. Here, covalent and ionic crosslinking of cryogels are combined with the hypothesis that this will result in a tough MA-alginate cryogel with improved injectability. All tough cryogels can be injected through a smaller, 18G needle without sustaining any damage, while covalently crosslinked-only cryogels break after injection. Cytosine-phosphodiester-guanine (CpG)-delivering tough cryogels effectively activate dendritic cells (DCs). Granulocyte macrophage colony-stimulating factor releasing tough cryogels recruit four times more DCs than blank gels by day 7 in vivo. The tough cryogel vaccine induces strong antigen-specific cytotoxic T-lymphocyte and humoral responses. These vaccines prevent tumor formation in 80% of mice inoculated with HER2/neu-overexpressing DD breast cancer cells. The MA-alginate tough cryogels provide a promising minimally invasive delivery platform for cancer vaccinations.

IPSC-derived rejuvenated T-cell therapy for Epstein-Barr virus-associated lymphomas

Extranodal natural killer (NK) /T-cell lymphoma (ENKL), nasal-type, is an aggressive lymphoma that is relatively common in Asia and is resistant to anthracycline-based chemotherapy. Antigen-specific cytotoxic T-lymphocyte (CTL) therapy can induce durable remission in selected tumors, such as melanomas and virus-related tumors. ENKLs are commonly infected with the Epstein-Barr virus (EBV) ; therefore, CTL therapy can be effective for these lymphomas. However, CTLs that are continuously exposed to viral or tumor antigens usually get exhausted. Antigen-specific CTLs generated from iPSCs have a higher proliferative capacity and longer telomeres than original CTLs and are functionally rejuvenated (rejuvenated T cell, rejT). For clinical translation, the tumorigenic potential of iPSCs and the malignant transformation of differentiated iPSCs are major safety concerns. To address these issues, we introduced inducible caspase-9 (iC9) -based safeguard system into iPSCs. iC9-rejTs exert strong anti-tumor effects against EBV-infected tumors in vivo, and the iC9 suicide gene system provides a reliable safeguard for rejT therapy. We initiated a preclinical study using this novel immunotherapy for EBV-associated lymphoma. We believe that rejT therapy can be a potential safe approach as an "off-the-shelf" therapy for refractory ENKL in the future.

Cloning and expansion of antigen-specific T cells using iPS cell technology: development of "off-the-shelf" T cells for the use in allogeneic transfusion settings.

Recent advances in adoptive immunotherapy using cytotoxic T lymphocytes (CTLs) have led to moderate therapeutic anti-cancer effects in clinical trials. However, a critical issue, namely that CTLs collected from patients are easily exhausted during expansion culture, has yet to be solved. To address this issue, we have been developing a strategy which utilizes induced pluripotent stem cell (iPSC) technology. This strategy is based on the idea that when iPSCs are produced from antigen-specific CTLs, CTLs regenerated from such iPSCs should show the same antigen specificity as the original CTLs. Pursuing this idea, we previously succeeded in regenerating melanoma antigen MART1-specific CTLs, and more recently in producing potent CTLs expressing CD8αβ heterodimer. We are now developing a novel method by which non-T derived iPSCs are transduced with exogenous T cell receptor genes. If this method is applied to Human Leukocyte Antigen(HLA) haplotype-homozygous iPSC stock, it will be possible to prepare "off-the-shelf" T cells. As a first-in-human trial, we are planning to apply our strategy to relapsed acute myeloid leukemia patients by targeting the WT1 antigen.

Nasal delivery of H5N1 avian influenza vaccine formulated with GenJet™ or in vivo-jetPEI® induces enhanced serological, cellular and protective immune responses

Avian influenza virus infection is a serious public health threat and preventive vaccination is the most cost-effective public health intervention strategy. Unfortunately, currently available unadjuvanted avian influenza vaccines are poorly immunogenic and alternative vaccine formulations and delivery strategies are in urgent need to reduce the high risk of avian influenza pandemics. Cationic polymers have been widely used as vectors for gene delivery in vitro and in vivo. In this study, we formulated H5N1 influenza vaccines with GenJet™ or in vivo-jetPEI®, and showed that these formulations significantly enhanced the immunogenicity of H5N1 vaccines and conferred protective immunity in a mouse model. Detailed analyses of adaptive immune responses revealed that both formulations induced mixed TH1/TH2 antigen-specific CD4 T-cell responses, antigen-specific cytotoxic CD8 T-cell and memory B-cell responses. Our findings suggest that cationic polymers merit future development as potential adjuvants for mucosal delivery of poorly immunogenic vaccines.

TCR-Identical CD8+ T-Cells Can Have Distinct Killing Efficacy Determined By Events Beyond the T-Cell Receptor

Introduction: Cytotoxic T lymphocytes (CTL) that encounter antigen proliferate from a single naïve T-cell to form a population with diverse effector function and differentiation states, that control and prevent infection and cancer. Antigen-specific CTL are extremely heterogeneous in terms of clonotype, differentiation state and efficacy. Factors that define CTL of superior efficacy are well explored. TCR signal strength is known to modulate the breadth and magnitude of CTL effector functions, and epigenetic marks modulate intrinsic states such as exhaustion that limit activation. It is not clear if or how TCR signal strength modulates contact-dependent killing, and TCR affinity, TCR avidity, or factors downstream of the TCR could all contribute. There is a critical period of contact when a TCR engages cognate peptide- MHC class I molecules on a target cell that determines if the cell will be killed or survive. This is important to explore as not all T-cell therapy products to treat cancer are equally efficacious despite lentiviral transduction with the same chimeric-antigen-receptor. Lack of CTL efficacy is also encountered in chronic viral infections. Indeed, antigen-specific CTL from HIV controllers suppress HIV replication in vitro unlike antigen-specific CTL from chronic progressors. Viral suppression correlates with target cell elimination suggesting a critical role for contact-dependent killing.Results: To identify factors that define superior CTL efficacy downstream of the TCR, we generated TCR-identical CD8+ CTL clones specific for a single epitope, HIV-1 FLKEKGGL (FL8) Nef (90-97) restricted by HLA B*0801, from individuals with HLA B*08-FL8 tetramer specific responses dominated by the use of a single TCR. Remarkably, clones that used the same TCR and bound tetramer with identical avidity, indicating the same surface expression of TCR, had distinct abilities to suppress HIV-1 in vitro. The mechanism of in vitro suppression correlated with target cell elimination demonstrating TCR-identical CTL clones can have distinct contact-dependent killing efficiency. Effective clones were highly responsive at low antigen densities, as might be encountered during physiological viral infection, with more rapid onset of signalling demonstrated by higher phospho-ERK MFI after 10 minutes of stimulation, faster onset of degranulation, and a higher final proportion of cells responding with CD107a expression, a marker of degranulation, at one hour. These novel distinctions in a reductionist in vitro model enabled us to dissect virus suppressive activity beyond initial TCR-antigen contact. On transcriptome examination we identified novel putative coreceptors containing ITAM (XX receptor to be revealedXX) or ITIM (XX two receptors to be revealed XX) motifs that were consistently over or under expressed on CTL clones that demonstrated superior contact-dependent killing.Furthermore, ex vivo RT-PCR analysis of TCR-identical single cells sorted from the HLA B*08-FL8 tetramer positive population from which the CTL clones were generated, identified two populations of CTL, defined by expression of these novel ITAM and ITIM receptors. Lentiviral transduction of Jurkat cells with the novel ITAM receptor enhanced MFI phospho-ERK expression at 10 minutes when activated using plate bound OKT3, to generate a TCR signal, suggesting that this ITAM receptor may act as a TCR co-stimulatory molecule. T-cell poise may be critical to efficient contact-dependent killing, particularly if antigen or CTL cell numbers are limiting, by modulation of the probability of target cell death during each CTL-TCR engagement with its cognate peptide- MHC complex. We also demonstrated that TCR-identical CTL clones from one individual had distinct epigenetic regulation of TNF secretion.Conclusion: Our results suggest that poise of the signalling cascade and intrinsic ontogenetic regulation of functions are critical to antiviral activity and identify putative novel check-point targets for therapeutic development. DisclosuresMead:BMS: Honoraria; Pfizer: Honoraria; Novartis: Honoraria, Research Funding, Speakers Bureau.

The Generation of Human γδT Cell-Derived Induced Pluripotent Stem Cells from Whole Peripheral Blood Mononuclear Cell Culture.

γδT cells constitute a small proportion of lymphocytes in peripheral blood. Unlike αβT cells, the anti‐tumor activities are exerted through several different pathways in a MHC‐unrestricted manner. Thus, immunotherapy using γδT cells is considered to be effective for various types of cancer. Occasionally, however, ex vivo expanded cells are not as effective as expected due to cell exhaustion. To overcome the issue of T‐cell exhaustion, researchers have generated induced pluripotent stem cells (iPSCs) that harbor the same T‐cell receptor (TCR) genes as their original T‐cells, which provide nearly limitless sources for antigen‐specific cytotoxic T lymphocytes (CTLs). However, these technologies have focused on αβT cells and require a population of antigen‐specific CTLs, which are purified by cell sorting with HLA‐peptide multimer, as the origin of iPS cells. In the present study, we aimed to develop an efficient and convenient system for generating iPSCs that harbor rearrangements of the TCRG and TCRD gene regions (γδT‐iPSCs) without cell‐sorting. We stimulated human whole peripheral blood mononuclear cell (PBMC) culture using Interleukin‐2 and Zoledronate to activate γδT cells. Gene transfer into those cells with the Sendai virus vector resulted in γδT cell‐dominant expression of exogenous genes. The introduction of reprogramming factors into the stimulated PBMC culture allowed us to establish iPSC lines. Around 70% of the established lines carried rearrangements at the TCRG and TCRD gene locus. The γδT‐iPSCs could differentiate into hematopoietic progenitors. Our technology will pave the way for new avenues toward novel immunotherapy that can be applied for various types of cancer. stem cells translational medicine 2018;7:34–44

IL-12 stimulates CTLs to secrete exosomes capable of activating bystander CD8+ T cells

An effective cytotoxic T lymphocyte (CTL) response against intracellular pathogens is generally accomplished by immense CTL expansion and activation, which can destroy infected cells. Vigorous immune responses can lead to activation of bystander CD8+ T cells, but the contribution from antigen-specific CTLs is not well understood. We found that CTLs secrete extracellular vesicles following antigen stimulation. These CTL-derived vesicles contain CTL proteins and exhibit markers and size profiles consistent with exosomes. Interestingly, further stimulation of CTLs with IL-12 impacts exosome size and leads to selective enrichment of certain exosomal proteins. More important, exosomes from IL-12-stimulated CTLs directly activated bystander naïve CD8+ T cells to produce interferon-γ (IFNγ) and granzyme B (GZB) in the absence of antigens, whereas control exosomes derived from antigen-stimulated CTLs did not. In addition, IL-12 induced exosomes are able to strengthen the effects of weak antigen stimulation on CTLs. Proteomic analysis demonstrates that IL-12 stimulation alters catalytic and binding activities of proteins in CTL exosomes. Our findings indicate that the biological function and morphology of exosomes secreted by CTLs can be influenced by the type of stimulation CTLs receive. Thus, a fully functional, ongoing, antigen-specific CTL response may influence bystander CD8+ T cells through secretion of exosomes.

Adoptive immunotherapy combined with FP treatment for head and neck cancer: An invitro study.

FP treatment, which combines 5-fluorouracil (5-FU) and cisplatin (CDDP) chemotherapy, is widely used for treatment of advanced head and neck cancer (HNC). It has been suggested that these drugs cause immunomodulation in the cancer microenvironment, for example, downregulation of immunosuppressive cells such as regulatory T-cells (Tregs) and myeloid-derived suppressive cells (MDSCs), activating dendritic cells (DCs), and upregulation of tumor antigens and major histocompatibility complex (MHC) molecules in cancer cells leads to enhancement of cancer immunity, which is important in cancer treatment, as well as providing a direct killing effect. Therefore, development of chemoimmuno-therapy by combining FP treatment with immunotherapy for HNC has become a recent challenging issue. However, the direct effects of these drugs on immune effector cells, especially cytotoxic T-lymphocytes (CTLs), are not well known. We have investigated the direct actions of these drugs on CTL functions in in vitro experiments using cytomegalovirus (CMV) pp65 antigen-specific CTLs (CMVpp65-CTLs) and oral squamous cell cancer (OSCC) cell lines overexpressing CMVpp65 antigen as target cells. Although CDDP partially inhibited proliferation of memory CMVpp65-CTL in peripheral blood, the proliferation was not inhibited by 5-FU. Cytotoxicity and the IFN-γ release response of the CMVpp65-CTLs were not inhibited by these drugs, and it is important to note that these drugs, especially 5-FU, sensitized OSCC cell lines to CMVpp65-CTL. Furthermore, CMVpp65-CTL cytotoxicity to CDDP-resistant OSCC cells, HSC-3/CDDP-R1, was the same as the cytotoxicity to the parental cells. Thus, we suggest that combined immunotherapy with FP treatment is an effective novel HNC treatment.

A Gut Microbial Mimic that Hijacks Diabetogenic Autoreactivity to Suppress Colitis

The gut microbiota contributes to the development of normal immunity but, when dysregulated, can promote autoimmunity through various non-antigen-specific effects on pathogenic and regulatory lymphocytes. Here, we show that an integrase expressed by several species of the gut microbial genus Bacteroides encodes a low-avidity mimotope of the pancreatic β cell autoantigen islet-specific glucose-6-phosphatase-catalytic-subunit-related protein (IGRP206-214). Studies in germ-free mice monocolonized with integrase-competent, integrase-deficient, and integrase-transgenic Bacteroides demonstrate that the microbial epitope promotes the recruitment of diabetogenic CD8+ Tcells to the gut. There, these effectors suppress colitis by targeting microbial antigen-loaded, antigen-presenting cells in an integrin β7-, perforin-, and majorhistocompatibility complex class I-dependent manner. Like their murine counterparts, human peripheral blood Tcells also recognize Bacteroides integrase. These data suggest that gut microbial antigen-specific cytotoxic Tcells may have therapeutic value in inflammatory bowel disease and unearth molecular mimicry as a novel mechanism by which the gut microbiota can regulate normal immune homeostasis. PAPERCLIP.

Biomimetic Magnetosomes as Versatile Artificial Antigen-Presenting Cells to Potentiate T-Cell-Based Anticancer Therapy.

Adoptive T-cell transfer for cancer therapy relies on both effective ex vivo T-cell expansion and in vivo targeting performance. One promising but challenging method for accomplishing this purpose is to construct multifunctional artificial antigen-presenting cells (aAPCs). We herein developed biomimetic magnetosomes as versatile aAPCs, wherein magnetic nanoclusters were coated with azide-engineered leucocyte membranes and then decorated with T-cell stimuli through copper-free click chemistry. These nano aAPCs not only exhibited high performance for antigen-specific cytotoxic T-cell (CTL) expansion and stimulation but also visually and effectively guided reinfused CTLs to tumor tissues through magnetic resonance imaging and magnetic control. The persisting T cells were able to delay tumor growth in a murine lymphoma model, while the systemic toxicity was not notable. These results together demonstrated the excellent potential of this "one-but-all" aAPC platform for T-cell-based anticancer immunotherapy.

Recycling endosomes in human cytotoxic T lymphocytes constitute an auxiliary intracellular trafficking pathway for newly synthesized perforin.

Although cytotoxic T lymphocytes (CTLs) store perforin within cytoplasmic secretory granules for immediate use, perforin is synthesized anew within hours of TCR stimulation. Previously, we observed new perforin protein at an immunologic synapse independent of secretory lysosomes; herein, we aimed to determine how new perforin transits to the synapse if not via lytic granules. We analyzed antigen-specific human CTLs via imaging flow cytometry and high-resolution confocal microscopy, with attention to intracellular trafficking components and new perforin. The recycling endosome compartments identified by rab8, rab11a, rab4, and rab37 co-localized with new perforin, as well as the SNAREs vti1b and VAMP4. After ablating the function of the recycling endosome pathway, we observed a relative accumulation of new perforin in rab8 vesicles. The recycling endosome pathway may serve as an auxiliary intracellular route for the delivery of new perforin to an immunologic synapse in order to perpetuate a cytotoxic response.

9-Phenanthrol enhances the generation of an CD8+ T cell response following transcutaneous immunization with imiquimod in mice

BackgroundTranscutaneous immunization (TCI) is a non-invasive vaccination strategy targeting the skin-associated lymphoid tissue. Topical application of the TLR7 agonist imiquimod as adjuvant in combination with peptide antigens activates the innate immune system and mounts cytotoxic T lymphocyte (CTL) responses. ObjectiveBased on the commercial 5% imiquimod-containing drug Aldara we aimed to develop an improved formulation with superior vaccination efficiencies. The primary target was the enhancement of mast cell activation as important key for the function of the innate immune system. MethodsWe investigated the effects of 9-phenanthrol (9-phe) on the activation of mast cells in vitro and in vivo. For TCI, we applied 0.2% 9-phe in Aldara or Aldara alone as adjuvants in combination with the MHC class I – restricted peptide SIINFEKL. To monitor vaccination, mast cell degranulation, migration of DC and frequencies of epitope-specific CTL was assessed. In a transgenic tumor model, the efficiencies of prophylactic immunization against a tumor antigen were also monitored. Results9-phe induced degranulation of mast cells in vitro and upon topical application in vivo. A mixture of 0.2% 9-phe in Aldara showed superior results regarding the migration of DC and the expansion of antigen-specific CTL. Consequently, prophylactic immunization with 0.2% 9-phe in Aldara caused enhanced protection against tumor inoculation. ConclusionOur data demonstrate that a simple modification of an adjuvant formulation can yield superior results in experimental vaccination protocols by boosting critical steps leading to the generation of an efficient CTL response.

Complex Consisting of β-Glucan and Antigenic Peptides with Cleavage Site for Glutathione and Aminopeptidases Induces Potent Cytotoxic T Lymphocytes.

The efficient induction of antigen-specific immune responses requires not only promotion of the uptake of antigens and adjuvant molecules into antigen-presenting cells but also control of their intracellular behavior. We previously demonstrated that the β-glucan schizophyllan (SPG) can form complexes with CpG oligonucleotides with attached dA40 (CpG-dA/SPG), which can accumulate in macrophages in the draining inguinal lymph nodes and induce strong immune responses. In this study, we prepared various conjugates composed of antigenic peptide (OVA257-264) and dA40 and made complexes with SPG. The conjugates with a disulfide bond between OVA257-264 and dA40 were easily cleaved by glutathione. The resultant peptides with a hydrophobic amino acid at the C-terminal end was recognized by puromycin-insensitive leucine aminopeptidase (PILS-AP), which trims antigenic peptide precursors and prepares peptides of eight or nine amino acids in length, which is the optimal length for binding to major histocompatibility complex (MHC)-I. The conjugate exposed to such enzymes induced a high antigen presentation level. The antigen presentation level was almost the same before and after the complexation with SPG. Immunization with a mixture of dA-OVA257-264/SPG and CpG-dA/SPG induced high antigen-specific cytotoxic T-lymphocyte activity at a much lower peptide dose than in previous studies. These results can be strongly ascribed to not only the cell-specific delivery by SPG but also the control of the intracellular behavior by the introduction of cleavage sites. Therefore, peptide-dA/SPG complexes could be used as potent vaccine antigens for the treatment of cancers and infectious diseases.

Artificial human antigen-presenting cells are superior to dendritic cells at inducing cytotoxic T-cell responses.

Peptide recognition through the MHC class I molecule by cytotoxic T lymphocytes (CTLs) leads to the killing of cancer cells. A potential challenge for T-cell immunotherapy is that dendritic cells (DCs) are exposed to the MHC class I-peptide complex for an insufficient amount of time. To improve tumour antigen presentation to T cells and thereby initiate a more effective T-cell response, we generated artificial antigen-presenting cells (aAPCs) by incubating human immature DCs (imDCs) with poly(lactic-co-glycolic) acid nanoparticles (PLGA-NPs) encapsulating tumour antigenic peptides, followed by maturation with lipopolysaccharide. Tumour antigen-specific CTLs were then induced using either peptide-loaded mature DCs (mDCs) or aAPCs, and their activities were analysed using both ELISpot and cytotoxicity assays. We found that the aAPCs induced significantly stronger tumour antigen-specific CTL responses than the controls, which included both mDCs and aAPCs loaded with empty nanoparticles. Moreover, frozen CTLs that were generated by exposure to aAPCs retained the capability to eradicate HLA-A2-positive tumour antigen-bearing cancer cells. These results indicated that aAPCs are superior to DCs when inducing the CTL response because the former are capable of continuously presenting tumour antigens to T cells in a sustained manner. The development of aAPCs with PLGA-NPs encapsulating tumour antigenic peptides is a promising approach for the generation of effective CTL responses in vitro and warrants further assessments in clinical trials.

Abstract 3722: In vitro induced regulatory T cells for understanding the nature of peripherally induced regulatory cells in relation to cell mediated immunotherapy for cancer

Abstract Background: pTregs are appearing to be one of the major obstacles of cellular immunotherapy of cancer. Tumor specific in vivo induced Cytotoxic T lymphocytes (CTL) are rapidly eliminated with concomitant expansion of pTreg cells. In human melanoma in ex vivo condition, tumor antigen specific CTL generated with CD8+ cells persisted for months while ex vivo induced CTL with whole PBL stimulated with Mart-127-35 A2 (tumor antigen) pulsed autologousDC, died within three weeks. Whereas Influenza (Flu 58-66) antigen specific CTL continued to expand and remained functional beyond four weeks. Method: Peripheral blood and tumors were obtained from patients diagnosed with metastatic melanoma after informed consent. Blood derived dendritic cells, PBL, CD4+ and CD8+ cells were isolated for in vitro co-cultures with Mart-1 or Flu peptide pulsed autologous DC or autologous tumor cells. CD8+ CTL response and CD4+ positive Treg responses were measured. Freshly obtained tumor tissue derived lymphocytes (TIL) were also used for the study. Results: Our results show that CTL response against Flu survived longer in culture with total PBL than CTL response against Mart-1 in identical culture conditions. CTL response using autologous tumor cells with PBL in culture lasted for a shorter duration but growth of Treg cells were observed. Cytokine analysis with expanding Treg cells showed secretion of IL-10 upon re-stimulation with autologous DC or anti-CD3 ab. Similarly, CD4+ cells isolated from freshly obtained tumor tissue (TIL, representing in vivo condition), suppressed T cell activation and secreted high amount of IL-10 upon re-stimulation. Conclusion: These findings suggested that in vitro induced iTreg from cultures or pTreg from TILs (in vivo), work identical way, to negatively regulate effector immune response by secreting IL-10. Further analysis with iTregs for their use of metabolic pathways would be important to identify the specific signaling molecules used by autologous (person specific) pTregs , as target molecules, to block the expansion of such pTregs for the better outcome for CTL mediated immunotherapy for cancer. Citation Format: Upendra P. Hegde, Nitya G. Chakraborty. In vitro induced regulatory T cells for understanding the nature of peripherally induced regulatory cells in relation to cell mediated immunotherapy for cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3722. doi:10.1158/1538-7445.AM2017-3722

Abstract 4607: Specific inhibition of PGE2-EP4 signaling by E7046 promotes anti-tumor activity of checkpoint blockade agents through boosting cytotoxic T cell activity

Abstract Purpose: Immunotherapies targeting immune checkpoint receptors have shown great promise for a subset of cancer patients; however, robust and safe combination therapies are still needed. In the tumor microenvironment, prostaglandin E2 receptor type 4 (EP4) signaling has been implicated in both protumoral myeloid cell differentiation and cytotoxic T cell exhaustion. We evaluated the combination of the EP4 antagonist E7046 (clinical trial NCT02540291) with anti-PD1 or anti-CTLA4 in preclinical tumor models, and also interrogated the relationship between PGE2 pathway activation and cancer patient survival. Materials/Methods: Mouse syngeneic tumor models CT-26 and 4T1 were used for pharmacological investigation. GMP grade E7046 was administered to tumor-bearing animals by oral gavage. Co-culture of EG7-OVA and OT1 cells in an antigen-specific cytotoxic T cell (CTL) activation assay provided mechanistic insights. For translational validation, transcripts of five major genes involved in PGE2 synthesis, transport and degradation were compared between malignant and normal tissues across all TCGA tumor types, and correlation of their expression with overall survival was assessed. Results: In the CT26 tumor model, the combination of E7046 and anti-PD1 resulted in significantly more tumor-free animals compared with either agent alone. In the 4T1 tumor model, the combination of E7046 and anti-CTLA4 was also more effective in suppressing tumor growth and tumor rejection compared with anti-CTLA4 alone, and was accompanied by a markedly increased accumulation of GZMB+CD8T+ CTLs in the treated tumors. Consistent with those findings, addition of anti-PD1 antibody promoted OVA-specific CTL activation in vitro while addition of PGE2 strongly inhibited it, as measured by IFNγ secretion. Inclusion of E7046 dose-dependently reversed the PGE2-induced suppressive activity in the presence of anti-PD1 antibody. Among major human PGE2 pathway genes, TCGA analysis showed that PTGES1 was upregulated and HPGD downregulated across a broad range of tumor types. In contrast, COX1, COX2 and PGT showed less difference between malignant and normal tissues. Importantly, these differences of one or multiple PGE2 pathway genes were strongly associated with patient survival in certain cancer types. Conclusions: A subset of human cancer types displays upregulated PGE2 pathway that is associated with a poorer prognosis. PGE2-EP4 signaling potently suppresses antigen-specific CTL activation in the presence of PD1 signaling blockade. The combination of EP4 antagonist E7046 with either anti-PD1 or anti-CTLA4 demonstrated superior anti-tumor activity compared with anti-PD1 or anti-CTLA4 alone. This increased activity was accompanied by increased CTL activation. Citation Format: Diana I. Albu, David Verbel, Yuan Huang, Donna Kolber-Simonds, Zichun Wang, Xulong Wang, Zoltan Dezso, Christy Ingersoll, Kuan-Chun Huang, Janna Hutz, Mary Woodall-Jappe, Xingfeng Bao. Specific inhibition of PGE2-EP4 signaling by E7046 promotes anti-tumor activity of checkpoint blockade agents through boosting cytotoxic T cell activity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4607. doi:10.1158/1538-7445.AM2017-4607

Evaluation of immunological efficacy of Japanese herbal medicine, hochu-ekki-to and keishi-bukuryo-gan, in patients with castration-resistant prostate cancer under personalized peptide vaccination.

e16584 Background: This randomized phase II study investigated the immunological efficacy of herbal medicines (HMs) using Hochu-ekki-to and Keishi-bukuryo-gan, in combination with personalized peptide vaccination (PPV) for castration-resistant prostate cancer (CRPC). Methods: Seventy patients with CRPC were randomly assigned (1:1) to receive PPV plus HMs, or PPV alone. PPV treatment used a maximum of four peptides chosen from 31 peptides derived from cancer antigens according to human leukocyte antigen types and antigen-specific humoral immune responses before PPV, for 8 subcutaneous weekly injections. Peptide-specific cytotoxic T lymphocyte (CTL), immunoglobulin G (IgG), regulatory T cells (Treg), monocytic myeloid-derived suppressor cells (Mo-MDSC) and interleukin-6 (IL-6) responses were measured before and 8th vaccination. Clinical outcomes were also analyzed. Results: The combination therapy of PPV with HMs was well tolerated without severe adverse events but had no significant impact on antigen-specific IgG and CTL, Treg and clinical outcomes. The combination therapy of PPV with HMs stabilized the frequency of M0-MDSCs (1.91% to 1.92%, p = 0.96) and serum levels of IL-6 (19.2 pg/ml to 16.1 pg/ml, p = 0.63). On the other hand, the frequency of Mo-MDSC and levels of IL-6 in the PPV alone were significantly increased (0.91% to 1.49% for Mo-MDSC and 9.2 pg/ml to 19.4 pg/ml for IL-6, respectively). Conclusions: These results suggested that the combination usage of HMs reveals a potential to prevent the immunosuppression induced by Mo-MDSC or IL-6 during the immunotherapy. More research is needed to validate the findings of the present study. Clinical trial information: 000010290.