Tumor Cell Vaccine Research Articles

The effect of microwave ablation combined with dendritic cell tumor vaccine treatment on mouse mammary carcinoma and its immunological mechanism

Objective To investigate the therapeutic effects of microwave ablation combined with dendritic cell (DC) tumor vaccine on a murine breast cancer model and to explore its immunological mechanism.Methods Forty-eight Balb/c mice were used to establish models of mouse mammary carcinoma,and then randomly divided into a sham-operation group,a microwave ablation treated group,a DC tumor vaccinated group and a microwave ablation plus DC tumor vaccinated group.Microwave ablation was conducted with the microwave ablation group on day 14 after establishing the model.DC tumor vaccination was performed on day 7 in the vaccinated group.In the microwave ablation plus DC tumor vaccinated group,DC tumor vaccination and microwave ablation were consecutively performed on days 7 and 14,respectively.Tumor growth,lung metastasis and survival were observed.The proportion of CD3+ and CD4+ T cells in splenocytes were analyzed by fluorescence Activated Cell Sorter (FACS) on the 14th day after microwave ablation.Serum levels of interferon-γ (IFN-γ) and interleukin-4 (IL-4) were also detected using ELISA.Results The survival time (56.4 ± 4.3 days),tumor size (67.3 ± 6.1 mm2) and lung metastasis index (0.6 ± 0.4) in the microwave ablation plus DC tumor vaccinated group were all significantly lower than the corresponding averages in the microwave ablation and DC tumor vaccinated group.The proportions of splenic CD3 + T cells (27.8 ±10.3 ％) and CD4+ T cells (16.7 ± 8.3 ％) in the microwave ablation plus DC tumor vaccinated group were significantly larger than in the control group.Average serum levels of IFN-γ (41.8 ± 22.9 pg/ml) in the microwave ablation plus DC tumor vaccinated group were also significantly larger than in the control group,while the average serum level of IL-4 (15.4± 6.4 pg/ml) was significantly lower.Conclusions Microwave ablation and DC tumor vaccination together could have synergistic effects in treating experimental breast cancer,which might be closely related to the enhanced immune response. Key words: Breast cancer; Microwave ablation; Dendritic tumor vaccine; Tumor metastasis

Cellular immunotherapy using irradiated lung cancer cell vaccine co-expressing GM-CSF and IL-18 can induce significant antitumor effects.

BackgroundAlthough the whole tumor cell vaccine can provide the best source of immunizing antigens, there is still a limitation that most tumors are not naturally immunogenic. Tumor cells genetically modified to secrete immune activating cytokines have been proved to be more immunogenic. IL-18 could augment proliferation of T cells and cytotoxicity of NK cells. GM-CSF could stimulate dendritic cells, macrophages and enhance presentation of tumor antigens. In our study, we used mouse GM-CSF combined with IL-18 to modify Lewis lung cancer LL/2, then investigated whether vaccination could suppress tumor growth and promote survival.MethodsThe Lewis lung cancer LL/2 was transfected with co-expressing mouse GM-CSF and IL-18 plasmid by cationic liposome, then irradiated with a sublethal dose X ray (100 Gy) to prepare vaccines. Mice were subcutaneously immunized with this inactivated vaccine and then inoculated with autologous LL/2 to estimate the antitumor efficacy.ResultsThe studies reported here showed that LL/2 tumor cell vaccine modified by a co-expressing mouse GM-CSF and IL-18 plasmid could significantly inhibit tumor growth and increased survival of the mice bearing LL/2 tumor whether prophylactic or adoptive immunotherapy in vivo. A significant reduction of proliferation and increase of apoptosis were also observed in the tumor treated with vaccine of co-expressing GM-CSF and IL-18. The potent antitumor effect correlated with higher secretion levels of pro-inflammatory cytokines such as IL-18, GM-CSF, interferon-γ in serum, the proliferation of CD4+ IFN-γ+, CD8+ IFN-γ+ T lymphocytes in spleen and the infiltration of CD4+, CD8+ T in tumor. Furthermore, the mechanism of tumor-specific immune response was further proved by 51Cr cytotoxicity assay in vitro and depletion of CD4, CD8, NK immune cell subsets in vivo. The results suggested that the antitumor mechanism was mainly depended on CD4+, CD8+ T lymphocytes.ConclusionsThese results provide a new insight into therapeutic mechanisms of IL-18 plus GM-CSF modified tumor cell vaccine and provide a potential clinical cancer immunotherapeutic agent for improved antitumor immunity.

High-Throughput Sequencing Of T Cell Receptors Detects Signatures Of T Cell Repertoire That Predict MRD Status In Patients With Mantle Cell Lymphoma Undergoing Immunotransplantation

Background A clinical trial is ongoing at Stanford for MCL patients in first remission that interdigitates an autologous CpG-stimulated tumor cell vaccine with autologous peripheral blood stem cell transplant (PSCT) (NCT00490529). In this trial, blood samples collected before and after vaccination and serially post-transplant are assayed for minimal residual disease (MRD) and for T cell repertoire using the LymphoSIGHT™ sequencing method (Faham et al., Blood 2012). We identified a set of T cell clones that appear to be responding to the vaccine, and therefore we investigated whether the number of these clonotypes was correlated with MRD status. Methods Using universal primer sets, we amplified rearranged IgH variable (V), diversity, and joining (J) gene segments from genomic DNA. Amplified products were sequenced to obtain >1 million reads. The B cell tumor-specific sequence was identified for each patient based on its high frequency in the original tumor biopsy. The presence of the tumor cells was then monitored in serial blood samples with a sensitivity of 1 cell per million leukocytes. The same blood samples were used for amplification, sequencing and analysis of the entire TCRβ repertoire. To facilitate identification of tumor vaccine-induced TCRβ clonotypes, we sequenced the TCRβ repertoire immediately before and after the administration of both the priming vaccination and a booster vaccination. We developed a metric called the vaccine response score (V score). This metric is calculated for each clonotype and reflects the increase in frequency after the initial vaccination AND after the boost. The formula for calculating V score is: V = F1 x F2 x square root [1/ (|F1 – F2| + 1)], where F1 and F2 represent the fold-change of the priming and boost vaccinations, respectively. Clonotypes with a V score >10 were deemed to be vaccination-induced by virtue of these frequency changes. Results In a series of 12 vaccinated patients, the number of clonotypes with V score ≥ 10 ranged between 0 and 262, with a median of 57. We utilized an antigen-specific analysis to validate that clones with high V scores (≥ 10) were in fact tumor-specific. For this analysis, we incubated peripheral blood mononuclear cells (PBMCs) with the tumor and then sequenced the TCRβ repertoire from cells obtained after culture. Clones that were enriched after culture compared to pre-stimulation PBMCs were deemed to be antigen-specific. These clones that are antigen-specific are highly likely to have a high V score compared to a random frequency-matched set of clones (P two tailed = 1.8 x 10-10), providing further evidence that clones with a high V score are tumor-specific. We then analyzed the relationship between V score and clinical outcome. Patients could be stratified into two groups with “high” (> 25) or “low” (<25) numbers of vaccine-responsive clonotypes. Patients in the high V score group, who had larger numbers of putative tumor-specific T cells, were more likely to have sustained molecular remission during the first-year post-transplant compared with patients in the low V score group (P = 0.018) (Figure 1). Conclusions T cell repertoire analysis identified clonotypes responding to the vaccination, and the presence of these vaccine-specific clonotypes correlates with MRD positivity at the important landmark of one year post-PSCT. Further analysis of additional patients enrolled on the MCL trial is ongoing. This data underscores the prognostic relevance of the sequencing-based V score metric and provides a novel approach for assessment of cancer immunotherapy responses. Disclosures: Faham: Sequenta: Employment, Equity Ownership, Membership on an entity’s Board of Directors or advisory committees.

Impact of androgen deprivation therapy on the thymus and the production of naïve T-cells

Purpose A clinical trial was conducted employing androgen deprivation therapy (ADT) +/- vaccine in patients (pts) with rising prostate specific antigen (PSA) after definitive therapy but no disease visible on bone or computed tomography (CT) scan. The primary endpoint was to determine if a whole tumor cell vaccine could prolong PSA recovery, but a key secondary endpoint was to evaluate the impact of ADT on the thymus and production of naive T-cells. Previous studies suggest that ADT regenerates the thymus (in mice) and increases naive T-cell production in humans [1]. Methods

High-dose IL-2 in metastatic melanoma: better survival in patients who also received patient-specific autologous tumor cell vaccine

Meeting abstracts Treatment with high-dose Interleukin-2 (IL-2) has been associated with long-term survival in small proportion of metastatic melanoma patients. We recently reported a median survival of 15.6 months, and a 20% 5-year survival rate for 150 such patients who were hospitalized for high

Localized interleukin‐12 delivery for immunotherapy of solid tumours

Interleukin (IL)-12 is the key cytokine in the initiation of a Th1 response and has shown promise as an anti-cancer agent; however, clinical trials involving IL-12 have been unsuccessful due to toxic side-effects. To address this issue, lentiviral vectors were used to transduce tumour cell lines that were injected as an autologous tumour cell vaccine. The focus of the current study was to test the efficacy of this approach in a solid tumour model. SCCVII cells that were transduced to produce IL-12 at different concentrations were then isolated. Subcutaneous injection of parental SCCVII cells results in tumour development, while a mixture of IL-12-producing and non-producing cells results in tumour clearance. Interestingly, when comparing mice injected a mixture of SCCVII and either high IL-12-producing tumour cells or low IL-12-producing tumour cells, we observed that mixtures containing small amounts of high producing cells lead to tumour clearance, whereas mixtures containing large amounts of low producing cells fail to elicit protection, despite the production of equal amounts of total IL-12 in both mixtures. Furthermore, immunizing mice with IL-12-producing cells leads to the establishment of both local and systemic immunity against challenge with SCCVII. Using depletion antibodies, it was shown that both CD4+ and CD8+ cells are crucial for therapy. Lastly, we have established cell clones of other solid tumour cell lines (RM-1, LLC1 and moto1.1) that produce IL-12. Our results show that the delivery of IL-12 by cancer cells is an effective route for immune activation.

Abstract PL07-03: Mechanisms of protective tumor immunity.

Abstract Efficacious cancer immunotherapies will likely require combinations of strategies that enhance tumor antigen presentation and antagonize negative immune regulatory circuits. We demonstrated that vaccination with irradiated, autologous melanoma cells engineered to secrete GM-CSF followed by antibody blockade of CTLA-4 accomplishes clinically significant tumor destruction with minimal toxicity in a majority of stage IV metastatic melanoma and some advanced ovarian carcinoma patients. The extent of tumor necrosis in post-treatment biopsies was linearly related to the natural logarithm of the ratio of infiltrating CD8+ effector T cells to FoxP3+ Tregs, suggesting that further Treg inhibition might increase the frequency of clinical responses. Through an analysis of cytokine deficient mice, we delineated a critical role for GM-CSF in Treg homeostasis. GM-CSF is required for the expression of the phosphatidylserine binding protein MFG-E8 in antigen presenting cells, whereas the uptake of apoptotic cells by phagocyte-derived MFG-E8 maintains peripheral Treg activity. The pharmacologic inhibition of MFG-E8 function through genetic or engineering-based approaches blocks Treg induction, which intensifies vaccine-induced responses, leading to the regression of established tumors in mice. The clinical translation of these therapeutic strategies to Phase I testing in humans is underway. The detailed analysis of patients achieving sustained clinical benefits from irradiated, autologous GM-CSF secreting tumor cell vaccines and CTLA-4 antibody blockade also affords a rich opportunity to identify antigens associated with immune-mediated tumor destruction and to delineate mechanisms of therapeutic immunity. We elucidated several of the molecular pathways that underlie these antitumor effects, including the NKG2D system and multiple secreted/or cell surface proteins that contribute to tumor promoting inflammation. The therapy-induced antibodies manifest functional activity in vitro, antagonizing tumor cell survival, invasive potential, and angiogenesis. These findings support a key role for humoral immunity in tumor destruction, and highlight interest in more detailed characterization of the antitumor B cell repertoire in vaccinated patients. Citation Information: Mol Cancer Ther 2013;12(11 Suppl):PL07-03. Citation Format: Glenn Dranoff. Mechanisms of protective tumor immunity. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr PL07-03.

Tumor cells loaded with α-galactosylceramide promote therapeutic NKT-dependent anti-tumor immunity in multiple myeloma

Tumor cells have been used as the tumor antigen sources for developing cancer vaccines. Due to their low immunogenicity, tumor antigens are combined with various adjuvants to enhance immunogenicity of cancer vaccines. Among them, a natural killer T cell (NKT)-ligand, α-galactosylceramide (αGC) has been reported as a powerful adjuvant showing therapeutic effects in solid tumors as well as hematological malignancies including lymphoma. In this study, we applied αGC-based tumor cell vaccine in mouse multiple myeloma model. The αGC-loaded MOPC315BM myeloma cell vaccine efficiently retarded tumor growth, induced regression of established tumors, and protected surviving mice from tumor rechallenge. Therapeutic responses were associated with induction of strong humoral immune responses, including myeloma-specific antibodies, and cellular immune responses, including myeloma-specific CD8+ cytotoxic T lymphocytes and memory T cells. In addition, regulatory T cells were significantly decreased in mice that received the αGC-loaded myeloma cell vaccine. Thus, our results demonstrated that αGC-loaded myeloma vaccine efficiently promoted NKT-dependent anti-tumor immunity in a mouse model. These findings are informative for improving the efficacy of tumor-cell-based immunotherapy for patients with MM and other CD1d-expressing tumors.

Immunological suppression of head and neck carcinoma by dendritic cell tumor fusion vaccine

The successful treatment of cancer with dendritic cell (DC) tumor vaccine is highly dependent on the efficacy of antigen presentation and T cell activation. In the present study, a novel vaccine of DCs fused with autologous tumor cells was introduced, which had a marked ability to suppress head and neck carcinoma. DCs generated from the bone marrow of mice were fused with an autologous tumor cell line using polyethylene glycol (PEG). To observe the fused cells, confocal microscopy and FACS analysis were performed. Subsequently, the activation and proliferation of T cells, as well as animal experiments, were examined. The efficiency of DC/tumor fusion was 18.03% and T cells were well-activated by the hybrids. The volumes of tumors on the tumor-bearing mice were controlled, survival time of tumor-bearing mice was prolonged and the level of IFN-γ in serum was significantly increased compared with the control group and lysate-pulsed DC group. The results indicate that the DC/tumor fusion vaccine appears to be more effective than DCs pulsed with tumor lysate for the treatment of head and neck carcinoma, which may be useful in future clinical studies.

Status of Active Specific Immunotherapy for Stage II, Stage III, and Resected Stage IV Colon Cancer

Colorectal cancer is one of the most prevalent types of cancer worldwide and a leading cause of cancer-related mortality. The reported incidence of recurrent disease increases with the stage, and the 5-year survival rate is poor, especially for tumors with regional spread and for late-stage disease. This has prompted the search for more advanced treatment options, and therefore avenues for clinical testing of rationally designed immunotherapeutic strategies, including vaccination, as adjuvant treatment are being explored. In this review, we discuss the study design and results of the clinical trials that have been conducted using active specific immunotherapy in colorectal cancer, including autologous and allogeneic tumor cell vaccines, peptide vaccines, viral-vector-based vaccines, and dendritic-cell-based vaccines as well as some future recommendations.

Comparative antitumor effect among GM-CSF, IL-12 and GM-CSF+IL-12 genetically modified tumor cell vaccines

Genetically modified cells have been shown to be one of the most effective cancer vaccine strategies. An evaluation is made of the efficacy of both preventive and therapeutic antitumor vaccines against murine melanoma, using C57BL/6 mice and irradiated B16 tumor cells expressing granulocyte and macrophage colony-stimulating factor (GM-CSF), interleukin-12 (IL-12) or both. Tumor was transplanted by the injection of wild-type B16 cells. Tumor growth and survival were measured to evaluate the efficacy of vaccination. Specific humoral response and immunoglobulin G (IgG) switch were evaluated measuring total IgG and IgG1 and IgG2a subtypes against tumor membrane proteins of B16 cells. In preventive vaccination, all treated groups showed delayed tumor growth. In addition, the group vaccinated to express only GM-CSF achieved 100% animal survival (P<0.005). Vaccination with GM-CSF+IL-12-producing B16 cells yielded lesser results (60% survival, P<0.005). Furthermore, all surviving animals remained disease-free after second tumor implantation 1 year later. The therapeutic vaccination strategies resulted in significantly delayed tumor growth, mainly using B16 cells producing GM-CSF+IL-12 cytokines, with 70% tumor growth inhibition (P<0.001)-although none of the animals reached overall survival. The results obtained suggest that the GM-CSF+IL-12 combination only increases the efficacy of therapeutic vaccines. No differences in classical regulatory T cells were found among the different groups.

Autologous CLL cell vaccination early after transplant induces leukemia-specific T cells

Patients with advanced hematologic malignancies remain at risk for relapse following reduced-intensity conditioning (RIC) allogeneic hematopoietic stem cell transplantation (allo-HSCT). We conducted a prospective clinical trial to test whether vaccination with whole leukemia cells early after transplantation facilitates the expansion of leukemia-reactive T cells and thereby enhances antitumor immunity. We enrolled 22 patients with advanced chronic lymphocytic leukemia (CLL), 18 of whom received up to 6 vaccines initiated between days 30 and 45 after transplantation. Each vaccine consisted of irradiated autologous tumor cells admixed with GM-CSF-secreting bystander cells. Serial patient PBMC samples following transplantation were collected, and the impact of vaccination on T cell activity was evaluated. At a median follow-up of 2.9 (range, 1-4) years, the estimated 2-year progression-free and overall survival rates of vaccinated subjects were 82% (95% CI, 54%-94%) and 88% (95% CI, 59%-97%), respectively. Although vaccination only had a modest impact on recovering T cell numbers, CD8+ T cells from vaccinated patients consistently reacted against autologous tumor, but not alloantigen-bearing recipient cells with increased secretion of the effector cytokine IFN-γ, unlike T cells from nonvaccinated CLL patients undergoing allo-HSCT. Further analysis confirmed that 17% (range, 13%-33%) of CD8+ T cell clones isolated from 4 vaccinated patients by limiting dilution of bulk tumor-reactive T cells solely reacted against CLL-associated antigens. Our studies suggest that autologous tumor cell vaccination is an effective strategy to advance long-term leukemia control following allo-HSCT. Clinicaltrials.gov NCT00442130. NCI (5R21CA115043-2), NHLBI (5R01HL103532-03), and Leukemia and Lymphoma Society Translational Research Program.

Nanoparticles-based multi-adjuvant whole cell tumor vaccine for cancer immunotherapy

Whole cell tumor vaccine (WCTV), as a potential treatment modality, elicits limited immune responses because of the poor immunogenicity. To address this issue, researchers have attempted to transduce a cytokine adjuvant into tumor cells, but these single-adjuvant WCTVs curtail the high expectations. In present study, we constructed a multi-adjuvant WCTV based on the nanoparticles modified with cell penetrating peptide, which could facilitate the transportation of granulocyte macrophage colony-stimulating factor (GM-CSF) and interleukin 2 (IL-2) into tumor cells. After inactivation, as-designed multi-adjuvant WCTV exhibited programmed promotions on DC recruitment, antigen presentation, and T-cell activation. In vivo evaluations demonstrated the satisfactory effects on tumor growth suppression, metastasis inhibition, and recurrence prevention. Therefore, the nanoparticles-based multi-adjuvant WCTV may serve as a high-performance treatment for anti-tumor immunotherapy.

Targeting the Acute Myeloid Leukemic Stem Cell Compartment By Enhancing Tumor Cell-Based Vaccines

Harvesting the potential of the immune system in order to eradicate (residual) acute myeloid leukemia (AML) cells is the long pursued goal of immunotherapy in AML. Strategies using apoptotic tumor cell vaccines have been explored for many years, without significant clinical improvements. In recent years insight has been gained into the mechanisms activating and interfering with tumor-directed immunity. With the arrival of novel immune-modulating agents allowing for the interference with regulatory molecules and interaction with immune-propelling mechanisms, new doors are opening for increasing vaccination efficacy. Combined with advances in the design of apoptotic tumor-based vaccines, we are on the verge of creating an effective AML vaccine strategy, offering a much needed novel therapeutic option for this devastating disease.

Autophagy enhances antitumor immune responses induced by irradiated hepatocellular carcinoma cells engineered to express hepatitis B virus X protein

HepatitisB virusX protein (HBx) plays a critical role in malignancy transformation of hepatitisB virus (HBV)-related hepatocellular carcinoma (HCC). HBx sequence has been mapped with multi-epitopes which can elicit robust specific cytolytic T lymphocyte (CTL) responses. In our previous study, we developed an adenoviral vaccine against HBx oncoproteins to prevent growth of HBV-associated HCC. However, due to the weak immunogenicity of tumor antigen and pre-existing virus-neutralizing antibodies to the vaccine carrier preventing the vector from transducing target cells, the development of novel methods to enhance antigen presentation is urgently required. In the present study, we developed an adenoviral‑mediated genetic engineering of hepatoma cell vaccine to express HBx and to evaluate if the novel vaccine could elicit specific immune responses. Our data showed that the irradiated tumor cells engineered to express HBx could significantly induce antitumor immune responses invivo. The novel vaccine could induce a specific CTL response to recognize and lyse HBx-positive hepatoma cells invitro. Both CD8+ T and CD4+ Tlymphocytes are involved in the antitumor immune response induced by the novel vaccine. Furthermore, numerous autophagosomes and autolysosomes were found in the irradiated tumor cells engineered to express HBx. The results demonstrated that the irradiated HBx-modified tumor cell vaccine was a potent and promising therapeutic agent against HBx-positive HCC via induction of autophagy-enhanced CD8+ T and CD4+ Tlymphocyte-mediated antitumor immune responses. The present findings have implications for the development of clinical immunotherapy against HBV-associated HCC.

402. Randomized Phase II Trial of Post-Operative Adjuvant Chemotherapy ±FANG™ Autologous Tumor Cell Vaccine in Colorectal Carcinoma with Liver Metastases

402. Randomized Phase II Trial of Post-Operative Adjuvant Chemotherapy ±FANG™ Autologous Tumor Cell Vaccine in Colorectal Carcinoma with Liver Metastases

503. Randomized Phase II Trial of Adjuvant Autologous Tumor Cell Vaccine (FANG™) for High Risk Stage III/IV Ovarian Cancer: Preliminary Results

503. Randomized Phase II Trial of Adjuvant Autologous Tumor Cell Vaccine (FANG™) for High Risk Stage III/IV Ovarian Cancer: Preliminary Results

α-Galactosylceramide-loaded tumor cell vaccine promotes NKT-dependent protective immunity against multiple myeloma (P2096)

Abstract Despite progress in the treatment of multiple myeloma (MM), this disease still remains fatal in the majority of patients. Thus, new immunotherapeutic approaches are required to eradicate minimal residual myeloma cells. Tumor cells can be a source of tumor-specific antigens for immunotherapy. However, tumor cells have been weak to promote tumor-specific immune responses and maintain the tumor-specific responses with large amounts of tumor burden in vivo. In this study, we evaluated and compared the efficacy of the vaccination of autologous myeloma cells loaded with artificial ligand for T cell receptor of NKT cells, α-galactosylceramide (αGC), in the myeloma mouse model. Our results showed that αGC-loaded MOPC315BM myeloma cell vaccines efficiently retarded tumor growth, induced tumor regression against established tumor, and protected surviving mice from tumor rechallenge. The therapeutic responses were associated with an induction of strong humoral immune responses including anti-myeloma cell antibodies and cellular immune responses including myeloma-specific CD8+ cytotoxic T lymphocytes and memory T cells. In addition, we found that regulatory T cells were significantly decreased in mice receiving αGC-loaded myeloma cell vaccines. Thus, our results demonstrate that αGC-loaded myeloma vaccine efficiently promote NKT-dependent anti-tumor immunity in our study.

Abstract 3976: PD-1 blockade combined with TEGVAX (TLR agonists-enhanced GVAX) can induce regression of established palpable tumors.

Abstract Background: Cell-based vaccines have been developed for several types of tumors, but these vaccines have two critical shortcomings that weaken their clinical efficacy. The first of which is a limited capability to activate antigen presenting cells. Second, they fail to address critical immune checkpoint molecules that dampen the subsequent T-cell response against the established tumor. In order to optimize the activation of antigen presenting cells capable of marshaling both an innate and adaptive immune response against the tumor, we formulated a GM-CSF secreting tumor cell vaccine with multiple TLR agonists. To address the immune checkpoint signaling pathway, we combined our formulated vaccine with a blocking αPD-1 antibody in two mouse models of established tumor - one with melanoma and the other with tongue cancer. Methods: To optimize in vivo efficacy of anti-tumor T-cell response, we engineered TEGVAX, a GM-CSF secreting cell-based tumor vaccine formulated with GLA (TLR4 agonist) and R848 (TLR7/8 agonists), molecules that are amenable for clinical translation. We then combined TEGVAX with αPD-1 blocking antibody (G4 clone) in the murine B16 melanoma and SCCFVII tongue cancer model. Furthermore, we studied immunological parameters that correlated with in vivo anti-tumor response. Results: In both B16 and SCCFVII treatment models, TEGVAX demonstrated statistically significantly (p&amp;lt;0.01) enhanced anti-tumor responses in comparison to the parental cell vaccine in vivo. For tumor bearing mice treated with TEGVAX, these potent anti-tumor responses were correlated with a statistically significant increase in CD4+ and CD8+ T-cells that secrete IFNγ in the tumor microenvironment. TEGVAX treated mice also had significantly higher levels of tumor antigen p15E-specific cell mediated killing in vivo. Blockade of the PD-1 immune checkpoint pathway further augmented the therapeutic potential of TEGVAX and induced the regression of established B16 and SCCFVII tumors. Conclusion: When combined with αPD-1 antibody, TEGVAX was able to induce regression of established B16 and SCCFVII tumors. Our results with these combinatorial immunotherapeutic strategies provide preclinical evidence to support the translation of these reagents for HNSCC or melanoma patients that are refractory to standard treatment modalities. Citation Format: Ian-James Malm, Juan Fu, Drew Pardoll, Young J. Kim. PD-1 blockade combined with TEGVAX (TLR agonists-enhanced GVAX) can induce regression of established palpable tumors. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3976. doi:10.1158/1538-7445.AM2013-3976

Abstract 4573: STINGVAX - A novel tumor vaccine with cyclic dinucleotides - can induce potent anti-tumor responses in vivo.

Abstract Cyclic dinucleotides (CDN) are ubiquitous bacterial intracellular messengers, and they have recently been shown to also function as a pathogen associated molecular pattern (PAMP) molecules that are sensed by eukaryotic host Stimulator of Interferon Genes (STING) that can activate the TBK-1/IRF-3 signaling pathway to induce type I interferon and other co-regulated genes. CDN was found to induce STING dependent augmentation of T-cell priming in multiple vaccination models, potentially by activating dendritic cells. We formulated CDN with a GM-CSF secreting tumor cell vaccine (STINGVAX) to mobilize and as well as activate dendritic cells both in vitro and in vivo. STINGVAX was tested in a stringent B16 melanoma treatment model, and we demonstrated significant reduction of tumor growth rate in vivo. STINGVAX's anti-tumor response was correlated with increased tumor infiltrating CD8 T-cells as well as increased number of p15E tumor-specific cytotoxic T-cells. STINGVAX's in vivo anti-tumor response was T-cell dependent as well as STING dependent. When we combined STINGVAX with multiple TLR 4/7/8 agonists signaling through the MyD88/TRIF pathway that is distinct from CDN/STING/TBK-1 signaling treatment of palpable B16 tumor resulted in regression of 30-60% of these non-immunogenic tumors. When the STINGVAX treated tumor microenvironment was examined, both IFNγ+CD8+ and PD-L1 was upregulated, potentially demonstrating an adaptive immune resistance mechanism which would render STINGVAX an excellent candidate to be combined with anti-PD-1 blockade. Cumulatively, STINGVAX is a novel tumor vaccine with a high potential for translation in clinical oncology. Citation Format: Thomas W. Dubensky, Meredith L. Leong, David B. Kanne, Edward E. Lemmens, Ken Metchette, Weiqun Liu, Marcella Fasso, Juan Fu, Joshua J. Woodward, Drew Pardoll, Daniel A. Portnoy, Young J. Kim. STINGVAX - A novel tumor vaccine with cyclic dinucleotides - can induce potent anti-tumor responses in vivo. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4573. doi:10.1158/1538-7445.AM2013-4573