Tumor Cell Vaccine Research Articles

Clinical trial in progress: A phase 3 study of maintenance bi-shRNA-furin/GM-CSF-expressing autologous tumor cell vaccine in women with stage IIIb-IV high-grade epithelial ovarian cancer.

TPS5604 Background: Vigil is an immuno-stimulatory autologous cellular therapy, which uses patient tumor cells transfected with a plasmid encoding genes for GM-CSF and furin (to down regulate TGFβ 1&2). In Phase I, systemic immune activation was demonstrated in the majority of patients using an IFNƔ ELISPOT assay. A randomized Phase 2 assessment of Vigil maintenance therapy vs. observation in ovarian cancer demonstrated prolonged relapse free survival (RFS) (Oh J, Barve M, et al. Gynecologic Oncology, 2016; 143: 504–510.). Based on these observations, a Phase 3 study of maintenance Vigil therapy in patients with advanced ovarian cancer was initiated (NCT02346747). Methods: This is a multicenter, randomized, double-blind, placebo-controlled, Phase 3 study of maintenance Vigil in women with Stage IIIb,c or IV high-grade papillary serous/clear cell/ endometrioid ovarian, fallopian tube or primary peritoneal cancer. Patients will have a minimum of 4 and a maximum of 12 Vigil doses manufactured from tumor obtained at primary debulking surgery. Patients must achieve a complete clinical remission following primary surgery and chemotherapy before being randomized 1:1 to receive either monthly intradermal Vigil or placebo. Randomization is stratified by extent of surgical cytoreduction (complete/microscopic vs. macroscopic residual disease) and neoadjuvant vs. adjuvant chemotherapy. The primary objective is to compare RFS of subjects randomized to Vigil vs. placebo, and the key secondary objective is overall survival (OS). The sample size calculation of 222 patients assumes 24 months for accrual and 36 months of follow-up with a median RFS of 19 months from randomization, in the control group. This provides 90% power to detect a hazard ratio (HR) of 0.6 favoring Vigil at the 0.05 level of significance. To date, 61 patients have been randomized and an additional 55 patients are receiving chemotherapy in anticipation of randomization. Tumor tissue is being obtained from approximately 20 patients per month at multiple sites across the U.S. At their last meeting in January, 2017 the independent DSMB recommended that the study continue without change. Clinical trial information: NCT02346747.

Japanese Kampo medicine ninjin'yoeito synergistically enhances tumor vaccine effects mediated by CD8+ T cells.

Although Japanese traditional herbal medicine (Kampo) has been widely applied to the treatment of various diseases, including cancer, their mechanisms of action have not yet been elucidated in detail, particularly regarding their role in tumor immunology. The present study investigated the antitumor effects of the Japanese Kampo medicine, ninjin'yoeito (NYT; Ren-Shen-Yang-Rong-Tang in Chinese), which was orally administered with or without an irradiated tumor cell vaccine to a subcutaneous CT26 colon carcinoma tumor model. The irradiated tumor cell vaccine in a prophylactic setting significantly delayed tumor growth in mice fed a control diet, whereas a diet containing NYT alone did not exert any antitumor effects in vivo. However, the inhibition of tumor growth was significantly greater in vaccinated mice fed the NYT diet compared with in vaccinated mice given the control diet. These results suggest that NYT synergistically enhances the effects of the antitumor vaccine. The depletion of cluster of differentiation (CD)8+ T cells abrogated these effects, indicating that antitumor activity required CD8+ T cells. Furthermore, reductions in CD4+ CD25+ and forkhead box protein 3+ T regulatory cell numbers were more apparent between vaccinated mice fed the NYT diet and non-vaccinated mice fed the control diet than between vaccinated mice and non-vaccinated mice fed the control diet, suggesting that the weaker impact of T regulatory cells contributes to the augmentation of antitumor immunity by CD8+ T cells in vaccinated mice fed with NYT. Overall, these results indicate that NYT synergistically enhances the effects of the prophylactic tumor vaccine mediated by CD8+ T cells and that this Japanese Kampo medicine has potential as a useful adjuvant agent for cancer immunotherapy.

Therapeutic Efficacy of 4-1BB Costimulation Is Abrogated by PD-1 Blockade in a Model of Spontaneous B-cell Lymphoma.

Combinations of mAbs that target various components of T-cell activation/inhibition may work synergistically to improve antitumor immunity against cancer. In this study, we investigated the therapeutic potential of combining an anticancer vaccination strategy with antibodies targeting an immune stimulatory (4-1BB) and immune inhibitory (PD-1) receptor, in a preclinical model of spontaneously arising c-Myc-driven B-cell lymphoma. In Eμ-myc transgenic mice, we reveal that 4-1BB agonistic mAb treatment alone was sufficient to drive antitumor immunity and prevent disease progression in 70% of mice. When combined with an α-GalCer-loaded, irradiated tumor cell vaccine, 4-1BB mAb treatment led to increased expansion of effector CD8 T-cell populations and protection of long-term surviving mice against tumor rechallenge. Unexpectedly, PD-1 blockade did not provide therapeutic benefit. The T-cell-promoting effects and antitumor activity of 4-1BB mAb were diminished when used simultaneously with a PD-1-blocking mAb. This was associated with a rapid and dramatic reduction in effector CD8+ T-cell subsets in the presence of PD-1 blockade. These findings reveal that supporting T-cell activation therapeutically is effective for controlling B-cell lymphomas; however, caution is required when combining antibody-mediated modulation of both costimulatory and coinhibitory T-cell receptors. Cancer Immunol Res; 5(3); 191-7. ©2017 AACR.

Irradiated VEGF164-modified tumor cell vaccine protected mice from the parental tumor challenge.

Vascular endothelial growth factor (VEGF) is an important regulating molecule of angiogenesis in tumor formation and progression. Cancer cells always secrete VEGF to stimulate angiogenesis that facilitate growth and invasion of the tumor. In this study, we established a VEGF164 overexpressing LL/2 lung cancer cell model and found that the postirradiated VEGF164-modified tumor cells protected the host against the challenge with LL/2 wild-type tumor cells. Histochemical assay showed that there were large areas of tumor necrosis with macrophage infiltration in the mice vaccinated with the VEGF164-modified tumor vaccine. T-cells isolated from the vaccinated mice showed cytotoxicity against the parental tumor cells in a dose-dependent manner. Meanwhile, sera from the mice vaccinated with LL/2-VEGF164 showed higher titers of antibodies against parental tumor cells compared with the nonvaccinated groups. Our results indicated that VEGF164-modified tumor vaccine could modulate host antitumor immune response and hold therapeutic potential for cancer.

Therapeutic vaccination based on side population cells transduced by the granulocyte-macrophage colony-stimulating factor gene elicits potent antitumor immunity.

Among cancer immunotherapies, granulocyte-macrophage colony-stimulating factor (GM-CSF) gene-transduced tumor cell vaccine (GVAX) therapies appear promising and have been shown to be safe and effective in multiple clinical trials. However, the antitumor efficacies of GVAX therapy alone are in some cases limited. Here we showed that GVAX therapy targeting cancer stem cells (CSCs) substantially suppressed tumor development in syngeneic immunocompetent mice recapitulating normal immune systems. CSCs were isolated as side population (SP) cells from 4T1 murine breast carcinoma cell line and transduced with GM-CSF gene delivered by non-transmissible Sendai virus (4T1-SP/GM). Impaired tumorigenicity of subcutaneously injected 4T1-SP/GM depended on CD8+ T cells in concert with CD4+ T cells and natural killer cells. Mice therapeutically vaccinated with irradiated 4T1-SP/GM cells had markedly suppressed tumor development of subcutaneously transplanted 4T1-SP cells compared with those treated with irradiated cells of non-transduced 4T1-SP cells or non-SP (4T1-NSP/GM) cells. Tumor suppression was accompanied by the robust accumulation of mature dendritic cells at vaccination sites and T-helper type 1-skewed systemic cellular immunity. Our results suggested that CSC cell-based GVAX immunotherapy might be clinically useful for inducing potent tumor-specific antitumor immunity.

Silencing of Foxp3 enhances the antitumor efficacy of GM-CSF genetically modified tumor cell vaccine against B16 melanoma.

The antitumor response after therapeutic vaccination has a limited effect and seems to be related to the presence of T regulatory cells (Treg), which express the immunoregulatory molecules CTLA4 and Foxp3. The blockage of CTLA4 using antibodies has shown an effective antitumor response conducing to the approval of the human anti-CTLA4 antibody ipilimumab by the US Food and Drug Administration. On the other hand, Foxp3 is crucial for Treg development. For this reason, it is an attractive target for cancer treatment. This study aims to evaluate whether combining therapeutic vaccination with CTLA4 or Foxp3 gene silencing enhances the antitumor response. First, the “in vitro” cell entrance and gene silencing efficacy of two tools, 2′-O-methyl phosphorotioate-modified oligonucleotides (2′-OMe-PS-ASOs) and polypurine reverse Hoogsteen hairpins (PPRHs), were evaluated in EL4 cells and cultured primary lymphocytes. Following B16 tumor transplant, C57BL6 mice were vaccinated with irradiated B16 tumor cells engineered to produce granulocyte-macrophage colony-stimulating factor (GM-CSF) and were intraperitoneally treated with CTLA4 and Foxp3 2′-OMe-PS-ASO before and after vaccination. Tumor growth, mice survival, and CTLA4 and Foxp3 expression in blood cells were measured. The following results were obtained: 1) only 2′-OMe-PS-ASO reached gene silencing efficacy “in vitro”; 2) an improved survival effect was achieved combining both therapeutic vaccine and Foxp3 antisense or CTLA4 antisense oligonucleotides (50% and 20%, respectively); 3) The blood CD4+CD25+Foxp3+ (Treg) and CD4+CTLA4+ cell counts were higher in mice that developed tumor on the day of sacrifice. Our data showed that tumor cell vaccine combined with Foxp3 or CTLA4 gene silencing can increase the efficacy of therapeutic antitumor vaccination.

MTE13.02 Basic Immunology for the Clinician

MTE13.02 Basic Immunology for the Clinician

SC05.04 Lung Cancer Vaccines: An Update

SC05.04 Lung Cancer Vaccines: An Update

Specific immunotherapy in renal cancer: a systematic review.

Renal cell cancer (RCC) is the tenth most common malignancy in adults. In recent years, several approaches of active and passive immunotherapy have been studied extensively in clinical trials of patients with RCC. The aim of this systematic review was to assess the clinical efficacy of various approaches of specific immunotherapy in patients with RCC. We searched Medline, Scopus, CENTRAL, TRIP, DART, OpenGrey and ProQuest without any language filter through to 9 October 2015. One author reviewed search results for irrelevant and duplicate studies and two other authors independently extracted data from the studies. We collated study findings and calculated a weighted treatment effect across studies using Review Manager (version 5.3. Copenhagen: The Nordic Cochrane Centre, the Cochrane Collaboration). We identified 14 controlled studies with 4013 RCC patients after excluding irrelevant and duplicate studies from 11,319 references retrieved from a literature search. Overall, five autologous tumor cell vaccines, one peptide-based vaccine, one virus-based vaccine and one dendritic cell (DC)-based vaccine were studied in nine controlled studies of active specific immunotherapies. A total of three passive immunotherapies including autologous cytokine-induced killer (CIK) cells, auto lymphocyte therapy (ALT) and autologous lymphokine-activated killer (LAK) cells were studied in four controlled studies. The clinical efficacy of tumor lysate-pulsed DCs, with CIK cells was studied in one controlled trial concurrently. The overall quality of studies was fair. Meta-analysis of seven studies showed that patients undergoing specific immunotherapy had significantly higher overall survival (OS) than those in the control group [hazard ratio (HR) = 0.72; 95% confidence interval (CI) = 0.58-0.89, p = 0.003]. In addition, a meta-analysis of four studies showed that there was a significant difference in progression-free survival (PFS) between patients undergoing specific immunotherapy and patients in control groups (HR = 0.86; 95% CI = 0.73-1, p = 0.05). Results of this systematic review suggest that some specific immunotherapies such as Reniale, ACHN-IL-2, Newcastle disease virus (NDV) virus-infected autologous tumor cells, ALT and CIK treatment could be beneficiary for the treatment of patients with RCC.

Immunological consequences of immunization with tumor lysate vaccine and propranolol as an adjuvant: A study on cytokine profiles in breast tumor microenvironment

In this study, we sought out to study the anti-cancer effects of propranolol (Pro) in combination with tumor lysate vaccine on lymphocyte proliferation activities as well as on IL-2, IL-4, IL-10, IL-12, IL-17 and IFN-γ cytokine concentration in the tumor microenvironment (TME). A tumor model was established in inbred Balb/C mice using transplantation of tumor to the flank of native mice. Tumor-bearing mice were immunized with lysate tumor cells (vaccine), a combination of Pro/Vaccine (Vac). Control groups consisted of tumor-bearing mice receiving only propranolol or PBS three times with one week interval via subcutaneous (s.c) injection. One week after the last immunization, tumor was removed, homogenate was prepared and the levels of IL-12, IL-17, 1L-2, IL-10, IL-4, IFN-γ cytokine concentrations were evaluated by commercial ELISA kits. In addition, spleen cell suspension was used for the lymphocyte proliferation assay using the BrdU method. Results from this study indicated that Pro/Vac had the ability to significantly increase lymphocyte proliferation, and to suppress tumor growth. Administration of breast tumor lysates with propranolol increased the concentration of IL-12, IL-17, 1L-2 and IFN-γ cytokines in tumor microenvironment. This study has proved the efficiency of propranolol as an adjuvant in combination with the tumor vaccine model on tumor suppression via cytokine pattern modulation in tumor microenvironment.

A novel cancer vaccine with the ability to simultaneously produce anti-PD-1 antibody and GM-CSF in cancer cells and enhance Th1-biased antitumor immunity.

Tumor escape from immune-mediated destruction has been associated with immunosuppressive mechanisms that inhibit T-cell activation. A promising strategy for cancer immunotherapy is to disrupt key pathways regulating immune tolerance, such as program death-1 (PD-1/PD-L1) pathway in the tumor environment. However, the determinants of response to anti-PD-1 monoclonal antibodies (mAbs) treatment remain incompletely understood. In murine models, PD-1 blockade alone fails to induce effective immune responses to poorly immunogenic tumors, but is successful when combined with additional interventions, such as cancer vaccines. Novel cancer vaccines combined with antibody may offer promising control of cancer development and progression. In this investigation, we generated a novel tumor cell vaccine simultaneously expressing anti-PD-1 mAbs and granulocyte-macrophage colony stimulating factor (GM-CSF) in CT26 colon cancer and B16-F10 melanoma. The antitumor effect of the vaccine was verified by therapeutic and adoptive animal experiments in vivo. The antitumor mechanism was analyzed using Flow cytometry, Elispot and in vivo intervention approaches. The results showed that tumor cell vaccine secreting PD-1 neutralizing antibodies and GM-CSF induced remarkable antitumor immune effects and prolonged the survival of tumor-bearing animals compared with animals treated with either PD-1 mAbs or GM-CSF alone. Antitumor effects and prolonged survival correlated with strong antigen-specific T-cell responses by analyzing CD11c+CD86+ DC, CD11b+F4/80+ MΦ cells, increased ratio of Teff/Treg in the tumor microenvironment, and higher secretion levels of Th1 proinflammatory cytokines in serum. Furthermore, the results of ELISPOT and in vivo blocking strategies further confirmed that the antitumor immune response is acquired by CD4 and CD8 T immune responses, primarily dependent on CD4 Th1 immune response, not NK innate immune response. The combination of PD-1 blockade with GM-CSF secretion potency creates a novel tumor cell vaccine immunotherapy, affording significantly improved antitumor responses by releasing the state of immunosuppressive microenvironment and augmenting the tumor-reactive T-cell responses.

Timing Is Everything: Combining Post-Transplantation Adoptive Cell Therapy and Tumor Vaccines

Timing Is Everything: Combining Post-Transplantation Adoptive Cell Therapy and Tumor Vaccines

38P - Antitumor immunity against hCG&bgr; induced by a tumor cell vaccine modified with a fusion gene of hCG&bgr; and polyarginines

38P - Antitumor immunity against hCG&bgr; induced by a tumor cell vaccine modified with a fusion gene of hCG&bgr; and polyarginines

Enhanced anti-tumor immunity against breast cancer induced by whole tumor cell vaccines genetically modified expressing α-Gal epitopes.

Whole tumor cell vaccines have shown much promise, but demonstrated poor efficiency in phaseIII trials. In this study, we modified MDA-MB‑231 tumor cells (MDA-MB‑231Gal+) to express α-1, 3-galactosyltransferase (α-1, 3-GT) protein, to potentially enhance antitumor effect of whole tumor cell vaccines. MDA-MB‑231 tumor cell vaccines were transfected with a reconstructed lentiviral containing α-1, 3-GT genes. Tumor growth, tumorigenesis and survival of Hu-NOD-SCID mice were observed when tumor-bearing mice were injected with tumor cell vaccines. Proliferation and apoptosis in MDA-MB‑231 tumor xenografts were observed by immunohistochemistry. The levels of cytokine secretion in the serum of mice were tested by ELISA. CD8+ T cells infiltrating tumors were assessed by flow cytometry. MDA-MB‑231Gal+ cells expressed active α-1, 3-GT and produced α-Gal invitro. MDA-MB‑231Gal+ cell vaccines suppressed tumor growth and tumorigenesis in immunized Hu-NOD-SCID mice. Additionally, decrease of TGF-β, IL-10 and increase of INF-γ, IL-12 were observed in tumor cell vaccinated mice. Furthermore, the cell vaccines enhanced infiltration of cytotoxic CD8+ T cells in the tumor microenvironment of immunized mice. The MDA-MB‑231Gal+ cell vaccines modified α-1, 3-GT genes improved the antitumor effect.

Abstract CT105: Randomized trial of dendritic vs tumor cell patient-specific vaccines: 5-year analysis

Abstract Eltrapuldencel-T (CLBS20) consists of autologous dendritic cells loaded with antigens from irradiated, self-renewing, autologous tumor cells that potentially present the entire repertoire of unique patient-specific tumor-associated antigens resulting from nonsynonymous mutations in each patient's melanoma tumor cell line. In a single-arm phase 2 trial, metastatic melanoma patients treated with s.c. injections of CLBS20 had a 2-year overall survival (OS) of 73% (NCT00948480). In a randomized phase 2 trial (NCT00436930), 2-year OS was 72% compared to 31% for a tumor cell vaccine (TCV) consisting of irradiated cancer cells from an autologous tumor cell line. Mild local injection site reactions was the most common toxicity. This report focuses on 5-year follow up data from the randomized trial. During October 2007 to February 2011 42 patients were randomized 1:1 to receive CLBS20 or TCV. After resection of a metastatic tumor, if/when a cell line was established, patients were eligible for randomization if/when they were referred by their managing physician. Both products were mixed in 500 micrograms GM-CSF and injected s.c. weekly for three weeks, then monthly for up to 5 months. Cell lines were successfully established rapidly enough for possible clinical use for 78/183 (43%); 42/78 (54%) patients were referred for randomization. The median time from tumor submission to cell line success was 3.0 months, then 2.5 weeks for safety testing and documentation, then another 3.7 months to randomization. At the time of tumor harvest 24 patients were stage 4 and 18 were recurrent stage 3; at randomization 33 were stage 4 and 9 stage 3. Trends toward imbalances of baseline characteristics were biased against the CLBS20 arm (elevated LDH, detectable disease, brain metastases). There were no differences in tumor resection site, days in cell culture, or days to randomization. Because of leukapheresis and dendritic cell production for CLBS20, the median time from randomization to first dose was 43 days for CLBS20 vs 8 days for TCV. All patients were treated as randomized; survival was calculated from randomization date. At this analysis, 33 (79%) were dead and the 9 survivors had been followed 5 years. OS was higher in the CLBS20 arm: median 42.2 vs 19.9 months for all and 40.4 vs 16.9 for stage 4 patients, and in subsets defined by measurable disease, and serum LDH. The only variable associated with 3-year OS was randomization to CLBS20 (p = 0.018). A patient with refractory progressive measurable disease experienced a delayed complete response that was ongoing at 5 years. In an era before widespread use of anti-BRAF/anti-MEK and anti-checkpoint agents, CLBS20 monotherapy was associated with encouraging 5-year OS. Because of its unique mechanism of action, absence of toxicity, and apparent benefit regardless of tumor burden, CLBS20 is worthy of further evaluation as a monotherapy or in combination with other anti-melanoma therapies. Citation Format: Robert O. Dillman, Edward F. McClay, Thomas T. Amatruda, Carol DePriest, Denysha J. Carbonell, Andrew N. Cornforth. Randomized trial of dendritic vs tumor cell patient-specific vaccines: 5-year analysis. [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 CT105.

Immunotherapy in non-small cell lung cancer: the clinical impact of immune response and targeting.

Non-small cell lung cancer (NSCLC) remains the leading cause of cancer-related death worldwide. In recent years, through a better understanding of the interactions between the immune system and tumor cells (TC), immunotherapy has emerged as a promising therapeutic strategy. Chemotherapy has long been reported to interfere with the immune response to the tumor and conversely, anti-tumor immunity may add to those effects. Anti-tumor vaccines, such as MAGE-A3, Tecetomide, TG4010, CIMAvax, tumor cell vaccines and dendritic cell (DC) vaccines emerged as potent inducers of the immune response against the tumor. More recently the approval of the anti-programmed cell death 1 (anti-PD-1) monoclonal antibodies nivolumab and pembrolizumab for previously treated advanced squamous and non-squamous NSCLC, as well as other immune checkpoint inhibitors delivering promising results, has radically transformed the therapeutic landscape of NSCLC. Combination strategies now appear as the next step. Notwithstanding these successes, immunotherapy still holds significant drawbacks and currently several improvements are needed before routine use in clinical practice, including identification of robust biomarkers for optimal patient selection, as well as defining the best way to evaluate response.

The Chinese Herbal Mixture Tien-Hsien Liquid Augments the Anticancer Immunity in Tumor Cell-Vaccinated Mice.

Background. The Chinese herbal mixture, Tien-Hsien liquid (THL), has been used as an anticancer dietary supplement for more than 20 years. Our previous studies have shown that THL can modulate immune responseand inhibit tumor growth. In this study, we further evaluated the effect of THL on anticancer immune response in mice vaccinated with γ-ray-irradiated tumor cells. Methods. The antitumor effect of THL was determined in mice vaccinated with low-tumorigenic CT-26-low colon cancer cells or γ-ray-irradiated high-tumorigenic CT-26-high colon cancer cells. The number of natural killer (NK) cells and T lymphocytes in the spleen was analyzed by flow cytometry. The tumor-killing activities of NK cells and cytotoxic T lymphocytes (CTLs) were analyzed by flow cytometry using YAC-1 and CT-26-high cells, respectively, as target cells. The levels of IFN-γ, IL-2, and TNF-α were determined by ELISA. Results. THL suppressed the growth of CT-26-high tumor in mice previously vaccinated with low-tumorigenic CT-26-low cells or γ-irradiated CT-26-high cells. THL increased the populations of NK cells and CD4+ T lymphocytes in the spleen and enhanced the tumor-killing activities of NK cells and CTL in mice vaccinated with γ-irradiated CT-26-high cells. THL increased the production of IFN-γ, IL-2, and TNF-α in mice vaccinated with γ-irradiated CT-26-high cells. Conclusion. THL can enhance the antitumor immune responses in mice vaccinated with killed tumor cells. These results suggest that THL may be used as a complementary medicine for cancer patients previously treated with killed tumor cell vaccines, radiotherapy, or chemotherapy.

Cancer Vaccines: Past, Present, and Future.

Cancer is a common and potentially deadly disease. Some of the cancers may be difficult to treat by conventional means such as surgery, radiation, and chemotherapy, but may be controlled by the stimulation of the immune response of the body with the help of cancer vaccines. The use of vaccines for preventing infections by oncogenic viruses such as hepatitis B virus and human papilloma virus has been extremely successful in reducing the incidence of cancers resulting from these infections. The use of vaccines for treating cancers that are not due to viral infections and that are already established is currently the object of numerous clinical trials. Several types of cancer vaccines are being tried. These include antigen vaccines, tumor cell vaccines, dendritic vaccines, deoxyribonucleic acid vaccines, and viral vector vaccines. The development of these therapeutic vaccines is proving difficult with only 1 recent success. However, there is significant enthusiasm and optimism regarding the development of effective therapeutic vaccines stemming from the fact that our understanding regarding the cancer immunology is considerably enhanced in recent years. This expanded knowledge regarding the mechanisms that cancers use to escape the immune system is likely to open new avenues in modulating the immune response to cancer, thus enhancing the effectiveness of therapeutic cancer vaccines.

Abstract P4-04-16: Characterization of an autologous tumor cell vaccine against breast cancer in mice

Abstract The vast majority of breast cancer-related deaths are due to progressive recurrences of non-metastatic disease. Current adjuvant therapies aimed at preventing breast cancer recurrence are ineffective for tens of thousands of women each year. In addition, current adjuvant therapies carry significant co-morbidities. Active, specific immune-based strategies have the potential to train a patient's immune system to recognize and eliminate occult metastases. Here, we explore autologous tumor cell vaccines (ATCVs) as a strategy to prevent tumor recurrence and improve survival. Because >90% of breast cancer patients undergo resection, autologous tumor cells are readily available for the production of personalized vaccine. Patient-specific vaccination is particularly attractive for breast cancer which is highly heterogeneous. The major disadvantage of ATCVs, is poor immunogenicity. Thus, in order to develop an effective, immunogenic ATCV against breast cancer, we wanted to understand the features of immunogenicity. In this study, we evaluated the immunogenicities of two murine breast cancer cell lines, EMT6 and 4T1. For tumor protection studies, BALB/c female mice were given priming and booster vaccinations, ten days apart, with 1,000,000 irradiated (100Gy) cells. Ten days after the booster vaccination, mice were challenged with live tumor cells. Mice vaccinated with EMT6 cells were completely protected against a live EMT6 challenge in 80% of mice. However, mice vaccinated with irradiated 4T1 cells failed to provide any protection against a live 4T1 challenge. Most interestingly, when mice were vaccinated with a mixture of irradiated EMT6 and 4T1 cells, the protective response against EMT6 challenge was significantly diminished as 60% of mice developed tumors. This finding implied that non-immunogenic 4T1 cells released one or more immunosuppressive factors that inhibited anti-EMT6 immunity. Thus, we investigated the levels of different immunosuppressive cytokines, GM-CSF, IL-6, MCP-1, TGF-β and VEGF released by both 4T1 and EMT6 cells before and after irradiation. Of the different cytokines measured, we found that only GM-CSF is produced at significantly higher levels by 4T1 cells than EMT6 cells. Since at higher levels (>200pg/ml) GM-CSF can induce the accumulation of large amounts of myeloid derived suppressor cells (MDSCs) in the tumor site and lymphoid organs, we believe it to be the reason for the failure of the hybrid vaccine. Future studies will determine if blocking GM-CSF production by 4T1 cells will decrease the accumulation of MDSCs and subsequently increase anti-tumor immunity. Citation Format: Ravindranathan S, Kurtz SL, Smith SG, Koppolu B, Nguyen KG, Zaharoff DA. Characterization of an autologous tumor cell vaccine against breast cancer in mice. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P4-04-16.

Progression of immunotherapy in gastric cancer

Gastric cancer is a malignant disease with high incidence and mortality. The therapeutic methods for advanced gastric cancer, including chemotherapy and targeted therapy are very limited. Immunotherapy is a new method for cancer treatment. The immune checkpoint inhibitors developed for cancer treatment mainly target the CTLA-4 and PD-1/PD-L pathways. There have already been several inhibitors approved for the treatment of melanoma and non-small cell lung cancer by the FDA, including Ipilimumab (fully human antibody against CTLA-4), Pembrolizumab (fully human antibody against PD-1) and Nivolumab (fully human antibody against PD-1). There are also many on-going clinical trials investigating the value of immune checkpoint inhibitors in treating various malignancies, including advanced gastric cancer. In KEYNOTE-012 trial, for advanced gastric and esophagogastric junction cancer anti-PD-1 therapy seemed to be safe and effective for advanced gastric cancer with PD-L1 positivity. Moreover, studies of adoptive cell therapy and tumor vaccine in gastric cancer are underway. Here the latest developments in immunotherapy for gastric cancer will be illustrated.