Prostate Cancer Vaccine Research Articles

Abstract A67: Reconditioning the tumor immune microenvironment for a breast cancer vaccine therapy.

Abstract The recent approval of a prostate cancer vaccine has re-energized the research on cancer immunotherapy. A critical barrier for immunotherapies remains the immunosuppressive tumor microenvironment, which is due to abnormal tumor vasculature, hypoxia and tumor-infiltrating myeloid suppressors. Judiciously used anti-angiogenic agents have the potential to modulate the tumor immune environment to improve immunotherapy, but they are often used at high doses in the clinic aiming to prune tumor vessels. However, this has been shown to compromise other concurrent therapies, e.g., chemotherapy. Here, we demonstrate that anti-vascular endothelial growth factor receptor 2 (VEGFR2) antibody treatment at lower “vascular normalizing” doses – but not high “anti-vascular” doses – results in a more homogeneous distribution of functional tumor vessels and reduces hypoxia. As a result, the lower doses are superior to the high doses at polarizing tumor-associated macrophages from immune inhibitory M2-like towards immune stimulatory M1-like phenotype, and in facilitating CD4+ and CD8+ T cell tumor infiltration. These findings indicate that vascular normalizing doses of anti-VEGFR2 antibody treatment can reprogram the tumor immune microenvironment from suppressive to stimulatory. Based on this mechanism, synchronizing vascular normalization with T cell activation induced by a whole cancer cell vaccine therapy enhanced anti-cancer efficacy in a CD8+ T cell-dependent manner in both immune tolerant and immunogenic murine breast cancer models. Given that the combinations of high doses of bevacizumab with chemotherapy have not improved overall survival of breast cancer patients, our study suggests a new strategy to more effectively use anti-angiogenic agents with active immunotherapy and potentially other anti-cancer therapies in a clinical setting. Citation Format: Yuhui Huang, Jianping Yuan, Elda Righi, Dan G. Duda, Dai Fukumura, Mark C. Poznansky, Rakesh K. Jain. Reconditioning the tumor immune microenvironment for a breast cancer vaccine therapy. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology: Multidisciplinary Science Driving Basic and Clinical Advances; Dec 2-5, 2012; Miami, FL. Philadelphia (PA): AACR; Cancer Res 2013;73(1 Suppl):Abstract nr A67.

Therapeutic cancer vaccines in prostate cancer: the quest for intermediate markers of response.

Despite recent advances in cancer immunotherapy, no prospectively validated intermediate biomarkers exist to predict response. These biomarkers are highly desirable given modern immunotherapy’s paradoxical pattern of clinical benefit; that is, improvement in overall survival without short-term change in progression. Immunotherapy clinical trials have evaluated biomarkers that may correlate with clinical outcomes. Many of them are performed on peripheral blood to evaluate the systemic response, such as tumor-targeted humoral and cellular immunity, and cytokine responses. Accumulating evidence suggests that immune infiltrates in tumors may suggest evidence for the therapy’s mechanism of action, and have greater potential for providing prognostic and predictive information. In addition, a non-immunologic biomarker, such as tumor growth kinetics, may explain this paradoxical pattern of clinical benefit, and predict survival in patients treated with an immunotherapy. Prospective assessment and validation of these and other intermediate markers would be required to better understand their potential clinical role.

Dendritic Cell-Directed Vaccination with a Lentivector Encoding PSCA for Prostate Cancer in Mice

Many studies have demonstrated that prostate stem cell antigen (PSCA) is an attractive target for immunotherapy based on its overexpression in prostate tumor tissue, especially in some metastatic tissues. In this study, we evaluated dendritic cell (DC)-directed lentiviral vector (DCLV) encoding murine PSCA (DCLV-PSCA) as a novel tumor vaccine for prostate cancer in mouse models. We showed that DCLV-PSCA could preferentially deliver the PSCA antigen gene to DC-SIGN-expressing 293T cells and bone marrow-derived DCs (BMDCs). Direct immunization with the DCLV-PSCA in male C57BL/6 mice elicited robust PSCA-responsive CD8+ and CD4+ T cells in vivo. In a transgenic adenocarcinoma mouse prostate cell line (TRAMP-C1) synergetic tumor model, we further demonstrated that DCLV-PSCA-vaccinated mice could be protected from lethal tumor challenge in a prophylactic model, whereas slower tumor growth was observed in a therapeutic model. This DCLV-PSCA vaccine also showed efficacy in inhibiting tumor metastases using a PSCA-expressing B16-F10 model. Taken together, these data suggest that DCLV is a potent vaccine carrier for PSCA in delivering anti-prostate cancer immunity.

DNA Vaccines for Prostate Cancer

Delivery of plasmid DNA encoding an antigen of interest has been demonstrated to be an effective means of immunization, capable of eliciting antigen-specific T cells. Plasmid DNA vaccines offer advantages over other anti-tumor vaccine approaches in terms of simplicity, manufacturing, and possibly safety. The primary disadvantage is their poor transfection efficiency and subsequent lower immunogenicity relative to other genetic vaccine approaches. However, multiple preclinical models demonstrate anti-tumor efficacy, and many efforts are underway to improve the immunogenicity and anti-tumor effect of these vaccines. Clinical trials using DNA vaccines as treatments for prostate cancer have begun, and to date have demonstrated safety and immunological effect. This review will focus on DNA vaccines as a specific means of antigen delivery, advantages and disadvantages of this type of immunization, previous experience in preclinical models and human trials specifically conducted for the treatment of prostate cancer, and future directions for the application of DNA vaccines to prostate cancer immunotherapy.

O11 Final analysis of a phase I/II study with CV9103: An intradermally administered prostate cancer vaccine based on self-adjuvanted mRNA (RNActive®)

O11 Final analysis of a phase I/II study with CV9103: An intradermally administered prostate cancer vaccine based on self-adjuvanted mRNA (RNActive®)

DNA vaccination for prostate cancer, from preclinical to clinical trials - where we stand?

Development of various vaccines for prostate cancer (PCa) is becoming an active research area. PCa vaccines are perceived to have less toxicity compared with the available cytotoxic agents. While various immune-based strategies can elicit anti-tumour responses, DNA vaccines present increased efficacy, inducing both humoural and cellular immunity. This immune activation has been proven effective in animal models and initial clinical trials are encouraging. However, to validate the role of DNA vaccination in currently available PCa management paradigms, strong clinical evidence is still lacking. This article provides an overview of the basic principles of DNA vaccines and aims to provide a summary of preclinical and clinical trials outlining the benefits of this immunotherapy in the management of PCa.

Vascular normalizing doses of antiangiogenic treatment reprogram the immunosuppressive tumor microenvironment and enhance immunotherapy

The recent approval of a prostate cancer vaccine has renewed hope for anticancer immunotherapies. However, the immunosuppressive tumor microenvironment may limit the effectiveness of current immunotherapies. Antiangiogenic agents have the potential to modulate the tumor microenvironment and improve immunotherapy, but they often are used at high doses in the clinic to prune tumor vessels and paradoxically may compromise various therapies. Here, we demonstrate that targeting tumor vasculature with lower vascular-normalizing doses, but not high antivascular/antiangiogenic doses, of an anti-VEGF receptor 2 (VEGFR2) antibody results in a more homogeneous distribution of functional tumor vessels. Furthermore, lower doses are superior to the high doses in polarizing tumor-associated macrophages from an immune inhibitory M2-like phenotype toward an immune stimulatory M1-like phenotype and in facilitating CD4(+) and CD8(+) T-cell tumor infiltration. Based on this mechanism, scheduling lower-dose anti-VEGFR2 therapy with T-cell activation induced by a whole cancer cell vaccine therapy enhanced anticancer efficacy in a CD8(+) T-cell-dependent manner in both immune-tolerant and immunogenic murine breast cancer models. These findings indicate that vascular-normalizing lower doses of anti-VEGFR2 antibody can reprogram the tumor microenvironment away from immunosuppression toward potentiation of cancer vaccine therapies. Given that the combinations of high doses of bevacizumab with chemotherapy have not improved overall survival of breast cancer patients, our study suggests a strategy to use antiangiogenic agents in breast cancer more effectively with active immunotherapy and potentially other anticancer therapies.

WS14-4 - The Clinical Role of Peptide Vaccines for Castration-Resistant Prostate Cancer

ABSTRACT Introduction Androgen deprivation therapy (ADT) is the standard treatment of metastatic prostate cancer. Although ADT achieves disease stabilization in the beginning of the treatment, most patients eventually develop castration-resistant prostate cancer (CRPC). Docetaxel (DTX)-based chemotherapy has been proved the efficacy for CRPC, however, the prognosis of patients after the induction of chemotherapy is limited. Therefore, extending the period from the diagnosis of CRPC to the induction of chemotherapy may contribute to improvement of overall survival of those patients. Immunotherapy is being developed for several malignancies including prostate cancer. We have previously carried out phase-I/II study of personalized peptide vaccination in metastatic CRPC patients, and showed the safety and effectiveness of peptide vaccination therapy. Since cancer immunotherapy may act more effectively in early stage of the disease before systemic chemotherapy, we conducted a randomized phase II study to evaluate the efficacy of the peptide vaccination therapy for chemotherapy-naive CRPC patients. Patients and methods The patients are randomly assigned to two groups; one (vaccination group) receives the combination therapy of peptide vaccines and low-dose (1 mg/day) dexamethasone (Dx) and the other receives Dx alone. In the vaccination group, maximum of four kinds of peptide from those that have been recognized by the patient-specific immune system (serum IgG antibodies) in the peripheral blood are selected as vaccines. 3mg of each peptide is administrated separately every 2 weeks. Dexamethasone 1 mg/day p.o. is started on the first day of peptide administration. The primary end point of the study is progression-free survival and secondary end points include objective response rate and subjective effects. Results Up to now, 72 CRPC patients were enrolled in this study and 60 were evaluable and analyzed in detail. Median age was 68 years old (48–80 years) and median serum PSA was 4.8 ng/ml. The patients in vaccination group showed a significantly longer PSA progression free survival (P

Nouvelles thérapeutiques dans le cancer de la prostate résistant à la castration : panorama des études pivotales et nouveaux schémas thérapeutiques à venir

Recently, new agents have been developed in the treatment of prostate cancer. Our aim was to review phase III studies that involved novel agents in the treatment of castration resistant prostate cancer. PubMed databases were searched for original articles published with the search terms: prostate cancer, castration resistant, metastatic, targeted therapy, biologic agents, immunotherapy and clinical trials. Proceedings from 2008of conferences of the American Society of Clinical Oncology, American Urological Association, and the European Association of Urology were also searched. We included phase III studies that involved: abiraterone, MDV3100, cabazitaxel, sipuleucel-T, radium-223, and denosumab. Abiraterone and MDV3100are two new hormotherapies that showed an increased overall survival of 15and 18months respectively before after docetaxel based chemotherapy in randomized trials. Cabazitaxel became the standard second line chemotherapy after docetaxel. Sipuleucel-T has emerged as the first approved vaccine in prostate cancer. It showed a 22% reduction of mortality and a prolonged survival time of 4.1months compared to placebo. A radium-223based metabolic radiotherapy has showed a better overall survival, delayed and reduced skeletal-related events in placebo controlled randomized trials. Denosumab also delayed the first skeletal-related event in a zoledronic acid controlled trial (20.7versus 17.1months, P=0.0002). Moreover, Denosumab delays bone metastases by 4.1months compared to placebo. The novel agents that emerged in the treatment of prostate cancer showed an efficacy in placebo controlled trials. They added new tools in the armamentarium of therapies of castration resistant prostate cancer.

Prostate cancer vaccines in clinical trials

This review presents important information about the current state of the art for vaccine immunotherapy of prostate cancer. It includes important preclinical research for each of the important prostate cancer vaccines to have reached clinical trials. To date, the only prostate cancer vaccine that has completed Phase III trials and has been approved and licensed by the US FDA is Sipuleucel-T, which immunizes patients against the prostate-associated antigen prostatic acid phosphatase. The benefits and concerns associated with the vaccine are presented. A current Phase III trial is currently underway using the vaccinia-based prostate-specific antigen vaccine Prostvac-TRICOM. Other immunotherapeutic vaccines in trials include the Ad/prostate-specific antigen vaccine Ad5-prostate-specific antigen and the DNA/prostatic acid phosphatase vaccine. A cellular vaccine, GVAX, has been in clinical trials but has not seen continuous study. This review also delves into the multiple immune regulatory elements that must be overcome in order to obtain strong antitumor-associated antigen immune responses capable of effectively destroying prostate tumor cells.

A Cytomegalovirus-based Vaccine Expressing a Single Tumor-specific CD8+ T-cell Epitope Delays Tumor Growth in a Murine Model of Prostate Cancer

Cytomegalovirus (CMV) is a highly immunogenic virus that results in a persistent, life-long infection in the host typically with no ill effects. Certain unique features of CMV, including its capacity to actively replicate in the presence of strong host CMV-specific immunity, may give CMV an advantage compared with other virus-based vaccine delivery platforms. In the present study, we tested the utility of mouse CMV (mCMV)-based vaccines expressing human prostate-specific antigen (PSA) for prostate cancer immunotherapy in double-transgenic mice expressing PSA and HLA-DRB1*1501 (DR2bxPSA F1 mice). We assessed the capacity of 2 mCMV-based vectors to induce PSA-specific CD8 T-cell responses and affect the growth of PSA-expressing Transgenic Adenocarcinoma of the Mouse Prostate tumors (TRAMP-PSA). In the absence of tumor challenge, immunization with mCMV vectors expressing either a H2-D(b)-restricted epitope PSA(65-73) (mCMV/PSA(65-73)) or the full-length gene for PSA (mCMV/PSA(FL)) induced comparable levels of CD8 T-cell responses that increased (inflated) with time. Upon challenge with TRAMP-PSA tumor cells, animals immunized with mCMV/PSA(65-73) had delay of tumor growth and increased PSA-specific CD8 T-cell responses, whereas animals immunized with mCMV/PSA(FL) showed progressive tumor growth and no increase in number of splenic PSA(65-73)-specific T cells. The data show that a prototype CMV-based prostate cancer vaccine can induce an effective antitumor immune response in a "humanized" double-transgenic mouse model. The observation that mCMV/PSA(FL) is not effective against TRAMP-PSA is consistent with our previous findings that HLA-DRB1*1501-restricted immune responses to PSA are associated with suppression of effective CD8 T-cell responses to TRAMP-PSA tumors.

Phase I trial of NY-ESO-1/LAGE1 peptide vaccine for metastatic castration resistant prostate cancer (mCRPC).

4643 Background: The NY-ESO-1 and LAGE-1 antigens are amplified in malignancies including prostate cancer. Preclinical induction of immune responses and anti-tumor activity has been demonstrated upon administration of these peptides. A phase I/II clinical trial evaluated the feasibility of a combined HLA class-I and class-II peptide vaccine in mCRPC. Methods: Men with progressive mCRPC, Performance Status ≤2, PSA ≥10 ng/ml and had appropriate HLA class I (A2) and class II haplotypes (DR4, DP4, DR13) were eligible. Three groups with 3 patients each received the vaccine subcutaneously every 2 weeks for 6 doses. Group 1 was treated with a peptide directed at a HLA class I haplotype (HLA A2), Group 2 was treated with a peptide reacting to a HLA class II haplotype (DR4, DP4, or DR13), and Group 3 received peptides directed at both Class I and II haplotypes. Group I and Group II received 1 dose of 1000 mcg and Group III received doses of 1000 mcg for each of 2 peptides. Androgen-deprivation was continued. Results: Of 14 patients enrolled, all were evaluable for toxicities and 9 patients completed all 6 treatments per amended protocol and were evaluable for efficacy. The median baseline PSA was 85.19 ng/ml. Four patients were chemo naive and 5 were post-docetaxel. One patient had a grade 5 event (myocardial infarction) unlikely therapy-related. Potential therapy related toxicities were local grade 1 injection site erythema (n=5), fatigue (n=2), flu-like symptoms (n=1), myalgias (n=1), anorexia (n=1), nausea (n=1) and leukocytosis (n=1). The median PSA doubling time pre-therapy and during therapy were 3.1 and 4.92 months, respectively. The PSA-DT was prolonged compared to baseline in 6 patients, including a negative PSA slope in 2 patients. Antigen-specific immune response determined by ELISPOT was observed, and its association with slowing of PSA-doubling time will be further examined. Conclusions: In men with mCRPC, HLA class-I and/or class-II restricted NY-ESO-1 and LAGE-1 peptides administered subcutaneously demonstrated excellent tolerability, slowing of PSA doubling time and antigen-specific immune responses. Further development of peptide vaccines alone or in combination with other regimens may be warranted.

Interim analysis of a phase II randomized clinical trial of samrium-153 (Sm-153) with or without PSA-TRICOM vaccine in metastatic castration-resistant prostate cancer after docetaxel.

2526 Background: A prior randomized, placebo-controlled, multi-center phase 2 trial of PSA-TRICOM (PROSTVAC) demonstrated an overall survival benefit. Sm-153 is a radiopharmaceutical that targets osteoblastic bone lesions. Preclinical data indicated that Sm-153 could alter tumor phenotype, causing upregulation of Fas, MHC Class I, and tumor-associated antigens, making tumor cells more amenable to immune-mediated killing. Methods: This is a phase 2 multi-center trial design intended to randomize 68 patients (pts) to Sm-153 with or without PROSTVAC. Eligibility included castrate resistant prostate cancer bone metastases, no visceral disease, prior docetaxel, ECOG ≤2, and normal organ function. Sm-153 was given at 1mCi/kg IV on day 8 and then every 12 weeks. PROSTVAC was given on days 1, 15, 29, then every 4 weeks. The 1° endpoint is a comparison of progression-free survival at 4 months (mo) utilizing PCCWG, but not PSA criteria. 68 patients will provide 80% power to detect a difference of 15% vs. 40% without progression at 4 mo with a one-tailed alpha = 0.10 assuming Fisher’s exact test comparing these fractions as the primary method of analysis. 2° endpoints are OS, ORR, PSA changes, immunologic, toxicity, and palliation. Reported here is the result of a pre-specified interim analysis, which required ≥20% conditional power to detect 15% vs. 40% without progression at 4 months for the trial to continue. Results: Of 37 enrolled pts, 3 were not evaluable for PFS. PFS and PSA findings are found below. Hematologic toxicities (anemia, thrombocytopenia, neutropenia, or lymphocytopenia) are most common, with grade 3 or 4 thrombocytopenia occurring in 22% and 26% of treatment cycles on Arms A and B, respectively. The conditional power for the comparison of fractions without progression at 4 mo is 77%. Conclusions: This interim analysis suggests the combination of PROSTVAC and Sm-153 is well tolerated with similar toxicity profile to Sm-153 alone. The early indication of improved TTP warrants continued study accrual. [Table: see text]

Relationship of alterations in the expression of nontargeted genes and suppression of bcl-2 by antisense oligonucleotides.

e13513 Background: Antisense oligos have been employed against prostate cancer models targeting proteins associated with growth/apoptosis. However gene therapy may not be totally specific. Oligos against bcl-2 are in clinical trials and it was of interest: 1) To see whether therapy produces non-specific effects compromising efficacy; 2) To identify genes whose activity may have to be maintained/replaced. Methods: In LNCaP cells we evaluated monospecific (directed against bcl-2) and bispecific (directed against bcl-2 & epidermal growth factor receptor) oligos which comparably suppressed bcl-2. Cells were evaluated by PCR for expression of non-targeted genes associated with apoptosis (caspase-3, clusterin); androgen regulation (androgen receptor [AR], p300, creb binding protein [CBP]); cytokines (interleukins 2 [IL-2], 4 [IL-4], interferon [IFN]); antigen expression (prostate specific antigen [PSA], prostate membrane antigen [PSMA], prostatic acid phosphatase [PAP]); and autocrine growth (insulin like growth factor [IGF1]). Results: Most non-targeted genes were unaffected. However following suppression of bcl-2 activity by mono- and bispecific oligos, cells compensated by suppressing caspase-3 (apoptosis promoter) and enhancing AR and coactivator p300 expression. This suggests an ability to reverse bcl-2 suppression of apoptosis through decreased expression of a promoter and increased androgen sensitivity. It identifies caspase-3 as an essential gene whose expression must be either maintained/replaced when bcl-2 is therapeutically suppressed. Among the differentiation antigens, cell surface PSMA expression was increased by bispecific oligos; secretory PSA and PAP were not. Increased PSMA may to be due to induced IFN expression produced by bispecific oligos, attributed to a 2X intrastrand conformation not seen in the monospecific oligo. Increased PSMA expression could make prostate cancer cells more recognizable to cytotoxic T cells and potentiate prostate cancer vaccines. Conclusions: If gene therapy is to be effective, the mechanisms for compensatory changes which contribute to tumor resistance must be further identified/controlled.

Combining active immunotherapy with immune checkpoint blockade for the treatment of advanced prostate cancer

Combination immunotherapy is emerging as a promising approach for the treatment of advanced prostate cancer. This research highlight discusses the combination of a PSA-directed poxviral vaccine and a monoclonal antibody blocking an important immune checkpoint molecule to treat men with metastatic castration-resistant prostate cancer. The results demonstrate feasibility and safety, as well as intriguing clinical responses to this combination therapy.

Immunogenic Peptides Derived from the Transcription Factor ERG as a Vaccine for Prostate Cancer (162.17)

Abstract The suitability of immunotherapy as a treatment for prostate cancer (PCa) has recently been demonstrated in a number of clinical trials. While these studies have provided a strong proof of principle, there is considerable room for improvement. One potential strategy is to identify new targets specific to PCa that could be immunized against and with this in mind, we have implemented an in silico-in vitro-in vivo¬ procedure for designing and assessing the suitability of MHC-I-restricted peptides as anti-PCa vaccines. In this study, we investigated peptides designed from ERG, a transcription factor expressed in around 50% of human PCa cases. We used in silico protein cleavage and peptide-binding algorithms to design HLA-A2.1 restricted peptides from the Erg protein. The binding of the in silico designed Erg peptides was then assessed in vitro and shown to bind HLA-A2.1 effectively. Additionally, when peptides were tested in vivo, they generated a strong immune response in humanized HLA-A2.1+ mice and overcame peripheral tolerance in prostate specific Erg expressing TRAMP-HLA-A2.1-ERG+ mice. Finally, it was found that a greater CD8+ T-cell recall response against human ERG+ PCa cell lines occurred in ERG immunized HLA-A2.1+ mice compared to controls. Together these data support the validity of our peptide design method and indicate that peptides derived from the overexpressed gene Erg could be used in an anti-PCa vaccine.

Breaking immune tolerance to prostate-associated tumor antigens through Tim-1 receptor (162.20)

Abstract It has been suggested that one factor limiting cancer immunotherapy in clinical trials are immunological checkpoints that impede vaccine-induced anti-tumor responses. We postulate that manipulating lymphocytes and dendritic cells through the Tim-1 receptor, a membrane protein that regulates the vigor and differentiation of these cells, using an agonist monoclonal antibody could enhance cytotoxic lymphocyte (CTL) responses to prostate tumor-associated antigens. We used an approach that combines concomitant immunization against a model prostate tumor-associated antigen (TAA) SV40 Tag and treatment with an agonist anti-Tim1 antibody and assessed Tag-specific CTL responses two weeks later. Ab treatment of TRAMP mice resulted in elevated Tag-specific CTL in both spleen and prostate-draining lymph nodes, indicating that manipulating Tim1 results in circumventing immune tolerance to Tag antigen. We then tested this strategy for human epitopes derived from the prostate cancer-specific antigen ERG and SIM2 by combining anti-Tim1 antibody with an ERG- and SIM2-derived HLA-A2.1-restricted peptide vaccine in HLA-A2.1 transgenic mice and showed that CTL responses to ERG and SIM2 epitopes are elevated in the presence of anti-Tim1 Ab. Further characterization of lymphocyte differentiation post-immunization/anti-Tim1 treatment revealed that major shifts in T cell differentiation occur. Our findings suggest that targeting Tim1 could be successfully combined with prostate cancer vaccines.

A novel iNKT cell-mediated vaccine maneuver induces potent long-lasting anti-tumor immunity for advanced prostate cancer by boosting CD8+T cell memory and function (53.24)

Abstract iNKT cells have considerable therapeutic promise in cancer, but so far this has not been fully realized. At issue has been delivering iNKT ligand and tumor Ag to the same APC for optimal processing and presentation. Also, although tumor-infiltrating APCs express CD1d in both prostate cancer (PCa) models and patients, tumor induced tolerance and suppression leads to defective iNKT activation. Whole-cell tumor vaccines represent a promising treatment approach and prevent tumor progression in multiple models of cancer. Here, we use an optimized approach consisting of alpha-galactosylceramide (aGalCer) and the GM-CSF-based PCa vaccine, ‘GVax’ combined with IL-12. This approach was capable of breaking tumor-induced tolerance and causing dramatic and substantial tumor regression and survival in large advanced prostate tumors in TRAMP mice. Remarkably, 10/12 vaccinated >9 month old mice rejected tumors, 'breaking tolerance', even at this late stage of tumor growth. The vaccine induced strong immune responses capable of reversing INKT defects in tumor-bearing mice as well as in patient iNKT in vitro. Both IL-12 and aGalCer were crucial for this response. Vaccinated mice had higher levels and activation of tumor-specific CD8 T, CD4 T and iNKT cells, and greater memory CD8 T cell expansion capable of producing the effector cytokines IFN-γ and TNF-α in response to tumor. These studies shed light on how whole cell vaccines targeting iNKTs can be utilized in PCa immunotherapy.

Metabolic profiling of T-cell differentiation and tolerance (115.5)

Abstract Metabolic pathways that drive T cell differentiation, activation and tolerance remain poorly understood. Here we used mass spectrometry to partially describe the metabolic profile of CD4 and CD8 T cells that underwent in vitro activation and differentiation in the presence or absence of prostate cancer conditioned media. T cell subsets were purified from mouse spleen or human PBMC, activated in vitro in the presence of various combinations of cytokines or prostate cancer cell line conditioned media. Metabolites were extracted using methanol, injected and analyzed using a 5500 QTRAP triple quadruple mass spectrometer coupled to a Prominence UFLC HPLC system via selected reaction monitoring (SRM) of a total of 255 endogenous water soluble metabolites for steady-state analyses of samples. Our data show that TCR/CD28-mediated activation imposes a distinct metabolic profile on mouse T cells. This profile is distinct for each cell lineage when activated cells are differentiated into either Th1, Th2, Th9, Th17 or regulatory T cell phenotypes. Likewise, metabolic profiles of activated CD4 and CD8 T cells from both mouse and human are significantly affected by the presence of prostate cancer cell line conditioned media, with major changes in the urea cycle, ammonia recycling, and protein and nucleotide biosynthesis . Together, our findings provide a basis for further development of drugs that could be used to manipulate T cells for a better outcome of prostate cancer vaccines.

Reconsidering the Paradigm of Cancer Immunotherapy by Computationally Aided Real-time Personalization

Although therapeutic vaccination often induces markers of tumor-specific immunity, therapeutic responses remain rare. An improved understanding of patient-specific dynamic interactions of immunity and tumor progression, combined with personalized application of immune therapeutics would increase the efficacy of immunotherapy. Here, we developed a method to predict and enhance the individual response to immunotherapy by using personalized mathematical models, constructed in the early phase of treatment. Our approach includes an iterative real-time in-treatment evaluation of patient-specific parameters from the accruing clinical data, construction of personalized models and their validation, model-based simulation of subsequent response to ongoing therapy, and suggestion of potentially more effective patient-specific modified treatment. Using a mathematical model of prostate cancer immunotherapy, we applied our model to data obtained in a clinical investigation of an allogeneic whole-cell therapeutic prostate cancer vaccine. Personalized models for the patients who responded to treatment were derived and validated by data collected before treatment and during its early phase. Simulations, based on personalized models, suggested that an increase in vaccine dose and administration frequency would stabilize the disease in most patients. Together, our findings suggest that application of our method could facilitate development of a new paradigm for studies of in-treatment personalization of the immune agent administration regimens (P-trials), with treatment modifications restricted to an approved range, resulting in more efficacious immunotherapies.