TARP vaccination is associated with slowing in PSA velocity and decreasing tumor growth rates in patients with Stage D0 prostate cancer

Boosting the Immune Response—Combining Local and Immune Therapy for Prostate Cancer Treatment

Due to its slow progression and susceptibility to radical forms of treatment, low-grade PC is associated with high overall survival (OS). With the clinical progression of PC, the therapy is becoming more complex. The immunosuppressive tumor microenvironment (TME) makes PC a difficult target for most immunotherapeutics. Its general immune resistance is established by e.g., immune evasion through Treg cells, synthesis of immunosuppressive mediators, and the defective expression of surface neoantigens. The success of sipuleucel-T in clinical trials initiated several other clinical studies that specifically target the immune escape of tumors and eliminate the immunosuppressive properties of the TME. In the settings of PC treatment, this can be commonly achieved with radiation therapy (RT). In addition, focal therapies usually applied for localized PC, such as high-intensity focused ultrasound (HIFU) therapy, cryotherapy, photodynamic therapy (PDT), and irreversible electroporation (IRE) were shown to boost the anti-cancer response. Nevertheless, the present guidelines restrict their application to the context of a clinical trial or a prospective cohort study. This review explains how RT and focal therapies enhance the immune response. We also provide data supporting the combination of RT and focal treatments with immune therapies.

Chronic IL-1 Exposed AR+ PCa Cell Lines Show Conserved Loss of IL-1 Sensitivity and Evolve Both Conserved and Unique Differential Gene Expression Profiles

INTRODUCTION

Inflammation drives prostate cancer (PCa) progression. While inflammation is a cancer hallmark, the underlying mechanisms mediating inflammation-induced PCa are still under investigation. Interleukin-1 (IL-1) is an inflammatory cytokine that promotes cancer progression, including PCa metastasis and castration resistance. We previously found that acute IL-1 exposure represses PCa androgen receptor (AR) expression concomitant with the upregulation of pro-survival proteins, causing de novo accumulation of castration-resistant PCa cells. However, acute inflammation is primarily anti-tumorigenic, while chronic inflammation is pro-tumorigenic. Thus, using the LNCaP PCa cell line as model, we found that PCa cells can evolve insensitivity to chronic IL-1 exposure, restoring AR and AR activity and acquiring castration resistance. In this paper we expanded our chronic IL-1 model to include the MDA-PCa-2b PCa cell line to investigate the response to acute versus chronic IL-1 exposure and to compare the gene expression patterns that evolve in the LNCaP and MDA-PCa-2b cells chronically exposed to IL-1.

METHODS

We chronically exposed MDA-PCa-2b cells to IL-1α or IL-1β for several months to establish sublines. Once established, we determined subline sensitivity to exogenous IL-1 using cell viability assay, RT-qPCR and western blot. RNA sequencing was performed for parental and subline cells and over representation analysis (ORA) for geneset enrichment of biological process/pathway was performed.

RESULTS

MDA-PCa-2b cells repress AR and AR activity in response to acute IL-1 exposure and evolve insensitivity to chronic IL-1 exposure. While cell biological and molecular response to acute IL-1 signaling is primarily conserved in LNCaP and MDA-PCa-2b cells, including upregulation of NF-κB signaling and downregulation of cell proliferation, the LNCaP and MDA-PCa-2b cells evolve conserved and unique molecular responses to chronic IL-1 signaling that may promote or support tumor progression.

CONCLUSIONS

Our chronic IL-1 subline models can be used to identify underlying molecular mechanisms that mediate IL-1-induced PCa progression.

In Silico Model Estimates the Clinical Trial Outcome of Cancer Vaccines

Over 30 years after the first cancer vaccine clinical trial (CT), scientists still search the missing link between immunogenicity and clinical responses. A predictor able to estimate the outcome of cancer vaccine CTs would greatly benefit vaccine development. Published results of 94 CTs with 64 therapeutic vaccines were collected. We found that preselection of CT subjects based on a single matching HLA allele does not increase immune response rates (IRR) compared with non-preselected CTs (median 60% vs. 57%, p = 0.4490). A representative in silico model population (MP) comprising HLA-genotyped subjects was used to retrospectively calculate in silico IRRs of CTs based on the percentage of MP-subjects having epitope(s) predicted to bind ≥ 1–4 autologous HLA allele(s). We found that in vitro measured IRRs correlated with the frequency of predicted multiple autologous allele-binding epitopes (AUC 0.63–0.79). Subgroup analysis of multi-antigen targeting vaccine CTs revealed correlation between clinical response rates (CRRs) and predicted multi-epitope IRRs when HLA threshold was ≥ 3 (r = 0.7463, p = 0.0004) but not for single HLA allele-binding epitopes (r = 0.2865, p = 0.2491). Our results suggest that CRR depends on the induction of broad T-cell responses and both IRR and CRR can be predicted when epitopes binding to multiple autologous HLAs are considered.

Spherical Nucleic Acid Vaccine Structure Markedly Influences Adaptive Immune Responses of Clinically Utilized Prostate Cancer Targets

Cancer vaccines, which activate the immune system against a target antigen, are attractive for prostate cancer, where multiple upregulated protein targets are identified. However, many clinical trials implementing peptides targeting these proteins have yielded suboptimal results. Using spherical nucleic acids (SNAs), we explore how precise architectural control of vaccine components can activate a robust antigen-specific immune response in comparison to clinical formulations of the same targets. The SNA vaccines incorporate peptides for human prostate-specific membrane antigen (PSMA) or T-cell receptor γ alternate reading frame protein (TARP) into an optimized architecture, resulting in high rates of immune activation and cytolytic ability in humanized mice and human peripheral blood mononuclear cells (hPBMCs). Specifically, administered SNAs elevate the production and secretion of cytokines and increase polyfunctional cytotoxic T cells and effector memory. Importantly, T cells raised from immunized mice potently kill targets, including clinically relevant cells expressing the whole PSMA protein. Treatment of hPBMCs increases costimulatory markers and cytolytically active T cells. This work demonstrates the importance of vaccine structure and its ability to reformulate and elevate clinical targets. Moreover, it encourages the field to reinvestigate ineffective peptide targets and repackage them into optimally structured vaccines to harness antigen potency and enhance clinical outcomes.

Should androgen deprivation therapy and other systemic treatments be used in men with prostate cancer and a rising PSA post-local treatments?

Biochemical recurrence is an evolving space in prostate cancer, with increasing multidisciplinary involvement. Androgen deprivation therapy has shown proof of its value in complementing salvage radiotherapy in high-risk biochemical relapsing patients; ongoing trials aim to further refine this treatment combination. As systemic treatments, and notably next-generation androgen receptor targeted agents, have moved towards early hormone-sensitive and non-metastatic stages, the prostate specific antigen (PSA)-relapse disease stage will be undoubtedly challenged by future evidence from such ongoing clinical trials. With the use of modern imaging and newer molecular technologies, including integration of tumoral genomic profiling and liquid biopsies in risk stratification, a path towards a precision oncology-focused approach will become a reality to guide in the future decisions for patients with a diagnosis of biochemical recurrence.

TARP as antigen in cancer immunotherapy

In recent decades, immunotherapy has become a pivotal element in cancer treatment. A remaining challenge is the identification of cancer-associated antigens suitable as targets for immunotherapeutics with potent on-target and few off-tumor effects. The T-cell receptor gamma (TCRγ) chain alternate reading frame protein (TARP) was first discovered in the human prostate and androgen-sensitive prostate cancer. Thereafter, TARP was also identified in breast and endometrial cancers, salivary gland tumors, and pediatric and adult acute myeloid leukemia. Interestingly, TARP promotes tumor cell proliferation and migration, which is reflected in an association with worse survival. TARP expression in malignant cells, its role in oncogenesis, and its limited expression in normal tissues raised interest in its potential utility as a therapeutic target, and led to development of immunotherapeutic targeting strategies. In this review, we provide an overview of TARP expression, its role in different cancer types, and currently investigated TARP-directed immunotherapeutic options.

Immune Escape in Prostate Cancer: Known and Predicted Mechanisms and Targets

Complex immune evasion mechanisms and lack of biomarkers predicting responsiveness to immune checkpoint blockade therapies compromise immunotherapy's therapeutic efficacy for patients with prostate cancer. The authors review established and nominated immune evasion mechanisms in prostate cancer and discuss how the precise treatment strategies can be developed to improve efficacy of immunotherapy.

The Potential Role for Immunotherapy in Biochemically Recurrent Prostate Cancer

Biochemically recurrent prostate cancer represents a stage of prostate cancer where conventional (continued on next page) computed tomography and technetium Tc 99m bone scan imaging are unable to detect disease after curative intervention despite rising prostate-specific antigen. There is no clear standard of care and no systemic therapy has been shown to improve survival. Immunotherapy-based treatments potentially are attractive options relative to androgen deprivation therapy due to the generally more favorable side-effect profile. Biochemically recurrent prostate cancer patients have a low tumor burden and likely lymph node-based disease, which may make them more likely to respond to immunotherapy.

Immunological Complexity of the Prostate Cancer Microenvironment Influences the Response to Immunotherapy

Prostate cancer is one of the most common cancers in men and a leading cause of cancer-related death. Recent advances in the treatment of advanced prostate cancer, including the use of more potent and selective inhibitors of the androgen signaling pathway, have provided significant clinical benefit for men with metastatic castration-resistant prostate cancer (mCRPC). However, most patients develop progressive lethal disease, highlighting the need for more effective treatments. One such approach is immunotherapy, which harness the power of the patient's immune system to identify and destroy cancer cells through the activation of cytotoxic CD8 T cells specific for tumor antigens. Although immunotherapy, particularly checkpoint blockade, can induce significant clinical responses in patients with solid tumors or hematological malignancies, minimal efficacy has been observed in men with mCRPC. In the current review, we discuss our current understanding of the immunological complexity of the immunosuppressive prostate cancer microenvironment, preclinical models of prostate cancer, and recent advances in immunotherapy clinical trials to improve outcomes for men with mCRPC.

Altered Lipid Tumor Environment and Its Potential Effects on NKT Cell Function in Tumor Immunity

Natural killer T (NKT) cells are CD1d restricted T cells that mostly recognize lipid antigens. These cells share characteristics with both adaptive and innate immune cells and have multiple immunoregulatory roles. In a manner similar to innate immune cells, they respond quickly to stimuli and secrete large amounts of cytokines, amplifying and modulating the immune response. As T cells, they express T cell receptors (TCRs) and respond in an antigen-specific manner like conventional T cells. There are at least two subtypes of NKT cells, type I and type II, that differ in the nature of their TCR, either semi-invariant (type I) or diverse (type II). The two sub-types generally have opposing functions in tumor immunity, with type I promoting and type II suppressing tumor immunity, and they cross-regulate each other, forming an immunoregulatory axis. The tumor has multiple mechanisms by which it can evade immune-surveillance. One such mechanism involves alteration in tumor lipid repertoire and accumulation of lipids and fatty acids that favor tumor growth and evade anti-tumor immunity. Since NKT cells mostly recognize lipid antigens, an altered tumor lipid metabolic profile will also alter the repertoire of lipid antigens that can potentially affect their immune-modulatory function. In this review, we will explore the effects of alterations in the lipid metabolites on tumor growth, antigen cross-presentation, and overall effect on anti-tumor immunity, especially in the context of NKT cells.

Strategies for developing and optimizing cancer vaccines

With the spotlight on cancer immunotherapy and the expanding use of immune checkpoint inhibitors, strategies to improve the response rate and duration of current cancer immunotherapeutics are highly sought. In that sense, investigators around the globe have been putting spurs on the development of effective cancer vaccines in humans after decades of efforts that led to limited clinical success. In more than three decades of research in pursuit of targeted and personalized immunotherapy, several platforms have been incorporated into the list of cancer vaccines from live viral or bacterial agents harboring antigens to synthetic peptides with the hope of stronger and durable immune responses that will tackle cancers better. Unlike adoptive cell therapy, cancer vaccines can take advantage of using a patient's entire immune system that can include more than engineered receptors or ligands in developing antigen-specific responses. Advances in molecular technology also secured the use of genetically modified genes or proteins of interest to enhance the chance of stronger immune responses. The formulation of vaccines to increase chances of immune recognition such as nanoparticles for peptide delivery is another area of great interest. Studies indicate that cancer vaccines alone may elicit tumor-specific cellular or humoral responses in immunologic assays and even regression or shrinkage of the cancer in select trials, but novel strategies, especially in combination with other cancer therapies, are under study and are likely to be critical to achieve and optimize reliable objective responses and survival benefit. In this review, cancer vaccine platforms with different approaches to deliver tumor antigens and boost immunity are discussed with the intention of summarizing what we know and what we need to improve in the clinical trial setting.

Trial watch: Peptide-based vaccines in anticancer therapy

Peptide-based anticancer vaccination aims at stimulating an immune response against one or multiple tumor-associated antigens (TAAs) following immunization with purified, recombinant or synthetically engineered epitopes. Despite high expectations, the peptide-based vaccines that have been explored in the clinic so far had limited therapeutic activity, largely due to cancer cell-intrinsic alterations that minimize antigenicity and/or changes in the tumor microenvironment that foster immunosuppression. Several strategies have been developed to overcome such limitations, including the use of immunostimulatory adjuvants, the co-treatment with cytotoxic anticancer therapies that enable the coordinated release of damage-associated molecular patterns, and the concomitant blockade of immune checkpoints. Personalized peptide-based vaccines are also being explored for therapeutic activity in the clinic. Here, we review recent preclinical and clinical progress in the use of peptide-based vaccines as anticancer therapeutics.Abbreviations: CMP: carbohydrate-mimetic peptide; CMV: cytomegalovirus; DC: dendritic cell; FDA: Food and Drug Administration; HPV: human papillomavirus; MDS: myelodysplastic syndrome; MHP: melanoma helper vaccine; NSCLC: non-small cell lung carcinoma; ODD: orphan drug designation; PPV: personalized peptide vaccination; SLP: synthetic long peptide; TAA: tumor-associated antigen; TNA: tumor neoantigen

Therapeutic cancer vaccine: building the future from lessons of the past

Anti-cancer vaccines have raised many hopes from the start of immunotherapy but have not yet been clinically successful. The few positive results of anti-cancer vaccines have been observed in clinical situations of low tumor burden or preneoplastic lesions. Several new concepts and new results reposition this therapeutic approach in the field of immunotherapy. Indeed, cancers that respond to anti-PD-1/PD-L1 (20-30%) are those that are infiltrated by anti-tumor T cells with an inflammatory infiltrate. However, 70% of cancers do not appear to have an anti-tumor immune reaction in the tumor microenvironment. To induce this anti-tumor immunity, therapeutic combinations between vaccines and anti-PD-1/PD-L1 are being evaluated. In addition, the identification of neoepitopes against which the immune system is less tolerated is giving rise to a new enthusiasm by the first clinical results of the vaccine including these neoepitopes in humans. The ability of anti-cancer vaccines to induce a population of anti-tumor T cells called memory resident T cells that play an important role in immunosurveillance is also a new criterion to consider in the design of therapeutic vaccines.

Plasma from some cancer patients inhibits adenoviral Ad5f35 vector transduction of dendritic cells

BACKGROUND

Pooled AB serum is often used as a media supplement for cell culture but it has the potential to transmit infectious diseases. To avoid this risk, we used autologous plasma as a media supplement for manufacturing dendritic cells (DCs) for cancer immunotherapy. We noticed inconsistencies in the DCs and investigated their nature and cause.

METHODS

Adenovirus human epidural growth factor receptor 2 (adHER2/neu) DCs for 21 patients were manufactured from autologous peripheral blood monocytes that were treated with granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin (IL)-4 for 3 days, transduced with Ad5f35HER2ECTM and then treated with lipopolysaccharide and interferon (IFN)-γ for 1 day. The cells were cultured in RPMI-1640 supplemented with either 10% heat inactivated autologous or AB plasma.

RESULTS

Twenty-eight adHER2/neu DCs were manufactured for 21 patients using autologous plasma and 68 were manufactured for 20 of those patients using AB plasma. The expression of human epidural growth factor receptor 2 (HER2/neu) was less for DCs manufactured with autologous plasma (70.3 ± 33.3% versus 86.1 ± 22.8%; P <0.01). Manufacturing adHER2/neu DCs using monocytes from three healthy subjects and plasma from one patient with low HER2/neu expression (18%) resulted in low HER2/neu expression by all three DCs (13%, 16% and 23%). Analysis of the levels of 1322 proteins in eight plasma samples associated with low HER2/neu expression and in 12 associated with high HER2/neu expression revealed that the levels of 14 predicted HER2/neu transduction efficiency.

CONCLUSION

The manufacture of adHER2/neu DC using autologous plasma as a media supplement resulted in inconsistent HER2/neu expression. It is likely that variability in the levels of multiple proteins in autologous plasma contributed to low HER2/neu expression.

Cancer vaccines: translation from mice to human clinical trials

Therapeutic cancer vaccines have been a long-sought approach to harness the exquisite specificity of the immune system to treat cancer, but until recently have not had much success as single agents in clinical trials. However, new understanding of the immunoregulatory mechanisms exploited by cancers has allowed the development of approaches to potentiate the effect of vaccines by removing the brakes while the vaccines step on the accelerator. Thus, vaccines that had induced a strong T cell response but no clinical therapeutic effect may now reach their full potential. Here, we review a number of promising approaches to cancer vaccines developed initially in mouse models and their translation into clinical trials, along with combinations of vaccines with other therapies that might allow cancer vaccines to finally achieve clinical efficacy against many types of cancer.

Future perspectives in melanoma research "Melanoma Bridge", Napoli, November 30th-3rd December 2016

Major advances have been made in the treatment of cancer with targeted therapy and immunotherapy; several FDA-approved agents with associated improvement of 1-year survival rates became available for stage IV melanoma patients. Before 2010, the 1-year survival were quite low, at 30%; in 2011, the rise to nearly 50% in the setting of treatment with Ipilimumab, and rise to 70% with BRAF inhibitor monotherapy in 2013 was observed. Even more impressive are 1-year survival rates considering combination strategies with both targeted therapy and immunotherapy, now exceeding 80%. Can we improve response rates even further, and bring these therapies to more patients? In fact, despite these advances, responses are heterogeneous and are not always durable. There is a critical need to better understand who will benefit from therapy, as well as proper timing, sequence and combination of different therapeutic agents. How can we better understand responses to therapy and optimize treatment regimens? The key to better understanding therapy and to optimizing responses is with insights gained from responses to targeted therapy and immunotherapy through translational research in human samples. Combination therapies including chemotherapy, radiotherapy, targeted therapy, electrochemotherapy with immunotherapy agents such as Immune Checkpoint Blockers are under investigation but there is much room for improvement. Adoptive T cell therapy including tumor infiltrating lymphocytes and chimeric antigen receptor modified T cells therapy is also efficacious in metastatic melanoma and outcome enhancement seem likely by improved homing capacity of chemokine receptor transduced T cells. Tumor infiltrating lymphocytes therapy is also efficacious in metastatic melanoma and outcome enhancement seem likely by improved homing capacity of chemokine receptor transduced T cells. Understanding the mechanisms behind the development of acquired resistance and tests for biomarkers for treatment decisions are also under study and will offer new opportunities for more efficient combination therapies. Knowledge of immunologic features of the tumor microenvironment associated with response and resistance will improve the identification of patients who will derive the most benefit from monotherapy and might reveal additional immunologic determinants that could be targeted in combination with checkpoint blockade. The future of advanced melanoma needs to involve education and trials, biobanks with a focus on primary tumors, bioinformatics and empowerment of patients and clinicians.

Cancer vaccine strategies: translation from mice to human clinical trials

We translated two cancer vaccine strategies from mice into human clinical trials. (1) In preclinical studies on TARP, an antigen expressed in most prostate cancers, we mapped epitopes presented by HLA-A*0201, modified them to increase affinity and immunogenicity in HLA transgenic mice, and induced human T cells that killed human cancer cells ("epitope enhancement"). In a clinical trial, HLA-A2⁺ prostate cancer patients with PSA biochemical recurrence (Stage D0) were vaccinated with two peptides either in Montanide-ISA51 or on autologous dendritic cells (DCs). In stage D0, the Prostate-Specific Antigen (PSA) slope is prognostic of time to radiographic evidence of metastases and death. With no difference between arms, 74% of combined subjects had a decreased PSA slope at 1 year compared to their own baseline slopes (p = 0.0004). For patients vaccinated with DCs, response inversely correlated with a tolerogenic DC signature. A randomized placebo-controlled phase II trial is underway. (2) HER2 is a driver surface oncogene product expressed in multiple tumors. We made an adenoviral vector vaccine expressing the extracellular and transmembrane domains of HER2 and cured mice with large established HER2⁺ tumors, dependent on antibodies to HER2, not T cells. The mechanism differed from that of trastuzumab. We tested a human version in advanced metastatic cancer patients naïve to HER2-directed therapies. At the second and third dose levels, 45% of evaluable patients showed clinical benefit. Circulating tumor cells also declined in some vaccinated patients. Thus, cancer vaccines developed in mice were successfully translated to humans with promising early results.

Expression of CD14, IL10, and Tolerogenic Signature in Dendritic Cells Inversely Correlate with Clinical and Immunologic Response to TARP Vaccination in Prostate Cancer Patients

Purpose: Despite the vast number of clinical trials conducted so far, dendritic cell (DC)-based cancer vaccines have mostly shown unsatisfactory results. Factors and manufacturing procedures essential for these therapeutics to induce effective antitumor immune responses have yet to be fully characterized. We here aimed to identify DC markers correlating with clinical and immunologic response in a prostate carcinoma vaccination regimen.Experimental Design: We performed an extensive characterization of DCs used to vaccinate 18 patients with prostate carcinoma enrolled in a pilot trial of T-cell receptor gamma alternate reading frame protein (TARP) peptide vaccination (NCT00908258). Peptide-pulsed DC preparations (114) manufactured were analyzed by gene expression profiling, cell surface marker expression and cytokine release secretion, and correlated with clinical and immunologic responses.Results: DCs showing lower expression of tolerogenic gene signature induced strong antigen-specific immune response and slowing in PSA velocity, a surrogate for clinical response. These DCs were also characterized by lower surface expression of CD14, secretion of IL10 and MCP-1, and greater secretion of MDC. When combined, these four factors were able to remarkably discriminate DCs that were sufficiently potent to induce strong immunologic response.Conclusions: DC factors essential for the activation of immune responses associated with TARP vaccination in prostate cancer patients were identified. This study highlights the importance of in-depth characterization of DC vaccines and other cellular therapies, to understand the critical factors that hinder potency and potential efficacy in patients. Clin Cancer Res; 23(13); 3352-64. ©2017 AACR.