Advances in Therapeutic Cancer Vaccines

Cancer Immunotherapy: Beyond Checkpoint Blockade

Blocking antibodies to the immune checkpoint receptors or their ligands have revolutionized the treatment of diverse malignancies. Many tumors are recognized by adaptive immunity, but these adaptive responses can be inhibited by immunosuppressive mechanisms within the tumor, often through pathways outside of the currently targeted checkpoints. For this reason, only a minority of cancer patients achieve durable responses to current immunotherapies. Multiple novel approaches strive to expand immunotherapy's reach. These may include targeting alternative immune checkpoints. However, many investigational strategies look beyond checkpoint blockade. These include cellular therapies to bypass endogenous immunity and efforts to stimulate new adaptive antitumor responses using vaccines, adjuvants, and combinations with cytotoxic therapy, as well as strategies to inhibit innate immune suppression and modulate metabolism within the tumor microenvironment. The challenge for immunotherapy going forward will be to select rational strategies for overcoming barriers to effective antitumor responses from the myriad possible targets.

Reprogramming lymphocytes for the treatment of melanoma: From biology to therapy

This decade has introduced drastic changes in melanoma therapy, predominantly due to the materialization of the long promise of immunotherapy. Cytotoxic T cells are the chief component of the immune system, which are targeted by different strategies aimed to increase their capacity against melanoma cells. To this end, reprogramming of T cells occurs by T cell centered manipulation, targeting the immunosuppressive tumor microenvironment or altering the whole patient. These are enabled by delivery of small molecules, functional monoclonal antibodies, different subunit vaccines, as well as living lymphocytes, native or genetically engineered. Current FDA-approved therapies are focused on direct T cell manipulation, such as immune checkpoint inhibitors blocking CTLA-4 and/or PD-1, which paves the way for an effective immunotherapy backbone available for combination with other modalities. Here we review the biology and clinical developments that enable melanoma immunotherapy today and in the future.

Anti-Cancer Vaccine for HPV-Associated Neoplasms: Focus on a Therapeutic HPV Vaccine Based on a Novel Tumor Antigen Delivery Method Using Endogenously Engineered Exosomes

Some human papillomavirus (HPV) genotypes are universally recognized as major etiological agents not only of ano-genital tumors but also of head and neck cancers, which show increasing incidence. The evaluation of current and future therapeutic approaches against HPV-induced tumors is a global health priority, despite an effective prophylactic vaccine against 7 of the 12 genotypes involved in the etiology of tumors being currently available. In this review, we present the main anti-HPV therapeutic approaches in clinical experimentation, with a focus on a novel tumor antigen delivery method using engineered exosomes, that we recently developed. Our system allows the induction of an efficient unrestricted cytotoxic T lymphocyte (CTL) immune response against the HPV16-E7 tumor-associated antigen, with the formation of endogenously engineered exosomes, i.e., nanovesicles spontaneously released by all cell types. Immunogenic exosomes are uploaded with HPV16-E7 due to the fusion with a unique exosome-anchoring protein referred to as Nefmut. Intramuscular injection of a DNA vector expressing the fusion protein generates exosomes sufficiently immunogenic to elicit a potent anti-16E7 CTL immune response. The approach is described here and the advantages over other existing methodologies are reported.

Biomaterials for vaccine-based cancer immunotherapy

The development of therapeutic cancer vaccines as a means to generate immune reactivity against tumors has been explored since the early discovery of tumor-specific antigens by Georg Klein in the 1960s. However, challenges including weak immunogenicity, systemic toxicity, and off-target effects of cancer vaccines remain as barriers to their broad clinical translation. Advances in the design and implementation of biomaterials are now enabling enhanced efficacy and reduced toxicity of cancer vaccines by controlling the presentation and release of vaccine components to immune cells and their microenvironment. Here, we discuss the rational design and clinical status of several classes of cancer vaccines (including DNA, mRNA, peptide/protein, and cell-based vaccines) along with novel biomaterial-based delivery technologies that improve their safety and efficacy. Further, strategies for designing new platforms for personalized cancer vaccines are also considered.

Regulatory perspective on in vitro potency assays for human dendritic cells used in anti-tumor immunotherapy

Dendritic cells (DCs) are key connectors between the innate and adaptive immune system and have an important role in modulating other immune cells. Therefore, their therapeutic application to steer immune responses is considered in various disorders, including cancer. Due to differences in the cell source and manufacturing process, each DC medicinal product is unique. Consequently, release tests to ensure consistent quality need to be product-specific. Although general guidance concerning quality control testing of cell-based therapies is available, cell type-specific regulation is still limited. Especially guidance related to potency testing is needed, because developing an in vitro assay measuring cell properties relevant for in vivo functionality is challenging. In this review, we provide DC-specific guidance for development of in vitro potency assays for characterisation and release. We present a broad overview of in vitro potency assays suggested for DC products to determine their anti-tumor functionality. Several advantages and limitations of these assays are discussed. Also, we provide some points to consider for selection and design of a potency test. The ideal functionality assay for anti-tumor products evaluates the capacity of DCs to stimulate antigen-specific T cells. Because this approach may not be feasible for release, use of surrogate potency markers could be considered, provided that these markers are sufficiently linked to the in vivo DC biological activity and clinical response. Further elucidation of the involvement of specific DC subsets in anti-tumor responses will result in improved manufacturing processes for DC-based products and should be considered during potency assay development.

Radiation and Local Anti-CD40 Generate an Effective in situ Vaccine in Preclinical Models of Pancreatic Cancer

Radiation therapy induces immunogenic cell death, which can theoretically stimulate T cell priming and induction of tumor-specific memory T cell responses, serving as an in situ vaccine. In practice, this abscopal effect is rarely observed. We use two mouse models of pancreatic cancer to show that a single dose of stereotactic body radiation therapy (SBRT) synergizes with intratumoral injection of agonistic anti-CD40, resulting in regression of non-treated contralateral tumors and formation of long-term immunologic memory. Long-term survival was not observed when mice received multiple fractions of SBRT, or when TGFβ blockade was combined with SBRT. SBRT and anti-CD40 was so effective at augmenting T cell priming, that memory CD8 T cell responses to both tumor and self-antigens were induced, resulting in vitiligo in long-term survivors.

Bovine herpesvirus 4-based vector delivering the full length xCT DNA efficiently protects mice from mammary cancer metastases by targeting cancer stem cells

Despite marked advancements in its treatment, breast cancer is still the second leading cause of cancer death in women, due to relapses and distal metastases. Breast cancer stem cells (CSCs), are a cellular reservoir for recurrence, metastatic evolution and disease progression, making the development of novel therapeutics that target CSCs, and thereby inhibit metastases, an urgent need. We have previously demonstrated that the cystine-glutamate antiporter xCT (SLC7A11), a protein that was shown to be overexpressed in mammary CSCs and that plays a key role in the maintenance of their redox balance, self-renewal and resistance to chemotherapy, is a potential target for mammary cancer immunotherapy. This paper reports on the development of an anti-xCT viral vaccine that is based on the bovine herpesvirus 4 (BoHV-4) vector, which we have previously showed to be a safe vaccine that can transduce cells in vivo and confer immunogenicity to tumor antigens. We show that the vaccination of BALB/c mice with BoHV-4 expressing xCT (BoHV-4-mxCT), impaired lung metastases induced by syngeneic mammary CSCs both in preventive and therapeutic settings. Vaccination induced T lymphocyte activation and the production of anti-xCT antibodies that can mediate antibody-dependent cell cytotoxicity (ADCC), and directly impair CSC phenotype, self-renewal and redox balance. Our findings pave the way for the potential future use of BoHV-4-based vector targeting xCT in metastatic breast cancer treatment.

Current Progress and Controversies in Prostate Cancer Management

Objective:

The optimal management strategy for prostate cancer (PCa) remains controversial. We performed a systemic review of current progress and controversies regarding the diagnosis and treatment of PCa.

Data Sources:

We searched PubMed for recently published articles up to July 2017 using the following key words: “prostate cancer,” “progress,” “controversy,” “immunotherapy,” and “prevention.”

Study Selection:

Articles were obtained and reviewed to provide a systematic review of the current progress and controversies regarding PCa management.

Results:

The value of serum prostate-specific antigen (PSA) screening remains controversial, but PSA screening is recommended to facilitate the early diagnosis of PCa in high-risk groups. Prostate biopsy via the transrectal or perineal approach has both advantages and disadvantages. There was a significant correlation between testosterone levels and PCa prognosis. The current research is focused on the mechanisms responsible for PCa. Active surveillance has been proposed as a management strategy for low-risk, localized PCa, but there is an urgent need for further clinical studies to establish the criteria for recommending this approach. The main complications of radical resection for PCa are urinary incontinence and erectile dysfunction, though three-dimensional laparoscopic and robot-assisted laparoscopic techniques have obvious advantages over radical surgery. Radiotherapy is also a therapeutic option for PCa, while immunotherapies may alter the prostate tumor microenvironment. Ongoing studies aim to provide guidance on effective sequential and combination strategies. Prevention remains an important strategy for reducing PCa morbidity and mortality.

Conclusions:

The diagnosis, treatment, and prevention of PCa are complex issues, worthy of intensive study. Further studies are needed to improve the management of PCa.

CD40L coding oncolytic adenovirus allows long-term survival of humanized mice receiving dendritic cell therapy

Dendritic cells (DCs) are crucial players in promoting immune responses. Logically, adoptive DC therapy is a promising approach in cancer immunotherapy. One of the major obstacles in cancer immunotherapy in general is the immunosuppressive tumor microenvironment, which hampers the maturation and activation of DCs. Therefore, human clinical outcomes with DC therapy alone have been disappointing. In this study, we use fully serotype 3 oncolytic adenovirus Ad3-hTERT-CMV-hCD40L, expressing human CD40L, to modulate the tumor microenvironment with subsequently improved function of DCs. We evaluated the synergistic effects of Ad3-hTERT-CMV-hCD40L and DCs in the presence of human peripheral blood mononuclear cells ex vivo and in vivo. Tumors treated with Ad3-hTERT-CMV-hCD40L and DCs featured greater antitumor effect compared with unarmed virus or either treatment alone. 100% of humanized mice survived to the end of the experiment, while mice in all other groups died by day 88. Moreover, adenovirally-delivered CD40L induced activation of DCs, leading to induction of Th1 immune responses. These results support clinical trials with Ad3-hTERT-CMV-hCD40L in patients receiving DC therapy.

Synthetic vaccine particles for durable cytolytic T lymphocyte responses and anti-tumor immunotherapy

We previously reported that synthetic vaccine particles (SVP) encapsulating antigens and TLR agonists resulted in augmentation of immune responses with minimal production of systemic inflammatory cytokines. Here we evaluated two different polymer formulations of SVP-encapsulated antigens and tested their ability to induce cytolytic T lymphocytes (CTL) in combination with SVP-encapsulated adjuvants. One formulation led to efficient antigen processing and cross-presentation, rapid and sustained CTL activity, and expansion of CD8⁺ T cell effector memory cells locally and centrally, which persisted for at least 1–2 years after a single immunization. SVP therapeutic dosing resulted in suppression of tumor growth and a substantial delay in mortality in several syngeneic mouse cancer models. Treatment with checkpoint inhibitors and/or cytotoxic drugs, while suboptimal on their own, showed considerable synergy with SVP immunization. SVP encapsulation of endosomal TLR agonists provided superior CTL induction, therapeutic benefit and/or improved safety profile compared to free adjuvants. SVP vaccines encapsulating mutated HPV-16 E7 and E6/E7 recombinant proteins led to induction of broad CTL activity and strong inhibition of TC-1 tumor growth, even when administered therapeutically 13–14 days after tumor inoculation in animals bearing palpable tumors. A pilot study in non-human primates showed that SVP-encapsulated E7/E6 adjuvanted with SVP-encapsulated poly(I:C) led to robust induction of antigen-specific T and B cell responses.

Defining and Understanding Adaptive Resistance in Cancer Immunotherapy

Despite the unprecedented tumor regression and long-term survival benefit observed with anti-programmed death (PD) [anti-PD-1 or anti-B7-homolog 1 (B7-H1)] therapy in patients with advanced cancers, a large portion of patients do not benefit from such treatment and a fraction of responders relapse. Current efforts to overcome resistance and improve efficacy of anti-PD therapy require a clear understanding of resistance and should precede current avenues using random combinations with available treatment regimens. Here, we categorized three types of resistance, namely target-missing, primary, and acquired resistance. This categorization requires reliable, accurate tissue sampling and appropriate interpretation of results based on the four classifications of tumor immunity in the microenvironment (TIME). We believe that fundamental understanding of these complex tumor-immune interactions and of the cellular and molecular mechanisms underlying these types of true resistance is the key for targeting the right targets in combination with or beyond anti-PD therapy in the future.

Injectable, Tough Alginate Cryogels as Cancer Vaccines

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

Current status and future directions of cancer immunotherapy

In the past decades, our knowledge about the relationship between cancer and the immune system has increased considerably. Recent years' success of cancer immunotherapy including monoclonal antibodies (mAbs), cancer vaccines, adoptive cancer therapy and the immune checkpoint therapy has revolutionized traditional cancer treatment. However, challenges still exist in this field. Personalized combination therapies via new techniques will be the next promising strategies for the future cancer treatment direction.

Towards personalized, tumour-specific, therapeutic vaccines for cancer

Cancer vaccines, which are designed to amplify tumour-specific T cell responses through active immunization, have long been envisioned as a key tool of effective cancer immunotherapy. Despite a clear rationale for such vaccines, extensive past efforts were unsuccessful in mediating clinically relevant antitumour activity in humans. Recently, however, next-generation sequencing and novel bioinformatics tools have enabled the systematic discovery of tumour neoantigens, which are highly desirable immunogens because they arise from somatic mutations of the tumour and are therefore tumour specific. As a result of the diversity of tumour neoepitopes between individuals, the development of personalized cancer vaccines is warranted. Here, we review the emerging field of personalized cancer vaccination and discuss recent developments and future directions for this promising treatment strategy.

Recent Successes and Future Directions in Immunotherapy of Cutaneous Melanoma

The global health burden associated with melanoma continues to increase while treatment options for metastatic melanoma are limited. Nevertheless, in the past decade, the field of cancer immunotherapy has witnessed remarkable advances for the treatment of a number of malignancies including metastatic melanoma. Although the earliest observations of an immunological antitumor response were made nearly a century ago, it was only in the past 30 years, that immunotherapy emerged as a viable therapeutic option, in particular for cutaneous melanoma. As such, melanoma remains the focus of various preclinical and clinical studies to understand the immunobiology of cancer and to test various tumor immunotherapies. Here, we review key recent developments in the field of immune-mediated therapy of melanoma. Our primary focus is on therapies that have received regulatory approval. Thus, a brief overview of the pathophysiology of melanoma is provided. The purported functions of various tumor-infiltrating immune cell subsets are described, in particular the recently described roles of intratumoral dendritic cells. The section on immunotherapies focuses on strategies that have proved to be the most clinically successful such as immune checkpoint blockade. Prospects for novel therapeutics and the potential for combinatorial approaches are delineated. Finally, we briefly discuss nanotechnology-based platforms which can in theory, activate multiple arms of immune system to fight cancer. The promising advances in the field of immunotherapy signal the dawn of a new era in cancer treatment and warrant further investigation to understand the opportunities and barriers for future progress.

Cancer vaccines in the era of checkpoint blockade: the magic is in the adjuvant

While T cell checkpoint blockade therapy of various cancers yields impressive clinical benefits, most patients are not cured. This is thought to result from insufficient spontaneous tumor-specific T cell responses, a situation that could be remedied with cancer-specific vaccination. Much work is underway to identify cancer-specific antigens, leaving open the question of how to formulate these antigens in a manner that provokes potent cancer-specific T cell responses. In this review I discuss paradigms guiding adjuvant development, and consider what may constitutes a clinically relevant T cell response. I also suggest that adjuvants providing multiple non-redundant signals may be the next frontier in the development of cancer vaccines that provide true clinical benefit when combined with T cell checkpoint blockade.

Engineering challenges for brain tumor immunotherapy

Malignant brain tumors represent one of the most devastating forms of cancer with abject survival rates that have not changed in the past 60years. This is partly because the brain is a critical organ, and poses unique anatomical, physiological, and immunological barriers. The unique interplay of these barriers also provides an opportunity for creative engineering solutions. Cancer immunotherapy, a means of harnessing the host immune system for anti-tumor efficacy, is becoming a standard approach for treating many cancers. However, its use in brain tumors is not widespread. This review discusses the current approaches, and hurdles to these approaches in treating brain tumors, with a focus on immunotherapies. We identify critical barriers to immunoengineering brain tumor therapies and discuss possible solutions to these challenges.

Exploiting lymphatic vessels for immunomodulation: Rationale, opportunities, and challenges

Lymphatic vessels are the primary route of communication from peripheral tissues to the immune system; as such, they represent an important component of local immunity. In addition to their transport functions, new immunomodulatory roles for lymphatic vessels and lymphatic endothelial cells have come to light in recent years, demonstrating that lymphatic vessels help shape immune responses in a variety of ways: promoting tolerance to self-antigens, archiving antigen for later presentation, dampening effector immune responses, and resolving inflammation, among others. In addition to these new biological insights, the growing field of immunoengineering has begun to explore therapeutic approaches to utilize or exploit the lymphatic system for immunotherapy.

Self-Assembling Peptide Epitopes as Novel Platform for Anticancer Vaccination

The aim of the present study was to improve the immunogenicity of peptide epitope vaccines using novel nanocarriers based on self-assembling materials. Several studies demonstrated that peptide antigens in nanoparticulate form induce stronger immune responses than their soluble forms. However, several issues such as poor loading and risk of inducing T cell anergy due to premature release of antigenic epitopes have challenged the clinical success of such systems. In the present study, we developed two vaccine delivery systems by appending a self-assembling peptide (Ac-AAVVLLLW-COOH) or a thermosensitive polymer poly(N-isopropylacrylamide (pNIPAm) to the N-terminus of different peptide antigens (OVA250-264, HPV-E743-57) to generate self-assembling peptide epitopes (SAPEs). The obtained results showed that the SAPEs were able to form nanostructures with a diameter from 20 to 200 nm. The SAPEs adjuvanted with CpG induced and expanded antigen-specific CD8+ T cells in mice. Furthermore, tumor-bearing mice vaccinated with SAPEs harboring the HPV E743-57 peptide showed a delayed tumor growth and an increased survival compared to sham-treated mice. In conclusion, self-assembling peptide based systems increase the immunogenicity of peptide epitope vaccines and therefore warrants further development toward clinical use.

Multistaged Nanovaccines Based on Porous Silicon@Acetalated Dextran@Cancer Cell Membrane for Cancer Immunotherapy

Immunoadjuvant porous silicon (PSi)-based nanovaccines are prepared by nanoprecipitation in a glass capillary microfluidics device. Vesicles, derived from cancer cell membranes encapsulating thermally oxidized PSi nanoparticles or PSi-polymer nanosystems binding a model antigen, are biocompatible over a wide range of concentrations, and show immunostimulant properties in human cells, promoting the expression of co-stimulatory signals and the secretion of pro-inflammatory cytokines.

Minimizing Hazards Associated With Live-Virus Immunotherapeutic Cancer Vaccines

Therapeutic cancer vaccines that use attenuated vaccinia viruses as delivery vectors are undergoing clinical trials at dozens of sites internationally. Even in an attenuated form, these live viruses can cause severe illness if they are accidentally transmitted to immunocompromised people, pregnant women, or people with certain skin conditions. Oncology nurses should become familiar with how to manage patients' vaccine injection sites to minimize these risks to patients' close contacts and the community at large.
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Tumor-directed immunotherapy can generate tumor-specific T cell responses through localized co-stimulation

The most important goals for the field of immuno-oncology are to improve the response rate and increase the number of tumor indications that respond to immunotherapy, without increasing adverse side effects. One approach to achieve these goals is to use tumor-directed immunotherapy, i.e., to focus the immune activation to the most relevant part of the immune system. This may improve anti-tumor efficacy as well as reduce immune-related adverse events. Tumor-directed immune activation can be achieved by local injections of immune modulators in the tumor area or by directing the immune modulator to the tumor using bispecific antibodies. In this review, we focus on therapies targeting checkpoint inhibitors and co-stimulatory receptors that can generate tumor-specific T cell responses through localized immune activation.