Trial watch: DNA vaccines for cancer therapy

Principles of risk assessment in colon cancer: immunity is key

In clinical practice, the administration of adjuvant chemotherapy (ACT) following tumor surgical resection raises a critical dilemma for stage II colon cancer (CC) patients. The prognostic features used to identify high-risk CC patients rely on the pathological assessment of tumor cells. Currently, these factors are considered for stratifying patients who may benefit from ACT at early CC stages. However, the extent to which these factors predict clinical outcomes (i.e. recurrence, survival) remains highly controversial, also uncertainty persists regarding patients' response to treatment, necessitating further investigation. Therefore, an imperious need is to explore novel biomarkers that can reliably stratify patients at risk, to optimize adjuvant treatment decisions. Recently, we evaluated the prognostic and predictive value of Immunoscore (IS), an immune digital-pathology assay, in stage II CC patients. IS emerged as the sole significant parameter for predicting disease-free survival (DFS) in high-risk patients. Moreover, IS effectively stratified patients who would benefit most from ACT based on their risk of recurrence, thus predicting their outcomes. Notably, our findings revealed that digital IS outperformed the visual quantitative assessment of the immune response conducted by expert pathologists. The latest edition of the WHO classification for digestive tumor has introduced the evaluation of the immune response, as assessed by IS, as desirable and essential diagnostic criterion. This supports the revision of current cancer guidelines and strongly recommends the implementation of IS into clinical practice as a patient stratification tool, to guide CC treatment decisions. This approach may provide appropriate personalized therapeutic decisions that could critically impact early-stage CC patient care.

Digital Pathology for Better Clinical Practice

(1) Background: Digital pathology (DP) is transforming the landscape of clinical practice, offering a revolutionary approach to traditional pathology analysis and diagnosis. (2) Methods: This innovative technology involves the digitization of traditional glass slides which enables pathologists to access, analyze, and share high-resolution whole-slide images (WSI) of tissue specimens in a digital format. By integrating cutting-edge imaging technology with advanced software, DP promises to enhance clinical practice in numerous ways. DP not only improves quality assurance and standardization but also allows remote collaboration among experts for a more accurate diagnosis. Artificial intelligence (AI) in pathology significantly improves cancer diagnosis, classification, and prognosis by automating various tasks. It also enhances the spatial analysis of tumor microenvironment (TME) and enables the discovery of new biomarkers, advancing their translation for therapeutic applications. (3) Results: The AI-driven immune assays, Immunoscore (IS) and Immunoscore-Immune Checkpoint (IS-IC), have emerged as powerful tools for improving cancer diagnosis, prognosis, and treatment selection by assessing the tumor immune contexture in cancer patients. Digital IS quantitative assessment performed on hematoxylin-eosin (H&E) and CD3+/CD8+ stained slides from colon cancer patients has proven to be more reproducible, concordant, and reliable than expert pathologists' evaluation of immune response. Outperforming traditional staging systems, IS demonstrated robust potential to enhance treatment efficiency in clinical practice, ultimately advancing cancer patient care. Certainly, addressing the challenges DP has encountered is essential to ensure its successful integration into clinical guidelines and its implementation into clinical use. (4) Conclusion: The ongoing progress in DP holds the potential to revolutionize pathology practices, emphasizing the need to incorporate powerful AI technologies, including IS, into clinical settings to enhance personalized cancer therapy.

Redefining the battle against colorectal cancer: a comprehensive review of emerging immunotherapies and their clinical efficacy

Colorectal cancer (CRC) is the third most common cancer globally and presents a significant challenge owing to its high mortality rate and the limitations of traditional treatment options such as surgery, radiotherapy, and chemotherapy. While these treatments are foundational, they are often poorly effective owing to tumor resistance. Immunotherapy is a groundbreaking alternative that has recently emerged and offers new hope for success by exploiting the body's own immune system. This article aims to provide an extensive review of clinical trials evaluating the efficacy of various immunotherapies, including CRC vaccines, chimeric antigen receptor T-cell therapies, and immune checkpoint inhibitors. We also discuss combining CRC vaccines with monoclonal antibodies, delve into preclinical studies of novel cancer vaccines, and assess the impact of these treatment methods on patient outcomes. This review seeks to provide a deeper understanding of the current state of CRC treatment by evaluating innovative treatments and their potential to redefine the prognosis of patients with CRC.

Light on life: immunoscore immune-checkpoint, a predictor of immunotherapy response

In the last decade, a plethora of immunotherapeutic strategies have been designed to modulate the tumor immune microenvironment. In particular, immune checkpoint (IC) blockade therapies present the most promising advances made in cancer treatment in recent years. In non-small cell lung cancer (NSCLC), biomarkers predicting response to IC treatments are currently lacking. We have recently identified Immunoscore-IC, a powerful biomarker that predicts the efficiency of immune-checkpoint inhibitors (ICIs) in NSCLC patients. Immunoscore-IC is an in vitro diagnostic assay that quantifies densities of PD-L1+, CD8+ cells, and distances between CD8+ and PD-L1+ cells in the tumor microenvironment. Immunoscore-IC can classify responder vs non-responder NSCLC patients for ICIs therapy and is revealed as a promising predictive marker of response to anti-PD-1/PD-L1 immunotherapy in these patients. Immunoscore-IC has also shown a significant predictive value, superior to the currently used PD-L1 marker. In colorectal cancer (CRC), the addition of atezolizumab to first-line FOLFOXIRI plus bevacizumab improved progression-free survival (PFS) in patients with previously untreated metastatic CRC. In the AtezoTRIBE trial, Immunoscore-IC emerged as the first biomarker with robust predictive value in stratifying pMMR metastatic CRC patients who critically benefit from checkpoint inhibitors. Thus, Immunoscore-IC could be a universal biomarker to predict response to PD-1/PD-L1 checkpoint inhibitor immunotherapy across multiple cancer indications. Therefore, cancer patient stratification (by Immunoscore-IC), based on the presence of T lymphocytes and PD-L1 potentially provides support for clinicians to guide them through combination cancer treatment decisions.

An Overview of Nanomaterial Applications in Pharmacology

Nanotechnology has become one of the most extensive fields of research. Nanoparticles (NPs) form the base for nanotechnology. Recently, nanomaterials (NMs) are widely used due to flexible chemical, biological, and physical characteristics with improved efficacy in comparison to bulk counterparts. The significance of each class of NMs is enhanced by identifying their properties. Day by day, there is an emergence of various applications of NMs, but the toxic effects associated with them cannot be avoided. NMs demonstrate therapeutic abilities by enhancing the drug delivery system, diagnosis, and therapeutic effects of numerous agents, but determining the benefits of NMs over other clinical applications (disease-specific) or substances is an ongoing investigation. This review is aimed at defining NMs and NPs and their types, synthesis, and pharmaceutical, biomedical, and clinical applications.

A Brief Introduction to Current Cancer Gene Therapy

Gene therapy has started in the late 1980s as novel, clinically applicable therapeutic option. It revolutionized the treatment of genetic diseases with the initial intent to repair or replace defective genes. Gene therapy has been adapted for treatment of malignant diseases to improve the outcome of cancer patients. In fact, cancer gene therapy has rapidly gained great interest and evolved into a research field with highest proportion of research activities in gene therapy. In this context, cancer gene therapy has long entered translation into clinical trials and therefore more than two-thirds of all gene therapy trials worldwide are aiming at the treatment of cancer disease using different therapeutic strategies. During the decades in cancer gene therapy, tremendous knowledge has accumulated. This led to significant improvements in vector design, transgene repertoire, more targeted interventions, use of novel gene therapeutic technologies such as CRISPR/Cas, sleeping beauty vectors, and development of effective cancer immunogene therapies. In this chapter, a brief overview of current key developments in cancer gene therapy is provided to gain insights into the recent directions in research as well as in clinical application of cancer gene therapy.

License to kill: microsatellite instability and immune contexture

Colorectal cancers (CRCs) with microsatellite instability (MSI) are due to a defect in the DNA mismatch repair (MMR) system resulting in an accumulation of frame-shift mutations. They are characterized by a tumor microenvironment richer in cytotoxic CD8 T-cells (CTLs) and a better prognosis compared to microsatellite stable (MSS) CRCs. The mechanisms by which defective MMR system may influence tumor-infiltrating immune cells and their impact on patient survival were still unclear. Thus, we performed a comprehensive analysis of MSI colorectal tumors.

We found that the numbers of frame-shift mutations potentially resulting in neo-epitopes were positively correlated to the density of tumor infiltrating CD8 T-cells but were lower than expected at random. We also evidenced that MSI patients could naturally harbor CTLs targeting frame-shift mutation-derived antigens. This favors the hypothesis of an active immunosurveillance in MSI colorectal tumors leading to the genetic evidence of an immunoediting. To evaluate the link between MSI tumor immune contexture and prognosis, we took advantage of a standardized assay that we developed to quantify tumor-infiltrating T-cells, the Immunoscore. Multivariate analyses revealed an advantage of Immunoscore over MSI in predicting recurrence and survival. Our data suggests that the prognostic value of MSI could be attributed to major underlying differences of infiltrating immune cells. Immunotherapeutic treatments, that are more efficient in patients with a preexisting anti-tumor immunity, were approved in MSI patients following successful clinical trials. We suggest that the Immunoscore could be used not only for colorectal tumor prognosis but also for predicting responses to immunotherapies.

Trial Watch: Tumor-targeting monoclonal antibodies in cancer therapy

In 1997, for the first time in history, a monoclonal antibody (mAb), i.e., the chimeric anti-CD20 molecule rituximab, was approved by the US Food and Drug Administration for use in cancer patients. Since then, the panel of mAbs that are approved by international regulatory agencies for the treatment of hematopoietic and solid malignancies has not stopped to expand, nowadays encompassing a stunning amount of 15 distinct molecules. This therapeutic armamentarium includes mAbs that target tumor-associated antigens, as well as molecules that interfere with tumor-stroma interactions or exert direct immunostimulatory effects. These three classes of mAbs exert antineoplastic activity via distinct mechanisms, which may or may not involve immune effectors other than the mAbs themselves. In previous issues of OncoImmunology, we provided a brief scientific background to the use of mAbs, all types confounded, in cancer therapy, and discussed the results of recent clinical trials investigating the safety and efficacy of this approach. Here, we focus on mAbs that primarily target malignant cells or their interactions with stromal components, as opposed to mAbs that mediate antineoplastic effects by activating the immune system. In particular, we discuss relevant clinical findings that have been published during the last 13 months as well as clinical trials that have been launched in the same period to investigate the therapeutic profile of hitherto investigational tumor-targeting mAbs.

The immune contexture and Immunoscore in cancer prognosis and therapeutic efficacy

The international American Joint Committee on Cancer/Union for International Cancer Control (AJCC/UICC) tumour-node-metastasis (TNM) staging system provides the current guidelines for the classification of cancer. However, among patients within the same stage, the clinical outcome can be very different. More recently, a novel definition of cancer has emerged, implicating at all stages a complex and dynamic interaction between tumour cells and the immune system. This has enabled the definition of the immune contexture, representing the pre-existing immune parameters associated with patient survival. Even so, the role of distinct immune cell types in modulating cancer progression is increasingly emerging. An immune-based assay named the 'Immunoscore' was defined to quantify the in situ T cell infiltrate and was demonstrated to be superior to the AJCC/UICC TNM classification for patients with colorectal cancer. This Review provides a broad overview of the main immune parameters positively or negatively shaping cancer development, including the Immunoscore, and their prognostic and predictive value. The importance of the immune system in cancer control is demonstrated by the requirement for a pre-existing intratumour adaptive immune response for effective immunotherapies, such as checkpoint inhibitors. Finally, we discuss how the combination of multiple immune parameters, rather than individual ones, might increase prognostic and/or predictive power.

Nanoparticle cancer vaccines: Design considerations and recent advances

Vaccines therapeutics manipulate host's immune system and have broad potential for cancer prevention and treatment. However, due to poor immunogenicity and limited safety, fewer cancer vaccines have been successful in clinical trials. Over the past decades, nanotechnology has been exploited to deliver cancer vaccines, eliciting long-lasting and effective immune responses. Compared to traditional vaccines, cancer vaccines delivered by nanomaterials can be tuned towards desired immune profiles by (1) optimizing the physicochemical properties of the nanomaterial carriers, (2) modifying the nanomaterials with targeting molecules, or (3) co-encapsulating with immunostimulators. In order to develop vaccines with desired immunogenicity, a thorough understanding of parameters that affect immune responses is required. Herein, we discussed the effects of physicochemical properties on antigen presentation and immune response, including but not limited to size, particle rigidity, intrinsic immunogenicity. Furthermore, we provided a detailed overview of recent preclinical and clinical advances in nanotechnology for cancer vaccines, and considerations for future directions in advancing the vaccine platform to widespread anti-cancer applications.

Advances in Designing and Developing Vaccines, Drugs and Therapeutic Approaches to Counter Human Papilloma Virus

Human papillomavirus (HPV) is a viral infection with skin-to-skin based transmission mode. HPV annually caused over 500,000 cancer cases including cervical, anogenital and oropharyngeal cancer among others. HPV vaccination has become a public-health concern, worldwide, to prevent the cases of HPV infections including precancerous lesions, cervical cancers, and genital warts especially in adolescent female and male population by launching national programs with international alliances. Currently, available prophylactic and therapeutic vaccines are expensive to be used in developing countries for vaccination programs. The recent progress in immunotherapy, biotechnology, recombinant DNA technology and molecular biology along with alternative and complementary medicinal systems have paved novel ways and valuable opportunities to design and develop effective prophylactic and therapeutic vaccines, drugs and treatment approach to counter HPV effectively. Exploration and more researches on such advances could result in the gradual reduction in the incidences of HPV cases across the world. The present review presents a current global scenario and futuristic prospects of the advanced prophylactic and therapeutic approaches against HPV along with recent patents coverage of the progress and advances in drugs, vaccines and therapeutic regimens to effectively combat HPV infections and its cancerous conditions.

Highly enhanced cancer immunotherapy by combining nanovaccine with hyaluronidase

Tumor vaccine has been one of the research hotspots for cancer immunotherapy in recent years. By introducing tumor antigens into the body, the patient's own immune system will be specifically activated to induce effective immune responses for controlling or eliminating the malignant tumor cells. In this study, a simple nanovaccine was developed to induce antigen-specific anti-tumor immune responses. Polycationic polyethylenimine (PEI) was utilized to co-deliver the antigen ovalbumin (OVA) and the adjuvant unmethylated cytosine-phosphate-guanine (CpG) by electrostatic binding. The positively charged PEI could be beneficial to augment the PEI/CpG/OVA nanovaccine uptake in dendritic cells (DCs) and facilitate the endosomal escape of the nanovaccine for antigen delivering into the cytoplasm. The nanovaccine showed significant stimulation on DCs' maturation in vitro, and it was further applied for in vivo anti-tumor immunotherapy. To enhance the tumor infiltration of the nanovaccine-generated tumor-specific T cells, hyaluronidase (HAase) was employed to increase the permeability of the tumor tissues by breaking down the hyaluronan (HA) in the extracellular matrix (ECM) of tumors. Highly enhanced in vivo anti-tumor therapeutic efficiency was achieved by combining the PEI/CpG/OVA nanovaccine with HAase, which was attributed to the increased quantity of OVA-specific T cells in tumor tissues. The combination of nanovaccine with HAase has offered a simple and efficient strategy for inducing powerful anti-tumor effect in cancer immunotherapy.

Trial watch: DNA-based vaccines for oncological indications

DNA-based vaccination is a promising approach to cancer immunotherapy. DNA-based vaccines specific for tumor-associated antigens (TAAs) are indeed relatively simple to produce, cost-efficient and well tolerated. However, the clinical efficacy of DNA-based vaccines for cancer therapy is considerably limited by central and peripheral tolerance. During the past decade, considerable efforts have been devoted to the development and characterization of novel DNA-based vaccines that would circumvent this obstacle. In this setting, particular attention has been dedicated to the route of administration, expression of modified TAAs, co-expression of immunostimulatory molecules, and co-delivery of immune checkpoint blockers. Here, we review preclinical and clinical progress on DNA-based vaccines for cancer therapy.

Antitumor Effect of a DNA Vaccine Harboring Prostate Cancer-Specific Antigen with IL-12 as an Intramolecular Adjuvant

To improve the lower immune intensity of DNA vaccines, we developed a DNA vaccine based on prostate cancer-specific antigen (PSA), which has been suggested as a potential target for prostate cancer therapy, and enhanced the DNA vaccine potency using interleukin-12 (IL-12) as an intramolecular adjuvant. A series of DNA plasmids encoding human PSA, IL-12, and their conjugates was constructed and injected into female mice intramuscularly, followed by an electric pulse. The humoral and cellular immune responses after immunization were detected by ELISA and ELISPOT, respectively. To evaluate the therapeutic efficacy of these plasmids, a mouse model with a PSA-expressing tumor was constructed. Mice vaccinated with PSA-IL-12 plasmids elicited the strongest PSA-specific humoral and cellular immune responses. Furthermore, these vaccinations inhibited the growth of PSA-expressing tumors and prolonged mouse survival. These observations emphasize the potential of the IL-12 gene as an intramolecular adjuvant for DNA vaccines. Moreover, the vaccine based on PSA and IL-12 may be a promising treatment for prostate cancer.

CSPG4: a prototype oncoantigen for translational immunotherapy studies

Thanks to striking progress in both the understanding of anti-tumor immune response and the characterization of several tumor associated antigens (TAA), a more rational design and more sophisticated strategies for anti-tumor vaccination have been possible. However, the effectiveness of cancer vaccines in clinical trial is still partial, indicating that additional studies are needed to optimize their design and their pre-clinical testing. Indeed, anti-tumor vaccination success relies on the choice of the best TAA to be targeted and on the translational power of the pre-clinical model used to assess its efficacy. The chondroitin sulfate proteoglycan-4 (CSPG4) is a cell surface proteoglycan overexpressed in a huge range of human and canine neoplastic lesions by tumor cells, tumor microenvironment and cancer initiating cells. CSPG4 plays a central role in the oncogenic pathways required for malignant progression and metastatization. Thanks to these features and to its poor expression in adult healthy tissues, CSPG4 represents an ideal oncoantigen and thus an attractive target for anti-tumor immunotherapy. In this review we explore the potential of CSPG4 immune-targeting. Moreover, since it has been clearly demonstrated that spontaneous canine tumors mimic the progression of human malignancies better than any other pre-clinical model available so far, we reported also our results indicating that CSPG4 DNA vaccination is safe and effective in significantly increasing the survival of canine melanoma patients. Therefore, anti-CSPG4 vaccination strategy could have a substantial impact for the treatment of the wider population of spontaneous CSPG4-positive tumor affected dogs with a priceless translational value and a revolutionary implication for human oncological patients.

Safety and efficacy of p62 DNA vaccine ELENAGEN in a first-in-human trial in patients with advanced solid tumors

Elenagen is a plasmid encoding p62/SQSTM1, the first DNA vaccine possessing two mutually complementing mechanisms of action: it elicits immune response against p62 and mitigates systemic chronic inflammation. Previously, Elenagen demonstrated anti-tumor efficacy and safety in rodent tumor models and spontaneous tumors in dogs. This multicenter I/IIa trial evaluated safety and clinical activity of Elenagen in patients with advanced solid tumors. Fifteen patients were treated with escalating doses of Elenagen (1- 5 mg per doses, 5 times weekly) and additional 12 patients received 1 mg dose. Ten patients with breast and ovary cancers that progressed after Elenagen were then treated with conventional chemotherapy. Adverse events (AE) were of Grade 1; no severe AE were observed. Cumulatively twelve patients (44%) with breast, ovary, lung, renal cancer and melanoma achieved stable disease for at least 8 wks, with 4 of them (15%) had tumor control for more than 24 wks, with a maximum of 32 wks. The patients with breast and ovary cancers achieved additional tumor stabilization for 12-28 wks when treated with chemotherapy following Elenagen treatment. Therefore, Elenagen demonstrated good safety profile and antitumor activity in advanced solid tumors. Especially encouraging is its ability to restore tumor sensitivity to chemotherapy.

Phase I clinical trial of idiotypic DNA vaccine administered as a complex with polyethylenimine to patients with B-cell lymphoma

We report on the design of a phase I, non-randomized, open-label study of idiotypic DNA vaccination in patients with B-cell non-Hodgkin's lymphoma (ISRCTN31090206). The study uses DNA fusion gene vaccination encoding patient-specific single chain variable fragment, or idiotype, linked to an immunostimulatory sequence. Two types of immunostimulatory sequence are being explored: potato virus X coat protein and human chemokine MIP3α. Linear polyethylenimine with low molecular weight (8 kDa) is used as a synthetic vehicle for vaccine delivery. Humoral and T-cellular immune responses to vaccination will be measured by ELISA and ELISPOT, respectively. The primary study endpoints are safety, tolerability and immunogenicity of DNA-PEI vaccination.

Fusion of the dendritic cell-targeting chemokine MIP3α to melanoma antigen Gp100 in a therapeutic DNA vaccine significantly enhances immunogenicity and survival in a mouse melanoma model

Background

Although therapeutic cancer vaccines have been mostly disappointing in the clinic, the advent of novel immunotherapies and the future promise of neoantigen-based therapies have created the need for new vaccine modalities that can easily adapt to current and future developments in cancer immunotherapy. One such novel platform is a DNA vaccine fusing the chemokine Macrophage Inflammatory Protein-3α (MIP-3α) to an antigen, here melanoma antigen gp100. Previous published work has indicated that MIP-3α targets nascent peptides to immature dendritic cells, leading to processing by class I and II MHC pathways. This platform has shown enhanced efficacy in prophylactic melanoma and therapeutic lymphoma model systems.

Methods

The B16F10 melanoma syngeneic mouse model system was utilized, with a standard therapeutic protocol: challenge with lethal dose of B16F10 cells (5 × 10⁴) on day 0 and then vaccinate by intramuscular electroporation with 50 μg plasmid on days three, 10, and 17. Efficacy was assessed by analysis of tumor burden, tumor growth, and mouse survival, using the statistical tests ANOVA, mixed effects regression, and log-rank, respectively. Immunogenicity was assessed by ELISA and flow cytometric methods, including intracellular cytokine staining to assess vaccine-specific T-cell responses, all tested by ANOVA.

Results

We demonstrate that the addition of MIP3α to gp100 significantly enhances systemic anti-gp100 immunological parameters. Further, chemokine-fusion vaccine therapy significantly reduces tumor burden, slows tumor growth, and enhances mouse overall survival compared to antigen-only, irrelevant-antigen, and mock vaccines, with efficacy mediated by both CD4+ and CD8+ effector T cells. Antigen-only, irrelevant-antigen, and chemokine-fusion vaccines elicit significantly higher and similar CD4+ and CD8+ tumor-infiltrating lymphocyte (TIL) levels compared to mock vaccine. However, vaccine-specific CD8+ TILs are significantly higher in the chemokine-fusion vaccine group, indicating that the critical step induced by the fusion vaccine construct is the enhancement of vaccine-specific T-cell effectors.

Conclusions

The current study shows that fusion of MIP3α to melanoma antigen gp100 enhances the immunogenicity and efficacy of a DNA vaccine in a therapeutic B16F10 mouse melanoma model. This study analyzes an adaptable and easily produced MIP3α-antigen modular vaccine platform that could lend itself to a variety of functionalities, including combination treatments and neoantigen vaccination in the pursuit of personalized cancer therapy.

Electronic supplementary material

The online version of this article (doi:10.1186/s40425-016-0189-y) contains supplementary material, which is available to authorized users.

Coadministration of a Plasmid Encoding HIV-1 Gag Enhances the Efficacy of Cancer DNA Vaccines

DNA vaccination holds great promise for the prevention and treatment of cancer and infectious diseases. However, the clinical ability of DNA vaccines is still controversial due to the limited immune response initially observed in humans. We hypothesized that electroporation of a plasmid encoding the HIV-1 Gag viral capsid protein would enhance cancer DNA vaccine potency. DNA electroporation used to deliver plasmids in vivo, induced type I interferons, thereby supporting the activation of innate immunity. The coadministration of ovalbumin (OVA) and HIV-1 Gag encoding plasmids modulated the adaptive immune response. This strategy favored antigen-specific Th1 immunity, delayed B16F10-OVA tumor growth and improved mouse survival in both prophylactic and therapeutic vaccination approaches. Similarly, a prophylactic DNA immunization against the melanoma-associated antigen gp100 was enhanced by the codelivery of the HIV-1 Gag plasmid. The adjuvant effect was not driven by the formation of HIV-1 Gag virus-like particles. This work highlights the ability of both electroporation and the HIV-1 Gag plasmid to stimulate innate immunity for enhancing cancer DNA vaccine immunogenicity and demonstrates interesting tracks for the design of new translational genetic adjuvants to overcome the current limitations of DNA vaccines in humans.

Antigen Selection for Enhanced Affinity T-Cell Receptor-Based Cancer Therapies

Evidence of adaptive immune responses in the prevention of cancer has been accumulating for decades. Spontaneous T-cell responses occur in multiple indications, bringing the study of de novo expressed cancer antigens to the fore and highlighting their potential as targets for cancer immunotherapy. Circumventing the immune-suppressive mechanisms that maintain tumor tolerance and driving an antitumor cytotoxic T-cell response in cancer patients may eradicate the tumor or block disease progression. Multiple strategies are being pursued to harness the cytotoxic potential of T cells clinically. Highly promising results are now emerging. The focus of this review is the target discovery process for cancer immune therapeutics based on affinity-matured T-cell receptors (TCRs). Target cancer antigens in the context of adoptive cell transfer technologies and soluble biologic agents are discussed. To appreciate the impact of TCR-based technology and understand the TCR discovery process, it is necessary to understand key differences between TCR-based therapy and other immunotherapy approaches. The review first summarizes key advances in the cancer immunotherapy field and then discusses the opportunities that TCR technology provides. The nature and breadth of molecular targets that are tractable to this approach are discussed, together with the challenges associated with finding them.

Vectors and strategies for nonviral cancer gene therapy

INTRODUCTION

This review presents recent developments in the use of nonviral vectors and transfer technologies in cancer gene therapy. Tremendous progress has been made in developing cancer gene therapy in ways that could be applicable to treatments. Numerous efforts are focused on methods of attacking known and novel targets more efficiently and specifically. In parallel to progress in nonviral vector design and delivery technologies, important achievements have been accomplished for suicide, gene replacement, gene suppression and immunostimulatory therapies. New nonviral cancer gene therapies have been developed based on emerging RNAi (si/shRNA-, miRNA) or ODN.

AREAS COVERED

This review provides an overview of recent gene therapeutic strategies in which nonviral vectors have been used experimentally and in clinical trials. Furthermore, we present current developments in nonviral vector systems in association with important chemical and physical gene delivery technologies and their potential for the future.

EXPERT OPINION

Nonviral gene therapy has maintained its position as an approach for treating cancer. This is reflected by the fact that more than 17% of all gene therapy trials employ nonviral approaches. Thus, nonviral vectors have emerged as a clinical alternative to viral vectors for the appropriate expression and delivery of therapeutic genes.

Intellectual Property in Vaccine Innovation: Impact of Recent Patent Developments

This chapter examines the issues on patentability of microorganisms and human genes under the US laws and analyzes their influence on vaccine innovation. The analysis will focus on three aspects, namely, the naturally existing state, unmodified isolated form (i.e., mere extraction from the natural environment), and human-modified/genetically engineered structure. The outcome of the assessment suggests that the impact of the recent US patent jurisprudence on vaccines may differ significantly depending on whether the preparation of a vaccine in question involves natural or man-made DNA material.

Clinical potential of electroporation for gene therapy and DNA vaccine delivery

INTRODUCTION

Electroporation allows efficient delivery of DNA into cells and tissues, thereby improving the expression of therapeutic or immunogenic proteins that are encoded by plasmid DNA. This simple and versatile method holds a great potential and could address unmet medical needs such as the prevention or treatment of many cancers or infectious diseases.

AREAS COVERED

This review explores the electroporation mechanism and the parameters affecting its efficacy. An analysis of past and current clinical trials focused on DNA electroporation is presented. The pathologies addressed, the protocol used, the treatment outcome and the tolerability are highlighted. In addition, several of the possible optimization strategies for improving patient compliance and therapeutic efficacy are discussed such as plasmid design, use of genetic adjuvants for DNA vaccines, choice of appropriate delivery site and electrodes as well as pulse parameters.

EXPERT OPINION

The growing number of clinical trials and the results already available underline the strong potential of DNA electroporation which combines both safety and efficiency. Nevertheless, it remains critical to further increase fundamental knowledge to refine future strategies, to develop concerted and common DNA electroporation protocols and to continue exploring new electroporation-based therapeutic options.

Trial Watch-Immunostimulation with cytokines in cancer therapy

During the past decade, great efforts have been dedicated to the development of clinically relevant interventions that would trigger potent (and hence potentially curative) anticancer immune responses. Indeed, developing neoplasms normally establish local and systemic immunosuppressive networks that inhibit tumor-targeting immune effector cells, be them natural or elicited by (immuno)therapy. One possible approach to boost anticancer immunity consists in the (generally systemic) administration of recombinant immunostimulatory cytokines. In a limited number of oncological indications, immunostimulatory cytokines mediate clinical activity as standalone immunotherapeutic interventions. Most often, however, immunostimulatory cytokines are employed as immunological adjuvants, i.e., to unleash the immunogenic potential of other immunotherapeutic agents, like tumor-targeting vaccines and checkpoint blockers. Here, we discuss recent preclinical and clinical advances in the use of some cytokines as immunostimulatory agents in oncological indications.

Short Peptide Vaccine Induces CD4+ T Helper Cells in Patients with Different Solid Cancers

Previous cancer vaccination trials often aimed to activate CD8(+) cytotoxic T-cell (CTL) responses with short (8-10mer) peptides and targeted CD4(+) helper T cells (TH) with HLA class II-binding longer peptides (12-16 mer) that were derived from tumor antigens. Accordingly, a study of immunomonitoring focused on the detection of CTL responses to the short, and TH responses to the long, peptides. The possible induction of concurrent TH responses to short peptides was widely neglected. In a recent phase I vaccination trial, 53 patients with different solid cancers were vaccinated with EMD640744, a cocktail of five survivin-derived short (9- or 10-mer) peptides in Montanide ISA 51VG. We monitored 49 patients and found strong CD8(+) T-cell responses in 63% of the patients. In addition, we unexpectedly found CD4(+) TH cell responses against at least two of the five short peptides in 61% (23/38) of the patients analyzed. The two peptides were recognized by HLA-DP4- and HLA-DR-restricted TH1 cells. Some short peptide-reactive (sp)CD4 T cells showed high functional avidity. Here, we show that a short peptide vaccine is able to activate a specific CD4(+) T-cell repertoire in many patients, facilitating a strong combined CD4(+)/CD8(+) T-cell response.

Pilot study of p62 DNA vaccine in dogs with mammary tumors

Our previous data demonstrated profound anti-tumor and anti-metastatic effects of p62 (sqstm1) DNA vaccine in rodents with various types of transplantable tumors. Testing anti-cancer medicine in dogs as an intermediary step of translational research program provides two major benefits. First, clinical data collected in target animals is required for FDA/USDA approval as a veterinary anti-cancer drug or vaccine. It is noteworthy that the veterinary community is in need of novel medicine for the prevention and treatment of canine and feline cancers. The second more important benefit of testing anti-cancer vaccines in dogs is that spontaneous tumors in dogs may provide invaluable information for human trials. Here, we evaluated the effect(s) of p62 DNA vaccine on mammary tumors of dogs. We found that p62 DNA vaccine administered i.m. decreased or stabilized growth of locally advanced lesions in absence of its overall toxic effects. The observed antitumor activity was associated with lymphocyte infiltration and tumor encapsulation via fibrotic reaction. This data justifies both human clinical trials and veterinary application of p62 DNA vaccine.

Nucleic acid vaccination strategies against infectious diseases

INTRODUCTION

Gene vaccines are an interesting and emerging alternative for the prevention of infectious diseases, as well as in the treatment of other pathologies including cancer, allergies, autoimmune diseases, or even drug dependencies. When applied to the target organism, these vaccines induce the expression of encoded antigens and elicit the corresponding immune response, with the potential ability of being able to induce antibody-, helper T cell-, and cytotoxic T cell-mediated immune responses.

AREAS COVERED

Special attention is paid to the variety of adjuvants that may be co-administered to enhance and/or to modulate immune responses, and to the methods of delivery. Finally, this article reviews the efficacy data of gene vaccines against infectious diseases released from current clinical trials.

EXPERT OPINION

Taken together, this approach will have a major impact on future strategies for the prevention of infectious diseases. Better-designed nucleic acid constructs, novel delivery technologies, as well as the clarification of the mechanisms for antigen presentation will improve the potential applications of this vaccination strategy against microbial pathogens.

Nanoparticle Drug Delivery Systems Designed to Improve Cancer Vaccines and Immunotherapy

Recent studies have demonstrated great therapeutic potential of educating and unleashing our own immune system for cancer treatment. However, there are still major challenges in cancer immunotherapy, including poor immunogenicity of cancer vaccines, off-target side effects of immunotherapeutics, as well as suboptimal outcomes of adoptive T cell transfer-based therapies. Nanomaterials with defined physico-biochemical properties are versatile drug delivery platforms that may address these key technical challenges facing cancer vaccines and immunotherapy. Nanoparticle systems have been shown to improve targeted delivery of tumor antigens and therapeutics against immune checkpoint molecules, amplify immune activation via the use of new stimuli-responsive or immunostimulatory materials, and augment the efficacy of adoptive cell therapies. Here, we review the current state-of-the-art in nanoparticle-based strategies designed to potentiate cancer immunotherapies, including cancer vaccines with subunit antigens (e.g., oncoproteins, mutated neo-antigens, DNA and mRNA antigens) and whole-cell tumor antigens, dendritic cell-based vaccines, artificial antigen-presenting cells, and immunotherapeutics based on immunogenic cell death, immune checkpoint blockade, and adoptive T-cell therapy.

Safety and preliminary evidence of biologic efficacy of a mammaglobin-a DNA vaccine in patients with stable metastatic breast cancer

PURPOSE

Mammaglobin-A (MAM-A) is overexpressed in 40% to 80% of primary breast cancers. We initiated a phase I clinical trial of a MAM-A DNA vaccine to evaluate its safety and biologic efficacy.

EXPERIMENTAL DESIGN

Patients with breast cancer with stable metastatic disease were eligible for enrollment. Safety was monitored with clinical and laboratory assessments. The CD8 T-cell response was measured by ELISPOT, flow cytometry, and cytotoxicity assays. Progression-free survival (PFS) was described using the Kaplan-Meier product limit estimator.

RESULTS

Fourteen subjects have been treated with the MAM-A DNA vaccine and no significant adverse events have been observed. Eight of 14 subjects were HLA-A2(+), and the CD8 T-cell response to vaccination was studied in detail. Flow cytometry demonstrated a significant increase in the frequency of MAM-A-specific CD8 T cells after vaccination (0.9% ± 0.5% vs. 3.8% ± 1.2%; P < 0.001), and ELISPOT analysis demonstrated an increase in the number of MAM-A-specific IFNγ-secreting T cells (41 ± 32 vs. 215 ± 67 spm; P < 0.001). Although this study was not powered to evaluate progression-free survival (PFS), preliminary evidence suggests that subjects treated with the MAM-A DNA vaccine had improved PFS compared with subjects who met all eligibility criteria, were enrolled in the trial, but were not vaccinated because of HLA phenotype.

CONCLUSION

The MAM-A DNA vaccine is safe, capable of eliciting MAM-A-specific CD8 T-cell responses, and preliminary evidence suggests improved PFS. Additional studies are required to define the potential of the MAM-A DNA vaccine for breast cancer prevention and/or therapy.

Feasibility analysis of p62 (SQSTM1)-encoding DNA vaccine as a novel cancer immunotherapy

Cancer immunotherapy is a thriving field, but its clinical achievements are modest so far. One of its major hurdles seems to be finding a feasible cancer antigen as a target for immune response. After many years of research, three major criteria for choice of tumor antigens emerged. An antigen should be: (i) immunogenic; (ii) essential for cancers cells (to avoid its loss through immunoediting), but dispensable for normal tissues to reduce the risk of toxicity, and (iii) overexpressed in tumors as compared to the normal tissues. Here we argue that p62 (SQSTM1), a protein involved in autophagy and signal transduction, fits all the above criteria and can be chosen as a novel cancer antigen. Accordingly, we carried out an extensive study and found antitumor and antimetastatic activity of p62-encoding DNA vaccine in five types of commonly used transplantable tumor models of mice and rats, and spontaneous tumors in several dogs. Given that toxicity of p62 vaccine was minimal, if any, we believe that p62-encoding vaccine merits further clinical development.

Vaccines, Adjuvants, and Dendritic Cell Activators--Current Status and Future Challenges

Cancer vaccines offer a low-toxicity approach to induce anticancer immune responses. They have shown promise for clinical benefit with one cancer vaccine approved in the United States for advanced prostate cancer. As other immune therapies are now clearly effective for treatment of advanced cancers of many histologies, there is renewed enthusiasm for optimizing cancer vaccines for use to prevent recurrence in early-stage cancers and/or to combine with other immune therapies for therapy of advanced cancers. Future advancements in vaccine therapy will involve the identification and selection of effective antigen formulations, optimization of adjuvants, dendritic cell (DC) activation, and combination therapies. In this summary we present the current practice, the broad collection of challenges, and the promising future directions of vaccine therapy for cancer.

Trial watch: Naked and vectored DNA-based anticancer vaccines

One type of anticancer vaccine relies on the administration of DNA constructs encoding one or multiple tumor-associated antigens (TAAs). The ultimate objective of these preparations, which can be naked or vectored by non-pathogenic viruses, bacteria or yeast cells, is to drive the synthesis of TAAs in the context of an immunostimulatory milieu, resulting in the (re-)elicitation of a tumor-targeting immune response. In spite of encouraging preclinical results, the clinical efficacy of DNA-based vaccines employed as standalone immunotherapeutic interventions in cancer patients appears to be limited. Thus, efforts are currently being devoted to the development of combinatorial regimens that allow DNA-based anticancer vaccines to elicit clinically relevant immune responses. Here, we discuss recent advances in the preclinical and clinical development of this therapeutic paradigm.

Trial Watch: Immunomodulatory monoclonal antibodies for oncological indications

Immunomodulatory monoclonal antibodies (mAbs) differ from their tumor-targeting counterparts because they exert therapeutic effects by directly interacting with soluble or (most often) cellular components of the immune system. Besides holding promise for the treatment of autoimmune and inflammatory disorders, immunomodulatory mAbs have recently been shown to constitute a potent therapeutic weapon against neoplastic conditions. One class of immunomodulatory mAbs operates by inhibiting safeguard systems that are frequently harnessed by cancer cells to establish immunological tolerance, the so-called "immune checkpoints." No less than 3 checkpoint-blocking mAbs have been approved worldwide for use in oncological indications, 2 of which during the past 12 months. These molecules not only mediate single-agent clinical activity in patients affected by specific neoplasms, but also significantly boost the efficacy of several anticancer chemo-, radio- or immunotherapies. Here, we summarize recent advances in the development of checkpoint-blocking mAbs, as well as of immunomodulatory mAbs with distinct mechanisms of action.

Induction of HER2 Immunity in Outbred Domestic Cats by DNA Electrovaccination

Domestic cats share human living environments and genetic traits. They develop spontaneous feline mammary carcinoma (FMC) with similar histopathology to human breast cancer. HER2 and AKT phosphorylation was demonstrated in primary FMC by immunoblot analysis, indicating HER2 as a therapeutic target. FMC lines K12 and K248 expressing HER1, HER2, and HER3 were sensitive to receptor tyrosine kinase (RTK) inhibitors gefitinib and lapatinib. To test HER2 vaccine response in cats, purpose-bred, healthy cats were electrovaccinated with heterologous (xenogeneic) or point-mutated feline HER2 DNA. T-cell reactivity to feline self-HER2 was detected in 4 of 10 cats that received bear HER2, human-rat fusion HER2 (E2Neu) or mutant feline HER2 (feHER2-K), which contains a single amino acid substitution. The variable T-cell responses may resemble that in the genetically heterogeneous human population. All immune sera to heterologous HER2 recognized feline HER2 expressed in 3T3 cells (3T3/HER2), but not that in FMC K12 or K248. Immune sera to mutant pfeHER2-K bound 3T3/HER2 cells weakly, but they showed better recognition of K12 and K248 cells that also express HER1 and HER3, suggesting distinct HER2 epitopes displayed by FMC that may be simulated by feHER2-K. In summary, HER2 DNA electroporation overcomes T-cell immune tolerance in approximately 40% of healthy cats and induces antibodies with distinct specificity. Vaccination studies in domestic cats can expedite vaccine iteration to guide human vaccine design and better predict outcome, with the added benefit of helping feline mammary tumor patients.

Trial watch: Tumor-targeting monoclonal antibodies for oncological indications

An expanding panel of monoclonal antibodies (mAbs) that specifically target malignant cells or intercept trophic factors delivered by the tumor stroma is now available for cancer therapy. These mAbs can exert direct antiproliferative/cytotoxic effects as they inhibit pro-survival signal transduction cascades or activate lethal receptors at the plasma membrane of cancer cells, they can opsonize neoplastic cells to initiate a tumor-targeting immune response, or they can be harnessed to specifically deliver toxins or radionuclides to transformed cells. As an indication of the success of this immunotherapeutic paradigm, international regulatory agencies approve new tumor-targeting mAbs for use in cancer patients every year. Moreover, the list of indications for previously licensed molecules is frequently expanded to other neoplastic disorders as the results of large, randomized clinical trials become available. Here, we discuss recent advances in the preclinical and clinical development of tumor-targeting mAbs for oncological indications.

Classification of current anticancer immunotherapies

During the past decades, anticancer immunotherapy has evolved from a promising therapeutic option to a robust clinical reality. Many immunotherapeutic regimens are now approved by the US Food and Drug Administration and the European Medicines Agency for use in cancer patients, and many others are being investigated as standalone therapeutic interventions or combined with conventional treatments in clinical studies. Immunotherapies may be subdivided into "passive" and "active" based on their ability to engage the host immune system against cancer. Since the anticancer activity of most passive immunotherapeutics (including tumor-targeting monoclonal antibodies) also relies on the host immune system, this classification does not properly reflect the complexity of the drug-host-tumor interaction. Alternatively, anticancer immunotherapeutics can be classified according to their antigen specificity. While some immunotherapies specifically target one (or a few) defined tumor-associated antigen(s), others operate in a relatively non-specific manner and boost natural or therapy-elicited anticancer immune responses of unknown and often broad specificity. Here, we propose a critical, integrated classification of anticancer immunotherapies and discuss the clinical relevance of these approaches.

Trial watch: IDO inhibitors in cancer therapy

Indoleamine 2,3-dioxigenase 1 (IDO1) is the main enzyme that catalyzes the first, rate-limiting step of the so-called "kynurenine pathway", i.e., the metabolic cascade that converts the essential amino acid L-tryptophan (Trp) into L-kynurenine (Kyn). IDO1, which is expressed constitutively by some tissues and in an inducible manner by specific subsets of antigen-presenting cells, has been shown to play a role in the establishment and maintenance of peripheral tolerance. At least in part, this reflects the capacity of IDO1 to restrict the microenvironmental availability of Trp and to favor the accumulation of Kyn and some of its derivatives. Also, several neoplastic lesions express IDO1, providing them with a means to evade anticancer immunosurveillance. This consideration has driven the development of several IDO1 inhibitors, some of which (including 1-methyltryptophan) have nowadays entered clinical evaluation. In animal tumor models, the inhibition of IDO1 by chemical or genetic interventions is indeed associated with the (re)activation of therapeutically relevant anticancer immune responses. This said, several immunotherapeutic regimens exert robust clinical activity in spite of their ability to promote the expression of IDO1. Moreover, 1-methyltryptophan has recently been shown to exert IDO1-independent immunostimulatory effects. Here, we summarize the preclinical and clinical studies testing the antineoplastic activity of IDO1-targeting interventions.

Optimization of a gene electrotransfer procedure for efficient intradermal immunization with an hTERT-based DNA vaccine in mice

DNA vaccination consists in administering an antigen-encoding plasmid in order to trigger a specific immune response. This specific vaccine strategy is of particular interest to fight against various infectious diseases and cancer. Gene electrotransfer is the most efficient and safest non-viral gene transfer procedure and specific electrical parameters have been developed for several target tissues. Here, a gene electrotransfer protocol into the skin has been optimized in mice for efficient intradermal immunization against the well-known telomerase tumor antigen. First, the luciferase reporter gene was used to evaluate gene electrotransfer efficiency into the skin as a function of the electrical parameters and electrodes, either non-invasive or invasive. In a second time, these parameters were tested for their potency to generate specific cellular CD8 immune responses against telomerase epitopes. These CD8 T-cells were fully functional as they secreted IFNγ and were endowed with specific cytotoxic activity towards target cells. This simple and optimized procedure for efficient gene electrotransfer into the skin using the telomerase antigen is to be used in cancer patients for the phase 1 clinical evaluation of a therapeutic cancer DNA vaccine called INVAC-1.

Different immunogenicity but similar antitumor efficacy of two DNA vaccines coding for an antigen secreted in different membrane vesicle-associated forms

The induction of an active immune response to control or eliminate tumours is still an unfulfilled challenge. We focused on plasmid DNA vaccines using an innovative approach whereby the antigen is expressed in association with extracellular vesicles (EVs) to facilitate antigen cross-presentation and improve induced immunity. Our two groups had independently shown previously that DNA vaccines encoding EV-associated antigens are more efficient at inducing cytotoxic T-cell responses than vaccines encoding the non-EV-associated antigen. Here, we compared our two approaches to associate the ovalbumin (OVA) antigen to EVs: (a) by fusion to the lipid-binding domain C1C2 of MFGE8(=lactadherin), which is exposed on the surface of secreted membrane vesicles; and (b) by fusion to retroviral Gag capsid protein, which is incorporated inside membrane-enclosed virus-like particles. Plasmids encoding either form of modified OVA were used as DNA-based vaccines (i.e. injected into mice to allow in vivo expression of the antigen associated to EVs). We show that both DNA vaccines induced, with similar efficiency, OVA-specific CD8(+) T cells and total IgG antibodies. By contrast, each vaccine preferentially stimulated different isotypes of immunoglobulins, and the OVA-C1C2-encoding vaccine favoured antigen-specific CD4(+) T lymphocyte induction as compared to the Gag-OVA vaccine. Nevertheless, both OVA-C1C2 and Gag-OVA vaccines efficiently prevented in vivo outgrowth of OVA-expressing tumours and reduced tumour progression when administered to tumour-bearing mice, although with variable efficacies depending on the tumour models. DNA vaccines encoding EV-associated antigens are thus promising immunotherapy tools in cancer but also potentially other diseases.