Immunity to Cancer Through Immune Recognition of Altered Self: Studies with Melanoma

RNA vaccines for cancer: Principles to practice

Vaccines are the most impactful medicines to improve health. Though potent against pathogens, vaccines for cancer remain an unfulfilled promise. However, recent advances in RNA technology coupled with scientific and clinical breakthroughs have spurred rapid discovery and potent delivery of tumor antigens at speed and scale, transforming cancer vaccines into a tantalizing prospect. Yet, despite being at a pivotal juncture, with several randomized clinical trials maturing in upcoming years, several critical questions remain: which antigens, tumors, platforms, and hosts can trigger potent immunity with clinical impact? Here, we address these questions with a principled framework of cancer vaccination from antigen detection to delivery. With this framework, we outline features of emergent RNA technology that enable rapid, robust, real-time vaccination with somatic mutation-derived neoantigens-an emerging "ideal" antigen class-and highlight latent features that have sparked the belief that RNA could realize the enduring vision for vaccines against cancer.

Exploring the Impact of mRNA Modifications on Translation Efficiency and Immune Tolerance to Self-Antigens

Therapeutic modified mRNAs are being developed for a broad range of human diseases. However, the impact of potential miscoding of modified mRNAs on self-tolerance remains unknown. Additionally, more studies are needed to explore the effects of nucleoside alkylation on translation. While all six tested modifications are tolerated as substrates by T7 RNA polymerase and inhibited mRNA immunogenicity, the translation efficiency varied significantly depending on the type of modification. In contrast to methylation, ethylation at the N1 position of pseudouridine (Ψ) hindered translation, suggesting that the C5-C1' glycosidic bond alone is not a critical element for high translation. Inhibition of mRNA translation was also observed with 5-methoxyuridine modification. However, this inhibition was partially alleviated through the optimization of mRNA coding sequences. BALB/c mice immunized with syngeneic ψ-modified mRNA encoding for Wilms' tumor antigen-1 (WT1) developed a low but significant level of anti-WT1 IgG antibodies compared to those immunized with either unmodified or N1-methyl ψ-modified mRNA. Overall, the data indicate that adding a simple ethyl group (-CH2CH3) at the N1 position of ψ has a major negative effect on translation despite its reduced immunogenicity. Additionally, mRNA containing Ψ may alter translation fidelity at certain codons, which could lead to a breakdown of immune tolerance to self-antigens. This concern should be taken into account during gene replacement therapies, although it could benefit mRNA-based vaccines by generating a diverse repertoire of antigens.

Key Activating and Inhibitory Ligands Involved in the Mobilization of Natural Killer Cells for Cancer Immunotherapies

Natural killer (NK) cells are the most potent arm of the innate immune system and play an important role in immunity, alloimmunity, autoimmunity, and cancer. NK cells recognize “altered-self” cells due to oncogenic transformation or stress due to viral infection and target to kill them. The effector functions of NK cells depend on the interaction of the activating and inhibitory receptors on their surface with their cognate ligand expressed on the target cells. These activating and inhibitory receptors interact with major histocompatibility complex I (MHC I) expressed on the target cells and make decisions to mount an immune response. NK cell immune response includes cytolytic activity and secretion of cytokines to help with the ongoing immune response. The advancement of our knowledge on the expression of inhibitory and activating molecules led us to exploit these molecules in the treatment of cancer. This review discusses the importance of activating and inhibitory receptors on NK cells and their clinical importance in cancer immunotherapy.

APOBEC and Cancer Viroimmunotherapy: Thinking the Unthinkable

The apolipoprotein B mRNA editing enzyme catalytic polypeptide (APOBEC) family protects against infection by degrading incoming viral genomes through cytosine deamination. Here, we review how the potential to unleash these potent DNA mutagens comes at a price as APOBEC DNA mutagenesis can contribute to development of multiple types of cancer. In addition, because viral infection induces its expression, APOBEC is seen as the enemy of oncolytic virotherapy through mutation of the viral genome and by generating virotherapy-resistant tumors. Therefore, overall APOBEC in cancer has received very poor press. However, we also speculate how there may be silver linings to the storm clouds (kataegis) associated with APOBEC activity. Thus, although mutagenic genomic chaos promotes emergence of ever more aggressive subclones, it also provides significant opportunity for cytotoxic and immune therapies. In particular, the superpower of cancer immunotherapy derives in part from mutation, wherein generation of tumor neoantigens-neoantigenesis-exposes tumor cells to functional T-cell repertoires, and susceptibility to immune checkpoint blockade. Moreover, APOBECs may be able to induce suprathreshold levels of cellular mutation leading to mitotic catastrophe and direct tumor cell killing. Finally, we discuss the possibility that linking predictable APOBEC-induced mutation with escape from specific frontline therapies could identify mutated molecules/pathways that can be targeted with small molecules and/or immunotherapies in a Trap and Ambush strategy. Together, these considerations lead to the counterintuitive hypothesis that, instead of attempting to expunge and excoriate APOBEC activity in cancer therapy, it might be exploited-and even, counterintuitively, encouraged.

Differential Immunomodulatory Effect of Carbon Dots Influenced by the Type of Surface Passivation Agent

Carbon nanodots (CDs) are often synthesized from natural sources including honey, molasses, fruits, and foods, and plant extracts simply through caramelization. They have wide biological applications especially as drug delivery vehicles and bioimaging agent due to their small size and biocompatibility. This article details the synthesis of carbon dots from carob and its derivatives by surface passivation with polyethylene glycol (PEG), polyvinyl alcohol (PVA), and alginate (ALG). We investigated the immune response against CDs and evaluated the effect of surface passivation agents on their immunomodulatory functions. CD_PVA had strong anti-inflammatory activities, whereas CD_ALG were pro-inflammatory. CD_PEG had mild anti-inflammatory activities suggesting that these CDs can be used in the drug delivery studies as inert carriers. These results showed that depending on the type of activated groups dominated on the surface, CDs exerted differential effects on the inflammatory potential of the macrophages by changing the pro-inflammatory TNFα and IL6 production levels.

Ruthenium Bipyridyl Dithiocyanate Complex Exerted Adjuvant Activity on the Activated Mammalian Macrophages in vitro

A cell's function can be regulated through its mechanism, and there has been a growing body of literature on how immune cells' metabolism shapes its overall immune response. Manipulation of the cells metabolic activity through a biocompatible material would present new venues to the field of medicine. These agents are known as immunomodulatory and immunostimulatory reagents. They can either stimulate the immune response in a disease case where the immune response is lacking the strength or they can determine the nature and strength of the immune response as an immunomodulator according to our needs to cope with certain disorders. In our recent studies, we have been examining different kinds of materials on the macrophages in order to delineate their immunostimulatory or immunomodulatory potentials. Ruthenium-based materials have gathered our attention due to their ability to get involved into the electron mobility processes in the solar cells. In line with our expectations, probably by interfering the electron transport processes of the macrophages, ruthenium bipyridyl dithiocyanate complex had a stark immunomodulatory function on the LPS-activated mammalian macrophages in vitro. Our results support that it can be utilized as an adjuvant in the new generation vaccines.

Differential Immunomodulatory Activities of Schiff Base Complexes Depending on their Metal Conjugation

Immunomodulatory compounds have become crucial with advances in immunotherapy. Using our own immune system cells, we can direct the immune cell function and develop desired response against a certain threat. Immunotherapy applications have been suggested against tumors, autoimmune disorders, and infectious diseases. Vaccination can be considered as one of the best known example of immunotherapy. Infectious agent's signature molecular structures are introduced to the immune cells together with the adjuvants that further activate the immune cells to mount a proper immune response and memory. Immunotherapy and vaccine formulations are in constant need of a library of immunomodulatory reagents that can be applied depending on the target. In order to expand the number of immunomodulatory reagents that can find medicinal applications, our group has been testing unique chemical structures on the immune system cells, especially macrophages. Schiff base complexes are known for their anti-inflammatory and antimicrobial activities. In this study, we used previously characterized Schiff base complexes with different metal conjugations. These molecules had differential immunostimulatory and immunomodulatory potentials on macrophages in vitro depending on the type of the conjugated metal. After light exposure, these complexes changed their characteristics and became powerful anti-inflammatory complexes. Due to their possible antimicrobial potentials, we also tested their activities against gram negative and gram positive bacteria. All of the complexes exerted antimicrobial activities which were not light responsive. Here, we present Schiff base complexes with differential immunostimulatory and immunomodulatory activities that can also efficiently eliminate gram positive and gram negative bacteria. Upon photo activation, they block the production of inflammatory TNFα cytokine. Therefore, together with the light, they can be used to treat bacterial infections associated with damaging inflammation. Graphical Abstract.

Heteroleptic Ruthenium Polypyridyl Complex Had Differential Effects on the Production of Pro-inflammatory Cytokines TNFα, IL1β, and IL6 by the Mammalian Macrophages In Vitro

Modulation of the immune system has gathered more attention in the field of medicine due to the immense potential that it presents. Our immune system has important roles against cancer to infectious diseases, as well as in the development of autoimmune disorders. Therefore, being able to manipulate our immune system cells would enable us to determine the type and strength of the immune response to certain danger stimuli. Macrophages play an important role in the regulation of the immune system by producing cytokines, chemokines and by presenting antigens to other immune system cells to enable their activation; in our study, we focused on their in vitro activity in terms of pro-inflammatory cytokine production. In order to screen new immunomodulatory or immunostimulatory drug candidates, we examined the effect of ruthenium polypyridyl-based complex K30 that is used in solar cells as photosensitizer. Due to its electron transfer capacity, this material has potential to change the electron transfer reactions therefore could alter the function of the cells through metabolic changes at a cellular level. Our results suggest that K30 was differentially regulating the secretion levels of the pro-inflammatory cytokines by the LPS-activated mammalian macrophages, while it did not stimulate the macrophages by itself. K30 has an anti-inflammatory potential while lacking the immunostimulatory effect in our in vitro results and has potential to be used as anti-inflammatory drug molecule in metallic implants of the fractured bones to prevent damaging inflammatory environment and enable more efficient transplant and healing.

Novel Copper Bearing Schiff Bases with Photodynamic Anti-Inflammatory and Anti-Microbial Activities

Schiff bases and their copper complexes have been previously studied for their anti-inflammatory, anti-tumor as well as anti-microbial activities. Schiff bases can be derivatized to gain photoluminiscence capacity. This property of the schiff bases enables the transfer of the electrons upon absorption of the light at a specific wavelength. In this study, we exploited this attribute of novel copper bearing schiff bases and tested their photodynamic biological activities. These compounds exerted photodynamic anti-inflammatory activities on the in vitro activated mammalian macrophages. Compared with salicylic acid control groups, these novel schiff bases had stronger activity which became more prominent with photo-induction. Moreover, they also had anti-microbial activity on gram negative bacteria E.coli and gram positive bacteria S.aureus.This anti-microbial activity was stronger than that of Neomycin on both bacterial strains. Our results suggest their potential use as anti-inflammatory and anti-microbial agents both in the dark as well as after photo-induction.

Immunotherapy a New Hope for Cancer Treatment: A Review

Cancer is a major burden of disease worldwide with considerable impact on society. The tide of immunotherapy has finally changed after decades of disappointing results and has become a clinically validated treatment for many cancers. Immunotherapy takes many forms in cancer treatment, including the adoptive transfer of ex vivo activated T cells, oncolytic viruses, natural killer cells, cancer vaccines and administration of antibodies or recombinant proteins that either costimulate cells or block the so-called immune checkpoint pathways. Recently, cancer immunotherapy has received a high degree of attention, which mainly contains the treatments for programmed death ligand 1 (PD-L1), programmed death 1 (PD-1), chimeric antigen receptors (CARs) and cytotoxic T lymphocyte-associated antigen 4 (CTLA-4). Here, this paper reviewed the current understandings of the main strategies in cancer immunotherapy (adoptive cellular immunotherapy, immune checkpoint blockade, oncolytic viruses and cancer vaccines) and discuss the progress in the synergistic design of immune-targeting combination therapies.

From peripherally unsubstituted subphthalocyanines with anti-inflammatory activity on macrophages to tri-iodo derivatives with adjuvant and immunostimulatory functions

In this study we evaluated the impact of iodine substitution on the ability of subphthalocyanines (SubPc) to stimulate or regulate the function of macrophages. Previous studies have focused on the usage of phthalocyanines and their derivatives as treatment options against different types of cancer. In order to obtain better prognosis rates, their possible effects on the immune system cells should be delineated. Unique subphthalocyanines were designed and synthesized by our group and a derivative was generated via iodine substitution. In our study we further tested the effects of the new Subpcs on macrophage cell lines. Macrophages play an important role in the immune system through cytokine production and antigen presentation to other types of the immune system cells. They can define the type and the strength of the immune responses against a particular danger signal. Based on pro-inflammatory cytokine (TNF[Formula: see text], IL1[Formula: see text] and IL6) production levels by macrophages, unsubstituted SubPc had anti-inflammatory properties. However, iodine substitution on the same SubPc created a completely opposite effect since these iodo-substituted SubPc exerted an immunostimulatory effect on macrophages based on significant increases in the pro-inflammatory cytokine production levels compared to the untreated controls. While SubPcs can be used to suppress the pro-inflammatory activities of the macrophages, iodine-substituted SubPcs have potentials to be used as adjuvants and immunostimulatory molecules.

Ruthenium pyridyl thiocyanate complex increased the production of pro-inflammatory TNFα and IL1β cytokines by the LPS stimulated mammalian macrophages in vitro

Every cell in our body depends on the electron transport processes in order to generate energy and function properly. Being able to regulate the metabolic activity of a cell would enable us altering its function and eventually lead us to a desired biological outcome at the cellular level and more desirably at a systemic level. Immunomodulatory or immunostimulatory molecules have been focus of the recent studies in order to regulate or boost the activities of the immune system cells and suppress or eliminate the disease conditions such as cancer, autoimmune reactions, inflammatory disorders as well as infections. In our study we used a ruthenium pyridyl thiocyanate complex, K330, to examine its effect on the activity of the innate immune system cells, macrophages in vitro. K330 was our candidate due to its application in the solar cells. Especially, due to its ability to get involved in electron transfer systems we hypothesized that it could change the activity of the immune system cells at cellular level, possibly by interfering the electron transfer reactions of the cells. Our results support our hypothesis since K330 lead to a significant increase in TNFα and IL1β cytokine production levels by LPS stimulated macrophages compared to only LPS treated control groups. Based on our in vitro results, K330 can also be utilized as an adjuvant candidate in vaccinations where the antigen itself is not sufficient to generate a proper immune response.

Novel vaccines for glioblastoma: clinical update and perspective

Glioblastoma is the most common primary brain cancer. Aggressive treatment with surgery, radiation therapy and chemotherapy provides limited overall survival benefit. Glioblastomas have a formidable tumor microenvironment that is hostile to immunological effector cells and these cancers produce profound systemic immunosuppression. However, surgical resection of these tumors creates conditions that favor the use of immunotherapeutic strategies. Therefore, extensive surgical resection, when feasible, will remain part of the equation to provide an environment in which active specific immunotherapy has the greatest chance of working. Toward that end, a number of vaccination protocols are under investigation. Vaccines studied to date have produced cellular and humoral antitumor responses, but unequivocal clinical efficacy has yet to be demonstrated. In addition, focus is shifting toward the prospect of therapies involving vaccines in combination with immune checkpoint inhibitors and other immunomodulatory agents so that effector cells remain active against their targets systemically and within the tumor microenvironment.

Challenges in the development of a survivin vaccine (SurVaxM) for malignant glioma

There is growing interest in immunotherapy for malignant gliomas. This interest stems from a number of immunological observations, together with the failure of conventional therapeutic agents to produce broad and clinically meaningful improvements in survival and quality of life. The challenges faced in translating laboratory-based immunological observations to Phase I and II clinical trials for immunotherapy of gliomas are substantial. Nevertheless, as our understanding of the effects of active specific vaccination in glioma patients grows, results support optimism that such methods may eventually prove useful as an adjunctive treatment for these cancers. This paper highlights a number of barriers encountered in the translational development of a survivin-targeted peptide vaccine (SurVaxM) for patients with malignant gliomas.

Plasmid DNA vaccines against cancer: cytotoxic T-lymphocyte induction against tumor antigens

In recent years, a number of tumor vaccination strategies have been developed. Most of these rely on the identification of tumor antigens that can be recognized by the immune system. DNA vaccination represents one such approach for the induction of both humoral and cellular immune responses against tumor antigens. Studies in animal models have demonstrated the feasibility of utilizing DNA vaccination to elicit protective antitumor immune responses. However, most tumor antigens expressed by cancer cells in humans are weakly immunogenic, and therefore require the development of strategies to potentiate DNA vaccine efficacy in the clinical setting. This review focuses on recent advances in understanding of the immunology of DNA vaccines, as well as strategies used to increase DNA vaccine potency with respect to cytotoxic T-lymphocyte activity.

Primary mucosal melanoma arising from the eustachian tube with CTLA-4, IL-17A, IL-17C, and IL-17E upregulation

Primary malignant melanoma arising from the eustachian tube is extremely rare. We report the case of a 63-year-old white man who presented with a 1-month history of left-sided hearing loss and aural fullness. Flexible fiberoptic laryngoscopy detected a blue-purple mass that appeared to arise from the left lateral nasopharynx. Computed tomography demonstrated an enhancing mass arising from an orifice of the left eustachian tube. The tumor was debulked endoscopically and was confirmed to have originated in the left eustachian tube. Histologically, the tumor was made up of heavily pigmented pleomorphic spindle cells with frequent mitoses. The tumor cells were immunohistochemically positive for S-100 protein, HMB-45, Melan-A, and PNL-2. The final diagnosis was a mucosal malignant melanoma. We also performed a nested polymerase chain reaction assay for several genes of interest, including CTLA-4, IL-17A, IL-17B, IL-17C, IL-17D, IL-17E, IL-17F, PLZF, Foxp3, RORγt, CD27, and CD70. These genes have been studied mainly in cutaneous melanomas, especially for the development of immunotherapy, but only very limited studies have been done on mucosal melanomas. Our investigation found upregulation of CTLA-4, IL-17A, IL-17C, and IL-17E. Based on our finding of CTLA-4 upregulation, it may be suggested that our patient might have had low antitumor immunity and that he might have benefited from CTLA-4 blockade. On the other hand, upregulation of IL-17A and IL-17E might reflect increased antitumor immunity, which could suggest that patients with a mucosal melanoma might benefit from immunomodulators associated with the effect of Th17. These genes also have great potential to help melanoma patients obtain tailored treatment, and they can be used as biomarkers for predicting prognosis.

Functional cloning of recurrence-specific antigens identifies molecular targets to treat tumor relapse

Aggressive regrowth of recurrent tumors following treatment-induced dormancy represents a major clinical challenge for treatment of malignant disease. We reported previously that recurrent prostate tumors, which underwent complete macroscopic regression followed by aggressive regrowth, could be cured with a vesicular stomatitis virus (VSV)-expressed cDNA library derived from recurrent tumor cells. By screening the protective, recurrence-derived VSV-cDNA library, here we identify topoisomerase-IIα (TOPO-IIα) as a recurrence-specific tumor antigen against which tolerance can be broken. Tumor recurrences, in two different types of tumor (prostate and melanoma), which had evaded two different frontline treatments (immunotherapy or chemotherapy), significantly overexpressed TOPO-IIα compared with their primary tumor counterparts, which conferred a novel sensitivity to doxorubicin (DOX) chemotherapy upon the recurrent tumors. This was exploited in vivo using combination therapies to cure mice, which would otherwise have relapsed, after suboptimal primary therapy in both models. Our data show that recurrent tumors-across histologies and primary treatments-express distinct antigens compared with the primary tumor which can be identified using the VSV-cDNA library technology. These results suggest that it may be possible to design a few common second-line therapies against a variety of tumor recurrences, in some cases using agents with no obvious activity against the primary tumor.

Using virally expressed melanoma cDNA libraries to identify tumor-associated antigens that cure melanoma

Multiple intravenous injections of a cDNA library, derived from human melanoma cell lines and expressed using the highly immunogenic vector vesicular stomatitis virus (VSV), cured mice with established melanoma tumors. Successful tumor eradication was associated with the ability of mouse lymphoid cells to mount a tumor-specific CD4(+) interleukin (IL)-17 recall response in vitro. We used this characteristic IL-17 response to screen the VSV-cDNA library and identified three different VSV-cDNA virus clones that, when used in combination but not alone, achieved the same efficacy against tumors as the complete parental virus library. VSV-expressed cDNA libraries can therefore be used to identify tumor rejection antigens that can cooperate to induce anti-tumor responses. This technology should be applicable to antigen discovery for other cancers, as well as for other diseases in which immune reactivity against more than one target antigen contributes to disease pathology.

Chronic inflammation promotes myeloid-derived suppressor cell activation blocking antitumor immunity in transgenic mouse melanoma model

Tumor microenvironment is characterized by chronic inflammation represented by infiltrating leukocytes and soluble mediators, which lead to a local and systemic immunosuppression associated with cancer progression. Here, we used the ret transgenic spontaneous murine melanoma model that mimics human melanoma. Skin tumors and metastatic lymph nodes showed increased levels of inflammatory factors such as IL-1β, GM-CSF, and IFN-γ, which correlated with tumor progression. Moreover, Gr1(+)CD11b(+) myeloid-derived suppressor cells (MDSCs), known to inhibit tumor reactive T cells, were enriched in melanoma lesions and lymphatic organs during tumor progression. MDSC infiltration was associated with a strong TCR ζ-chain down-regulation in all T cells. Coculturing normal splenocytes with tumor-derived MDSC induced a decreased T-cell proliferation and ζ-chain expression, verifying the MDSC immunosuppressive function and suggesting that the tumor inflammatory microenvironment supports MDSC recruitment and immunosuppressive activity. Indeed, upon manipulation of the melanoma microenvironment with the phosphodiesterase-5 inhibitor sildenafil, we observed reduced levels of numerous inflammatory mediators (e.g., IL-1β, IL-6, VEGF, S100A9) in association with decreased MDSC amounts and immunosuppressive function, indicating an antiinflammatory effect of sildenafil. This led to a partial restoration of ζ-chain expression in T cells and to a significantly increased survival of tumor-bearing mice. CD8 T-cell depletion resulted in an abrogation of sildenafil beneficial outcome, suggesting the involvement of MDSC and CD8 T cells in the observed therapeutic effects. Our data imply that inhibition of chronic inflammation in the tumor microenvironment should be applied in conjunction with melanoma immunotherapies to increase their efficacy.

Engagement of NK receptor NKG2D, but not 2B4, results in self-reactive CD8+ T cells and autoimmune vitiligo

In this study, we demonstrate that engagement of two different natural killer receptors (NKRs) can lead to contrasting effects in the development of self-reactive CD8+T cells and autoimmune vitiligo. Specifically, using a mouse model, we show that CD8+T-cell targeting of a melanocyte antigen, tyrosinase-related protein-1 (TRP-1) in combination with delivery of the NKG2D ligands (Rae-1ϵ or H60), results in strong CD8+T-cell responses against TRP-1 and in the development of autoimmune vitiligo. In contrast, targeting of TRP-1 in combination with delivery of CD48, the natural ligand for the NKR 2B4, leads to reduced formation of TRP-1-reactive CD8+T-cell responses and decreased development of vitiligo. These data indicate that autoimmune vitiligo is limited by insufficient signals, despite plentiful self-reactive T cells in the peripheral immune system. To our knowledge, this is the first experimental evidence supporting the role of NKRs in modulating CD8+T-cell autoimmune vitiligo. This study supports the utilization of NKR signaling as a therapeutic avenue toward prevention of vitiligo and other autoimmune diseases.

Cytotoxic T lymphocyte responses against melanocytes and melanoma

Background

Vitiligo is a common toxicity associated with immunotherapy for melanoma. Cytotoxic T lymphocytes (CTLs) against melanoma commonly target melanoma-associated antigens (MAAs) which are also expressed by melanocytes. To uncouple vitiligo from melanoma destruction, it is important to understand if CTLs can respond against melanoma and melanocytes at different levels.

Methods

To understand the dichotomous role of MAA-specific CTL, we characterized the functional reactivities of established CTL clones directed to MAAs against melanoma and melanocyte cell lines.

Results

CTL clones generated from melanoma patients were capable of eliciting MHC-restricted, MAA-specific lysis against melanocyte cell lines as well as melanoma cells. Among the tested HLA-A*0201-restricted CTL clones, melanocytes evoked equal to slightly higher degranulation and cytolytic responses as compared to melanoma cells. Moreover, MAA-specific T cells from vaccinated patients responded directly ex vivo to melanoma and melanocytes. Melanoma cells express slightly higher levels of MART-1 and gp100 than melanocytes as measured by quantitative reverse-transcriptase polymerase chain reaction (qRT-PCR) and immunohistochemistry.

Conclusions

Our data suggest that CTLs respond to melanoma and melanocytes equally in vitro and directly ex vivo.

Broad antigenic coverage induced by vaccination with virus-based cDNA libraries cures established tumors

Effective cancer immunotherapy requires the release of a broad spectrum of tumor antigens in the context of potent immune activation. We show here that a cDNA library of normal tissue, expressed from a highly immunogenic viral platform, cures established tumors of the same histological type from which the cDNA library was derived. Immune escape occurred with suboptimal vaccination, but tumor cells that escaped the immune pressure were readily treated by second-line virus-based immunotherapy. This approach has several major advantages. Use of the cDNA library leads to presentation of a broad repertoire of (undefined) tumor-associated antigens, which reduces emergence of treatment-resistant variants and also permits rational, combined-modality approaches in the clinic. Finally, the viral vectors can be delivered systemically, without the need for tumor targeting, and are amenable to clinical-grade production. Therefore, virus-expressed cDNA libraries represent a novel paradigm for cancer treatment addressing many of the key issues that have undermined the efficacy of immuno- and virotherapy to date.

Development of tumor-infiltrating CD8+ T cell memory precursor effector cells and antimelanoma memory responses are the result of vaccination and TGF-β blockade during the perioperative period of tumor resection

A main goal of cancer immunology research is the formation of Ag-specific memory T cell immunity capable of activation upon tumor re-encounter. The requirements necessary to overcome the inhibitory signals present in the tumor microenvironment and form such memory T cell responses are unknown. In contrast to previous studies targeting tumors expressing highly immunogenic model Ags, we demonstrate that alleviating tumor-induced suppression along with vaccination against authentic Ags during the perioperative period provides long-lasting protection against a highly suppressive and poorly immunogenic melanoma. In this study, we employed DNA vaccination with an immunologically optimized mouse melanoma-shared Ag, Trp1ee/ng, combined with systemic TGF-β blockade during the perioperative period of primary tumor resection, to confer protection against B16 melanoma, and against JBRH, an independently derived melanoma unrelated to B16. Importantly, we demonstrate that correlative to memory responses, perioperative immunotherapy increases the formation of tumor-infiltrating and tumor-reactive CD8(+) T cells expressing low levels of the transcription factor T-bet, defined as memory precursor effector cells. We show that conditions for an immunologically fertile environment are met when TGF-β blockade and vaccination are applied during the perioperative period of primary tumor resection. These findings address limitations of current CD8(+) T cell immunotherapies against cancer by generating effective CD8(+) T cell memory recall responses.

Antitumor cytotoxic T-cell response induced by a survivin peptide mimic

Survivin is a tumor-associated antigen with significant potential as a cancer vaccine target. We have identified a survivin peptide mimic containing human MHC class I epitopes and a potential class II ligand that induces a potent antitumor response in C57BL/6 mice with GL261 cerebral gliomas. This peptide is able to elicit both CD8+ CTL and T helper cell responses in C57BL/6 mice. The corresponding region of the human survivin molecule represented by peptide SVN53-67 is 100% homologous to the murine protein, but SVN53-67 is weakly immunogenic in man. We evaluated several amino acid substitutions in putative human MHC I anchor positions in SVN53-67 to identify potential peptide mimics that could provide an enhanced antitumor immune response against human glioma and primary central nervous system lymphoma (PCNSL) cells in culture. We evaluated survivin peptides with predicted binding to human HLA-A*0201 antigen using peptide-loaded dendritic cells from PBMC of patients with these malignancies. One alteration (M57) led to binding to HLA-A*0201 with significantly higher affinity. We compared the ability of autologous dendritic cells loaded with SVN53-67 peptide and SVN53-67/M57 in CTL assays against allomatched and autologous, survivin-expressing, human malignant glioma and PCNSL cells. Both SVN53-67 and SVN53-67/M57 produced CTL-mediated killing of malignant target cells; however, SVN53-67/M57 was significantly more effective than SVN53-67. Thus, SVN53-67/M57 may act as a peptide mimic to induce an enhanced antitumor CTL response in tumor patients. The use of SVN53-67/M57 as a cancer vaccine might have application for cancer vaccine therapy.

Vaccination with human pluripotent stem cells generates a broad spectrum of immunological and clinical responses against colon cancer

The history of immunizing with embryonic materials to generate an antitumor immune response dates back to a century ago. The premise is that cancer cells share the expression of oncofetal antigens with embryonic materials and that the immune response against these antigens in the embryonic tissues is cross-protective against cancer. However, such a practice has never advanced beyond experimental animal settings, because of lack of uniformed source tissues and ethical challenges. With the availability of well-characterized human pluripotent stem cells, it is now possible to ask whether tumor protective immunity could indeed be elicited with stem cells. Herein, we investigated whether vaccination with defined human embryonic stem cells (hESCs) or induced pluripotent stem (iPS) cells was effective against a colon carcinoma. We discovered that vaccination of mice with hESC line H9 generated consistent cellular and humoral immune responses against CT26 colon carcinoma. Protection correlated strongly with the expansion of tumor-responsive and interferon-gamma-producing cells and the profound loss of CD11b(+)Gr-1(+) myeloid-derived suppressor cells in the spleen. No evidence of autoimmunity was observed. We also compared the immunogenicity against colon cancer between a hESC line CT2 and an iPS cell line TZ1 that were generated in the same stem cell facility. We found that the iPS cell line was inferior to the hESC line in conferring tumor protection, suggesting that there is heterogeneity of expression of oncofetal antigens by hESCs and iPS cells. We conclude that the hESC-based vaccine is a promising modality for immunotherapy of cancer.

Skin electroporation: effects on transgene expression, DNA persistence and local tissue environment

Background

Electrical pulses have been used to enhance uptake of molecules into living cells for decades. This technique, often referred to as electroporation, has become an increasingly popular method to enhance in vivo DNA delivery for both gene therapy applications as well as for delivery of vaccines against both infectious diseases and cancer. In vivo electrovaccination (gene delivery followed by electroporation) is currently being investigated in several clinical trials, including DNA delivery to healthy volunteers. However, the mode of action at molecular level is not yet fully understood.

Methodology/Principal Findings

This study investigates intradermal DNA electrovaccination in detail and describes the effects on expression of the vaccine antigen, plasmid persistence and the local tissue environment. Gene profiling of the vaccination site showed that the combination of DNA and electroporation induced a significant up-regulation of pro-inflammatory genes. In vivo imaging of luciferase activity after electrovaccination demonstrated a rapid onset (minutes) and a long duration (months) of transgene expression. However, when the more immunogenic prostate specific antigen (PSA) was co-administered, PSA-specific T cells were induced and concurrently the luciferase expression became undetectable. Electroporation did not affect the long-term persistence of the PSA-expressing plasmid.

Conclusions/Significance

This study provides important insights to how DNA delivery by intradermal electrovaccination affects the local immunological responses of the skin, transgene expression and clearance of the plasmid. As the described vaccination approach is currently being evaluated in clinical trials, the data provided will be of high significance.

Prevalence of antitumor antibodies in laying hen model of human ovarian cancer

Antitumor antibodies are associated with tumors in human cancers. There is relatively little information on the timing and progression of antibody response to tumors. The objective of the study was to determine if spontaneous ovarian cancer in the egg-laying hen is associated with antitumor antibodies. Antibodies were detected by immunoassay and immunoblotting using proteins from normal ovary and ovarian tumors. Candidate antigens were identified by mass spectrometry of immunoreactive spots cut from 2-dimensional gels and Western blot. Antitumor (serum reacting against tumor ovarian extract) and antiovarian (serum reacting against normal ovarian extract) antibodies were significantly associated with ovarian cancer (67%; P <or= 0.001) compared with normal control hens. Hens with abnormal histology but no gross tumor had antitumor antibodies (63%; P <or= 0.025) but not antiovarian antibodies. There were common as well as different immunoreactions against normal ovary and homologous and heterologous tumor proteins in 2-dimensional Western blots. The candidate antigens included those commonly associated with human cancers and other diseases such as vimentin, apolipoprotein A1, Annexin II, enolase, DJ-1, and so on. The results suggest that antitumor antibodies are associated with ovarian cancer in hens, similar to human ovarian cancer. The egg-laying hen may be a model for understanding the antitumor humoral immune response, particularly at early tumor stages that are not readily accessible in human ovarian cancer.

Immune rejection of mouse tumors expressing mutated self

How the immune system recognizes and responds to mutations expressed by cancer cells is a critical issue for cancer immunology. Mutated self-polypeptides are particularly strong tumor-specific rejection antigens for natural tumor immunity, but we know remarkably little about T-cell responses to mutated self during tumor growth in vivo, including levels of response, kinetics, and correlates that predict tumor rejection. To address these questions, a mutated self-antigen, designated tyrosinase-related protein 1 (Tyrp1)-WM, derived from Tyrp1 was expressed in the poorly immunogenic, spontaneously arising B16 melanoma and the immunogenic, chemically induced LiHa fibrosarcoma. Syngeneic mice challenged with LiHa fibrosarcoma cells expressing Tyrp1-WM, but not native Tyrp1, induced specific CD8(+) and CD4(+) T-cell responses against defined mutated epitopes in tumor-draining lymph nodes and in tumors. Subsequently, specific CD8(+) T-cell responses contracted as a minority of tumors progressed. B16 melanomas expressing Tyrp1-WM induced minimal T-cell responses, and no tumor immunity was detected. Treatment with an agonist monoclonal antibody against glucocorticoid-induced tumor necrosis factor receptor family-related gene (GITR) increased the level of CD8(+) T cells recognizing a peptide derived from the Tyrp1-WM sequence and the proportion of mice rejecting tumors. These results show that B16 tumors expressing mutations that generate strongly immunogenic epitopes naturally induce T-cell responses, which are insufficient to reject tumors. Immune modulation, such as inducing GITR signaling, is required to enhance CD8(+) T-cell responses to specific mutations and to lead to tumor rejection.

Distinct CD8+ T cell repertoires primed with agonist and native peptides derived from a tumor-associated antigen

Heteroclitic peptides are used to enhance the immunogenicity of tumor-associated Ags to break T cell tolerance to these self-proteins. One such altered peptide ligand (Cap1-6D) has been derived from an epitope in human carcinoembryonic Ag, CEA(605-613) (Cap1). Clinical responses have been seen in colon cancer patients receiving a tumor vaccine comprised of this altered peptide. Whether Cap1-6D serves as a T cell agonist for Cap1-specific T cells or induces different T cells is unknown. We, therefore, examined the T cell repertoires elicited by Cap1-6D and Cap1. Human CTL lines and clones were generated with either Cap1-6D peptide (6D-CTLs) or Cap1 peptide (Cap1-CTLs). The TCR Vbeta usage and functional avidity of the T cells induced in parallel against these target peptides were assessed. The predominant CTL repertoire induced by agonist Cap1-6D is limited to TCR Vbeta1-J2 with homogenous CDR3 lengths. In contrast, the majority of Cap1-CTLs use different Vbeta1 genes and also had diverse CDR3 lengths. 6D-CTLs produce IFN-gamma in response to Cap1-6D peptide with high avidity, but respond with lower avidity to the native Cap1 peptide when compared with the Cap1-CTLs. Nevertheless, 6D-CTLs could still lyse targets bearing the native epitope. Consistent with these functional results, 6D-CTLs possess TCRs that bind Cap-1 peptide/MHC tetramer with higher intensity than Cap1-CTLs but form less stable interactions with peptide/MHC as measured by tetramer decay. These results demonstrate that priming with this CEA-derived altered peptide ligand can induce distinct carcinoembryonic Ag-reactive T cells with different functional capacities.

Natural killer cells and lung transplantation, roles in rejection, infection, and tolerance

Despite improvements in surgical technique, organ preservation, immunosuppression, and management of infection, the long term survival following lung transplantation remains low, mainly due to immune mediated complications such as acute and chronic rejection. Almost all immunosuppressive agents used in the prophylaxis and treatment of rejection following lung transplantation are targets of T cell maturation, function or proliferation, which in theory should cause sufficient disruption of the adaptive immune system to prevent graft rejection. However the five year survival rate of only 50% suggests this is not the case. More recent evidence suggests that NK cells may play a significant role in immune processes following lung transplantation. This article reviews the literature on the potential function of NK cells in rejection, infection, malignancy and tolerance following lung transplantation.

DNA vaccines: precision tools for activating effective immunity against cancer

DNA vaccination has suddenly become a favoured strategy for inducing immunity. The molecular precision offered by gene-based vaccines, together with the facility to include additional genes to direct and amplify immunity, has always been attractive. However, the apparent failure to translate operational success in preclinical models to the clinic, for reasons that are now rather obvious, reduced initial enthusiasm. Recently, novel delivery systems, especially electroporation, have overcome this translational block. Here, we assess the development, current performance and potential of DNA vaccines for the treatment of cancer.

The combined activation of positive costimulatory signals with modulation of a negative costimulatory signal for the enhancement of vaccine-mediated T-cell responses

Blockade of CTLA-4 by monoclonal antibodies (mAb) can mediate regression of tumors and increase the efficacy of tumor antigen specific vaccines. Blockade of CTLA-4 has also been shown to significantly increase the avidity of antigen-specific T cells after immunization with live recombinant viral vector based vaccine. Here, we demonstrate a biological synergy between CTLA-4 blockade and active vaccine therapy consisting of recombinant vaccinia and avipox viruses expressing carcinoembryonic antigen (CEA) and three T cell costimulatory molecules to enhance antitumor effects. However, this synergy was very much dependent on the temporal relationship of scheduling of the two agents. We evaluated the strategies in both a foreign antigen model using beta-galactosidase as immunogen, and in a "self" antigen model using CEA as immunogen. For antitumor activity the model used consisted of mice transgenic for human CEA and a murine carcinoma cell line transfected with CEA. The enhanced antitumor activity after vaccine and CTLA-4 blockade did not result in any signs of autoimmunity. These studies form a rational basis for the use of vector-based vaccines with anti-CTLA-4 and demonstrate that both enhancement of positive costimulatory signals and inhibition of negative costimulatory signals can be simultaneously exploited. These studies also underscore the importance of "drug" scheduling in vaccine combination therapies.

Canine Oral Melanoma

Melanoma is the most common oral malignancy in the dog. Oral and/or mucosal melanoma has been routinely considered an extremely malignant tumor with a high degree of local invasiveness and high metastatic propensity. Primary tumor size has been found to be extremely prognostic. The World Health Organization staging scheme for dogs with oral melanoma is based on size, with stage I = <2-cm-diameter tumor, stage II = 2- to <4-cm-diameter tumor, stage III = > or = 4cm tumor and/or lymph node metastasis, and stage IV = distant metastasis. Median survival times for dogs with oral melanoma treated with surgery are approximately 17 to 18, 5 to 6, and 3 months with stage I, II, and III disease, respectively. Significant negative prognostic factors include stage, size, evidence of metastasis, and a variety of histologic criteria. Standardized treatments such as surgery, coarse-fractionation radiation therapy, and chemotherapy have afforded minimal to modest stage-dependent clinical benefits and death is usually due to systemic metastasis. Numerous immunotherapeutic strategies have been employed to date with limited clinical efficacy; however, the use of xenogeneic DNA vaccines may represent a leap forward in clinical efficacy. Oral melanoma is a spontaneous syngeneic cancer occurring in outbred, immunocompetent dogs and appears to be a more clinically faithful therapeutic model for human melanoma; further use of canine melanoma as a therapeutic model for human melanoma is strongly encouraged. In addition, the development of an expanded but clinically relevant staging system incorporating the aforementioned prognostic factors is also strongly encouraged.

Impact of Orthologous Melan-A Peptide Immunizations on the Anti-Self Melan-A/HLA-A2 T Cell Cross-Reactivity

In HLA-A2 individuals, the CD8 T cell response against the differentiation Ag Melan-A is mainly directed toward the peptide Melan-A26-35. The murine Melan-A24-33 sequence encodes a peptide that is identical with the human Melan-A26-35 decamer, except for a Thr-to-Ile substitution at the penultimate position. Here, we show that the murine Melan-A24-33 is naturally processed and presented by HLA-A2 molecules. Based on these findings, we compared the CD8 T cell response to human and murine Melan-A peptide by immunizing HLA-A2 transgenic mice. Even though the magnitude of the CTL response elicited by the murine Melan-A peptide was lower than the one elicited by the human Melan-A peptide, both populations of CTL recognized the corresponding immunizing peptide with the same functional avidity. Interestingly, CTL specific for the murine Melan-A peptide were completely cross-reactive against the orthologous human peptide, whereas anti-human Melan-A CTL recognized the murine Melan-A peptide with lower avidity. Structurally, this discrepancy could be explained by the fact that Ile32 of murine Melan-A24-33 created a larger TCR contact area than Thr34 of human Melan-A26-35. These data indicate that, even if immunizations with orthologous peptides can induce strong specific T cell responses, the quality of this response against syngeneic targets might be suboptimal due to the structure of the peptide-TCR contact surface.

Vaccines for tumour prevention

Despite tremendous progress in basic and epidemiological research, effective prevention of most types of cancer is still lacking. Vaccine use in cancer therapy remains a promising but difficult prospect. However, new mouse models that recapitulate significant features of human cancer progression show that vaccines can keep precancerous lesions under control and might eventually be the spearhead of effective and reliable ways to prevent cancer.

Anti-Tumor Antibodies in Ovarian Cancer

Anti-tumor antibodies have potential as cancer biomarkers. There is relatively limited identification of anti-tumor antibodies in response to ovarian cancer, compared with studies for other cancers. There is also very limited information on the prevalence of anti-tumor antibodies among ovarian cancer patients. Although most anti-tumor antibodies react with antigens common to both tumor and normal tissue, the anti-tumor response tends to be confined to individuals with ovarian cancer, similar to other cancers. Antibodies to HOXA7, a differentiation antigen, have the highest reported prevalence in ovarian cancer (67%). Antibodies to other ubiquitous antigens including NY-ESO-1, Ep-CAM (epithelial cell adhesion molecule), HSP-90 (heat shock protein 90), and mutated p53 have been identified in ovarian cancer. Anti-tumor antibody specificity reflects the heterogeneity of antigen expression in tumors. Tests based on panels of a combination of anti-tumor antibodies may be more predictive for ovarian cancer, as no single specificity accounts for ovarian tumors. In addition to characterization of anti-tumor antibodies as diagnostic markers, study of anti-tumor antibodies is likely to provide insights into mechanisms of tumor development. There is evidence of antibodies to tumor antigens and of activated T cells, suggesting immune recognition of tumor antigens occurred. Nonetheless, as tumors are not 'rejected', it is likely that there are alterations in the immune system. The basis for tumor growth in the face of immune activity remains to be determined.

Expression of gp130 in Tumors and Inflammatory Disorders of the Skin: Formal Proof of its Identity as CD146 (MUC18, Mel-CAM)

Two antibodies, BT14 and L101, detect a tumor-associated cell surface glycoprotein (gp130) whose properties in normal and diseased skin were assessed, and whose molecular identity was determined in this study. In normal skin, gp130 was constitutively expressed on dermal blood vessels and epidermal appendages, but not in interfollicular epidermis. Marked induction was detected within benign and malignant tumors of various origins including viral warts, basal cell carcinomas, squamous cell carcinomas, metastatic melanomas, and cutaneous T cell lymphomas. In vitro studies confirmed the general upregulation of gp130 expression in malignantly transformed cells. Surprisingly, gp130 was also induced in inflammatory skin diseases including psoriasis and allergic contact dermatitis. Halting proliferation of transformed keratinocytes through cytostatic drugs or increasing the Ca2+ concentration in the medium resulted in increased gp130 expression. In addition, overexpression of Bcl-2 led to upregulation of gp130. When the protein was purified and analyzed by peptide mass fingerprinting, we could demonstrate that it is MUC18 (Mel-CAM, CD146). Sequential immunoprecipitations and western blot analyses confirmed the identity of the antigen. Thus, both expression pattern and regulation characteristics of the now-known glycoprotein gp130 extended beyond previously published data regarding MUC18, thus shedding some new light on a supposedly well-known antigen.

Provision of Granulocyte-Macrophage Colony-Stimulating Factor Converts an Autoimmune Response to a Self-Antigen into an Antitumor Response

Many tumor Ags recognized by T cells are self-Ags. Because high avidity, self-reactive T cells are deleted in the thymus, any residual self-reactive T cells existing in the periphery are likely to be low avidity and nonresponsive due to peripheral tolerance mechanisms. Activation of these residual T cells is critical for targeting tumors for immunotherapy. In this study, we studied immune responses against the murine B16 melanoma using a tyrosinase-related protein 2 (TRP-2) peptide as a model tumor/self-Ag. Our results showed that TRP-2 peptide vaccination alone elicited a weak T cell response and modestly decreased B16 lung tumor nodules. The combination of peptide vaccination and treatment with an Ab directed against the inhibitory receptor CTLA-4 enhanced the immune response against TRP-2 peptide, inducing autoimmune depigmentation and further decreasing lung tumor nodules. However, both vaccination methods failed to protect against orthotopic (s.c.) B16 tumor challenge. The addition of an irradiated GM-CSF-expressing, amelanotic tumor cell vaccine significantly delayed s.c. B16 tumor growth. Subsequent studies revealed that provision of GM-CSF increased dendritic cell numbers in lymph nodes and spleen. Furthermore, addition of CTLA-4 blockade increased the frequency of TRP-2-specific, IFN-secreting T cells in spleen and lymph nodes. Overall, our results indicate that combining enhancement of Ag presentation with removal of CTLA-4-mediated inhibition can convert a "weaker" autoimmune response into a more potent antitumor immune response.

Sensitivity of Undifferentiated, High-TCR Density CD8+ Cells to Methylene Groups Appended to Tumor Antigen Determines Their Differentiation or Death

CD8(+) cells expressing high numbers of TCR per cell (TCR(hi)) are considered important mediators of antitumor effects. To understand the relationship between TCR density and antigen affinity for TCR in the outcome of stimulation with antigen and differentiation of CTL recognizing tumor antigen, we analyzed perforin induction in ovarian tumor-associated lymphocytes in response to the smallest possible changes in the atomic forces of interaction between antigen and TCR. Stimulating undifferentiated, apoptosis-resistant CD8(+) cells expressing high levels of E75-TCR (TCR(hi)) with variants of the CTL epitope E75, HER-2 (369-377), induced their stepwise differentiation, first to IFN-gamma(+) Perf(-) and to TCR(hi) IFN-gamma(+) Perf(+) cells. Blocking caspase-9 activation at antigen stimulation also enhanced the generation of TCR(hi) Perf(hi) cells, demonstrating that TCR density dictated the pathway of death activated by stimulation with the same agonist. Expansion and differentiation of TCR(hi) Perf(+) CTL required an agonist of optimal CH(2) side chain length, which in this study was equal to two CH(2) groups appended to E75 at the Gly(4) position. Side chains one CH(2) shorter or longer than optimal were either less stimulatory or induced death of TCR(hi) Perf(+) cells. Differentiation of TCR(hi) CD8(+) cells can be finely tuned by synthetic amino acids in the peptide, whose side chains induce small increments in the affinity of the antigen for TCR below the affinity which induce apoptosis.