Vaccination for the prevention and treatment of breast cancer with special focus on Her-2/neu peptide vaccines

Immunomodulatory Peptides for Tumor Treatment

Peptides exhibit various biological activities, including biorecognition, cell targeting, and tumor penetration, and can stimulate immune cells to elicit immune responses for tumor immunotherapy. Peptide self-assemblies and peptide-functionalized nanocarriers can reduce the effect of various biological barriers and the degradation by peptidases, enhancing the efficiency of peptide delivery and improving antitumor immune responses. To date, the design and development of peptides with various functionalities have been extensively reviewed for enhanced chemotherapy; however, peptide-mediated tumor immunotherapy using peptides acting on different immune cells, to the knowledge, has not yet been summarized. Thus, this work provides a review of this emerging subject of research, focusing on immunomodulatory anticancer peptides. This review introduces the role of peptides in the immunomodulation of innate and adaptive immune cells, followed by a link between peptides in the innate and adaptive immune systems. The peptides are discussed in detail, following a classification according to their effects on different innate and adaptive immune cells, as well as immune checkpoints. Subsequently, two delivery strategies for peptides as drugs are presented: peptide self-assemblies and peptide-functionalized nanocarriers. The concluding remarks regarding the challenges and potential solutions of peptides for tumor immunotherapy are presented.

Preclinical support for tumor protein D52 as a cancer vaccine antigen

Overexpressed tumor-associated antigens (TAAs) are a large group that includes proteins found at increased levels in tumors compared to healthy cells. Universal tumor expression can be defined as overexpression in all cancers examined as has been shown for Tumor Protein D52. TPD52 is an over expressed TAA actively involved in transformation, leading to increased proliferation and metastasis. TPD52 overexpression has been demonstrated in many human adult and pediatric malignancies. The murine orthologue of TPD52 (mD52) parallels normal tissue expression patterns and known functions of human TPD52 (hD52). Here in we present our preclinical studies over the past 15 years which have demonstrated that vaccine induced immunity against mD52 is effective against multiple cancers in murine models, without inducing autoimmunity against healthy tissues and cells.

A Biomimetic, Silaffin R5-Based Antigen Delivery Platform

Nature offers a wide range of evolutionary optimized materials that combine unique properties with intrinsic biocompatibility and that can be exploited as biomimetic materials. The R5 and RRIL peptides employed here are derived from silaffin proteins that play a crucial role in the biomineralization of marine diatom silica shells and are also able to form silica materials in vitro. Here, we demonstrate the application of biomimetic silica particles as a vaccine delivery and adjuvant platform by linking the precipitating peptides R5 and the RRIL motif to a variety of peptide antigens. The resulting antigen-loaded silica particles combine the advantages of biomaterial-based vaccines with the proven intracellular uptake of silica particles. These particles induce NETosis in human neutrophils as well as IL-6 and TNF-α secretion in murine bone marrow-derived dendritic cells.

The Role of Tumor-Associated Antigen HER2/neu in Tumor Development and the Different Approaches for Using It in Treatment: Many Choices and Future Directions

The treatment of HER2-positive cancers has changed significantly over the past ten years thanks to a significant number of promising new approaches that have been added to our arsenal in the fight against cancer, including monoclonal antibodies, inhibitors of tyrosine kinase, antibody-drug conjugates, vaccination, and particularly, adoptive-T-cell therapy after its great success in hematological malignancies. Equally important is the new methodology for determining patients eligible for targeted HER2 therapy, which has doubled the number of patients who can benefit from these treatments. However, despite the initial enthusiasm, there are still several problems in this field represented by drug resistance and tumor recurrence that require the further development of new more efficient drugs. In this review, we discuss various approaches for targeting the HER2 molecule in cancer treatment, highlighting their benefits and drawbacks, along with the different mechanisms responsible for resistance to HER2-targeted therapies and how to overcome them.

Development of the B cell cancer vaccine HER-vaxx for the treatment of her-2 expressing cancers

Her-2/neu is a tumor-associated protein that is overexpressed in a number of malignancies, including advanced cancer of the stomach, and has been proposed as a human cancer vaccine target. Overexpression of Her-2/neu in human breast and gastric carcinomas correlates with a more aggressive course of disease that results in poorer overall survival rates and shorter times to disease progression than in patients with tumors without overexpression of Her-2/neu. Cancer vaccines have the ability to stimulate the native immune system and in particular engineered B cell epitopes can elicit high affinity polyclonal antibodies with similar efficacy to Her-2 monoclonal antibodies such as trastuzumab (Roche). HER-Vaxx is under development as a therapeutic B cell vaccine for the treatment of gastric cancer in patients with Her-2/neu overexpressing metastatic or advanced adenocarcinoma of the stomach or gastroesophageal junction, referred to as advanced cancer of the stomach. P467-CRM197, the vaccine's immunogenic component, contains a single peptide antigen composed of 3 individual linear B cell epitope peptide sequences selected from the oncoprotein Her-2/neu that induce the patient's own B cells to produce endogenous anti-Her-2/neu antibodies. This review provides results from comprehensive preclinical studies encompassing primary and secondary pharmacodynamics, biodistribution and safety studies. These studies were performed to support clinical development of HER-Vaxx. Results from the GLP toxicology study in rodents showed that the vaccine did not produce any observable adverse effects suggesting that the doses proposed for the clinical trial should be well tolerated in patients.

Phenylboronic ester-modified polymeric nanoparticles for promoting TRP2 peptide antigen delivery in cancer immunotherapy

The tremendous development of peptide-based cancer vaccine has attracted incremental interest as a powerful approach in cancer management, prevention and treatment. As successful as tumor vaccine has been, major challenges associated with achieving efficient immune response against cancer are (1) drainage to and retention in lymph nodes; (2) uptake by dendritic cells (DCs); (3) activation of DCs. In order to overcome these barriers, here we construct PBE-modified TRP2 nanovaccine, which comprises TRP2 peptide tumor antigen and diblock copolymer PEG-b-PAsp grafted with phenylboronic ester (PBE). We confirmed that this TRP2 nanovaccine can be effectively trapped into lymph node, uptake by dendritic cells and induce DC maturation, relying on increased negative charge, ROS response and pH response. Consistently, this vehicle loaded with TRP2 peptide could boost the strongest T cell immune response against melanoma in vivo and potentiate antitumor efficacy both in tumor prevention and tumor treatment without any exogenous adjuvant. Furthermore, the TRP2 nanovaccine can suppress the tumor growth and prolong animal survival time, which may result from its synergistic effect of inhibiting tumor immunosuppression and increasing cytotoxic lymphocyte (CTL) response. Hence this type of PBE-modified nanovaccine would be widely used as a simple, safe and robust platform to deliver other antigen in cancer immunotherapy.

Combined Vaccination with B Cell Peptides Targeting Her-2/neu and Immune Checkpoints as Emerging Treatment Option in Cancer

The application of monoclonal antibodies (mAbs), targeting tumor-associated (TAAs) or tumor-specific antigens or immune checkpoints (ICs), has shown tremendous success in cancer therapy. However, the application of mAbs suffers from a series of limitations, including the necessity of frequent administration, the limited duration of clinical response and the emergence of frequently pronounced immune-related adverse events. However, the introduction of mAbs has also resulted in a multitude of novel developments for the treatment of cancers, including vaccinations against various tumor cell-associated epitopes. Here, we reviewed recent clinical trials involving combination therapies with mAbs targeting the PD-1/PD-L1 axis and Her-2/neu, which was chosen as a paradigm for a clinically highly relevant TAA. Our recent findings from murine immunizations against the PD-1 pathway and Her-2/neu with peptides representing the mimotopes/B cell peptides of therapeutic antibodies targeting these molecules are an important focus of the present review. Moreover, concerns regarding the safety of vaccination approaches targeting PD-1, in the context of the continuing immune response, as a result of induced immunological memory, are also addressed. Hence, we describe a new frontier of cancer treatment by active immunization using combined mimotopes/B cell peptides aimed at various targets relevant to cancer biology.

Breast cancer vaccines: New insights into immunomodulatory and nano-therapeutic approaches

Breast cancer (BC) is known to be a highly heterogeneous disease that is clinically subdivided into four primary molecular subtypes, each having distinct morphology and clinical implications. These subtypes are principally defined by hormone receptors and other proteins involved (or not involved) in BC development. BC therapeutic vaccines [including peptide-based vaccines, protein-based vaccines, nucleic acid-based vaccines (DNA/RNA vaccines), bacterial/viral-based vaccines, and different immune cell-based vaccines] have emerged as an appealing class of cancer immunotherapeutics when used alone or combined with other immunotherapies. Employing the immune system to eliminate BC cells is a novel therapeutic modality. The benefit of active immunotherapies is that they develop protection against neoplastic tissue and readjust the immune system to an anti-tumor monitoring state. Such immunovaccines have not yet shown effectiveness for BC treatment in clinical trials. In recent years, nanomedicines have opened new windows to increase the effectiveness of vaccinations to treat BC. In this context, some nanoplatforms have been designed to efficiently deliver molecular, cellular, or subcellular vaccines to BC cells, increasing the efficacy and persistence of anti-tumor immunity while minimizing undesirable side effects. Immunostimulatory nano-adjuvants, liposomal-based vaccines, polymeric vaccines, virus-like particles, lipid/calcium/phosphate nanoparticles, chitosan-derived nanostructures, porous silicon microparticles, and selenium nanoparticles are among the newly designed nanostructures that have been used to facilitate antigen internalization and presentation by antigen-presenting cells, increase antigen stability, enhance vaccine antigenicity and remedial effectivity, promote antigen escape from the endosome, improve cytotoxic T lymphocyte responses, and produce humoral immune responses in BC cells. Here, we summarized the existing subtypes of BC and shed light on immunomodulatory and nano-therapeutic strategies for BC vaccination. Finally, we reviewed ongoing clinical trials on BC vaccination and highlighted near-term opportunities for moving forward.

Immunological Landscape of HER-2 Positive Breast Cancer

Understanding the biological aspects of immune response in HER2+ breast cancer is crucial to implementing new treatment strategies in these patients. It is well known that anti-HER2 therapy has improved survival in this population, yet a substantial percentage may relapse, creating a need within the scientific community to uncover resistance mechanisms and determine how to overcome them. This systematic review indicates the immunological mechanisms through which trastuzumab and other agents target cancer cells, also outlining the main trials studying immune checkpoint blockade. Finally, we report on anti-HER2 vaccines and include a figure exemplifying their mechanisms of action.

Vaccination against Her-2/neu, with focus on peptide-based vaccines

Immunotherapy has been a milestone in combatting cancer, by complementing or even replacing classic treatments like surgery, chemotherapy, radiation, and anti-hormonal therapy. In 15%-30% of breast cancers, overexpression of the human epidermal growth factor receptor 2 (Her-2/neu) is associated with more aggressive tumor development. Passive immunization/immunotherapy with the recombinantly produced Her-2/neu-targeting monoclonal antibodies (mAbs) pertuzumab and trastuzumab has been shown to effectively treat breast cancer and lead to a significantly better prognosis. However, allergic and hypersensitivity reactions, cardiotoxicity, development of resistance, lack of immunological memory which results in continuous application over a long period, and cost-intensiveness are among the drawbacks associated with this treatment. Furthermore, intrinsic or acquired resistance is associated with the application of therapeutic mAbs, leading to the disease recurrence. Conversely, these drawbacks could be potentially overcome by vaccination, i.e. an active immunization/immunotherapy approach by activating the patient’s own immune system to target cancer, along with inducing immunological memory. This review aims to summarize the main approaches investigated and undertaken for the production of Her-2/neu vaccine candidates, with the main focus on peptide-based vaccines and their evaluation in clinical settings.

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Her-2/neu is overexpressed in 10%-30% of breast and gastric cancer patients and this correlates with poor clinical outcomes.

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Passive application of trastuzumab and pertuzumab has outstandingly improved the Her-2/neu-related clinical outcomes.

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Treatment with mAbs is associated with frequent administration, cost-intensiveness, and resistance.

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Vaccination against Her-2/neu with e.g. mimotope- or peptide-based vaccines can alternatively overcome the mAbs’ drawbacks.

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Such alternatives may pave the way to therapeutics which could be used as monotherapy or in combination therapies with mAbs.

Coordinated regulation of immune contexture: crosstalk between STAT3 and immune cells during breast cancer progression

Recent insights into the molecular and cellular mechanisms underlying cancer development have revealed the tumor microenvironment (TME) immune cells to functionally affect the development and progression of breast cancer. However, insufficient evidence of TME immune modulators limit the clinical application of immunotherapy for advanced and metastatic breast cancers. Intercellular STAT3 activation of immune cells plays a central role in breast cancer TME immunosuppression and distant metastasis. Accumulating evidence suggests that targeting STAT3 and/or in combination with radiotherapy may enhance anti-cancer immune responses and rescue the systemic immunologic microenvironment in breast cancer. Indeed, apart from its oncogenic role in tumor cells, the functions of STAT3 in TME of breast cancer involve multiple types of immunosuppression and is associated with tumor cell metastasis. In this review, we summarize the available information on the functions of STAT3-related immune cells in TME of breast cancer, as well as the specific upstream and downstream targets. Additionally, we provide insights about the potential immunosuppression mechanisms of each type of evaluated immune cells. Video abstract.

Cancer Vaccines: Adjuvant Potency, Importance of Age, Lifestyle, and Treatments

Although the discovery and characterization of multiple tumor antigens have sparked the development of many antigen/derived cancer vaccines, many are poorly immunogenic and thus, lack clinical efficacy. Adjuvants are therefore incorporated into vaccine formulations to trigger strong and long-lasting immune responses. Adjuvants have generally been classified into two categories: those that ‘depot’ antigens (e.g. mineral salts such as aluminum hydroxide, emulsions, liposomes) and those that act as immunostimulants (Toll Like Receptor agonists, saponins, cytokines). In addition, several novel technologies using vector-based delivery of antigens have been used. Unfortunately, the immune system declines with age, a phenomenon known as immunosenescence, and this is characterized by functional changes in both innate and adaptive cellular immunity systems as well as in lymph node architecture. While many of the immune functions decline over time, others paradoxically increase. Indeed, aging is known to be associated with a low level of chronic inflammation—inflamm-aging. Given that the median age of cancer diagnosis is 66 years and that immunotherapeutic interventions such as cancer vaccines are currently given in combination with or after other forms of treatments which themselves have immune-modulating potential such as surgery, chemotherapy and radiotherapy, the choice of adjuvants requires careful consideration in order to achieve the maximum immune response in a compromised environment. In addition, more clinical trials need to be performed to carefully assess how less conventional form of immune adjuvants, such as exercise, diet and psychological care which have all be shown to influence immune responses can be incorporated to improve the efficacy of cancer vaccines. In this review, adjuvants will be discussed with respect to the above-mentioned important elements.

Cancer Vaccines, Treatment of the Future: With Emphasis on HER2-Positive Breast Cancer

Breast cancer is one of the leading causes of death in women. With improvements in early-stage diagnosis and targeted therapies, there has been an improvement in the overall survival rate in breast cancer over the past decade. Despite the development of targeted therapies, tyrosine kinase inhibitors, as well as monoclonal antibodies and their toxin conjugates, all metastatic tumors develop resistance, and nearly one-third of HER2+ breast cancer patients develop resistance to all these therapies. Although antibody therapy has shown promising results in breast cancer patients, passive immunotherapy approaches have limitations and need continuous administration over a long period. Vaccine therapy introduces antigens that act on cancer cells causing prolonged activation of the immune system. In particular, cancer relapse could be avoided due to the presence of a longer period of immunological memory with an effective vaccine that can protect against various tumor antigens. Cancer vaccines are broadly classified as preventive and therapeutic. Preventive vaccines are used to ward off any future infections and therapeutic vaccines are used to treat a person with active disease. In this article, we provided details about the tumor environment, different types of vaccines, their advantages and disadvantages, and the current status of various vaccine candidates with a focus on vaccines for breast cancer. Current data indicate that therapeutic vaccines themselves have limitations in terms of efficacy and are used in combination with other chemotherapeutic or targeting agents. The majority of breast cancer vaccines are undergoing clinical trials and the next decade will see the fruitfulness of breast cancer vaccine therapy.

A New Strategy Toward B Cell-Based Cancer Vaccines by Active Immunization With Mimotopes of Immune Checkpoint Inhibitors

Therapeutic monoclonal antibodies (mAbs), targeting tumor antigens, or immune checkpoints, have demonstrated a remarkable anti-tumor effect against various malignancies. However, high costs for mono- or combination therapies, associated with adverse effects or possible development of resistance in some patients, warrant further development and modification to gain more flexibility for this immunotherapy approach. An attractive alternative to passive immunization with therapeutic antibodies might be active immunization with mimotopes (B-cell peptides) representing the mAbs' binding epitopes, to activate the patient's own anti-tumor immune response following immunization. Here, we identified and examined the feasibility of inducing anti-tumor effects in vivo following active immunization with a mimotope of the immune checkpoint programmed cell death 1 (PD1), alone or in combination with a Her-2/neu B-cell peptide vaccine. Overlapping peptides spanning the extracellular domains of human PD1 (hPD1) were used to identify hPD1-derived mimotopes, using the therapeutic mAb Nivolumab as a proof of concept. Additionally, for in vivo evaluation in a tumor mouse model, a mouse PD1 (mPD1)-derived mimotope was identified using an anti-mPD1 mAb with mPD1/mPDL-1 blocking capacity. The identified mimotopes were characterized by in vitro assays, including a reporter cell-based assay, and their anti-tumor effects were evaluated in a syngeneic tumor mouse model stably expressing human Her-2/neu. The identified PD1-derived mimotopes were shown to significantly block the mAbs' capacity in inhibiting the respective PD1/PD-L1 interactions. A significant reduction in tumor growth in vivo was observed following active immunization with the mPD1-derived mimotope, associated with a significant reduction in proliferation and increased apoptotic rates in the tumors. Particularly, combined vaccination with the mPD1-derived mimotope and a multiple B-cell epitope Her-2/neu vaccine potentiated the vaccine's anti-tumor effect. Our results suggest active immunization with mimotopes of immune checkpoint inhibitors either as monotherapy or as combination therapy with tumor-specific vaccines, as a new strategy for cancer treatment.

Peptide-based materials for cancer immunotherapy

Peptide-based materials hold great promise as immunotherapeutic agents for the treatment of many malignant cancers. Extensive studies have focused on the development of peptide-based cancer vaccines and delivery systems by mimicking the functional domains of proteins with highly specific immuno-regulatory functions or tumor cells fate controls. However, a systemic understanding of the interactions between the different peptides and immune systems remains unknown. This review describes the role of peptides in regulating the functions of the innate and adaptive immune systems and provides a comprehensive focus on the design, categories, and applications of peptide-based cancer vaccines. By elucidating the impacts of peptide length and formulations on their immunogenicity, peptide-based immunomodulating agents can be better utilized and dramatic breakthroughs may also be realized. Moreover, some critical challenges for translating peptides into large-scale synthesis, safe delivery, and efficient cancer immunotherapy are posed to improve the next-generation peptide-based immunotherapy.

Epidermal growth factor receptor peptide vaccination induces cross-reactive immunity to human EGFR, HER2, and HER3

Current treatments for tumors expressing epidermal growth factor receptor (EGFR) include anti-EGFR monoclonal antibodies, often used in conjunction with the standard chemotherapy, radiation therapy, or other EGFR inhibitors. While monoclonal antibody treatment is efficacious in many patients, drawbacks include its high cost of treatment and side effects associated with multiple drug infusions. As an alternative to monoclonal antibody treatments, we have focused on peptide-based vaccination to trigger natural anti-tumor antibodies. Here, we demonstrate that peptides based on a region of the EGFR extracellular domain IV break immune tolerance to EGFR and elicit anti-tumor immunity. Mice immunized with isoforms of EGFR peptide p580-598 generated anti-EGFR antibody and T-cell responses. Iso-aspartyl (iso-Asp)-modified EGFR p580 immune sera inhibit in vitro growth of EGFR overexpressing human A431 tumor cells, as well as promote antibody-dependent cell-mediated cytotoxicity (ADCC). Antibodies induced by Asp and iso-Asp p580 bound homologous regions of the EGFR family members HER2 and HER3. EGFR p580 immune sera also inhibited the growth of the human tumor cell line MDA-MB-453 that expresses HER2 but not EGFR. Asp and iso-Asp EGFR p580 induced antibodies were also able to inhibit the in vivo growth of EGFR-expressing tumors. These data demonstrate that EGFR peptides from a region of the EGFR extracellular domain IV promote anti-tumor immunity, tumor cell killing, and antibodies that are cross reactive with ErbB family members.

Improvement of Antitumor Therapies Based on Vaccines and Immune-Checkpoint Inhibitors by Counteracting Tumor-Immunostimulation

Immune-checkpoint inhibitors and antitumor vaccines may produce both tumor-inhibitory and tumor-stimulatory effects on growing tumors depending on the stage of tumor growth at which treatment is initiated. These paradoxical results are not necessarily incompatible with current tumor immunology but they might better be explained assuming the involvement of the phenomenon of tumor immunostimulation. This phenomenon was originally postulated on the basis that the immune response (IR) evoked in Winn tests by strong chemical murine tumors was not linear but biphasic, with strong IR producing inhibition and weak IR inducing stimulation of tumor growth. Herein, we extended those former observations to weak spontaneous murine tumors growing in pre-immunized, immune-competent and immune-depressed mice. Furthermore, we demonstrated that the interaction of specifical T cells and target tumor cells at low stimulatory ratios enhanced the production of chemokines aimed to recruit macrophages at the tumor site, which, upon activation of toll-like receptor 4 and p38 signaling pathways, would recruit and activate more macrophages and other inflammatory cells which would produce growth-stimulating signals leading to an accelerated tumor growth. On this basis, the paradoxical effects achieved by immunological therapies on growing tumors could be explained depending upon where the therapy-induced IR stands on the biphasic IR curve at each stage of tumor growth. At stages where tumor growth was enhanced (medium and large-sized tumors), counteraction of the tumor-immunostimulatory effect with anti-inflammatory strategies or, more efficiently, with selective inhibitors of p38 signaling pathways enabled the otherwise tumor-promoting immunological strategies to produce significant inhibition of tumor growth.

Immunotherapy for breast cancer: past, present, and future

Immunotherapy has shown promise in many solid tumors including melanoma and non-small cell lung cancer with an evolving role in breast cancer. Immunotherapy encompasses a wide range of therapies including immune checkpoint inhibition, monoclonal antibodies, bispecific antibodies, vaccinations, antibody-drug conjugates, and identifying other emerging interventions targeting the tumor microenvironment. Increasing efficacy of these treatments in breast cancer patients requires identification of better biomarkers to guide patient selection; recognizing when to initiate these therapies in multi-modality treatment plans; establishing novel assays to monitor immune-mediated responses; and creating combined systemic therapy options incorporating conventional treatments such as chemotherapy and endocrine therapy. This review will focus on the current role and future directions of many of these immunotherapies in breast cancer, as well as highlighting clinical trials that are investigating several of these active issues.

Enhanced and long term immunogenicity of a Her-2/neu multi-epitope vaccine conjugated to the carrier CRM197 in conjunction with the adjuvant Montanide

Background

We previously identified three short single peptides (P4, P6 and P7) representing different B-cell epitopes on the extracellular domain of Her-2/neu for a vaccine that was tested in a phase-I clinical trial. Here we describe the improvement of the multi peptide vaccine by fusing the single peptides to a hybrid peptide P467.

Methods

After coupling to either virosomes or to diphtheria toxoid CRM197 (CRM), the hybrid peptide was tested in different concentrations in combination with either Montanide or Aluminium hydroxide (Alum) in preclinical studies.

Results

Already low amount (10 μg) of P467 conjugated to CRM led to faster onset of high antibody levels compared to the P467-virosome. The formulation P467-CRM-Montanide induced higher serum IgG antibody titers, compared with P467-CRM-Alum, as examined by ELISA using recombinant Her-2/neu or Her-2/neu natively expressed on the tumor cell line SK-BR-3. Compared to P467-CRM-Alum, higher in vitro production of IL-2 and IFNγ in the Montanide-immunized mice was induced after re-stimulation of splenocytes with CRM but also with P467, indicating a clear Th1-biased response. In contrast to the single B cell peptides, the hybrid peptide led to T cell proliferation and cytokine production as CD4 T cell epitopes were generated in the fusion region of the single peptides P4 and P6 or P6 and P7. Additionally, a significantly higher proportion IFNγ-producing CD8+ T cells was found in the P467-CRM-Montanide immunized mice, probably by Montanide-driven bystander activation. Importantly, anti-P467 IgG antibodies exhibited anti-tumor properties and the combination of anti-P467 specific IgG with Herceptin® was found to inhibit the proliferation of Her-2/neu-overexpressing cell line SK-BR-3 in a significantly higher capacity than Herceptin® alone.

Conclusions

Fusion of the B cell peptides has led to additional generation of CD4 T cell epitopes, and this P467-multi epitope vaccine was found to induce polyclonal antibody responses with anti-proliferative capacity against Her-2/neu. The hybrid vaccine together with Montanide induced higher and long-lasting antibody levels, Th1-biased cellular responses being superior to vaccination with the single B cell peptides. This vaccine formulation is now planned to be evaluated in a phase Ib/II study in Her-2/neu overexpressing cancer patients.

Successful engineering of a highly potent single-chain variable-fragment (scFv) bispecific antibody to target disialoganglioside (GD2) positive tumors

Engineering potent bispecific antibodies from single-chain variable fragments (scFv) remains difficult due to the inherent instability and insufficient binding of scFv's compared to their parental immunoglobulin format. Previously, we described a scFv-based bispecific antibody (scBA) against disialoganglioside (GD2) based on the anti-GD2 murine 5F11-scFv and the anti-CD3 huOKT3-scFv (5F11-scBA). In this study, we substituted the 5F11-scFv with the higher affinity (13-fold) hu3F8-scFv to form hu3F8-scBA. With this modification, hu3F8-scBA redirected T cells to kill GD2(+) cancer cell lines with up to 5,000-fold higher potency (femtomolar EC₅₀) compared with 5F11-scBA (picomolar EC₅₀) in cytotoxicity assays, even against target cells with low GD2 densities. Furthermore, hu3F8-scBA induced stronger T-cell activation than 5F11-scBA, as measured by Ca²⁺ flux and cytokine release. Additionally, in vivo, hu3F8-scBA suppressed tumor growth and prolonged mice survival much more effectively than 5F11-scBA, in both neuroblastoma and melanoma xenograft models. We conclude that the functional properties of scBA's can be increased substantially by relatively modest increases in antigen affinity.

A paradigm shift: Cancer therapy with peptide-based B-cell epitopes and peptide immunotherapeutics targeting multiple solid tumor types: Emerging concepts and validation of combination immunotherapy

There is a recognizable and urgent need to speed the development and application of novel, more efficacious anti-cancer vaccine therapies that inhibit tumor progression and prevent acquisition of tumor resistance. We have created and established a portfolio of validated peptide epitopes against multiple receptor tyrosine kinases and we have identified the most biologically effective combinations of EGFR (HER-1), HER-2, HER-3, VEGF and IGF-1R peptide vaccines/mimics to selectively inhibit multiple receptors and signaling pathways. The strategy is based on the use of chimeric conformational B-cell epitope peptides incorporating "promiscuous" T-cell epitopes that afford the possibility of generating an enduring immune response, eliciting protein-reactive high-affinity anti-peptide antibodies as potential vaccines and peptide mimics that act as antagonists to receptor signaling that drive cancer metastasis. In this review we will summarize our ongoing studies based on the development of combinatorial immunotherapeutic strategies that act synergistically to enhance immune-mediated tumor killing aimed at addressing mechanisms of tumor resistance for several tumor types.

Design and characterization of the tumor vaccine MGN1601, allogeneic fourfold gene-modified vaccine cells combined with a TLR-9 agonist

The tumor vaccine MGN1601 was designed and developed for treatment of metastatic renal cell carcinoma (mRCC). MGN1601 consists of a combination of fourfold gene-modified cells with the toll-like receptor 9 agonist dSLIM, a powerful connector of innate and adaptive immunity. Vaccine cells originate from a renal cell carcinoma cell line (grown from renal cell carcinoma tissue), express a variety of known tumor-associated antigens (TAA), and are gene modified to transiently express two co-stimulatory molecules, CD80 and CD154, and two cytokines, GM-CSF and IL-7, aimed to support immune response. Proof of concept of the designed vaccine was shown in mice: The murine homologue of the vaccine efficiently (100%) prevented tumor growth when used as prophylactic vaccine in a syngeneic setting. Use of the vaccine in a therapeutic setting showed complete response in 92% of mice as well as synergistic action and necessity of the components. In addition, specific cellular and humoral immune responses in mice were found when used in an allogeneic setting. Immune response to the vaccine was also shown in mRCC patients treated with MGN1601: Peptide array analysis revealed humoral CD4-based immune response to TAA expressed on vaccine cells, including survivin, cyclin D1, and stromelysin.

Overexpressed oncogenic tumor-self antigens

Overexpressed tumor-self antigens represent the largest group of candidate vaccine targets. Those exhibiting a role in oncogenesis may be some of the least studied but perhaps most promising. This review considers this subset of self antigens by highlighting vaccine efforts for some of the better known members and focusing on TPD52, a new promising vaccine target. We shed light on the importance of both preclinical and clinical vaccine studies demonstrating that tolerance and autoimmunity (presumed to preclude this class of antigens from vaccine development) can be overcome and do not present the obstacle that might have been expected. The potential of this class of antigens for broad application is considered, possibly in the context of low tumor burden or adjuvant therapy, as is the need to understand mechanisms of tolerance that are relatively understudied.

Current status of autologous breast tumor cell-based vaccines

Approximately nine out of ten breast cancer-related deaths are attributable to metastasis. Yet, less than 4% of breast cancer patients are initially diagnosed with metastatic cancer. Therefore, the majority of breast cancer-related deaths are due to recurrence and progression of non-metastatic disease. There is tremendous clinical opportunity for novel adjuvant strategies, such as immunotherapies, that have the potential to prevent progressive recurrences. In particular, autologous tumor cell-based vaccines (ATCVs) can train a patient's immune system to recognize and eliminate occult disease. ATCVs have several advantages including safety, multivalency and patient specificity. Furthermore, because lumpectomy or mastectomy is indicated for the vast majority of breast cancer patients, resected tumors offer a readily available, patient-specific source of tumor antigen. Disadvantages of ATCVs include poor immunogenicity and production inconsistencies. This review summarizes recent progress in the development of autologous breast tumor vaccines and offers insight for overcoming existing limitations.

Harnessing the immune system for the treatment of breast cancer

Standard treatment options for breast cancer include surgery, chemotherapy, radiation, and targeted therapies, such as adjuvant hormonal therapy and monoclonal antibodies. Recently, the recognition that chronic inflammation in the tumor microenvironment promotes tumor growth and survival during different stages of breast cancer development has led to the development of novel immunotherapies. Several immunotherapeutic strategies have been studied both preclinically and clinically and already have been shown to enhance the efficacy of conventional treatment modalities. Therefore, therapies targeting the immune system may represent a promising next-generation approach for the treatment of breast cancers. This review will discuss recent findings that elucidate the roles of suppressive immune cells and proinflammatory cytokines and chemokines in the tumor-promoting microenvironment, and the most current immunotherapeutic strategies in breast cancer.

Influenza virosomes as vaccine adjuvant and carrier system

The basic concept of virosomes is the controlled in vitro assembly of virus-like particles from purified components. The first generation of influenza virosomes developed two decades ago is successfully applied in licensed vaccines, providing a solid clinical safety and efficacy track record for the technology. In the meantime, a second generation of influenza virosomes has evolved as a carrier and adjuvant system, which is currently applied in preclinical and clinical stage vaccine candidates targeting various prophylactic and therapeutic indications. The inclusion of additional components to optimize particle assembly, to stabilize the formulations, or to enhance the immunostimulatory properties have further improved and broadened the applicability of the platform.

Suitable trial designs and cohorts for preventive breast cancer agents

Effective chemoprevention of oestrogen receptor (ER)-positive breast cancer has been shown convincingly using several selective ER modulators and the aromatase inhibitor exemestane. Although these agents are well tolerated and the numbers needed-to-treat in the prevention setting are similar to other established preventive interventions, uptake has been poor in clinical practice because of difficulties in visualizing risk, predicting individual outcomes and measuring treatment benefit. In addition, new agents targeting ER-negative breast cancer are urgently needed. The development of new agents is hampered by the lack of suitable biomarkers and targets, as well as regulatory and financial considerations. Establishing breast cancer chemoprevention in standard clinical practice will require advances in many different fields, including biomarker research, the development of more powerful tools to predict and communicate the risks and benefits of treatments and establishing innovative trial designs. Furthermore, changes in regulatory procedures could reduce the size and cost of trials needed in the prevention setting. Identification of biomarkers for risk and efficacy that are easily accessible, such as blood-based biomarkers, will be key to future chemoprevention strategies.