Circulating regulatory T cells (CD4+CD25+FOXP3+) decrease in breast cancer patients after vaccination with a modified MHC class II HER2/neu (AE37) peptide

AE37 HER2-targeted vaccine in the prevention of breast cancer recurrence: A mini narrative review of current evidence

Breast cancer remains a significant global health challenge, necessitating innovative therapeutic strategies. This review synthesizes findings from multiple studies investigating the safety profile and efficacy of the AE37 human epidermal growth factor receptor 2 (HER2)-targeted vaccine, offering insights into its potential role in breast cancer immunotherapy. A systematic search of electronic databases, including PubMed, MEDLINE, Scopus, and Web of Science, was conducted to identify relevant articles published up to October 2023. The search strategy utilized a combination of keywords, including "AE37 HER2 vaccine," "breast cancer recurrence prevention," and related terms. Boolean operators (AND, OR) were employed to refine the search. The AE37 vaccine exhibited a favorable safety profile across all studies, with minimal adverse effects reported. Efficacy outcomes varied, with promising trends observed in specific breast cancer subgroups, such as advanced-stage, HER2 under-expressed, and triple-negative breast cancer patients. Subgroup analyses suggested potential benefits, emphasizing the need for precise patient stratification. While the AE37 HER2-targeted vaccine demonstrates a promising safety profile and potential efficacy in specific breast cancer subgroups, an understanding requires addressing identified limitations and advancing research in nuanced directions. This paper provides a foundation for navigating the complex landscape of breast cancer immunotherapy with the AE37 vaccine.

The therapeutic potential of immunotherapy in the treatment of breast cancer: Rational strategies and recent progress

The second leading cause of cancer death in women worldwide is breast cancer (BC), and despite significant advances in BC therapies, a significant proportion of patients develop metastasis and disease recurrence. Currently used treatments, like radiotherapy, chemotherapy, and hormone replacement therapy, result in poor responses and high recurrence rates. Alternative therapies are therefore needed for this type of cancer. Cancer patients may benefit from immunotherapy, a novel treatment strategy in cancer treatment. Even though immunotherapy has been successful in many cases, some patients do not respond to the treatment or those who do respond relapse or progress. The purpose of this review is to discuss several different immunotherapy approaches approved for the treatment of BC, as well as different strategies for immunotherapy for the treatment of BC.

Complexity and diversity of FOXP3 isoforms: Novel insights into the regulation of the immune response in metastatic breast cancer

FOXP3 is a key transcription factor in the regulation of immune responses, and recent studies have uncovered the complexity and diversity of FOXP3 isoforms in various cancers, including metastatic breast cancers (mBCs). It has dual role in the tumor microenvironment of mBCs. This review aims to provide novel insights into the complexity and diversity of FOXP3 isoforms in the regulation of the immune response in breast cancer. We discuss the molecular mechanisms underlying the function of FOXP3 isoforms, including their interaction with other proteins, regulation of gene expression, and impact on the immune system. We also highlight the importance of understanding the role of FOXP3 isoforms in breast cancer and the potential for using them as therapeutic targets. This review highlights the crucial role of FOXP3 isoforms in the regulation of the immune response in breast cancer and underscores the need for further research to fully comprehend their complex and diverse functions.

Cancer Vaccines for Triple-Negative Breast Cancer: A Systematic Review

Triple-negative breast cancer (TNBC) is the subtype of breast cancer with the poorest outcomes, and is associated with a high risk of relapse and metastasis. The treatment choices for this malignancy have been confined to conventional chemotherapeutic agents, due to a lack of expression of the canonical molecular targets. Immunotherapy has been recently changing the treatment paradigm for many types of tumors, and the approach of evoking active immune responses in the milieu of breast tumors through cancer vaccines has been introduced as one of the most novel immunotherapeutic approaches. Accordingly, a number of vaccines for the treatment or prevention of recurrence have been developed and are currently being studied in TNBC patients, while none have yet received any approvals. To elucidate the efficacy and safety of these vaccines, we performed a systematic review of the available literature on the topic. After searching the PubMed, Scopus, Web of Science, Embase, Cochrane CENTRAL, and Google Scholar databases, a total of 5701 results were obtained, from which 42 clinical studies were eventually included based on the predefined criteria. The overall quality of the included studies was acceptable. However, due to a lack of reporting outcomes of survival or progression in some studies (which were presented as conference abstracts) as well as the heterogeneity of the reported outcomes and study designs, we were not able to carry out a meta-analysis. A total of 32 different vaccines have so far been evaluated in TNBC patients, with the majority belonging to the peptide-based vaccine type. The other vaccines were in the cell or nucleic acid (RNA/DNA)-based categories. Most vaccines proved to be safe with low-grade, local adverse events and could efficiently evoke cellular immune responses; however, most trials were not able to demonstrate significant improvements in clinical indices of efficacy. This is in part due to the limited number of randomized studies, as well as the limited TNBC population of each trial. However, due to the encouraging results of the currently published trials, we anticipate that this strategy could show its potential through larger, phase III randomized studies in the near future.

Immunoinformatics Approach for Epitope-Based Vaccine Design: Key Steps for Breast Cancer Vaccine

Vaccines are an upcoming medical intervention for breast cancer. By targeting the tumor antigen, cancer vaccines can be designed to train the immune system to recognize tumor cells. Therefore, along with technological advances, the vaccine design process is now starting to be carried out with more rational methods such as designing epitope-based peptide vaccines using immunoinformatics methods. Immunoinformatics methods can assist vaccine design in terms of antigenicity and safety. Common protocols used to design epitope-based peptide vaccines include tumor antigen identification, protein structure analysis, T cell epitope prediction, epitope characterization, and evaluation of protein-epitope interactions. Tumor antigen can be divided into two types: tumor associated antigen and tumor specific antigen. We will discuss the identification of tumor antigens using high-throughput technologies. Protein structure analysis comprises the physiochemical, hydrochemical, and antigenicity of the protein. T cell epitope prediction models are widely available with various prediction parameters as well as filtering tools for the prediction results. Epitope characterization such as allergenicity and toxicity can be done in silico as well using allergenicity and toxicity predictors. Evaluation of protein-epitope interactions can also be carried out in silico with molecular simulation. We will also discuss current and future developments of breast cancer vaccines using an immunoinformatics approach. Finally, although prediction models have high accuracy, the opposite can happen after being tested in vitro and in vivo. Therefore, further studies are needed to ensure the effectiveness of the vaccine to be developed. Although epitope-based peptide vaccines have the disadvantage of low immunogenicity, the addition of adjuvants can be a solution.

Breast Cancer Vaccines: Disappointing or Promising?

Breast cancer has become the most commonly diagnosed cancer globally. The relapse and metastasis of breast cancer remain a great challenge despite advances in chemotherapy, endocrine therapy, and HER2 targeted therapy in the past decades. Innovative therapeutic strategies are still critically in need. Cancer vaccine is an attractive option as it aims to induce a durable immunologic response to eradicate tumor cells. Different types of breast cancer vaccines have been evaluated in clinical trials, but none has led to significant benefits. Despite the disappointing results at present, new promise from the latest study indicates the possibility of applying vaccines in combination with anti-HER2 monoclonal antibodies or immune checkpoint blockade. This review summarizes the principles and mechanisms underlying breast cancer vaccines, recapitulates the type and administration routes of vaccine, reviews the current results of relevant clinical trials, and addresses the potential reasons for the setbacks and future directions to explore.

Cancer vaccines as a targeted immunotherapy approach for breast cancer: an update of clinical evidence

INTRODUCTION

Breast cancer (BC) is the first common neoplastic malignancy and the second leading cause of death in women worldwide. Conventional treatments for BC are often associated with severe side effects and may even lead to late recurrence. For this reason, in recent years, cancer immunotherapy (e.g., cancer vaccines), a novel approach based on the specificity and amplification of acquired immune responses, has been considered as a potential candidate in particular to treat metastatic BC.

AREAS COVERED

In this review, we summarize and discuss the recent development of therapeutic vaccines for BC, use of specific BC cellular antigens, antigen selection, and probable causes for their insufficient effectiveness.

EXPERT OPINION

Despite development of several different BC vaccines strategies including protein/peptide, dendritic cell, and genetic vaccines, until now, no BC vaccine has been approved for clinical use. Most of the current BC vaccines themselves fail to bring clinical benefit to BC patients and are applied in combination with radiotherapy, chemotherapy, or targeted therapy. It is hoped that with advances in our knowledge about tumor microenvironment and the development of novel combination strategies, the tumor immunosuppressive mechanisms can be overcome and prolonged immunologic and effective anti-tumor response can be developed in patients.

AE37: a HER2-targeted vaccine for the prevention of breast cancer recurrence

INTRODUCTION

HER2 is a prevalent growth factor in a variety of malignancies, most prominently breast cancer. Over-expression has been correlated with the poorest overall survival and has been the target of successful therapies such as trastuzumab. AE37 is a novel, HER2-directed vaccine based on the AE36 hybrid peptide (aa776-790), which is derived from the intracellular portion of the HER2 protein, and the core portion of the MHC Class II invariant chain (the Ii-Key peptide). This hybrid peptide is given with GM-CSF immunoadjuvant as the AE37 vaccine.

AREAS COVERED

This article describes in detail the preclinical science leading to the creation of the AE37 vaccine and examines use of this agent in multiple clinical trials for breast and prostate cancer. The safety profile of AE37 is discussed and opinions on the potential of the vaccine in breast and prostate cancer patient subsets along with other malignancies, are offered.

EXPERT OPINION

Future trials utilizing the AE37 vaccine to treat other HER2-expressing malignancies are likely to see similar success, and this will be enhanced by combination immunotherapy. Ii-Key modification of other peptides of interest across oncology and virology could yield impressive results over the longer term.

Analysis of the Heterogeneity of CD4+CD25+ T Cell TCR β CDR3 Repertoires in Breast Tumor Tissues, Lung Metastatic Tissues, and Spleens from 4T1 Tumor-Bearing BALB/c Mice

To study the homogeneity and heterogeneity of CD4⁺CD25⁺ T cells receptor β-chain complementarity determining region 3 (TCR β CDR3) repertoires in breast tumor tissues, lung metastatic tissues, and spleens from 4T1 tumor-bearing BALB/c mice. We used high-throughput sequencing to analyze the characteristics and changes of CD4⁺CD25⁺ TCR β CDR3 repertoires among tumor tissues, lung metastatic tissues, and spleens. The diversity of the CD4⁺CD25⁺ TCR β CDR3 repertoires in breast tumor tissue was similar to that of lung metastatic tissues and less pronounced than that of spleen tissues. Breast tumor tissues and lung metastatic tissues had a greater number of high-frequency CDR3 sequences and intermediate-frequency CDR3 sequences than those of spleens. The proportion of unique productive CDR3 sequences in breast tumor tissues and lung metastatic tissues was significantly greater than that in the spleens. The diversity and frequency of the CDR3 repertoires remained homogeneous in breast tumors and lung metastatic tissues and showed great heterogeneity in the spleens, which suggested that the breast tissues and lung metastatic tissues have characteristics of CD4⁺CD25⁺ T cells that relate to the tumor microenvironment. However, the number and characteristics of overlapping CDR3 sequences suggested that there were some different CD4⁺CD25⁺ T cells in tumors and in the circulatory immune system. The study may be used to further explore the characteristics of the CDR3 repertoires and determine the source of the CD4⁺CD25⁺ T cells in the breast cancer microenvironment.

Prospective, randomized, single-blinded, multi-center phase II trial of two HER2 peptide vaccines, GP2 and AE37, in breast cancer patients to prevent recurrence

Purpose

AE37 and GP2 are HER2 derived peptide vaccines. AE37 primarily elicits a CD4+ response while GP2 elicits a CD8+ response against the HER2 antigen. These peptides were tested in a large randomized trial to assess their ability to prevent recurrence in HER2 expressing breast cancer patients. The primary analyses found no difference in 5-year overall disease-free survival (DFS) but possible benefit in subgroups. Here, we present the final landmark analysis.

Methods

In this 4-arm, prospective, randomized, single-blinded, multi-center phase II trial, disease-free node positive and high-risk node negative breast cancer patients enrolled after standard of care therapy. Six monthly inoculations of vaccine (VG) vs. control (CG) were given as the primary vaccine series with 4 boosters at 6-month intervals. Demographic, safety, immunologic, and DFS data were evaluated.

Results

456 patients were enrolled; 154 patients in the VG and 147 in CG for AE37, 89 patients in the VG and 91 in CG for GP2. The AE37 arm had no difference in DFS as compared to CG, but pre-specified exploratory subgroup analyses showed a trend towards benefit in advanced stage (p = 0.132, HR 0.573 CI 0.275–1.193), HER2 under-expression (p = 0.181, HR 0.756 CI 0.499–1.145), and triple-negative breast cancer (p = 0.266, HR 0.443 CI 0.114–1.717). In patients with both HER2 under-expression and advanced stage, there was significant benefit in the VG (p = 0.039, HR 0.375 CI 0.142–0.988) as compared to CG. The GP2 arm had no significant difference in DFS as compared to CG, but on subgroup analysis, HER2 positive patients had no recurrences with a trend toward improved DFS (p = 0.052) in VG as compared to CG.

Conclusions

This phase II trial reveals that AE37 and GP2 are safe and possibly associated with improved clinical outcomes of DFS in certain subgroups of breast cancer patients. With these findings, further evaluations are warranted of AE37 and GP2 vaccines given in combination and/or separately for specific subsets of breast cancer patients based on their disease biology.

Immunotherapy for HER2-positive breast cancer: recent advances and combination therapeutic approaches

Cancer immunotherapy has evolved dramatically with improved understanding of immune microenvironment and immunosurveillance. The immunogenicity of breast cancer is rather heterogeneous. Specific subtypes of breast cancer such as estrogen receptor (ER)-negative, human EGF receptor 2 (HER2)-positive, and triple-negative breast cancer (TNBC) have shown evidence of immunogenicity based on tumor–immune interactions. Several preclinical and clinical studies have explored the potential for immunotherapy to improve the clinical outcomes for different subtypes of breast cancer. This review describes the immune microenvironment of HER2-positive breast cancer and summarizes recent clinical advances of immunotherapeutic treatments in this breast cancer subtype. The review provides rationale and ongoing clinical evidence to the use of immune checkpoint inhibitors, therapeutic vaccines, and adoptive T cell immunotherapy in breast cancer. In addition, the present paper describes the most relevant clinical progress of strategies for the combination of immunotherapy with standard treatment modalities in HER2-positive breast cancer including chemotherapy, targeted therapy, and radiotherapy.

Breast cancer genomics and immuno-oncological markers to guide immune therapies

There is an increasing awareness of the importance of tumor - immune cell interactions to the evolution and therapy responses of breast cancer (BC). Not surprisingly, numerous studies are currently assessing the clinical value of immune modulation for BC patients. However, till now durable clinical responses are only rarely observed. It is important to realize that BC is a heterogeneous disease comprising several histological and molecular subtypes, which cannot be expected to be equally immunogenic and therefore not equally sensitive to single immune therapies. Here we review the characteristics of infiltrating leukocytes in healthy and malignant breast tissue, the prognostic and predictive values of immune cell subsets across different BC subtypes and the various existing immune evasive mechanisms. Furthermore, we describe the presence of certain groups of antigens as putative targets for treatment, evaluate the outcomes of current clinical immunotherapy trials, and finally, we propose a strategy to better implement immuno-oncological markers to guide future immune therapies in BC.

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.

Treating breast cancer with cell-based approaches: an overview

INTRODUCTION

Breast cancer is the most common malignancy in women. Despite there being considerable progress in the treatment of this disease, metastatic dissemination is still considered an incurable condition at the present time, causing 500,000 deaths worldwide every year. Although most of the research efforts have been focused on pharmacological approaches, over the last three decades, the use of bone marrow and peripheral blood-derived cell therapy approaches have been attempted and developed. Areas covered: This review will briefly address cell therapy for breast cancer, including autologous stem cell transplantations for overcoming the myelosuppressive effects of high-dose chemotherapy, allogeneic stem cell transplants and adoptive immunotherapy using bone-marrow derived T-cells. Expert opinion: The treatment of breast cancer using bone marrow or peripheral-blood derived cells has evolved from a supportive care approach to allow dose escalation of conventional chemotherapy to a therapeutic strategy aimed at eliciting immune cell mediated anticancer immunity. This latter principle has led to the development of adoptive immunotherapies, either with 'natural' or genetically engineered effectors, which are being intensively investigated for their great potential against several solid tumors, including breast cancer.

[The anti-tumor immune response in breast cancer: Update and therapeutic perspectives]

The role of the immune response in breast cancer is now well recognized and increasingly taken in account. The goal of this article is, in the first part, to underline its prognostic impact and to precise the immunosurvelliance, immunoselection and the immunosubversion concepts involved in the control and evasion of breast carcinoma. In the second part, therapeutic strategies for the restauration of anti-tumor immunity are developed. Vaccination strategies and checkpoints inhibitors blockade strategies are discussed as well as the immunogenic death linked to the conventional treatments of breast cancer.

A novel multi-drug metronomic chemotherapy significantly delays tumor growth in mice

BACKGROUND

The tumor immunosuppressive microenvironment represents a major obstacle to an effective tumor-specific cellular immune response.

METHODS

In the present study, the counterbalance effect of a novel metronomic chemotherapy protocol on such an immunosuppressive microenvironment was evaluated in a mouse model upon sub-cutaneous ectopic implantation of B16 melanoma cells. The chemotherapy consisted of a novel multi-drug cocktail including taxanes and alkylating agents, administered in a daily metronomic fashion. The newly designed strategy was shown to be safe, well tolerated and significantly efficacious.

RESULTS

Treated animals showed a remarkable delay in tumor growth and prolonged survival as compared to control group. Such an effect was directly correlated with CD4(+) T cell reduction and CD8(+) T cell increase. Furthermore, a significant reduction in the percentage of both CD25(+)FoxP3(+) and CD25(+)CD127(low) regulatory T cell population was found both in the spleens and in the tumor lesions. Finally, the metronomic chemotherapy induced an intrinsic CD8(+) T cell response specific to B16 naturally expressed Trp2 TAA.

CONCLUSION

The novel multi-drug daily metronomic chemotherapy evaluated in the present study was very effective in counterbalancing the immunosuppressive tumor microenvironment. Consequently, the intrinsic anti-tumor T cell immunity could exert its function, targeting specific TAA and significantly containing tumor growth. Overall, the results show that this represents a promising adjuvant approach to significantly enhance efficacy of intrinsic or vaccine-elicited tumor-specific cellular immunity.

Peptide-Based Cancer Vaccine Strategies and Clinical Results

Active cancer immunotherapy is an exciting and developing field in oncology research. Peptide vaccines, the use of isolated immunogenic tumor-associated antigen (TAA) epitopes to generate an anticancer immune response, are an attractive option as they are easily produced and administered with minimal toxicity. Multiple TAA-derived peptides have been identified and evaluated with various vaccine strategies currently in clinical testing. Research suggests that utilizing vaccines in patients with minimal-residual disease may be a more effective strategy compared to targeting patients with widely metastatic disease as it avoids the immune suppression and tolerance associated with higher volumes of more established disease. Clinical trials also suggest that vaccines may need to be tailored and administered to specific cancer subtypes to achieve maximum efficacy. Additionally, numerous immunomodulators now in research and development show potential synergy with peptide vaccines. Our group has focused on a simpler, single-peptide strategy largely from the HER2/neu protein. We will discuss our experience thus far as well as review other peptide vaccine strategies that have shown clinical efficacy.

Adjuvant HER2/neu peptide cancer vaccines in breast cancer

Active cancer immunotherapy remains an exciting and rapidly advancing field in oncology. Peptide cancer vaccines are an attractive therapeutic option as they are safe and easily produced and administered. Peptide cancer vaccines may be most effective in patients with a lower disease burden, when cancer tolerance is minimized. Our experience with three peptide cancer vaccines, E75, GP2 and AE37, in clinically disease-free breast cancer patients provides encouraging results that this method may be effective. Furthermore, the combined results of the initial trials suggest that the vaccine administered may need to be tailored to the specific subtype of cancer and tumor antigen expression level to achieve maximum effectiveness. The results also suggest that combining peptide vaccines with other immunotherapy may lead to a synergistic effect.

Peptide vaccines in breast cancer: The immunological basis for clinical response

This review discusses peptide-based vaccines in breast cancer, immune responses and clinical outcomes, which include studies on animal models and phase I, phase I/II, phase II and phase III clinical trials. Peptide-based vaccines are powerful neoadjuvant immunotherapies that can directly target proteins expressed in tumor cells, mainly tumor-associated antigens (TAAs). The most common breast cancer TAA epitopes are derived from MUC1, HER2/neu and CEA proteins. Peptides derived from TAAs could be successfully used to elicit CD8 and CD4 T cell-specific responses. Thus, choosing peptides that adapt to natural variations of human leukocyte antigen (HLA) genes is critical. The most attractive advantage is that the target response is more specific and less toxic than for other therapies and vaccines. Prominent studies on NeuVax - E75 (epitope for HER2/neu and GM-CSF) in breast cancer and DPX-0907 (HLA-A2-TAAs) expressed in breast cancer, ovarian and prostate cancer have shown the efficacy of peptide-based vaccines as neoadjuvant immunotherapy against cancer. Future peptide vaccine strategies, although a challenge to be applied in a broad range of breast cancers, point to the development of degenerate multi-epitope immunogens against multiple targets.

Novel metronomic chemotherapy and cancer vaccine combinatorial strategy for hepatocellular carcinoma in a mouse model

Hepatocellular carcinoma (HCC) is the most frequent primary liver cancer and represents the third and the fifth leading cause of cancer-related death worldwide in men and women, respectively. Hepatitis B virus (HBV) and hepatitis C virus (HCV) chronic infections account for pathogenesis of more than 80 % of primary HCC. HCC prognosis greatly varies according to stage at beginning of treatment, but the overall 5-year survival rate is approximately 5-6 %. Given the limited number of effective therapeutic strategies available, immunotherapies and therapeutic cancer vaccines may help in improving the clinical outcome for HCC patients. However, the few clinical trials conducted to date have shown contrasting results, indicating the need for improvements. In the present study, a novel combinatorial strategy, based on metronomic chemotherapy plus vaccine, is evaluated in a mouse model. The chemotherapy is a multi-drug cocktail including taxanes and alkylating agents, which is administered in a metronomic-like fashion. The vaccine is a multi-peptide cocktail including HCV as well as universal tumor antigen TERT epitopes. The combinatorial strategy designed and evaluated in the present study induces an enhanced specific T cell response, when compared to vaccine alone, which correlates to a reduced Treg frequency. Such results are highly promising and may pave way to relevant improvements in immunotherapeutic strategies for HCC and beyond.

AE37 peptide vaccination in prostate cancer: a 4-year immunological assessment updates on a phase I trial

In our recent phase I trial, we demonstrated that the AE37 vaccine is safe and induces HER-2/neu-specific immunity in a heterogeneous population of HER-2/neu (+) prostate cancer patients. Herein, we tested whether one AE37 boost can induce long-lasting immunological memory in these patients. Twenty-three patients from the phase I study received one AE37 boost 6-month post-primary vaccinations. Local/systemic toxicities were evaluated following the booster injection. Immunological responses were monitored 1-month (long-term booster; LTB) and 3-year (long-term immunity; LTI) post-booster by delayed-type hypersensitivity, IFN-γ ELISPOT and proliferation assays. Regulatory T cell (Treg) frequencies, plasma transforming growth factor-β (TGF-β) and indoleamine 2,3-deoxygenase (IDO) activity levels were also determined at the same time points. The AE37 booster was safe and well tolerated. Immunological monitoring revealed vaccine-specific long-term immunity in most of the evaluated patients during both LTB and LTI, although individual levels of immunity during LTI were decreased compared with those measured 3 years earlier during LTB. This was paralleled with increased Tregs, TGF-β levels and IDO activity. One AE37 booster generated long-term immunological memory in HER-2/neu (+) prostate cancer patients, which was detectable 3 years later, albeit with a tendency to decline. Boosted patients had favorable clinical outcome in terms of overall and/or metastasis-free survival compared with historical groups with similar clinical characteristics at diagnosis. We suggest that more boosters and/or concomitant disarming of suppressor circuits may be necessary to sustain immunological memory, and therefore, further studies to optimize the AE37 booster schedule are warranted.

Monitoring regulatory immune responses in tumor immunotherapy clinical trials

While immune monitoring of tumor immunotherapy often focuses on the generation of productive Th1-type inflammatory immune responses, the importance of regulatory immune responses is often overlooked, despite the well-documented effects of regulatory immune responses in suppressing anti-tumor immunity. In a variety of malignancies, the frequency of regulatory cell populations has been shown to correlate with disease progression and a poor prognosis, further emphasizing the importance of characterizing the effects of immunotherapy on these populations. This review focuses on the role of suppressive immune populations (regulatory T cells, myeloid-derived suppressor cells, and tumor-associated macrophages) in inhibiting anti-tumor immunity, how these populations have been used in the immune monitoring of clinical trials, the prognostic value of these responses, and how the monitoring of these regulatory responses can be improved in the future.

Prostate cancer vaccines: an old yet novel target, the androgen receptor

Cancer vaccines have been utilized as a therapeutic modality to treat prostate cancer in clinical studies for several decades. Recently with the approval of sipuleucel-T, vaccines have now been accepted as standard therapy for this disease. The androgen receptorhas long been recognized as a therapeutic target for the treatment of patients with locally advanced as well as metastatic disease. Recent preclinical studies described by Olson et al. have focused on the androgen receptor as a target for prostate cancer immunotherapy. They have developed and tested a DNA vaccine targeting the ligand-binding domain of the androgen receptor and have demonstrated in animal studies the ability to elicit T-cell responses towards the vaccine that have resulted in both antitumor activity as well as increased survival in the animal models described.

Modern subunit vaccines: development, components, and research opportunities

Traditional vaccines, based on the administration of killed or attenuated microorganisms, have proven to be among the most effective methods for disease prevention. Safety issues related to administering these complex mixtures, however, prevent their universal application. Through identification of the microbial components responsible for protective immunity, vaccine formulations can be simplified, enabling molecular-level vaccine characterization, improved safety profiles, prospects to develop new high-priority vaccines (e.g. for HIV, tuberculosis, and malaria), and the opportunity for extensive vaccine component optimization. This subunit approach, however, comes at the expense of decreased immunity, requiring the addition of immunostimulatory agents (adjuvants). As few adjuvants are currently used in licensed vaccines, adjuvant development represents an exciting area for medicinal chemists to play a role in the future of vaccine development. In addition, immune responses can be further customized though optimization of delivery systems, tuning the size of particulate vaccines, targeting specific cells of the immune system (e.g. dendritic cells), and adding components to aid vaccine efficacy in whole immunized populations (e.g. promiscuous T-helper epitopes). Herein we review the current state of the art and future direction in subunit vaccine development, with a focus on the described components and their potential to steer the immune response toward a desired response.

Breast cancer immunobiology driving immunotherapy: vaccines and immune checkpoint blockade

Breast cancer is immunogenic, and infiltrating immune cells in primary breast tumors convey important clinical prognostic and predictive information. Furthermore, the immune system is critically involved in clinical responses to some standard cancer therapies. Early breast cancer vaccine trials have established the safety and bioactivity of breast cancer immunotherapy, with hints of clinical activity. Novel strategies for modulating regulators of immunity, including regulatory T cells, myeloid-derived suppressor cells and immune checkpoint pathways (monoclonal antibodies specific for the cytotoxic T-lymphocyte antigen-4 or programmed death), are now available. In particular, immune checkpoint blockade has enormous therapeutic potential. Integrative breast cancer immunotherapies that strategically combine established breast cancer therapies with breast cancer vaccines, immune checkpoint blockade or both should result in durable clinical responses and increased cures.

AE37: a novel T-cell-eliciting vaccine for breast cancer

INTRODUCTION

Immunotherapy, including vaccines targeting the human EGFR2 (HER-2/neu) protein, is an active area of investigation in combatting breast cancer. Several vaccines are currently undergoing clinical trials, most of which are CD8(+) T-cell-eliciting vaccines. AE37 is a promising primarily CD4(+) T-cell-eliciting HER-2/neu breast cancer vaccine currently in clinical trials.

AREAS COVERED

This article reviews preclinical investigations as well as findings from completed and ongoing Phase I and Phase II clinical trials of the AE37 vaccine.

EXPERT OPINION

Clinical trials have shown the AE37 vaccine to be safe and capable of generating peptide-specific, durable immune responses. This has been shown in patients with any level of HER-2/neu expression. Early clinical findings suggest there may be benefit to AE37 vaccination in preventing breast cancer recurrence.

The dual role of the X-linked FoxP3 gene in human cancers

The FoxP3 (forkhead box P3) gene is an X-linked gene that is submitted to inactivation. It is an essential transcription factor in CD4(+)CD25(+)FoxP3 regulatory T cells, which are therapeutic targets in disseminated cutaneous melanoma. Moreover, FoxP3 is an important tumor suppressor gene in carcinomas and has putative cancer suppressor gene function in cutaneous melanoma as well. Therefore understanding the structure and function of the FoxP3 gene is crucial to gaining insight into the biology of melanoma to better develop immunotherapeutics and future therapeutic strategies.