Advancements in clinical aspects of targeted therapy and immunotherapy in breast cancer

Breast cancer is the second leading cause of death for women worldwide. The heterogeneity of this disease presents a big challenge in its therapeutic management. However, recent advances in molecular biology and immunology enable to develop highly targeted therapies for many forms of breast cancer. The primary objective of targeted therapy is to inhibit a specific target/molecule that supports tumor progression. Ak strain transforming, cyclin-dependent kinases, poly (ADP-ribose) polymerase, and different growth factors have emerged as potential therapeutic targets for specific breast cancer subtypes. Many targeted drugs are currently undergoing clinical trials, and some have already received the FDA approval as monotherapy or in combination with other drugs for the treatment of different forms of breast cancer. However, the targeted drugs have yet to achieve therapeutic promise against triple-negative breast cancer (TNBC). In this aspect, immune therapy has come up as a promising therapeutic approach specifically for TNBC patients. Different immunotherapeutic modalities including immune-checkpoint blockade, vaccination, and adoptive cell transfer have been extensively studied in the clinical setting of breast cancer, especially in TNBC patients. The FDA has already approved some immune-checkpoint blockers in combination with chemotherapeutic drugs to treat TNBC and several trials are ongoing. This review provides an overview of clinical developments and recent advancements in targeted therapies and immunotherapies for breast cancer treatment. The successes, challenges, and prospects were critically discussed to portray their profound prospects.

Potential association factors for developing effective peptide-based cancer vaccines

Peptide-based cancer vaccines have been shown to boost immune systems to kill tumor cells in cancer patients. However, designing an effective T cell epitope peptide-based cancer vaccine still remains a challenge and is a major hurdle for the application of cancer vaccines. In this study, we constructed for the first time a library of peptide-based cancer vaccines and their clinical attributes, named CancerVaccine (https://peptidecancervaccine.weebly.com/). To investigate the association factors that influence the effectiveness of cancer vaccines, these peptide-based cancer vaccines were classified into high (HCR) and low (LCR) clinical responses based on their clinical efficacy. Our study highlights that modified peptides derived from artificially modified proteins are suitable as cancer vaccines, especially for melanoma. It may be possible to advance cancer vaccines by screening for HLA class II affinity peptides may be an effective therapeutic strategy. In addition, the treatment regimen has the potential to influence the clinical response of a cancer vaccine, and Montanide ISA-51 might be an effective adjuvant. Finally, we constructed a high sensitivity and specificity machine learning model to assist in designing peptide-based cancer vaccines capable of providing high clinical responses. Together, our findings illustrate that a high clinical response following peptide-based cancer vaccination is correlated with the right type of peptide, the appropriate adjuvant, and a matched HLA allele, as well as an appropriate treatment regimen. This study would allow for enhanced development of cancer vaccines.

Application of HER2 peptide vaccines in patients with breast cancer: a systematic review and meta-analysis

Background

The E75 and GP2 vaccines are the few therapeutic vaccines targeting HER2 currently under clinical research for patients with breast cancer.

Methods

Databases, including the Cochrane Library, PubMed, Medline, Embase, and Web of Science, were used to retrieve clinical studies on E75 and GP2 vaccines. Retrieval time was from the beginning of database construction until May 31st, 2021.

Results

A total of 24 clinical studies were included in this analysis, including 1704 patients in the vaccinated group and 1248 patients in the control group. For the E75 vaccine, there were significant differences between the vaccinated group and the control group in the delayed-type hypersensitivity reaction (SMD = 0.685 95% CI 0.52–0.85, P_{Heterogeneity} = 0.186, P_DTH < 0.05) and the change in CD8⁺ T-cell numbers (SMD = − 0.864, 95% CI − 1.02 to − 0.709, P_{Heterogeneity} = 0.085, P_{CD8+ T cell} < 0.05) before and after injection. For the GP2 vaccine, there was a significant difference between the vaccinated group and the control group in the change in CD8⁺ T-cell numbers (SMD = − 0.584, 95% CI − 0.803 to − 0.294, P_{Heterogeneity} = 0.397, P_{CD8+ T cell} < 0.05) before and after injection. In addition, the clinical outcomes, including recurrence rate (RR = 0.568, 95% CI 0.444–0.727, P_{Heterogeneity} = 0.955, P_Recurrence < 0.05) and disease-free survival rate (RR = 1.149, 95% CI 1.050–1.256, P_{Heterogeneity} = 0.003, P_DFS < 0.05), of the E75-vaccinated group were different from those of the control group. However, we found that the overall survival rate with the E75 vaccine (RR = 1.032, 95% CI 0.998–1.067, P_{Heterogeneity} = 0.476, P_OS > 0.05) was not different between the two groups. Local and systemic toxicity assessments of the two vaccines showed minimal side effects.

Conclusions

The E75 vaccine was effective and safe in patients with breast cancer. The GP2 vaccine could elicit a strong immune response, but more trials are needed to confirm its clinical efficacy.

Immunotherapy for the Breast Cancer treatment: Current Evidence and Therapeutic Options

Breast cancer (BC) stands at the first position among all forms of malignancies found in women globally. The available therapeutic approaches for breast cancer includes chemotherapy, radiation therapy, hormonal therapy and finally surgery. Despite the conventional therapies, in recent years the advance immunology based therapeutics emerge a potential in breast cancer treatment, including immune checkpoint blockades, vaccines and in combination with other treatment strategies. Although, commonly used treatments like trastuzumab/pertuzumab for human epidermal growth factor receptor 2 (Her2) positive and hormone therapy for estrogen receptor (ER) positive and/or progesterone receptor (PR) positive BC are specific but triple negative breast cancer (TNBC) cases remain a great challenge for treatment measures. Immune checkpoint inhibitors (anti-PD-1/ anti-CTLA-4) and anti-cancer vaccines (NeuVax, Muc-1, AVX901, INO-1400 and CEA), either alone or in combination with other therapies have created new paradigm in therapeutic world. In this review, we highlighted the current immunotherapeutic aspects and their ongoing trials towards the better treatment regimen for BC.

Recent progress in immunotherapy of breast cancer targeting the human epidermal growth factor receptor 2 (HER2)

OBJECTIVE

Breast cancer is responsible for most of the cancer-induced deaths in women around the world. The current review will discuss different approaches of targeting HER2, an epidermal growth factor overexpressed in 30% of breast cancer cases.

DATA SOURCES

We conducted a search on Pubmed and Scopus databases to find studies relevant to HER2+ breast cancers and targeting HER2 as means of immunotherapy. Out of 1043 articles, 105 studies were included in this review.

DATA SUMMARY

As well as the introduction of HER2 and breast cancer subtypes, we discussed various aspects of HER2-targeting immunotherapy including monoclonal antibodies, Antibody-drug conjugates (ADCs), Chimeric Antigen Receptor (CAR) T-cells and vaccines.

CONCLUSIONS

Despite several ways of controlling breast cancer, the need to investigate new drugs and approaches seems to be much significant as this cancer still has a heavy burden on people's health and survival.

Peptide-Based Vaccines: Current Progress and Future Challenges

Vaccines have had a profound impact on the management and prevention of infectious disease. In addition, the development of vaccines against chronic diseases has attracted considerable interest as an approach to prevent, rather than treat, conditions such as cancer, Alzheimer's disease, and others. Subunit vaccines consist of nongenetic components of the infectious agent or disease-related epitope. In this Review, we discuss peptide-based vaccines and their potential in three therapeutic areas: infectious disease, Alzheimer's disease, and cancer. We discuss factors that contribute to vaccine efficacy and how these parameters may potentially be modulated by design. We examine both clinically tested vaccines as well as nascent approaches and explore current challenges and potential remedies. While peptide vaccines hold substantial promise in the prevention of human disease, many obstacles remain that have hampered their clinical use; thus, continued research efforts to address these challenges are warranted.

Cancer vaccines: translation from mice to human clinical trials

Therapeutic cancer vaccines have been a long-sought approach to harness the exquisite specificity of the immune system to treat cancer, but until recently have not had much success as single agents in clinical trials. However, new understanding of the immunoregulatory mechanisms exploited by cancers has allowed the development of approaches to potentiate the effect of vaccines by removing the brakes while the vaccines step on the accelerator. Thus, vaccines that had induced a strong T cell response but no clinical therapeutic effect may now reach their full potential. Here, we review a number of promising approaches to cancer vaccines developed initially in mouse models and their translation into clinical trials, along with combinations of vaccines with other therapies that might allow cancer vaccines to finally achieve clinical efficacy against many types of cancer.

A pilot study of the immunogenicity of a 9-peptide breast cancer vaccine plus poly-ICLC in early stage breast cancer

BACKGROUND

Breast cancer remains a leading cause of cancer death worldwide. There is evidence that immunotherapy may play a role in the eradication of residual disease. Peptide vaccines for immunotherapy are capable of durable immune memory, but vaccines alone have shown sparse clinical activity against breast cancer to date. Toll-like receptor (TLR) agonists and helper peptides are excellent adjuvants for vaccine immunotherapy and they are examined in this human clinical trial.

METHODS

A vaccine consisting of 9 MHC class I-restricted breast cancer-associated peptides (from MAGE-A1, -A3, and -A10, CEA, NY-ESO-1, and HER2 proteins) was combined with a TLR3 agonist, poly-ICLC, along with a helper peptide derived from tetanus toxoid. The vaccine was administered on days 1, 8, 15, 36, 57, 78. CD8⁺ T cell responses to the vaccine were assessed by both direct and stimulated interferon gamma ELIspot assays.

RESULTS

Twelve patients with breast cancer were treated: five had estrogen receptor positive disease and five were HER2 amplified. There were no dose-limiting toxicities. Toxicities were limited to Grade 1 and Grade 2 and included mild injection site reactions and flu-like symptoms, which occurred in most patients. The most common toxicities were injection site reaction/induration and fatigue, which were experienced by 100% and 92% of participants, respectively. In the stimulated ELIspot assays, peptide-specific CD8⁺ T cell responses were detected in 4 of 11 evaluable patients. Two patients had borderline immune responses to the vaccine. The two peptides derived from CEA were immunogenic. No difference in immune response was evident between patients receiving endocrine therapy and those not receiving endocrine therapy during the vaccine series.

CONCLUSIONS

Peptide vaccine administered in the adjuvant breast cancer setting was safe and feasible. The TLR3 adjuvant, poly-ICLC, plus helper peptide mixture provided modest immune stimulation. Further optimization is required for this multi-peptide vaccine/adjuvant combination.

TRIAL REGISTRATION

ClinicalTrials.gov (posted 2/15/2012): NCT01532960. Registered 2/8/2012. https://clinicaltrials.gov/show/NCT01532960.

Cancer vaccine strategies: translation from mice to human clinical trials

We translated two cancer vaccine strategies from mice into human clinical trials. (1) In preclinical studies on TARP, an antigen expressed in most prostate cancers, we mapped epitopes presented by HLA-A*0201, modified them to increase affinity and immunogenicity in HLA transgenic mice, and induced human T cells that killed human cancer cells ("epitope enhancement"). In a clinical trial, HLA-A2⁺ prostate cancer patients with PSA biochemical recurrence (Stage D0) were vaccinated with two peptides either in Montanide-ISA51 or on autologous dendritic cells (DCs). In stage D0, the Prostate-Specific Antigen (PSA) slope is prognostic of time to radiographic evidence of metastases and death. With no difference between arms, 74% of combined subjects had a decreased PSA slope at 1 year compared to their own baseline slopes (p = 0.0004). For patients vaccinated with DCs, response inversely correlated with a tolerogenic DC signature. A randomized placebo-controlled phase II trial is underway. (2) HER2 is a driver surface oncogene product expressed in multiple tumors. We made an adenoviral vector vaccine expressing the extracellular and transmembrane domains of HER2 and cured mice with large established HER2⁺ tumors, dependent on antibodies to HER2, not T cells. The mechanism differed from that of trastuzumab. We tested a human version in advanced metastatic cancer patients naïve to HER2-directed therapies. At the second and third dose levels, 45% of evaluable patients showed clinical benefit. Circulating tumor cells also declined in some vaccinated patients. Thus, cancer vaccines developed in mice were successfully translated to humans with promising early results.

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.

The clinical development of vaccines for HER2+ breast cancer: Current landscape and future perspectives

Human epidermal growth factor receptor 2 (HER2) is a tumor associated antigen over-expressed in 20-30% of cases of breast cancer. Passive immune therapy with HER2-directed monoclonal antibodies (mabs) has changed the natural history of this subset of breast tumors both in the localized and metastatic settings. The safety and efficacy of HER2 vaccines have been assessed in early phase clinical trials but to date clinically relevant results in late phase trials remain an elusive target. Here, we review the recent translational discoveries related to the interactions between the adaptive immune system and the HER2 antigen in breast cancer, results of published clinical trials, and future directions in the field of HER2 vaccine treatment development.

[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.

The importance of correctly timing cancer immunotherapy

INTRODUCTION

The treatment options for cancer-surgery, radiotherapy and chemotherapy-are now supplemented with immunotherapy. Previously underappreciated but now gaining strong interest are the immune modulatory properties of the three conventional modalities. Moreover, there is a better understanding of the needs and potential of the different immune therapeutic platforms. Key to improved treatment will be the combinations of modalities that complete each other's shortcomings. Area covered: Tumor-specific T-cells are required for optimal immunotherapy. In this review, the authors focus on the correct timing of different types of chemotherapeutic agents or immune modulators and immunotherapeutic drugs, not only for the activation and expansion of tumor-specific T-cells but also to support and enhance their anti-tumor efficacy. Expert opinion: At an early phase of disease, clinical success can be obtained using single treatment modalities but at later disease stages, combinations of several modalities are required. The gain in success is determined by a thorough understanding of the direct and indirect immune effects of the modalities used. Profound knowledge of these effects requires optimal tuning of immunomonitoring. This will guide the appropriate combination of treatments and allow for correct sequencing the order and interval of the different therapeutic modalities.

The development and use of the E75 (HER2 369-377) peptide vaccine

E75 (nelipepimut-S) is an immunogenic peptide derived from the HER2 protein. When combined with the immunoadjuvant granulocyte-macrophage colony-stimulating factor (GM-CSF), nelipepimut-S has been used as a vaccine that is capable of eliciting a robust anti-HER2 immune response. Early-phase clinical trials that enrolled women with node-positive or high-risk node-negative breast cancer who had been rendered disease free with standard of care therapy but were at risk for recurrence, demonstrated the vaccine to be safe with a suggestion of clinical benefit. Nelipepimut-S is currently being evaluated in a Phase III clinical trial. This article covers the preclinical and clinical development of nelipepimut-S.

Vaccines for established cancer: overcoming the challenges posed by immune evasion

Therapeutic vaccines preferentially stimulate T cells against tumour-specific epitopes that are created by DNA mutations or oncogenic viruses. In the setting of premalignant disease, carcinoma in situ or minimal residual disease, therapeutic vaccination can be clinically successful as monotherapy; however, in established cancers, therapeutic vaccines will require co-treatments to overcome immune evasion and to become fully effective. In this Review, we discuss the progress that has been made in overcoming immune evasion controlled by tumour cell-intrinsic factors and the tumour microenvironment. We summarize how therapeutic benefit can be maximized in patients with established cancers by improving vaccine design and by using vaccines to increase the effects of standard chemotherapies, to establish and/or maintain tumour-specific T cells that are re-energized by checkpoint blockade and other therapies, and to sustain the antitumour response of adoptively transferred T cells.

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.

Immunotherapy for the treatment of breast cancer

Decades of research are now leading to therapeutics that target the molecular mechanisms of the cancer-specific immune response. These therapeutics include tumor antigen vaccines, dendritic cell activators, adjuvants that activate innate immunity, adoptive cellular therapy, and checkpoint blockade. The advances in targeted immunotherapy have led to clinical advances in the treatment of solid tumors such as melanoma, prostate cancer, lung cancer, and hematologic malignancies. Preclinical and translational studies suggest that patients with breast cancer may also benefit from augmenting effective immune responses. These results have led to early-phase clinical trials of tumor antigen vaccines, adjuvants, and combinations of checkpoint inhibitor blockade to boost breast cancer-specific immunity in patients. This review focuses on the current and emerging development of cancer immunotherapy for breast cancer.

HER2-family signalling mechanisms, clinical implications and targeting in breast cancer

Approximately 20 % of human breast cancers (BC) overexpress HER2 protein, and HER2-positivity is associated with a worse prognosis. Although HER2-targeted therapies have significantly improved outcomes for HER2-positive BC patients, resistance to trastuzumab-based therapy remains a clinical problem. In order to better understand resistance to HER2-targeted therapies in HER2-positive BC, it is necessary to examine HER family signalling as a whole. An extensive literature search was carried out to critically assess the current knowledge of HER family signalling in HER2-positive BC and response to HER2-targeted therapy. Known mechanisms of trastuzumab resistance include reduced receptor-antibody binding (MUC4, p95HER2), increased signalling through alternative HER family receptor tyrosine kinases (RTK), altered intracellular signalling involving loss of PTEN, reduced p27kip1, or increased PI3K/AKT activity and altered signalling via non-HER family RTKs such as IGF1R. Emerging strategies to circumvent resistance to HER2-targeted therapies in HER2-positive BC include co-targeting HER2/PI3K, pan-HER family inhibition, and novel therapies such as T-DM1. There is evidence that immunity plays a key role in the efficacy of HER-targeted therapy, and efforts are being made to exploit the immune system in order to improve the efficacy of current anti-HER therapies. With our rapidly expanding understanding of HER2 signalling mechanisms along with the repertoire of HER family and other targeted therapies, it is likely that the near future holds further dramatic improvements to the prognosis of women with HER2-positive BC.

Guidance for peptide vaccines for the treatment of cancer

Recent progress in fundamental understanding of tumor immunology has opened a new avenue of cancer vaccines. Currently, the development of new cancer vaccines is a global topic and has attracted attention as one of the most important issues in Japan. There is an urgent need for the development of guidance for cancer vaccine clinical studies in order to lead to drug development. Peptide vaccines characteristically have the effect of indirectly acting against cancer through the immune system - a mechanism of action that clearly differs from anticancer drugs that exert a direct effect. Thus, the clinical development of cancer peptide vaccines should be planned and implemented based on the mechanism of action, which differs significantly from conventional anticancer drug research. The Japanese Society for Biological Therapy has created and published Guidance for peptide vaccines for the treatment of cancer as part of its mission and responsibilities towards cancer peptide vaccine development, which is now pursued globally. We welcome comments from regulators and business people as well as researchers in this area.

Advances in the study of HLA-restricted epitope vaccines

Vaccination is a proven strategy for protection from disease. An ideal vaccine would include antigens that elicit a safe and effective protective immune response. HLA-restricted epitope vaccines, which include T-lymphocyte epitopes restricted by HLA alleles, represent a new and promising immunization approach. In recent years, research in HLA-restricted epitope vaccines for the treatment of tumors and for the prevention of viral, bacterial, and parasite-induced infectious diseases have achieved substantial progress. Approaches for the improvement of the immunogenicity of epitope vaccines include (1) improving the accuracy of the methods used for the prediction of epitopes, (2) making use of additional HLA-restricted CD8(+) T-cell epitopes, (3) the inclusion of specific CD4(+) T-cell epitopes, (4) adding B-cell epitopes to the vaccine construction, (5) finding more effective adjuvants and delivery systems, (6) using immunogenic carrier proteins, and (7) using multiple proteins as epitopes sources. In this manuscript, we review recent research into HLA-restricted epitope vaccines.

Active immunotherapy in HER2 overexpressing breast cancer: current status and future perspectives

BACKGROUND

The use of anti-HER2 monoclonal antibodies (mAbs) has improved the clinical outcome of HER2-overexpressing breast cancers (BCs). Unfortunately, often these tumors tend to relapse and, when metastatic, the duration of clinical benefit is limited over time and almost invariably followed by tumor progression. Alternative approaches to this essentially passive immunotherapy are therefore needed in HER2-overexpressing BC patients. As HER2 is one of the most suitable targets for active immunotherapy in BC, manipulating the immune system is a highly attractive approach.

MATERIAL AND METHODS

A computer-based literature search was carried out using PubMed (keywords: breast neoplasm, HER2 vaccine, immunology); data reported at international meetings were included.

RESULTS

This review provides a focus on the following active vaccinal approaches under clinical investigation against HER2-overexpressing BC: (i) peptide and protein based; (ii) DNA based; (iii) whole tumor cell based; (iv) dendritic cell based. Moreover, the review discuss future challenges in the field, trying to define the best setting for the development of this innovative strategy, considering both immunological and clinical aspects of HER2 targeting.

CONCLUSIONS

Development of effective vaccines for BC remains a distinct challenge but is likely to become a substantial advance for patients with HER2-overexpressing BCs.

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.

Adaptive immune responses associated with breast cancer relapse

The generation, survival, and differentiation of breast cancer stem cells (BCSC) in immunocompetent hosts remain elusive. Some investigators have shown that BCSC can be induced from epithelial tumor cells by the pathologic epithelial to mesenchymal transition (EMT). Emerging evidence suggests that the induction of EMT among epithelial tumor cells originates from signals produced by the non-tumor cells that constitute the tumor microenvironment, including the immune effectors that infiltrate the tumors. Thus, this suggests that the immune system not only has anti-tumor function, but also paradoxically immunoedits tumors, facilitating tumor escape and progression. Indeed, many studies in human breast cancers show both positive and negative associations between the infiltration of various immune effectors (e.g., CD4 and CD8 T cells) and the propensity to relapse with metastatic disease. These observations suggest that distinct types of immune effector cells may induce or inhibit tumor relapse. This review focuses on recent advances in identifying components of the immune system that may directly induce tumor escape and relapse. We propose that levels of interferon (IFN)-γ production or levels of the expression of IFN-γ receptor α on tumor cells may determine whether tumor inhibitory or relapse-promoting effect of IFN-γ may prevail.

Treatment of HER2-positive breast cancer: current status and future perspectives

The advent of HER2-directed therapies has significantly improved the outlook for patients with HER2-positive early stage breast cancer. However, a significant proportion of these patients still relapse and die of breast cancer. Trials to define, refine and optimize the use of the two approved HER2-targeted agents (trastuzumab and lapatinib) in patients with HER2-positive early stage breast cancer are ongoing. In addition, promising new approaches are being developed including monoclonal antibodies and small-molecule tyrosine kinase inhibitors targeting HER2 or other HER family members, antibodies linked to cytotoxic moieties or modified to improve their immunological function, immunostimulatory peptides, and targeting the PI3K and IGF-1R pathways. Improved understanding of the HER2 signaling pathway, its relationship with other signaling pathways and mechanisms of resistance has also led to the development of rational combination therapies and to a greater insight into treatment response in patients with HER2-positive breast cancer. Based on promising results with new agents in HER2-positive advanced-stage disease, a series of large trials in the adjuvant and neoadjuvant settings are planned or ongoing. This Review focuses on current treatment for patients with HER2-positive breast cancer and aims to update practicing clinicians on likely future developments in the treatment for this disease according to ongoing clinical trials and translational research.

Clinical trial results of the HER-2/neu (E75) vaccine to prevent breast cancer recurrence in high-risk patients: from US Military Cancer Institute Clinical Trials Group Study I-01 and I-02

BACKGROUND

The authors conducted exploratory phase 1-2 clinical trials vaccinating breast cancer patients with E75, a human leukocyte antigen (HLA) A2/A3-restricted HER-2/neu (HER2) peptide, and granulocyte-macrophage colony-stimulating factor. The vaccine is given as adjuvant therapy to prevent disease recurrence. They previously reported that the vaccine is safe and effective in stimulating expansion of E75-specific cytotoxic T cells. Here, they report 24-month landmark analyses of disease-free survival (DFS).

METHODS

These dose escalation/schedule optimization trials enrolled lymph node-positive and high-risk lymph node-negative patients with HER2 (immunohistochemistry [IHC] 1-3(+) ) expressing tumors. HLA-A2/A3(+) patients were vaccinated; others were followed prospectively as controls for recurrence. DFS was analyzed by Kaplan-Meier curves; groups were compared using log-rank tests.

RESULTS

Of 195 enrolled patients, 182 were evaluable: 106 (58.2%) in the vaccinated group and 76 (41.8%) in the control group. The 24-month landmark analysis DFS was 94.3% in the vaccinated group and 86.8% in the control group (P = .08). Importantly, because of trial design, 65% of patients received a lower than optimal vaccine dose. In subset analyses, patients who benefited most from vaccination (vaccinated group vs control group) had lymph node-positive (DFS, 90.2% vs 79.1%; P = .13), HER2 IHC 1+-2+ (DFS, 94.0% vs 79.4%; P = .04), or grade 1 or 2 (DFS, 98.4% vs 86.0%; P = .01) tumors and were optimally dosed (DFS, 97.3% vs 86.8%; P = .08). A booster program has been initiated; no patients receiving booster inoculations have recurred.

CONCLUSIONS

The E75 vaccine has clinical efficacy that is more prominent in certain patients. A phase 3 trial enrolling lymph node-positive patients with HER2 low-expressing tumors is warranted.

Comparison of different HER2/neu vaccines in adjuvant breast cancer trials: implications for dosing of peptide vaccines

We have performed multiple adjuvant clinical trials using immunogenic peptides from the HER2/neu protein (AE37/E75/GP2) plus (GM-CSF) given intradermally to breast cancer patients. Four trials were performed with similar dose-escalation design with increasing doses of peptide (AE37/E75/GP2) and varying amounts of GM-CSF. Dose reductions (DRs) were made for significant local and/or systemic toxicity by decreasing GM-CSF for subsequent inoculations. Ex vivo and in vivo immunologic responses were used to compare groups. Of 132 patients, 39 required DR (30 for robust local reactions [DR-L]). DR patients, particularly DR-L, had greater immune responses both ex vivo and in vivo. Postvaccine delayed-type hypersensitivity in DR-L patients compared with all others was larger for E75 (p = 0.001), AE37 (p = 0.077) and GP2 (p = 0.076). All three peptide vaccines were safe and well-tolerated. These findings have led to a clinically relevant optimal vaccine dosing strategy, which may be applicable to other peptide-based cancer vaccines.

Use of booster inoculations to sustain the clinical effect of an adjuvant breast cancer vaccine: from US Military Cancer Institute Clinical Trials Group Study I-01 and I-02

BACKGROUND

The authors are conducting clinical trials of the HER-2/neu E75-peptide vaccine in clinically disease-free breast cancer (BC) patients. Their phase 1-2 trials revealed that the E75 + granulocyte-macrophage colony-stimulating factor (GM-CSF) vaccine is safe and effective in stimulating clonal expansion of E75-specific CD8(+) T cells. They assessed the need for and response to a booster after completion of primary vaccination series.

METHODS

BC patients enrolled in the E75 vaccine trials who were ≥6 months from completion of their primary vaccination series were offered boosters with E75 + GM-CSF. Patients were monitored for toxicity. E75-specific CD8(+) T cells were quantified using the human leukocyte antigen-A2:immunoglobulin G dimer before and after boosting.

RESULTS

Fifty-three patients received the vaccine booster. Median time from primary vaccination series was 9 months (range, 6-35 months), and median residual E75-specific immunity was 0.70% (range, 0-3.49%) CD8(+) lymphocytes. Elevated residual immunity (ERI) (CD8(+) E75-specific T cells >0.5%) was seen in 94.4% of patients at 6 months from primary vaccination series versus 48% of patients at >6 months (P = .002). The booster was well tolerated, with only grade 1 and 2 toxicity observed. Local reactions were more robust in patients receiving the booster at 6 months from primary vaccination series compared with those at >6 months (99.4 ± 6.1 mm vs 81.8 ± 4.1 mm, P = .01). In patients lacking ERI, 85% had increased ERI after vaccination (P = .0014).

CONCLUSIONS

The HER-2/neu E75 peptide vaccine E75 stimulates specific immunity in disease-free BC patients. However, immunity wanes with time. A vaccine booster is safe and effective in stimulating E75-specific immunity in those patients without ERI. These results suggest that the booster may be most effective at 6 months after completion of the primary vaccination series.

A virosomal formulated Her-2/neu multi-peptide vaccine induces Her-2/neu-specific immune responses in patients with metastatic breast cancer: a phase I study

We have previously shown in mice that vaccination with three Her-2-peptides representing B-cell epitopes of the extracellular domain of Her-2/neu induces Her-2/neu-specific IgG antibodies with strong anti-tumor activity in vitro and in vivo. We have now finalized a phase I clinical trial with an anti-Her-2/neu vaccine-construct of immunopotentiating reconstituted influenza virosomes with the three peptides in patients with metastatic breast cancer (MBC). Ten MBC patients with low protein overexpression of Her-2/neu of MBC (+ or ++ upon immunohistochemistry, FISH negative) and positive hormone receptor status were enrolled in a single center phase I study. The virosomal formulated vaccine, consisting of 10 microg/peptide, was intramuscularly applied three times on days 1, 28, and 56. The primary endpoint of the study, which lasted 12 weeks, was safety, the secondary endpoint immunogenicity. Local erythema at the injection site was the only vaccine-related side effect occurring in four patients. In 8 of 10 patients an increase in peptide-specific antibody titer measured by ELISA was found. Importantly, the induced antibodies were also directed against the native Her-2/neu protein. Cellular immune responses, as measured by in vitro production of IL-2, IFN-c, and TNF-a of PBMCs showed a marked increase after vaccination in the majority of vaccinees. Notably, the number of CD4+CD25+Foxp3+T regulatory cells, which were significantly increased compared to healthy controls prior to vaccination, was markedly reduced following vaccination. In all, the immunological responses after vaccination indicated that the patients in stage IV of disease were immunocompetent and susceptible to vaccination. The Her-2/neu multipeptide vaccine was safe, well tolerated and effective in overcoming immunological tolerance to Her-2/neu. The induction of anti-Her-2-specific antibodies could result in clinical benefit comparable to passive anti-Her-2 antibody therapy.

The delayed type hypersensitivity assay using protein and xenogeneic cell antigens

The delayed-type hypersensitivity (DTH) assay has a lengthy history in immunotoxicity testing since it was one of the original functional assays included in the National Toxicology Program (NTP) immunotoxicology test panel. Based on NTP data analysis, the DTH assay is among the most predictive immunotoxicity tests when included with at least two other immune parameters. The DTH assay has the advantage of being: (1) a useful measure of cell-mediated immunity, (2) an in vivo assay where there is less opportunity for ex vivo confounders and (3) a clinically significant human correlate to the tuberculin test. Disadvantages of the DTH assay are that it is potentially labor-intensive to perform, it is somewhat resistant to automation and, when compared with the cyctotoxic T lymphocyte (CTL) assay, it is a relatively crude measurement. However, some groups have been attempting to address the limitations of the DTH assays (see Note 1).The assay is related to the contact hypersensitivity response (CHR), which is covered in another chapter. The DTH response has been used as an indicator of cell-mediated immune status and is dependent upon both T helper 1(Th1)-driven responses as well as cell recruitment and chemotaxis to a local site. As a result, the DTH functional response may be influenced by disruption of either Th1-driven, antigen-dependent T cell development or mobilization of sensitized T cells to a local site. The present chapter describes four common protocols with consideration restricted to protein and xenogeneic cell immunogens.

Intranodal immunization with a vaccinia virus encoding multiple antigenic epitopes and costimulatory molecules in metastatic melanoma

Recombinant vaccinia virus (rVV) encoding tumor-associated antigens (TAAs) and adhesion or costimulatory molecules may represent important immunogenic reagents for cancer immunotherapy. Recently, intranodal (IN) antigen administration was suggested to be more immunogenic than intradermal (ID) vaccination. However, IN rVV administration has not been attempted so far. We used a rVV encoding gp100(280-288), Melan-A/MART-1(27-35) and tyrosinase(1-9) HLA-A0201 restricted epitopes and CD80 and CD86 costimulatory molecules in stage III and IV melanoma patients in a phase 1/2 trial. Of 15 patients initiating treatment, including two cycles of IN immunization, each comprising one rVV administration and three recall injections of the corresponding peptides, accompanied by subcutaneous granulocyte macrophage-colony stimulating factor supplementation, five withdrew due to progressing disease. Of 10 remaining patients seven showed evidence of induction of cytotoxic T lymphocytes (CTLs) directed against at least one epitope under investigation, as detectable by limiting dilution analysis (LDA) of specific precursors and multimer staining. Adverse reactions were mild (National Cancer Institute (NCI) grade 1-2) and mainly represented by fever, skin rashes, and pruritus. These data indicate that IN administration of rVV encoding melanoma-associated epitopes and costimulatory molecules is safe and immunogenic.

Strategies to enhance the therapeutic activity of cancer vaccines: using melanoma as a model

Although there has been initial success with some types of immunotherapy, such as adoptive cellular therapy and monoclonal antibody therapy for cancer, the experience with therapeutic cancer vaccines has been much less encouraging. Almost all randomized phase III trials testing therapeutic cancer vaccines have failed to meet their end points. There are several potential explanations for this, ranging from factors related to the clinical trial design and the vaccine itself. Perhaps the most important are host-related factors. Specifically, progression and metastases of many cancers are associated with induction of multiple cancer-specific immune-inhibitory pathways. These inhibitory pathways include induction of T-cell anergy through dendritic cell dysfunction, release of immunosuppressive cytokines, T-cell exhaustion through inhibitory T-cell signaling and T regulatory cell-mediated tumor-specific immune suppression. All of these pathways have been shown to be operational in patients with melanoma. To enhance the activity of therapeutic cancer vaccines, these immunosupressive pathways need to be addressed and reversed. A number of new immunomodulatory reagents that are able to interfere with some of these pathways are now being assessed in the clinic. Sanofi Pasteur designed a clinical trial in patients with advanced or metastatic melanoma that is intended to both induce tumor-specific T-cell responses and modulate or reverse some of the immune suppression pathways that the melanoma has induced. To accomplish this, the recently optimized ALVAC melanoma multi-antigen vaccine is administered with high doses of IFN-alpha. Clinical trial parameters have also been optimized to enhance the likelihood of inducing and documenting antitumor activity. Success with other therapeutic cancer vaccine approaches will likely require similar approaches in which promising immunogenic vaccines are integrated with biologically and clinically active immunomodulatory reagents.

HER-2/neu (657-665) represents an immunogenic epitope of HER-2/neu oncoprotein with potent antitumor properties

The HER-2/neu oncoprotein is a promising cancer vaccine target. We describe herein a novel HLA-A2.1-restricted epitope, encompassing amino acids 657-665 (AVVGILLVV), which is naturally presented by human breast and ovarian cell lines. HER-2/neu(657-665), [HER-2(9(657))], binds with high affinity to HLA-A2.1 molecules as revealed by a prediction algorithm (SYFPEITHI) and in functional assays. This peptide was found to be immunogenic in HLA-A2.1 transgenic (HHD) mice inducing peptide-specific CTL, which responded with increased IFNgamma production, degranulation, and in vitro as well as in vivo cytotoxicity. Most important, HER-2(9(657)) functioned as a therapeutic vaccine by enabling HHD mice to reject established transplantable tumors. Cured mice resisted tumor growth when re-challenged with the same tumor, demonstrating the capacity of HER-2(9(657)) to generate tumor-specific memory immune response. Finally, this peptide was also found to be immunogenic in PBMCs from HLA-A2.1(+) patients with HER-2/neu(+) breast cancer. Our data encourage further exploitation of HER-2(9(657)) as a promising candidate for peptide-based cancer vaccines.

The impact of HER2/neu expression level on response to the E75 vaccine: from U.S. Military Cancer Institute Clinical Trials Group Study I-01 and I-02

PURPOSE

HER2/neu, a source of immunogenic peptides, is expressed in >75% of breast cancer patients. We have conducted clinical trials with the HER2/neu E75 peptide vaccine in breast cancer patients with varying levels of HER2/neu expression. Vaccine response based on HER2/neu expression level was analyzed.

EXPERIMENTAL DESIGN

Patients were stratified by HER2/neu expression. Low expressors (n = 100) were defined as HER2/neu immunohistochemistry (IHC) 1(+) to 2(+) or fluorescence in situ hybridization < 2.0. Overexpressors (n = 51) were defined as IHC 3(+) or fluorescence in situ hybridization > or = 2.0. Additional analyses were done stratifying by IHC status (0-3(+)). Standard clinocopathlogic factors, immunologic response (in vivo delayed-type hypersensitivity reactions; ex vivo human leukocyte antigen A2:immunoglobulin G dimer assay), and clinical responses (recurrence; mortality) were assessed.

RESULTS

Low-expressor (control, 44; vaccinated, 56) versus overexpressor patients (control, 22; vaccinated, 29) were assessed. Low expressors, overexpressors, and most IHC-status vaccinated groups responded immunologically. Vaccinated low-expressor patients had larger maximum immunologic responses compared with overexpressor patients (P = 0.04), and vaccinated IHC 1(+) patients had increased long-term immune response (P = 0.08). More importantly, compared with controls, low-expressor patients had a mortality reduction (P = 0.08). The largest decrease in mortality was seen in IHC 1(+) patients (P = 0.05). In addition, a subset of overexpressor patients (n = 7) received trastuzumab before vaccination, and this combination seems safe and immunologically beneficial.

CONCLUSIONS

Most patients with various levels of HER2/neu expression responded immunologically and seemed to benefit from vaccination. The low expressors, specifically IHC 1(+) patients, had more robust immunologic responses and may derive the greatest clinical benefit from the E75 vaccine.