Antibody association with HER-2/neu-targeted vaccine enhances CD8 T cell responses in mice through Fc-mediated activation of DCs

A bibliometric analysis of drug resistance in immunotherapy for breast cancer: trends, themes, and research focus

While breast cancer treatments have advanced significantly nowadays, yet metastatic, especially triple-negative breast cancer (TNBC), remains challenging with low survival. Cancer immunotherapy, a promising approach for HER2-positive and TNBC, still faces resistance hurdles. Recently, numerous studies have set their sights on the resistance of immunotherapy for breast cancer. Our study provides a thorough comprehension of the current research landscape, hotspots, and emerging breakthroughs in this critical area through a meticulous bibliometric analysis. As of March 26, 2024, a total of 1341 articles on immunology resistance in breast cancer have been gathered from Web of Science Core Collection, including 765 articles and 576 reviews. Bibliometrix, CiteSpace and VOSviewer software were utilized to examine publications and citations per year, prolific countries, contributive institutions, high-level journals and scholars, as well as highly cited articles, references and keywords. The research of immunotherapy resistance in breast cancer has witnessed a remarkable surge over the past seven years. The United States and China have made significant contributions, with Harvard Medical School being the most prolific institution and actively engaging in collaborations. The most contributive author is Curigliano, G from the European Institute of Oncology in Italy, while Wucherpfennig, K. W. from the Dana-Farber Cancer Institute in the USA, had the highest citations. Journals highly productive primarily focus on clinical, immunology and oncology research. Common keywords include "resistance", "expression", "tumor microenvironment", "cancer", "T cell", "therapy", "chemotherapy" and "cell". Current research endeavors to unravel the mechanisms of immune resistance in breast cancer through the integration of bioinformatics, basic experiments, and clinical trials. Efforts are underway to develop strategies that improve the effectiveness of immunotherapy, including the exploration of combination therapies and advancements in drug delivery systems. Additionally, there is a strong focus on identifying novel biomarkers that can predict patient response to immunology. This study will provide researchers with an up-to-date overview of the present knowledge in drug resistance of immunology for breast cancer, serving as a valuable resource for informed decision-making and further research on innovative approaches to address immunotherapy resistance.

Update on current and new potential immunotherapies in breast cancer, from bench to bedside

Impressive advances have been seen in cancer immunotherapy during the last years. Although breast cancer (BC) has been long considered as non-immunogenic, immunotherapy for the treatment of BC is now emerging as a new promising therapeutic approach with considerable potential. This is supported by a plethora of completed and ongoing preclinical and clinical studies in various types of immunotherapies. However, a significant gap between clinical oncology and basic cancer research impairs the understanding of cancer immunology and immunotherapy, hampering cancer therapy research and development. To exploit the accumulating available data in an optimal way, both fundamental mechanisms at play in BC immunotherapy and its clinical pitfalls must be integrated. Then, clinical trials must be critically designed with appropriate combinations of conventional and immunotherapeutic strategies. While there is room for major improvement, this updated review details the immunotherapeutic tools available to date, from bench to bedside, in the hope that this will lead to rethinking and optimizing standards of care for BC patients.

EGFR inhibitor erlotinib plus monoclonal antibody versus erlotinib alone for first-line treatment of advanced non-small cell lung carcinoma: A systematic review and meta-analysis

PURPOSE

Immuno-combination therapy is emerging as an effective treatment for advanced non-small cell lung carcinoma (NSCLC). However, compared to monotherapy, such as monoclonal antibodies or kinase inhibitors, whether combination therapy can enhance antitumor efficacy or alleviate side effects remains unclear.

METHODS

A systematic literature search was undertaken using the PubMed, Embase, Web of Science and Cochrane Central Register of Controlled Trials databases to identify eligible studies concentrating on treatment with erlotinib or erlotinib plus monoclonal antibodies in NSCLC patients published between January 2017 and June 2022. The primary outcomes included progression-free survival (PFS), overall survival (OS), response rate (RR) and treatment-related adverse events (AEs).

RESULTS

Seven independent randomized, controlled clinical trials including 1513 patients were obtained for the final analysis. Erlotinib plus monoclonal antibodies was significantly associated with the improvement of PFS (hazards ratio [HR], 0.60; 95% CI 0.53-0.69; z = 7.59, P < 0.01) and with moderate performance regarding OS (HR, 0.81; 95% CI 0.58-1.13; z = 1.23, P = 0.22) and RR (odds ratio [OR], 1.25; 95% CI 0.98-1.59; z = 1.80, P = 0.07), irrespective of EGFR mutation status. In the safety evaluation, erlotinib plus monoclonal antibodies had a markedly higher occurrence of adverse events (AEs) of Clavien grade 3 or higher (OR, 3.32; 95% CI 2.66-4.15; z = 10.64, P < 0.01).

CONCLUSION

Compared with erlotinib alone, combination therapy (erlotinib plus monoclonal antibodies) was associated with significantly improved PFS in NSCLC therapy, accompanied by increased treatment-related AEs.

REGISTRATION

Our systematic review protocol was registered in the PROSPERO international register of systematic reviews (CRD42022347667).

Enhancement of antitumor immune response by radiation therapy combined with dual immune checkpoint inhibitor in a metastatic model of HER2-positive murine tumor

PURPOSE

Treatments for metastatic human epidermal growth factor receptor 2 (HER2)-positive tumors are improving but remain inadequate. We investigated activating antitumor immune response by combining radiation therapy with immune checkpoint inhibitors using mouse tumors overexpressing HER2, a pivotal driver oncogenic antigen, to develop new immunotherapies for metastatic HER2-positive tumors.

MATERIALS AND METHODS

NT2.5 cells were inoculated into the two mammary fat pads of FVB/N mice, which were divided into four groups: no treatment (Non), anti-PD-1 and anti-CTLA4 antibodies (P1C4), irradiation of the large tumor (Rad), and combination (R + P1C4) groups. Tumor growth, immunostaining of tumor-infiltrating lymphocytes, and the proportion of HER2-tumor antigen-specific CD8-positive T cells in the spleen and tumor-infiltrating lymphocytes were analyzed.

RESULTS

In the Rad group, unirradiated and irradiated tumors shrank after treatment. Besides the directly irradiated tumors, the unirradiated tumors in the R + P1C4 group shrank the most. In the unirradiated tumors, CD8-positive T cells and FOXP3-positive T cells accumulated significantly more in the R + P1C4 group than in the P1C4 and the Rad groups (all p < 0.001). CD4-positive helper T cells accumulated significantly more in the R + P1C4 group than in the Rad group (p < 0.05), but this was not significantly different from the P1C4 group. HER2-specific CD8-positive T cells in the spleen and tumor-infiltrating lymphocytes were significantly increased in the R + P1C4 group compared to the P1C4 and Rad groups (all p < 0.0001).

CONCLUSION

Irradiation of HER2-positive tumors induced an antitumor immune effect against the unirradiated tumor, which was enhanced by the combined use of immune checkpoint inhibitors and was mediated by enhanced recruitment of HER2-tumor antigen-specific cytotoxic T lymphocytes at the tumor site in an HER2-positive mouse tumor model. Harnessing the distant antitumor immune response induced by the combination of radiation therapy and immune checkpoint inhibitors could be a promising treatment strategy for metastatic HER2-positive tumors.

Mechanisms of Therapeutic Antitumor Monoclonal Antibodies

Monoclonal antibodies (mAb) are a major component of cancer therapy. In this review, we summarize the different therapeutic mAbs that have been successfully developed against various tumor-expressed antigens and examine our current understanding of their different mechanisms of antitumor action. These mechanisms of action (MOA) largely center on the stimulation of different innate immune effector processes, which appear to be principally responsible for the efficacy of most unconjugated mAb therapies against cancer. This is evident in studies of mAbs targeting antigens for hematologic cancers, with emerging data also demonstrating the critical nature of innate immune-mediated mechanisms in the efficacy of anti-HER2 mAbs against solid HER2+ cancers. Although HER2-targeted mAbs were originally described as inhibitors of HER2-mediated signaling, multiple studies have since demonstrated these mAbs function largely through their engagement with Fc receptors to activate innate immune effector functions as well as complement activity. Next-generation mAbs are capitalizing on these MOAs through improvements to enhance Fc-activity, although regulation of these mechanisms may vary in different tumor microenvironments. In addition, novel antibody-drug conjugates have emerged as an important means to activate different MOAs. Although many unknowns remain, an improved understanding of these immunologic MOAs will be essential for the future of mAb therapy and cancer immunotherapy.

Nanomaterials Enhance the Immunomodulatory Effect of Molecular Targeted Therapy

Molecular targeted therapy, a tumor therapy strategy that inhibits specific oncogenic targets, has been shown to modulate the immune response. In addition to directly inhibiting the proliferation and metastasis of tumor cells, molecular targeted drugs can activate the immune system through a variety of mechanisms, including by promoting tumor antigen processing and presentation, increasing intratumoral T cell infiltration, enhancing T cell activation and function, and attenuating the immunosuppressive effect of the tumor microenvironment. However, poor water solubility, insufficient accumulation at the tumor site, and nonspecific targeting of immune cells limit their application. To this end, a variety of nanomaterials have been developed to overcome these obstacles and amplify the immunomodulatory effects of molecular targeted drugs. In this review, we summarize the impact of molecular targeted drugs on the antitumor immune response according to their mechanisms, highlight the advantages of nanomaterials in enhancing the immunomodulatory effect of molecular targeted therapy, and discuss the current challenges and future prospects.

Trial Watch: Monoclonal antibodies in cancer therapy

Since the advent of hybridoma technology, dating back to 1975, monoclonal antibodies have become an irreplaceable diagnostic and therapeutic tool for a wide array of human diseases. During the last 15 years, several monoclonal antibodies (mAbs) have been approved by FDA for cancer therapy. These mAbs are designed to (1) activate the immune system against tumor cells, (2) inhibit cancer cell-intrinsic signaling pathways, (3) bring toxins in the close proximity of cancer cells, or (4) interfere with the tumor-stroma interaction. More recently, major efforts have been made for the development of immunostimulatory mAbs that either enhance cancer-directed immune responses or limit tumor- (or therapy-) driven immunosuppression. Some of these antibodies, which are thought to facilitate tumor eradication by initiating or sustaining a tumor-specific immune response, have already entered clinical trials. In this Trial Watch, we will review and discuss the clinical progress of the most important mAbs that are have entered clinical trials after January 2008.

The Role of the Tumor Microenvironment in Developing Successful Therapeutic and Secondary Prophylactic Breast Cancer Vaccines

Breast cancer affects roughly one in eight women over their lifetime and is a leading cause of cancer-related death in women. While outcomes have improved in recent years, prognosis remains poor for patients who present with either disseminated disease or aggressive molecular subtypes. Cancer immunotherapy has revolutionized the treatment of several cancers, with therapeutic vaccines aiming to direct the cytotoxic immune program against tumor cells showing particular promise. However, these results have yet to translate to breast cancer, which remains largely refractory from such approaches. Recent evidence suggests that the breast tumor microenvironment (TME) is an important and long understudied barrier to the efficacy of therapeutic vaccines. Through an improved understanding of the complex and biologically diverse breast TME, it may be possible to advance new combination strategies to render breast carcinomas sensitive to the effects of therapeutic vaccines. Here, we discuss past and present efforts to advance therapeutic vaccines in the treatment of breast cancer, the molecular mechanisms through which the TME contributes to the failure of such approaches, as well as the potential means through which these can be overcome.

Clinical research progress of immune checkpoint inhibitors in treatment of primary liver cancer

Primary liver cancer (PLC) is a common malignant tumor of the digestive system in China. At present, the main treatments for liver cancer (LC) are surgical resection, radiofrequency ablation, chemotherapy, transarterial chemoembolization, and liver transplantation. Due to the limited treatment options, the overall 5-year survival rate of patients with advanced LC is still low. New treatments are urgently needed to prolong their survival and improve their quality of life. In recent years, immune checkpoint inhibitors reprensented by programmed death receptor-1 and cytotoxic T lymphocyte-associated antigen-4 have made breakthrough progress in the treatment of LC, and bring new hope for LC patients. In this paper, the clinical research progress of immune checkpoint inhibitors in the treatment of PLC is reviewed.

Role of innate and adaptive immunity in the efficacy of anti-HER2 monoclonal antibodies for HER2-positive breast cancer

Anti-HER2 monoclonal antibodies (mAbs) such as trastuzumab are effective for all stages of HER2-positive breast cancer (BC). However, intrinsic or acquired resistance to these drugs may occur in a significant number of patients (pts) and, except for HER2 status, no validated predictive factors of response/resistance have been identified to date. This lack is in part due to the not yet fully elucidated mechanism of action of mAbs in vivo. Increasing evidence suggests a significant contribution of both innate and adaptive immunity to the antitumor effects of mAbs. The aim of this review was to describe the role of innate and adaptive immunity in the efficacy of anti-HER2 mAbs and to report known and novel strategies to be used for optimizing immune effects of anti-HER2 therapies for HER2-positive BC.

Infiltration of CD4, CD8, CD56, and Fox-P3-positive lymphocytes in breast carcinoma tissue after neoadjuvant chemotherapy with or without trastuzumab

BACKGROUND

Trastuzumab (Tz) is assumed to prime antibody-dependent cellular cytotoxicity (ADCC); however, it remains unclear whether Tz therapy can clinically induce adaptive cellular immunity.

OBJECTIVE

Adaptive Cellular Immune Effect of Tz Therapy.

METHODS

This study included 29 surgical invasive breast carcinomas administered neoadjuvant chemotherapy with Tz (15 cases) or without Tz (14 cases). The numbers of immunoreactive cells (CD4, CD8, CD56, and Fox-P3) in three different compartments (intratumoral, adjacent stromal, and distant stromal) were determined.

RESULTS

The average number of adjacent stromal CD4-positive, CD8-positive, and Fox-P3-positive cells in the Tz+ group was significantly greater than that in the Tz- group (p = 0.036, 0.0049, and 0.043, respectively). However, the number of Fox-P3-positive cells was much less than that of CD4-positive cells. Moreover, distant stromal CD4-positive and CD8-positive cells in the Tz+ group was also significantly greater than that of the Tz- group (p = 0.029 and 0.032, respectively). Only a small number of CD56-positive natural killer cells, playing a main role in ADCC, accumulated at the tumor site after Tz therapy.

CONCLUSIONS

The results suggest that Tz therapy induces adaptive cellular immunity, including infiltration of both CD4-positive helper T cells and CD8-positive cytotoxic T cells into the breast carcinoma lesion.

A CD40 Agonist and PD-1 Antagonist Antibody Reprogram the Microenvironment of Nonimmunogenic Tumors to Allow T-cell-Mediated Anticancer Activity

In cancers with tumor-infiltrating lymphocytes (TILs), monoclonal antibodies (mAbs) that block immune checkpoints such as CTLA-4 and PD-1/PD-L1 promote antitumor T-cell immunity. Unfortunately, most cancers fail to respond to single-agent immunotherapies. T regulatory cells, myeloid derived suppressor cells (MDSCs), and extensive stromal networks within the tumor microenvironment (TME) dampen antitumor immune responses by preventing T-cell infiltration and/or activation. Few studies have explored combinations of immune-checkpoint antibodies that target multiple suppressive cell populations within the TME, and fewer have studied the combinations of both agonist and antagonist mAbs on changes within the TME. Here, we test the hypothesis that combining a T-cell-inducing vaccine with both a PD-1 antagonist and CD40 agonist mAbs (triple therapy) will induce T-cell priming and TIL activation in mouse models of nonimmunogenic solid malignancies. In an orthotopic breast cancer model and both subcutaneous and metastatic pancreatic cancer mouse models, only triple therapy was able to eradicate most tumors. The survival benefit was accompanied by significant tumor infiltration of IFNγ-, Granzyme B-, and TNFα-secreting effector T cells. Further characterization of immune populations was carried out by high-dimensional flow-cytometric clustering analysis and visualized by t-distributed stochastic neighbor embedding (t-SNE). Triple therapy also resulted in increased infiltration of dendritic cells, maturation of antigen-presenting cells, and a significant decrease in granulocytic MDSCs. These studies reveal that combination CD40 agonist and PD-1 antagonist mAbs reprogram immune resistant tumors in favor of antitumor immunity.

Immune Complex Vaccination

Antibody/antigen binding results in immune complexes (IC) that have a variety of regulatory functions. One important feature is the enhanced host immune activation against antigen contained in the complex. ICs play important roles at several critical steps that lead to B and T cell activation, including antigen targeting/retention, facilitated antigen uptake, antigen presenting cell activation and proper balancing of positive and negative stimulatory signals. In both poultry industry and clinical health care, ICs have been used as preventive and therapeutic vaccines. With our deepening understanding of antibody biology, particularly in light of new revelations of regulatory functions of Fc receptors, mechanistically more precise engineering has spearheaded tailored use of this tool for infection control and cancer therapy. IC-based treatment and prophylaxis have been tested to different extents in HBV, HIV and influenza viral infection control and are actively examined as an alternative treatment for several forms of tumor. As a part of this book series, this chapter aims to discuss the mechanistic aspects of IC signaling and their impact on immune cells. We give samples how this old technology has been used by practitioners over the last several decades and suggest potential paths for future development of IC-based immune therapy.

Memory-Like NK Cells: Remembering a Previous Activation by Cytokines and NK Cell Receptors

Natural Killer (NK) cells are cytotoxic innate lymphoid cells serving at the front line against infection and cancer. In inflammatory microenvironments, multiple soluble and contact-dependent signals modulate NK cell responsiveness. Besides their innate cytotoxic and immunostimulatory activity, it has been uncovered in recent years that NK cells constitute a heterogeneous and versatile cell subset. Persistent memory-like NK populations that mount a robust recall response were reported during viral infection, contact hypersensitivity reactions, and after stimulation by pro-inflammatory cytokines or activating receptor pathways. In this review, we highlight recent findings on the generation, functionality, and clinical applicability of memory-like NK cells and describe common features in comparison to other recent concepts of memory NK cells. Understanding of these features will facilitate the conception and design of novel NK cell-based immunotherapies.

Evaluation of T regulatory lymphocytes and serum concentration of selected cytokines in dogs with perianal tumors

The purpose of this study was to determine concentrations of IL-2, IL-10, TGF-β1 in serum and T regulatory cell (Treg) percentage in peripheral blood of dogs with perianal tumours. Investigations were conducted on 32 male dogs of mixed breed. The animals were divided into 4 experimental groups and control group. The groups were established depending on the tumour malignancy degree and the type of dominant hormones. All measurements of serum cytokine concentrations were conducted by the use of commercial diagnostic ELISA kits. Treg lymphocyte percentage was measured by flow cytometry. In both groups with benign tumours cytokine levels decreased during therapy, whilst in groups with malignant tumors, in spite of applying anti-tumour therapy, concentrations of cytokines in serum markedly increased. The mean percentage of Treg lymphocytes in dogs with benign tumours (group I and II) was significantly lower than the mean percentage of these cells in control group at all time points, but after applying of anti-hormonal therapy, the significant increase of Treg percentage was observed compared to baseline values. By contrast, in both groups with malignant tumours (group III and IV), the mean percentage of Treg lymphocytes was significantly higher at the beginning of the experiment comparing with the control group as well as both groups with benign tumours and this percentage increased during anti-tumour therapy. The results of this study suggest that monitoring changes in cytokine serum concentrations and Treg percentage in the bloodstream during anti-hormonal therapy may constitute a subsidiary marker in the monitoring of therapy effectiveness, in prognosis the outcome of a disease or in differentiating tumour degree of malignancy.

Developing anti-HER2 vaccines: Breast cancer experience

Breast cancer accounts for more than one million new cases annually and is the leading cause of death in women globally. HER2 overexpression induces cellular and humoral immune responses against the HER2 protein and is associated with higher tumor proliferation rates. Trastuzumab-based therapies are effectively and widely used as standard of care in HER2-amplified/overexpressed breast cancer patients; one cited mechanism of action is the induction of passive immunity and antibody-dependent cellular cytotoxicity against malignant breast cancer cells. These findings drove the efforts to generate antigen-specific immunotherapy to trigger the patient's immune system to target HER2-overexpressing tumor cells, which led to the development of various vaccines against the HER2 antigen. This article discusses the various anti-HER2 vaccine formulations and strategies and their potential role in the metastatic and adjuvant settings.

Breast Cancer Immunotherapy: Facts and Hopes

Immunotherapy is revolutionizing the management of multiple solid tumors, and early data have revealed the clinical activity of programmed cell death-1/programmed death ligand-1 (PD-1/PD-L1) antagonists in small numbers of patients with metastatic breast cancer. Clinical activity appears more likely if the tumor is triple negative, PD-L1+, and/or harbors higher levels of tumor-infiltrating leukocytes. Responses to atezolizumab and pembrolizumab appear to be durable in metastatic triple-negative breast cancer (TNBC), suggesting that these agents may transform the lives of responding patients. Current clinical efforts are focused on developing immunotherapy combinations that convert nonresponders to responders, deepen those responses that do occur, and surmount acquired resistance to immunotherapy. Identifying biomarkers that can predict the potential for response to single-agent immunotherapy, identify the best immunotherapy combinations for a particular patient, and guide salvage immunotherapy in patients with progressive disease are high priorities for clinical development. Smart clinical trials testing rational immunotherapy combinations that include robust biomarker evaluations will accelerate clinical progress, moving us closer to effective immunotherapy for almost all patients with breast cancer. Clin Cancer Res; 24(3); 511-20. ©2017 AACR.

Human HER2 overexpressing mouse breast cancer cell lines derived from MMTV.f.HuHER2 mice: characterization and use in a model of metastatic breast cancer

Preclinical evaluation of therapeutic agents against metastatic breast cancer require cell lines and animal models that recapitulate clinical metastatic breast cancer as much as possible. We have previously used cell lines derived from the neu-N transgenic model to investigate anti-neu targeting of metastatic breast cancer using an alpha-emitter labeled antibody reactive with the rat variant of HER2/neu expressed by the neu-N model. To investigate alpha-particle emitter targeting of metastatic breast cancer using clinically relevant, commercially available anti-HER2/neu antibodies, we have developed cell lines derived from primary tumors and lung metastases from HuHER2 transgenic mice. We extracted primary mammary gland tumors, isolated the epithelial breast cancer cells, and established seven different cell lines. We also established 2 different cell lines from spontaneous lung metastases and cell lines from a serial transplantation of tumor tissues in HuHER2 transgenic mice. HuHER2 protein was overexpressed in all of the established cell lines. The mRNA level of ER (estrogen receptor) and PR (progesterone receptor) was relatively low in the cell lines compared to normal mammary gland (MG). As EMT markers, the expression of E-Cadherin in the cell lines was downregulated while the expression of TWIST1 and Vimentin were upregulated, relative to MG. Furthermore, trastuzumab directly inhibited cellular viability. Biodistribution studies with ¹¹¹In-DTPA-trastuzumab in HuHER2 cell tumor xenografts demonstrated specific targeting with a clinically relevant antibody. Collectively, these cell lines show all the hallmarks of highly aggressive, metastatic breast cancer and are being used to evaluate combination therapy with alpha-particle emitter labeled HER2/neu reactive antibodies.

Trastuzumab Increases HER2 Uptake and Cross-Presentation by Dendritic Cells

Early-phase clinical trials evaluating CD8⁺ T cell-eliciting, HER2-derived peptide vaccines administered to HER2⁺ breast cancer patients in the adjuvant setting suggest synergy between the vaccines and trastuzumab, the mAb targeting the HER2 protein. Among 60 patients enrolled in clinical trials evaluating the E75 + GM-CSF and GP2 + GM-CSF vaccines, there have been no recurrences in patients vaccinated after receiving trastuzumab as part of standard therapy in the per treatment analyses conducted after a median follow-up of greater than 34 months. Here, we describe a mechanism by which this synergy may occur. Flow cytometry showed that trastuzumab facilitated uptake of HER2 by dendritic cells (DC), which was mediated by the Fc receptor and was specific to trastuzumab. In vitro, increased HER2 uptake by DC increased cross-presentation of E75, the immunodominant epitope derived from the HER2 protein, an observation confirmed in two in vivo mouse models. This increased E75 cross-presentation, mediated by trastuzumab treatment, enabled more efficient expansion of E75-specific cytotoxic T cells (E75-CTL). These results demonstrate a mechanism by which trastuzumab links innate and adaptive immunity by facilitating activation of antigen-specific T cells. On the basis of these data, we conclude that HER2-positive breast cancer patients that have been treated with trastuzumab may experience a more robust antitumor immune response by restimulation of T cells with the E75 peptide vaccine, thereby accounting for the improved disease-free survival observed with combination therapy. Cancer Res; 77(19); 5374-83. ©2017 AACR.

Impact of Depleting Therapeutic Monoclonal Antibodies on the Host Adaptive Immunity: A Bonus or a Malus?

Clinical responses to anti-tumor monoclonal antibody (mAb) treatment have been regarded for many years only as a consequence of the ability of mAbs to destroy tumor cells by innate immune effector mechanisms. More recently, it has also been shown that anti-tumor antibodies can induce a long-lasting anti-tumor adaptive immunity, likely responsible for durable clinical responses, a phenomenon that has been termed the vaccinal effect of antibodies. However, some of these anti-tumor antibodies are directed against molecules expressed both by tumor cells and normal immune cells, in particular lymphocytes, and, hence, can also strongly affect the host adaptive immunity. In addition to a delayed recovery of target cells, lymphocyte depleting-mAb treatments can have dramatic consequences on the adaptive immune cell network, its rebound, and its functional capacities. Thus, in this review, we will not only discuss the mAb-induced vaccinal effect that has emerged from experimental preclinical studies and clinical trials but also the multifaceted impact of lymphocytes-depleting therapeutic antibodies on the host adaptive immunity. We will also discuss some of the molecular and cellular mechanisms of action whereby therapeutic mAbs induce a long-term protective anti-tumor effect and the relationship between the mAb-induced vaccinal effect and the immune response against self-antigens.

Antitumor Antibodies Can Drive Therapeutic T Cell Responses

The classical view of therapeutic monoclonal antibodies (mAbs) against tumor-associated antigens (TAAs) is that their mechanism of action is dominated by signal blocking or the cytotoxicity of Fc-driven innate immune effector functions. We review here a mounting body of evidence that anti-TAA mAbs are capable of profoundly synergizing with T cell-directed immunotherapies such as checkpoint blockade and adoptive cell therapy. Two key components account for this synergy: (i) a self-vaccinal effect mediated by dendritic cells (DCs); and (ii) an inflammatory repolarization of the tumor microenvironment. Efficient exploitation of these mechanisms has tremendous therapeutic potential.

Mechanisms of tumour escape from immune surveillance

The progressive growth and spread of tumour cells in the form of metastases requires an interaction of healthy host cells, such as endothelial cells, fibroblasts, and other cells of mesenchymal origin with immune cells taking part in innate and adaptive responses within the tumour lesion and entire body. The host cells interact with tumour cells to create a dynamic tumour microenvironment, in which healthy cells can both positively and negatively influence the growth and spread of the tumour. The balance of cellular homeostasis and the effect of substances they secrete on the tumour microenvironment determine whether the tumour has a tendency to grow or disappear, and whether the cells remain within the lesion or are capable of metastasis to other regions of the body. Intercellular interactions also determine the tumour’s susceptibility to radiation or other types of cancer treatment. They may also be a rational explanation for differences in treatment outcomes, in which some metastases regress and others progress in response to the same treatment method.

PolyI:C and CpG Synergize with Anti-ErbB2 mAb for Treatment of Breast Tumors Resistant to Immune Checkpoint Inhibitors

Innate and adaptive immune cells play an important role in the therapeutic activity of anti-ErbB2 mAbs, such as trastuzumab. In the clinic, breast tumors poorly infiltrated with immune cells are more resistant to trastuzumab, and patients have a worse prognosis. Because type I and II IFNs are critical to the immune-mediated activity of anti-ErbB2 mAb, we investigated the effect of combining polyI:C and CpG with trastuzumab-like therapy in immunocompetent mouse models of ErbB2⁺ breast cancer. We demonstrated that in situ delivery of polyI:C and CpG combined to systemic anti-ErbB2 mAb triggered a potent inflammatory response in breast tumors able to induce long-lasting CD8⁺ T cell-dependent antitumor immunity. Remarkably, polyI:C and CpG was superior to combined PD-1/CTLA-4 blockade in sensitizing tumors to anti-ErbB2 mAb therapy. Local injection of CpG and polyI:C in a primary tumor significantly enhanced the activity of systemic anti-ErbB2 mAb against a distant untreated tumor. Type I and II IFNs, as well as natural killer cells and CD8⁺ T cells, were indispensible to the synergistic activity of the combination treatment. Because synthetic RNA analogues and CpG oligodeoxynucleotides have been safely used in clinical trials, our study supports combination treatments with anti-ErbB2 mAbs. Cancer Res; 77(2); 312-9. ©2016 AACR.

Immunoregulatory functions of immune complexes in vaccine and therapy

Clinical and experimental preparations of IgG/soluble antigen complexes, as well as those formed following antibody therapy in vivo, are multifaceted immune regulators. These immune complexes (ICs) have been tested in humans and animal models, mostly in forms of experimental or clinical vaccination, for at least a century. With intensified research on Fcγ receptor-mediated immune modulation, as well as with immune complex-directed antigen processing, presentation, and inflammatory responses, there are renewed interests of using ICs in vaccines and immunotherapies. Currently, IC-based immune therapy has been broadly experimented in HBV and HIV viral infection control and antitumor treatments. However, mechanistic insights of IC-based treatments are relatively recent subjects of study; strong efforts are needed to establish links to connect laboratory findings with clinical practices. This review covers the history, mechanisms, and in vivo outcomes of this safe and effective therapeutic tool, with a clear aim to bridge laboratory findings with evolving clinical applications.

Oncolytic Adenovirus Expressing Monoclonal Antibody Trastuzumab for Treatment of HER2-Positive Cancer

Monoclonal anti-HER2 antibody trastuzumab has significantly improved the survival of patients with HER2-overexpressing tumors. Nevertheless, systemic antibody therapy is expensive, limited in efficacy due to physical tumor barriers, and carries the risk of severe side effects such as cardiomyopathy. Oncolytic viruses mediate cancer-selective transgene expression, kill infected cancer cells while mounting antitumor immune responses, and have recently demonstrated promising efficacy in combination treatments. Here, we armed an oncolytic adenovirus with full-length trastuzumab to achieve effective in situ antibody production coupled with progressive oncolytic cancer cell killing. We constructed an infectivity-enhanced serotype 5 oncolytic adenovirus, Ad5/3-Δ24-tras, coding for human trastuzumab antibody heavy- and light-chain genes, connected by an internal ribosome entry site. Infected cancer cells were able to assemble full-length functional antibody, as confirmed by Western blot, ELISA, and antibody-dependent cell-mediated cytotoxicity assay. Importantly, oncolysis was required for release of the antibody into tumors, providing additional spatial selectivity. Ad5/3-Δ24-tras showed potent in vitro cytotoxicity and enhanced antitumor efficacy over oncolytic control virus Ad5/3-Δ24 or commercial trastuzumab in HER2-positive cancer models in vivo (both P < 0.05). Furthermore, Ad5/3-Δ24-tras resulted in significantly higher tumor-to-systemic antibody concentrations (P < 0.001) over conventional delivery. Immunological analyses revealed dendritic cell activation and natural killer cell accumulation in tumor-draining lymph nodes. Thus, Ad5/3-Δ24-tras is an attractive anticancer approach combining oncolytic immunotherapy with local trastuzumab production, resulting in improved in vivo efficacy and immune cell activation in HER2-positive cancer. Moreover, the finding that tumor cells can produce functional antibody as directed by oncolytic virus could lead to many valuable antitumor approaches. Mol Cancer Ther; 15(9); 2259-69. ©2016 AACR.

A Therapeutic Her2/neu Vaccine Targeting Dendritic Cells Preferentially Inhibits the Growth of Low Her2/neu-Expressing Tumor in HLA-A2 Transgenic Mice

PURPOSE

E75, a peptide derived from the Her2/neu protein, is the most clinically advanced vaccine approach against breast cancer. In this study, we aimed to optimize the E75 vaccine using a delivery vector targeting dendritic cells, the B-subunit of Shiga toxin (STxB), and to assess the role of various parameters (Her2/neu expression, combination with trastuzumab) in the efficacy of this cancer vaccine in a relevant preclinical model.

EXPERIMENTAL DESIGN

We compared the differential ability of the free E75 peptide or the STxB-E75 vaccine to elicit CD8(+) T cells, and the impact of the vaccine on murine HLA-A2 tumors expressing low or high levels of Her2/neu.

RESULTS

STxB-E75 synergized with granulocyte macrophage colony-stimulating factors and CpG and proved to be more efficient than the free E75 peptide in the induction of multifunctional and high-avidity E75-specific anti-CD8(+) T cells resulting in a potent tumor protection in HLA-A2 transgenic mice. High expression of HER2/neu inhibited the expression of HLA-class I molecules, leading to a poor recognition of human or murine tumors by E75-specific cytotoxic CD8(+) T cells. In line with these results, STxB-E75 preferentially inhibited the growth of HLA-A2 tumors expressing low levels of Her2/neu. Coadministration of anti-Her2/neu mAb potentiated this effect.

CONCLUSIONS

STxB-E75 vaccine is a potent candidate to be tested in patients with low Her2/neu-expressing tumors. It could also be indicated in patients expressing high levels of Her2/neu and low intratumoral T-cell infiltration to boost the recruitment of T cells-a key parameter in the efficacy of anti-Her2/neu mAb therapy. Clin Cancer Res; 22(16); 4133-44. ©2016 AACR.

The Role of Adaptive Immunity in the Efficacy of Targeted Cancer Therapies

Accumulating evidence indicates that the efficacy of tumor-targeted therapies relies on the host immune response, including targeted small-molecule and antibody approaches that were not previously thought to have an immune component. Here, we review the current understanding of how targeted therapies on tumor cells could have a major impact on the immune response, and how this relates to the therapeutic efficacy of these approaches. In this context, we evaluate different strategies that combine targeted therapies with immunotherapy approaches, and discuss past and ongoing clinical trials. We highlight gaps in knowledge, and argue that significant progress for combined therapies will require a better understanding of the complex interactions between immune cells, the tumor, and the tumor microenvironment (TME) in different cancer settings.

Antibody Therapies in Cancer

Antibody-based immunotherapy has become a standard treatment for a variety of cancers. Many well-developed antibodies disrupt signaling of various growth factor receptors for the treatment of a number of cancers by targeting surface antigens expressed on tumor cells. In recent years, a new family of antibodies is currently emerging in the clinic, which target immune cells rather than cancer cells. These immune-targeted therapies strive to augment antitumor immune responses by antagonizing immunosuppressive pathways or providing exogenous immune-activating stimuli, which have achieved dramatic results in several cancers. The future of cancer therapies is likely to combine these approaches with other treatments, including conventional therapies, to generate more effective treatments.

Improved Natural Killer cell activity and retained anti-tumor CD8(+) T cell responses contribute to the induction of a pathological complete response in HER2-positive breast cancer patients undergoing neoadjuvant chemotherapy

Background

Locally advanced HER2-overexpressing breast cancer (BC) patients achieve a high rate of pathological complete responses (pCR) after neoadjuvant chemotherapy (NC). The apparently unaltered immune proficiency of these patients together with the immune-modulating activities of NC drugs suggest a potential contribution of host immunity in mediating clinical responses. We thus performed an extensive immunomonitoring in locally advanced BC patients undergoing NC to identify immunological correlates of pCR induction.

Methods

The immune profile of 40 HER2-positive and 38 HER2-negative BC patients was characterized at diagnosis and throughout NC (Paclitaxel and Trastuzumab, or Docetaxel and Epirubicin, respectively). The percentages of circulating immune cell subsets including T and B lymphocytes, Natural Killer (NK) cells, regulatory T cells, T helper 17 lymphocytes, were quantified by multiparametric flow cytometry. NK cells functional activity was evaluated through the analysis of NF-kB nuclear translocation by Multispectral flow cytometry, and with the in vitro monitoring of Trastuzumab-mediated antibody-dependent cell cytotoxicity (ADCC). CD8⁺ T cell responses against six different tumor-associated antigens (TAA) were characterized by IFN-γ ELISPOT and IFN-γ/IL-2 DualSpot assays.

Results

After NC, HER2-positive patients showed a significant increase in the number of NK cells and regulatory T cells irrespective of the pathological response, whereas patients undergoing a pCR disclosed higher percentages of T helper 17 cells. Notably, a significant increase in the number of activated NK cells was observed only in HER2-positive patients achieving a pCR. Characterization of anti-tumor T cell responses highlighted sustained levels of CD8⁺ T cells specific for survivin and mammaglobin-A throughout NC in patients undergoing a pCR in both arms. Moreover, HER2-positive patients achieving a pCR were characterized by a multi-epitopic and polyfunctional anti-tumor T cell response, markedly reduced in case of partial response.

Conclusions

These results indicate that maintenance of functional T cell responses against selected antigens and improvement of NK cell proficiency during NC are probably critical requirements for pCR induction, especially in HER2-positive BC patients.

Trail registration: Trial registration number: NCT02307227, registered on ClinicalTrials.gov (http://www.clinicaltrials.gov, November 26, 2014).

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-015-0567-0) contains supplementary material, which is available to authorized users.

Influenza virus-like particles engineered by protein transfer with tumor-associated antigens induces protective antitumor immunity

Delivery of antigen in particulate form using either synthetic or natural particles induces stronger immunity than soluble forms of the antigen. Among naturally occurring particles, virus-like particles (VLPs) have been genetically engineered to express tumor-associated antigens (TAAs) and have shown to induce strong TAA-specific immune responses due to their nano-particulate size and ability to bind and activate antigen-presenting cells. In this report, we demonstrate that influenza VLPs can be modified by a protein transfer technology to express TAAs for induction of effective antitumor immune responses. We converted the breast cancer HER-2 antigen to a glycosylphosphatidylinositol (GPI)-anchored form and incorporated GPI-HER-2 onto VLPs by a rapid protein transfer process. Expression levels on VLPs depended on the GPI-HER-2 concentration added during protein transfer. Vaccination of mice with protein transferred GPI-HER-2-VLPs induced a strong Th1 and Th2-type anti-HER-2 antibody response and protected mice against a HER-2-expressing tumor challenge. The Soluble form of GPI-HER-2 induced only a weak Th2 response under similar conditions. These results suggest that influenza VLPs can be enriched with TAAs by protein transfer to develop effective VLP-based subunit vaccines against cancer without chemical or genetic modifications and thus preserve the immune stimulating properties of VLPs for easier production of antigen-specific therapeutic cancer vaccines.

Tumor antigen-targeting monoclonal antibody-based immunotherapy: Orchestrating combined strategies for the development of long-term antitumor immunity

Tumor antigen (TA)-targeting monoclonal antibody (mAb)-based treatments are considered to be one of the most successful strategies in cancer therapy. Besides targeting TAs and inducing tumor cell death, such antibodies interact with immune cells through Fc-dependent mechanisms to induce adaptive memory immune responses. However, multiple inhibitory/immunosuppressive pathways can be induced by tumor cells to limit the establishment of an efficient antitumor response and consequently a sustained clinical response to TA-targeting mAbs. Here, we provide an overview on how TA-targeting mAbs in combination with conventional cancer therapies and/or inhibitors of key immunosuppressive pathways might represent promising approaches to achieve long-term tumor control.

A feasibility study of cyclophosphamide, trastuzumab, and an allogeneic GM-CSF-secreting breast tumor vaccine for HER2+ metastatic breast cancer

Granulocyte-macrophage colony-stimulating factor (GM-CSF)-secreting tumor vaccines are bioactive, but limited by disease burden and immune tolerance. Cyclophosphamide augments vaccine activity in tolerant neu mice and in patients with metastatic breast cancer. HER2-specific monoclonal antibodies (mAb) enhance vaccine activity in neu mice. We hypothesized that cyclophosphamide-modulated vaccination with HER2-specific mAb safely induces relevant HER2-specific immunity in neu mice and patients with HER2+ metastatic breast cancer. Adding both cyclophosphamide and the HER2-specific mAb 7.16.4 to vaccination maximized HER2-specific CD8+ T-cell immunity and tumor-free survival in neu transgenic mice. We, therefore, conducted a single-arm feasibility study of cyclophosphamide, an allogeneic HER2+ GM-CSF-secreting breast tumor vaccine, and weekly trastuzumab in 20 patients with HER2+ metastatic breast cancer. Primary clinical trial objectives were safety and clinical benefit, in which clinical benefit represents complete response + partial response + stable disease. Secondary study objectives were to assess HER2-specific T-cell responses by delayed type hypersensitivity (DTH) and intracellular cytokine staining. Patients received three monthly vaccinations, with a boost 6 to 8 months from trial entry. This combination immunotherapy was safe, with clinical benefit rates at 6 months and 1 year of 55% [95% confidence interval (CI), 32%-77%; P = 0.013] and 40% (95% CI, 19%-64%), respectively. Median progression-free survival and overall survival durations were 7 months (95% CI, 4-16) and 42 months (95% CI, 22-70), respectively. Increased HER2-specific DTH developed in 7 of 20 patients [of whom 4 had clinical benefit (95% CI, 18-90)], with a trend toward longer progression-free survival and overall survival in DTH responders. Polyfunctional HER2-specific CD8+ T cells progressively expanded across vaccination cycles. Further investigation of cyclophosphamide-modulated vaccination with trastuzumab is warranted.

Tumor antigen-specific monoclonal antibodies and induction of T-cell immunity

For decades the primary available cancer therapies were relatively nonspecific cytotoxic agents which, while effective in some patients, were limited by narrow therapeutic indices, extensive toxicity and development of resistance, likely due to tumor heterogeneity. Although these chemotherapies remain common tools of conventional treatment, the approval of a growing number of tumor antigen (TA)-specific monoclonal antibodies (mAbs) by the US Food and Drug Administration has driven a shift in the paradigm of cancer therapy. For a subset of patients with lymphoma, colorectal, head and neck, and breast cancers, the inclusion of rituximab (anti-CD20), cetuximab (anti-human epidermal growth factor 1), and trastuzumab (anti-human epidermal growth factor 2) has resulted in overall improved clinical response rates and survival advantages. The mechanisms that contribute to these effects are limited not only to inhibition of signaling pathways but also include cell-mediated cytotoxicity by innate immune cells and priming of effector cells of adoptive immunity triggered by the TA-specific mAb. However, as the use of these therapeutic mAbs has become more widespread, it has been observed that there is significant variability of response in patients treated with these agents. Thus, the factors that mediate this variability in clinical responses must be elucidated to optimize the use of TA-specific mAbs.

The immune system and response to HER2-targeted treatment in breast cancer

The monoclonal antibody trastuzumab targets the growth factor receptor HER2 and has profoundly improved the course of disease and survival of women with HER2-overexpressing breast cancer. Because trastuzumab targets aberrant expression of HER2 in tumours addicted to HER2 activation, its clinical activity is credited largely to inhibition of intracellular signalling. A growing body of preclinical and clinical evidence shows that the immune system contributes substantially to the therapeutic effects of trastuzumab and other monoclonal antibodies in vivo. Furthermore, findings indicate that immune-related markers can provide useful predictive information and that increased clinical activity might follow activation of the immune system. Development of immunomodulatory drugs with remarkable activity in many solid tumours defines a scenario in which the combination of immune modulation with trastuzumab, or other HER2-directed drugs, will result in augmented response and clinical outcome.

Immune-based mechanisms of cytotoxic chemotherapy: implications for the design of novel and rationale-based combined treatments against cancer

Conventional anticancer chemotherapy has been historically thought to act through direct killing of tumor cells. This concept stems from the fact that cytotoxic drugs interfere with DNA synthesis and replication. Accumulating evidence, however, indicates that the antitumor activities of chemotherapy also rely on several off-target effects, especially directed to the host immune system, that cooperate for successful tumor eradication. Chemotherapeutic agents stimulate both the innate and adaptive arms of the immune system through several modalities: (i) by promoting specific rearrangements on dying tumor cells, which render them visible to the immune system; (ii) by influencing the homeostasis of the hematopoietic compartment through transient lymphodepletion followed by rebound replenishment of immune cell pools; (iii) by subverting tumor-induced immunosuppressive mechanisms and (iv) by exerting direct or indirect stimulatory effects on immune effectors. Among the indirect ways of immune cell stimulation, some cytotoxic drugs have been shown to induce an immunogenic type of cell death in tumor cells, resulting in the emission of specific signals that trigger phagocytosis of cell debris and promote the maturation of dendritic cells, ultimately resulting in the induction of potent antitumor responses. Here, we provide an extensive overview of the multiple immune-based mechanisms exploited by the most commonly employed cytotoxic drugs, with the final aim of identifying prerequisites for optimal combination with immunotherapy strategies for the development of more effective treatments against cancer.

Antibody-based therapy in colorectal cancer

Treatment in patients with nonresectable and resectable colorectal cancer at the advanced stage is challenging, therefore intensive strategies such as chemotherapy, signaling inhibitors and monoclonal antibodies (mAbs) to control the disease are required. mAbs are particularly promising tools owing to their target specificities and strong antitumor activities through multiple mechanisms, as shown by rituximab in B-cell non-Hodgkin's lymphoma and trastuzumab in breast cancer. Three mAbs (cetuximab, bevacizumab and panitumumab) have been approved for the treatment of colorectal cancer in the USA and many other mAbs are being tested in clinical trials. The potential of antibody therapy is associated with several mechanisms including interference of vital signaling pathways targeted by the antibody and immune cytotoxicity selectively directed against tumor cells by tumor-bound antibody through the Fc portion of the antibody, such as antibody-dependent cellular cytotoxicity and complement-dependent cytotoxicity. Moreover, recent experimental findings have shown that immune complexes formed by therapeutic mAbs with tumor-released antigens could augment the induction of tumor-specific cytotoxic CD8(+) T cells through activation of APCs. In addition, antibodies targeting immune checkpoints on hematopoietic cells have recently opened a new avenue for the treatment of cancer. In this review, we focus on mAb treatment in colorectal cancer and its immunological aspects.

Eradication of non-Hodgkin lymphoma through the induction of tumor-specific T-cell immunity by CD20-Flex BiFP

Although monoclonal antibodies, including CD20 antibody rituximab, are standard therapeutics for several cancers, their efficacy remains variable and often modest. There is an urgent need to enhance the efficacy of the current generation of anticancer antibodies. Flt3 ligand, a soluble protein, has the ability to induce substantial expansion of dendritic cells (DCs). In this study, we constructed a bispecific immunoglobulin G-like bispecific fusion protein (BiFP) targeting both CD20 and Flt3 (CD20-Flex) by using CrossMab technology. We found that the BiFP exhibited stabilities that were comparable with the parental antibody rituximab and were able to bind to both targets with unaltered binding affinity. Notably, our data indicated that CD20-Flex BiFP could not only eliminate lymphoma temporarily but also potentiate tumor-specific T-cell immunity, which affords a long-lasting protection from tumor recurrence. The results showed that the expansion and infiltration of DCs into tumor tissues by CD20-Flex BiFP could be an effective way to generate protective immune responses against cancer, suggesting that the CD20-Flex BiFP could be a promising therapeutic agent against B-cell lymphomas.

Challenges in cancer vaccine development for hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the most common liver malignancy, representing the third and fifth leading cause of death from cancer worldwide in men and women, respectively. The main risk factor for the development of HCC is the hepatitis B and C virus (HBV and HCV) infection; non-viral causes (e.g., alcoholism and aflatoxin) are additional risk factors. HCC prognosis is generally poor because of the low effectiveness of available treatments and the overall 5-year survival rate is approximately 5-6%. In this framework, immunotherapeutic interventions, including cancer vaccines, may represent a novel and effective therapeutic tool. However, only few immunotherapy trials for HCC have been conducted so far with contrasting results, suggesting that improvements in several aspects of the immunotherapy approaches need to be implemented. In particular, identification of novel specific tumor antigens and evaluation of most advanced combinatorial strategies could result in unprecedented clinical outcomes with great beneficial effect for HCC patients. The state of the art in immunotherapy strategies for HCC and future perspectives are reported in the present review.

Cetuximab-activated natural killer and dendritic cells collaborate to trigger tumor antigen-specific T-cell immunity in head and neck cancer patients

PURPOSE

Tumor antigen-specific monoclonal antibodies (mAb) block oncogenic signaling and induce Fcγ receptor (FcγR)-mediated cytotoxicity. However, the role of CD8(+) CTL and FcγR in initiating innate and adaptive immune responses in mAb-treated human patients with cancer is still emerging.

EXPERIMENTAL DESIGN

FcγRIIIa codon 158 polymorphism was correlated with survival in 107 cetuximab-treated patients with head and neck cancer (HNC). Flow cytometry was carried out to quantify EGF receptor (EGFR)-specific T cells in cetuximab-treated patients with HNC. The effect of cetuximab on natural killer (NK) cell, dendritic cell (DC), and T-cell activation was measured using IFN-γ release assays and flow cytometry.

RESULTS

FcγRIIIa polymorphism did not predict clinical outcome in cetuximab-treated patients with HNC; however, elevated circulating EGFR(853-861)-specific CD8(+) T cells were found in cetuximab-treated patients with HNC (P < 0.005). Cetuximab promoted EGFR-specific cellular immunity through the interaction of EGFR(+) tumor cells and FcγRIIIa on NK cells but not on the polymorphism per se. Cetuximab-activated NK cells induced IFN-γ-dependent expression of DC maturation markers, antigen processing machinery components such as TAP-1/2 and T-helper cell (T(H)1) chemokines through NKG2D/MICA binding. Cetuximab initiated adaptive immune responses via NK cell-induced DC maturation, which enhanced cross-presentation to CTL specific for EGFR as well as another tumor antigen, MAGE-3.

CONCLUSION

Cetuximab-activated NK cells promote DC maturation and CD8(+) T-cell priming, leading to tumor antigen spreading and TH1 cytokine release through "NK-DC cross-talk." FcγRIIIa polymorphism did not predict clinical response to cetuximab but was necessary for NK-DC interaction and mAb-induced cross-presentation. EGFR-specific T cells in cetuximab-treated patients with HNC may contribute to clinical response.

Strategies for enhancing vaccine-induced CTL antitumor immune responses

Vaccine-induced cytotoxic T lymphocytes (CTLs) play a critical role in adaptive immunity against cancers. An important goal of current vaccine research is to induce durable and long-lasting functional CTLs that can mediate cytotoxic effects on tumor cells. To attain this goal, there are four distinct steps that must be achieved. To initiate a vaccine-induced CTL antitumor immune response, dendritic cells (DCs) must capture antigens derived from exogenous tumor vaccines in vivo or autologous DCs directly loaded in vitro with tumor antigens must be injected. Next, tumor-antigen-loaded DCs must activate CTLs in lymphoid organs. Subsequently, activated CTLs must enter the tumor microenvironment to perform their functions, at which point a variety of negative regulatory signals suppress the immune response. Finally, CTL-mediated cytotoxic effects must overcome the tolerance induced by tumor cells. Each step is a complex process that may be impeded in many ways. However, if these steps happen under appropriate regulation, the vaccine-induced CTL antitumor immune response will be more successful. For this reason, we should gain a better understanding of the basic mechanisms that govern the immune response. This paper, based on the steps necessary to induce an immune response, discusses current strategies for enhancing vaccine-induced CTL antitumor immune responses.

IL-15 augments antitumoral activity of an ErbB2/HER2 cancer vaccine targeted to professional antigen-presenting cells

Targeted delivery of tumor-associated antigens to professional antigen-presenting cells (APC) is being explored as a strategy to enhance the antitumoral activity of cancer vaccines. Here, we generated a cell-based system for continuous in vivo production of a CTLA-4-ErbB2 fusion protein as a therapeutic vaccine. The chimeric CTLA-4-ErbB2 molecule contains the extracellular domain of CTLA-4 for specific targeting to costimulatory B7 molecules on the surface of APC, genetically fused to residues 1-222 of human ErbB2 (HER2) as an antigenic determinant. In wild-type BALB/c mice, inoculation of syngeneic epithelial cells continuously secreting the CTLA-4-ErbB2 fusion vaccine in the vicinity of subcutaneously growing ErbB2-expressing renal cell carcinomas resulted in the rejection of established tumors, accompanied by the induction of ErbB2-specific antibodies and cytotoxic T cells. In contrast, treatment with CTLA-4-ErbB2 vaccine-secreting producer cells alone was insufficient to induce tumor rejection in ErbB2-transgenic WAP-Her-2 F1 mice, which are characterized by pronounced immunological tolerance to the human self-antigen. When CTLA-4-ErbB2 producer cells were modified to additionally secrete interleukin (IL)-15, antigen-specific antitumoral activity of the vaccine in WAP-Her-2 F1 mice was restored, documented by an increase in survival, and marked inhibition of the growth of established ErbB2-expressing, but not antigen-negative tumors. Our results demonstrate that continuous in vivo expression of an APC-targeted ErbB2 fusion protein results in antigen-specific immune responses and antitumoral activity in tumor-bearing hosts, which is augmented by the pleiotropic cytokine IL-15. This provides a rationale for further development of this approach for specific cancer immunotherapy.

Whole cell vaccines--past progress and future strategies

Cancer vaccines have shown success in curing tumors in preclinical models. Accumulating evidence also supports their ability to induce immune responses in patients. In many cases, these responses correlate with improved clinical outcomes. However, cancer vaccines have not yet demonstrated their true potential in clinical trials. This is likely due to the difficulty in mounting a significant anti-tumor response in patients with advanced disease because of pre-existing tolerance mechanisms that are actively turning off immune recognition in cancer patients. This review will examine the recent progress being made in the design and implementation of whole cell cancer vaccines, one vaccine approach that simultaneously targets multiple tumor antigens to activate the immune response. These vaccines have been shown to induce antigen-specific T-cell responses. Preclinical studies evaluating these vaccines given in sequence with other agents and cancer treatment modalities support the use of immunomodulating doses of chemotherapy and radiation, as well as immune-modulating pathway-targeted monoclonal antibodies, to enhance the efficacy of cancer vaccines. Based on emerging preclinical data, clinical trials are currently exploring the use of combinatorial immune-based therapies for the treatment of cancer.

Toward integrative cancer immunotherapy: targeting the tumor microenvironment

The development of cancer has historically been attributed to genomic alterations of normal host cells. Accordingly, the aim of most traditional cancer therapies has been to destroy the transformed cells themselves. There is now widespread appreciation that the progressive growth and metastatic spread of cancer cells requires the cooperation of normal host cells (endothelial cells, fibroblasts, other mesenchymal cells, and immune cells), both local to, and at sites distant from, the site at which malignant transformation occurs. It is the balance of these cellular interactions that both determines the natural history of the cancer, and influences its response to therapy. This active tumor-host dynamic has stimulated interest in the tumor microenvironment as a key target for both cancer diagnosis and therapy. Recent data has demonstrated both that the presence of CD8⁺ T cells within a tumor is associated with a good prognosis, and that the eradication of all malignantly transformed cells within a tumor requires that the intra-tumoral concentration of cytolytically active CD8⁺ effector T cells remain above a critical concentration until every tumor cell has been killed. These findings have stimulated two initiatives in the field of cancer immunotherapy that focus on the tumor microenvironment. The first is the development of the immune score as part of the routine diagnostic and prognostic evaluation of human cancers, and the second is the development of combinatorial immune-based therapies that reduce tumor-associated immune suppression to unleash pre-existing or therapeutically-induced tumor immunity. In support of these efforts, the Society for the Immunotherapy of Cancer (SITC) is sponsoring a workshop entitled "Focus on the Target: The Tumor Microenvironment" to be held October 24-25, 2012 in Bethesda, Maryland. This meeting should support development of the immune score, and result in a position paper highlighting opportunities for the development of integrative cancer immunotherapies that sculpt the tumor microenvironment to promote definitive tumor rejection.

Intracellular Tumor-Associated Antigens Represent Effective Targets for Passive Immunotherapy

Monoclonal antibody (mAb) therapy against tumor antigens expressed on the tumor surface is associated with clinical benefit. However, many tumor antigens are intracellular molecules that generally would not be considered suitable targets for mAb therapy. In this study, we provide evidence challenging this view through an investigation of the efficacy of mAb directed against NY-ESO-1, a widely expressed immunogen in human tumors that is expressed intracellularly rather than on the surface of cells. On their own, NY-ESO-1 mAb could neither augment antigen-specific CD8+ T-cell induction nor cause tumor eradication. To facilitate mAb access to intracellular target molecules, we combined anti-NY-ESO-1 mAb with anticancer drugs to accentuate the release of intracellular NY-ESO-1 from dying tumor cells. Strikingly, combination therapy induced a strong antitumor effect that was accompanied by the development of NY-ESO-1–specific effector/memory CD8+ T cells that were not elicited by single treatments alone. The combinatorial effect was also associated with upregulation of maturation markers on dendritic cells, consistent with the organization of an effective antitumor T-cell response. Administration of Fc-depleted F(ab) mAb or combination treatment in Fcγ receptor–deficient host mice abolished the therapeutic effect. Together, our findings show that intracellular tumor antigens can be captured by mAbs and engaged in an efficient induction of CD8+ T-cell responses, greatly expanding the possible use of mAb for passive cancer immunotherapy. Cancer Res; 72(7); 1672–82. ©2012 AACR.

Re-purposing cancer therapeutics for breast cancer immunotherapy

After decades of work to develop immune-based therapies for cancer, the first drugs designed specifically to engage the host anti-tumor immune response for therapeutic benefit were recently approved for clinical use. Sipuleucel-T, a vaccine for advanced prostate cancer, and ipilimumab, a monoclonal antibody that mitigates the negative impact of cytotoxic T lymphocyte antigen-4 signaling on tumor immunity, provide a modest clinical benefit in some patients. The arrival of these drugs in the clinic is a significant advance that we can capitalize on for even better clinical outcomes. The strategic and scientifically rational integration of vaccines and other direct immunomodulators with standard cancer therapeutics should lead to therapeutic synergy and high rates of tumor rejection. This review focuses on the use of cyclophosphamide, doxorubicin, and HER-2-specific monoclonal antibodies to dissect mechanisms of immune tolerance relevant to breast cancer patients and illustrates how appropriate preclinical models can powerfully inform clinical translation. The immune-modulating activity of targeted, pathway-specific, small molecule therapeutics is also discussed. Fully understanding how cancer drugs impact the immune system should lead to the ultimate personalized cancer medicine: effective combinatorial immunotherapy strategies that simultaneously target signaling pathways essential for tumor growth and progression, and systematically break multiple, distinct immune tolerance pathways to maximize tumor rejection and effect cure.

Cancer therapy with trifunctional antibodies: linking innate and adaptive immunity

Trifunctional antibodies (trAbs) are promising novel anticancer biologics with a particular mode of action capable of linking innate with adaptive immunity. Based on their unique structure, trifunctional IgG-like heterodimeric antibodies, consisting of nonhuman mouse and rat immunoglobulin halves are able to redirect T lymphocytes, as well as accessory cells, to the tumor site. This recruitment of immune cells is accompanied by cellular activation events elicited by anti-CD3, as well as Fcγ-receptor engagement of trAbs supported by a proinflammatory Th1-biased cytokine milieu. All necessary immunological factors required for long-term vaccination-like effects are stimulated along trAb-mediated therapeutic interventions. Thus, the concerted interplay of antibody-dependent cellular cytotoxicity plus the polyclonal T-cell cytotoxicity and Fcγ-receptor-driven induction of long-lasting immune responses after the initial tumor cell elimination represent the major hallmarks of trAb-mediated treatment of malignant diseases.

Combining immunotherapy and targeted therapies in cancer treatment

During the past two decades, the paradigm for cancer treatment has evolved from relatively nonspecific cytotoxic agents to selective, mechanism-based therapeutics. Cancer chemotherapies were initially identified through screens for compounds that killed rapidly dividing cells. These drugs remain the backbone of current treatment, but they are limited by a narrow therapeutic index, significant toxicities and frequently acquired resistance. More recently, an improved understanding of cancer pathogenesis has given rise to new treatment options, including targeted agents and cancer immunotherapy. Targeted approaches aim to inhibit molecular pathways that are crucial for tumour growth and maintenance; whereas, immunotherapy endeavours to stimulate a host immune response that effectuates long-lived tumour destruction. Targeted therapies and cytotoxic agents also modulate immune responses, which raises the possibility that these treatment strategies might be effectively combined with immunotherapy to improve clinical outcomes.

Trafficking of high avidity HER-2/neu-specific T cells into HER-2/neu-expressing tumors after depletion of effector/memory-like regulatory T cells

Background

Cancer vaccines are designed to activate and enhance cancer-antigen-targeted T cells that are suppressed through multiple mechanisms of immune tolerance in cancer-bearing hosts. T regulatory cell (Treg) suppression of tumor-specific T cells is one barrier to effective immunization. A second mechanism is the deletion of high avidity tumor-specific T cells, which leaves a less effective low avidity tumor specific T cell repertoire available for activation by vaccines. Treg depleting agents including low dose cyclophosphamide (Cy) and antibodies that deplete CD25-expressing Tregs have been used with limited success to enhance the potency of tumor-specific vaccines. In addition, few studies have evaluated mechanisms that activate low avidity cancer antigen-specific T cells. Therefore, we developed high and low avidity HER-2/neu-specific TCR transgenic mouse colonies specific for the same HER-2/neu epitope to define the tolerance mechanisms that specifically affect high versus low avidity tumor-specific T cells.

Methodology/Principal Findings

High and low avidity CD8⁺ T cell receptor (TCR) transgenic mice specific for the breast cancer antigen HER-2/neu (neu) were developed to provide a purified source of naïve, tumor-specific T cells that can be used to study tolerance mechanisms. Adoptive transfer studies into tolerant FVB/N-derived HER-2/neu transgenic (neu-N) mice demonstrated that high avidity, but not low avidity, neu-specific T cells are inhibited by Tregs as the dominant tolerizing mechanism. High avidity T cells persisted, produced IFNγ, trafficked into tumors, and lysed tumors after adoptive transfer into mice treated with a neu-specific vaccine and low dose Cy to deplete Tregs. Analysis of Treg subsets revealed a Cy-sensitive CD4⁺Foxp3⁺CD25^low tumor-seeking migratory phenotype, characteristic of effector/memory Tregs, and capable of high avidity T cell suppression.

Conclusion/Significance

Depletion of CD25^low Tregs allows activation of tumor-clearing high avidity T cells. Thus, the development of agents that specifically deplete Treg subsets should translate into more effective immunotherapies while avoiding autoimmunity.

Using monoclonal antibodies to stimulate antitumor cellular immunity

Monoclonal antibodies (mAbs) have an established role in current cancer therapy with seven approved for the treatment of a wide variety of tumors. The approved mAbs directly target tumor cells; however, it is becoming increasingly clear that as well as their direct effects, these mAbs can present antigens to the immune system. This stimulates long-lasting T-cell immunity, which may correlate with long-term survival. A more direct approach is to use mAbs to target antigens directly to antigen-presenting cells. One approach, ImmunoBody, which has just entered the clinic, stimulates antitumor immunity using mAbs genetically engineered to express tumor-specific T-cell epitopes. T cells not only respond via their T-cell receptors recognizing T-cell epitopes presented on MHC but are also influenced by stimulation of a wide variety of costimulatory molecules. mAbs targeting these molecules can also influence antitumor immunity. The main protagonist in this class of mAbs is ipilimumab, which has recently been shown to improve survival at 2 years in 23% of advanced melanoma patients. Combinations of mAbs targeting tumor antigens to activated antigen-presenting cells and mAbs targeting costimulatory receptors may provide effective therapy for a broad range of tumors.