Current developments in cancer vaccines and cellular immunotherapy.

This article reviews the immunologic basis of clinical trials that test means of tumor antigen recognition and immune activation, with the goal to provide the clinician with a mechanistic understanding of ongoing cancer vaccine and cellular immunotherapy clinical trials. Multiple novel immunotherapy strategies have reached the stage of testing in clinical trials that were accelerated by recent advances in the characterization of tumor antigens and by a more precise knowledge of the regulation of cell-mediated immune responses. The key steps in the generation of an immune response to cancer cells include loading of tumor antigens onto antigen-presenting cells in vitro or in vivo, presenting antigen in the appropriate immune stimulatory environment, activating cytotoxic lymphocytes, and blocking autoregulatory control mechanisms. This knowledge has opened the door to antigen-specific immunization for cancer using tumor-derived proteins or RNA, or synthetically generated peptide epitopes, RNA, or DNA. The critical step of antigen presentation has been facilitated by the coadministration of powerful immunologic adjuvants, the provision of costimulatory molecules and immune stimulatory cytokines, and the ability to culture dendritic cells. Advances in the understanding of the nature of tumor antigens and their optimal presentation, and in the regulatory mechanisms that govern the immune system, have provided multiple novel immunotherapy intervention strategies that are being tested in clinical trials.     

Challenges to the development of antigen-specific breast cancer vaccines

Continued progress in the development of antigen-specific breast cancer vaccines depends on the identification of appropriate target antigens, the establishment of effective immunization strategies, and the ability to circumvent immune escape mechanisms. Methods such as T cell epitope cloning and serological expression cloning (SEREX) have led to the identification of a number target antigens expressed in breast cancer. Improved immunization strategies, such as using dendritic cells to present tumor-associated antigens to T lymphocytes, have been shown to induce antigen-specific T cell responses in vivo and, in some cases, objective clinical responses. An outcome of successful tumor immunity is the evolution of antigen-loss tumor variants. The development of a polyvalent breast cancer vaccine, directed against a panel of tumor-associated antigens, may counteract this form of immune escape.     

Tumor microenvironment: what have we learned studying the immune response in this puzzling battlefield?

Recent developments hallmark the progress in the understanding of tumor immunology and related therapeutic strategies. The administration of interleukin-2 (IL-2) to patients with cancer has shown that immune manipulation can mediate the regression of established cancers. The identification of the genes encoding cancer antigens and the development of means for effectively immunizing against these antigens has opened new avenues for the development of active immunization of patients with cancer. However, an efficient immune response against tumor comprises an intricate molecular network still poorly understood. Only when the code governing immune responsiveness of cancer will be deciphered, new therapeutic strategies could be designed to fit biologically defined mechanisms of immune rejection of cancer. In this review, we propose that the mechanisms regulating tumor rejection in response to vaccination will be more efficiently identified by following the evolution of treatment induced events within the tumor microenvironment taking advantage of recently developed technological tools. As a model, we will discuss the observed immune response to tumor antigen -specific immunization and its relationship with the systemic administration of IL-2.     

Vaccination for malignant melanoma: recent developments

The identification of tumor-associated antigens recognized by cellular or humoral effectors of the immune system has opened new perspectives for cancer immunotherapy. Different categories of cancer-associated antigens have been described as targets for CD8+ T cells in vitro and in vivo: (1) 'cancer-testis' (CT) antigens expressed in different tumors and normal testis; (2) melanocyte differentiation antigens; (3) point mutations of normal genes; (4) antigens that are overexpressed in malignant tissues, and (5) viral antigens. Clinical trials with antigenic peptides have been initiated to induce specific immunological responses in vivo. Immunological and clinical parameters for the assessment of peptide-specific reactions have been defined: DTH, CD8+ T cell, autoimmune and tumor regression responses. Preliminary results show that tumor-associated peptides alone elicit specific DTH and CD8+ T cell responses associated with tumor regression after intradermal vaccination. Granulocyte macrophage colony-stimulating factor has been shown to enhance peptide-specific immune reactions by amplification of dermal antigen-presenting dendritic cells. Complete tumor regressions have been observed after the induction of CD8+ T cell responses by peptide immunization. Based on these results, active immunotherapy with tumor-associated antigens may be a promising approach for patients in adjuvant treatment situations, who are at high risk for tumor recurrence. Recently, a strategy utilizing spontaneous antibody responses to tumor-associated antigens (SEREX) has led to the identification of a new CT antigen, NY-ESO-1. NY-ESO-1-specific spontaneous humoral and cellular immune responses were found in approximately 50% of patients with NY-ESO-1-positive tumors. Clinical studies have been initiated to evaluate the immunological effects of immunization with NY-ESO-1 peptides in cancer patients with detectable or absent immunity against NY-ESO-1.     

CTL-defined Cancer Vaccines: Perspectives for Active Immunotherapeutic Interventions in Minimal Residual Disease

The characterization of tumor-associated antigens recognized by cellular or humoral effectors of the immune system has opened new perspectives for cancer therapy. Several categories of cancer-associated antigens have been described as targets for cytotoxic T lymphocytes (CTL) in vitro and in vivo: (1) Cancer-Testis (CT) antigens expressed in different tumors and normal testis, (2) melanocyte differentiation antigens, (3) point mutations of normal genes, (4) antigens that are overexpressed in malignant tissues, and (5) viral antigens. Clinical studies with peptides derived from these antigens have been initiated to induce specific CTL responses in vivo. Immunological and clinical parameters for the assessment of peptide-specific reactions have been defined, i.e. induction of DTH-, CTL-, autoimmune-, and tumor-regression responses. Preliminary results demonstrate that tumor-associated peptides alone elicit specific DTH- and CTL-responses leading to tumor regression after intradermal injection. GM-CSF was proven effective to enhance peptide-specific immune reactions by amplification of dermal peptide-presenting dendritic cells. Long lasting complete tumor regressions have been observed after induction of CTL by peptide immunization. Based on these results, active immunotherapy with tumor-associated antigens may be a promising approach for patients with minimal residual disease, who are at high risk for tumor recurrence. However, in single cases with disease progression after an initial tumor response either a loss of the respective tumor antigen targeted by CTL or of the presenting MHC class I molecule was detected as mechanisms of immune escape under immunization in vivo. Based on these observations, cytokines to enhance antigen- and MHC-class I expression in vivo are being evaluated to prevent immunoselection. Recently, a strategy utilizing spontaneous antibody responses to tumor-associated antigens (SEREX) has led to the identification of a new CT antigen, NY-ESO-1. In a melanoma patient with high titer antibody against NY-ESO-1 also a strong HLA-A2 restricted CTL reactivity against the same antigen was found. Clinical studies involving tumor antigens that induce both antibody- and CTL-responses will show whether these are better candidates for immunotherapy of cancer.     

Cancer immunotherapy in clinical oncology

The identification of tumor-associated antigens recognized by cellular or humoral effectors of the immune system has opened new perspectives for cancer therapy. Different groups of cancer-associated antigens have been described as targets for cytotoxic T lymphocytes (CTLs) in vitro and in vivo: 1) cancer-testis (CT) antigens, which are expressed in different tumors and normal testis; 2) melanocyte differentiation antigens; 3) point mutations of normal genes; 4) antigens that are overexpressed in malignant tissues; and 5) viral antigens. Clinical studies with peptides derived from these antigens have been initiated to induce specific CTL responses in vivo. Immunological and clinical parameters for the assessment of peptide-specific reactions have been defined, i.e., delayed-type hypersensitivity (DTH), CTL, autoimmmune, and tumor regression responses. Preliminary results demonstrate that tumor-associated peptides alone elicit specific DTH and CTL responses leading to tumor regression after intradermal injection. Granulocyte-macrophage colony-stimulating factor (GM-CSF) was proven effective in enhancing peptide-specific immune reactions by amplification of dermal peptide-presenting dendritic cells. Long-lasting complete tumor regressions have been observed after induction of peptide-specific CTLs. However, in single cases with disease progression after an initial tumor response, either a loss of the respective tumor antigen targeted by CTLs or of the presenting major histocompatibility complex (MHC) class I allele was detected as a mechanism of immune escape under immunization. Based on these observations, cytokines to enhance antigen and MHC class I expression in vivo are being evaluated to prevent immunoselection. Recently, a strategy utilizing spontaneous antibody responses to tumor-associated antigens (SEREX) has led to the identification of a new CT antigen, NY-ESO-1, which is regarded as one of the most immunogenic antigens known today inducing spontaneous immune responses in 50% of patients with NY-ESO-1-expressing cancers. Clinical studies involving antigenic constructs that induce both antibody and CTL responses will show whether these are more effective for immunotherapy of cancer.     

黑色素瘤相关抗原家族在细胞生命活动中的作用

迄今为止,黑色素瘤相关抗原家族(melanoma-associated antigens,MAGEs)已经发现了几十种基因,可分为Ⅰ类和Ⅱ类两个亚类。其中属于癌/睾丸抗原的Ⅰ类MAGE家族基因只在肿瘤细胞和生殖细胞中表达,其中部分抗原或多肽已经在多种肿瘤中进行免疫治疗的临床试验,并取得了较好的临床疗效评价。尽管对于MAGE家族基因在细胞生命活动中的作用还知之较少,但人们已经注意到MAGE家族基因在胚胎发育、生殖细胞发生、细胞凋亡等生命活动中发挥着重要的生理或病理作用。有理由推测Ⅰ类MAGE家族基因在胚胎阶段表达并发挥重要作用后,被基因甲基化等机制灭活,一旦这些基因再次被激活,机体可能发生肿瘤,由这些基因编码的蛋白可被机体免疫系统识别并受到攻击,因此,Ⅰ类MAGE可能在某些肿瘤的免疫监视中起重要作用。本文即对MAGE家族的基因种类及生物功能进行综述。     

Identification of human tumor antigens and its implications for diagnosis and treatment of cancer

Human tumor antigens recognized by T cells have been identified by means of various molecular biological and immunological methods, including cDNA expression cloning with patients' T cells and antibodies, cDNA subtraction using RDA and PCR differential display, systematic gene analysis such as DNA sequencing, CGH, DNA chip/microarray and SAGE, in vitro T cell induction and immunization of HLA transgenic mice. The identification of human tumor antigens has led to a better understanding of the nature of tumor antigens, anti-tumor immune responses in patients before and after immunotherapy, and tumor escape mechanisms. The information obtained from these researches has enabled us to develop and improve immunotherapy by attempting to overcome the identified problems, including intrinsically low immunogenicity of tumor antigens and several escape mechanisms, such as regulatory T cell induction. The existence of immunogenic unique antigens derived from genetic alterations in tumor cells, and the varied immunogenicity of shared tumor antigens among patients due to differing expression in tumor cells and immunoreactivity of patients, indicates that individualized immunotherapy should ideally be performed. The identified antigens will also be useful for development of diagnostic methods and molecular targeting therapy for cancer.     

Immune approaches to the treatment of breast cancer,around the corner?

Immunotherapy for the treatment of breast cancer can be categorized as either (a) specific stimulation of the immune system by active immunization, with cancer vaccines, or (b) passive immunization, such as tumor-specific antibodies (including immune modulators) or adoptive cell therapy that inhibit the function of, or directly kill, tumor cells. We will present the current information and the future perspectives of immunotherapy in patients with breast cancer, including the prognostic role of tumor infiltrating lymphocytes, immune signatures, targeted therapies modulating the immune system, and tumor antigen cancer vaccines. Active immunotherapy in breast cancer and its implementation into clinical trials have been largely a frustrating experience in the last decades. The concept that the immune system regulates cancer development is experiencing a new era of interest. It is clear that the cancer immunosurveillance process indeed exists and potentially acts as an extrinsic tumor suppressor. Also, the immune system can facilitate tumor progression by sculpting the immunogenic phenotype of tumors as they develop. Cancer immunoediting represents a refinement of the cancer immunosurveillance hypothesis and resumes the complex interaction between tumor and immune system into three phases: elimination, equilibrium, and escape. Major topics in the field of immunology deserve a response: what do we know about tumor immunogenicity, and how might we therapeutically improve tumor immunogenicity? How can we modulate response of the immune system? Is there any gene signature predictive of response to immune modulators? The success of future immunotherapy strategies will depend on the identification of additional immunogenic antigens that can serve as the best tumor-rejection targets. Therapeutic success will depend on developing the best antigen delivery systems and on the elucidation of the entire network of immune signaling pathways that regulate immune responses in the tumor microenvironment.     

Evidence of determinant spreading in the antibody responses to prostate cell surface antigens in patients immunized with prostate-specific antigen.

PURPOSE: Prostate cancer consistently remains a difficult clinical problem. The development of novel therapy strategies for effective control and treatment of prostate cancer is essential. The prostate represents a unique site for immunotherapy, in part because prostate-specific immunity would most probably be without significant long-term sequellae. Antibodies and cell-mediated immunity, induced by either active or passive immunization, represent potential means to specifically target prostate tumor cells. EXPERIMENTAL DESIGN: The serum IgG response to cell surface antigens expressed on LNCAP [prostate-specific antigen (PSA)-positive] and PC-3 (PSA-negative) were analyzed in individuals with advanced disease receiving vaccinia- or fowlpox-expressed PSA (v-PSA or f-PSA, respectively) by flow cytometry. RESULTS: Sera from all seven patients in a Phase I study of v-PSA, collected prior to the third immunization, reacted with both prostate tumor cell lines. The majority of individuals (n = 12) in a Phase II trial of v-PSA and f-PSA developed sustainable antibody responses to cell surface antigens on the prostate tumor cell lines. The magnitude and kinetics of these responses were dependent on the immunization schedule. Of importance, the baseline serum of only one of nine patients tested had reactivity with nonprostate tumor cell lines. Sera from three normal males also lacked reactivity with prostate tumor cells. CONCLUSIONS: PSA vaccine constructs are immunogenic and induce antibody responses to a multitude of surface antigens on prostate tumor cell lines by epitope or determinant spreading after stimulation of the immune system by PSA immunization.     

Cancer vaccines.

It has been more than 100 years since the first reported attempts to activate a patient's immune system to eradicate developing cancers. Although a few of the subsequent vaccine studies demonstrated clinically significant treatment effects, active immunotherapy has not yet become an established cancer treatment modality. Two recent advances have allowed the design of more specific cancer vaccine approaches: improved molecular biology techniques and a greater understanding of the mechanisms involved in the activation of T cells. These advances have resulted in improved systemic antitumor immune responses in animal models. Because most tumor antigens recognized by T cells are still not known, the tumor cell itself is the best source of immunizing antigens. For this reason, most vaccine approaches currently being tested in the clinics use whole cancer cells that have been genetically modified to express genes that are now known to be critical mediators of immune system activation. In the future, the molecular definition of tumor-specific antigens that are recognized by activated T cells will allow the development of targeted antigen-specific vaccines for the treatment of patients with cancer.     

Gene-based therapy of malignant melanoma

Melanoma continues to present a major therapeutic challenge to oncologists, oncologic surgeons, and dermatologists. Recent advances in molecular genetics and improvement in our understanding of immune responses to tumors have generated an interest in using gene-based treatment strategies to fight melanoma. Several basic strategies have emerged: (1) strengthening of the immune response against tumors by genetic modification of some target cell populations of the host using immunostimulatory genes such as cytokines and by genetic immunization with the genes coding for melanoma-associated antigens recognized by cytotoxic T cells; (2) interference with signaling cascades; and (3) suicide gene strategies. This article reviews these novel strategies and summarizes the most recent data generated by European groups either in experimental studies or in clinical trials.     

DNA vaccines against cancer: From genes to therapy

After an erratic history, there is at last a clear opportunity for mobilizing an immune attack against cancer cells. The new strategies are dependent on the techniques of molecular biology, which are able both to identify potential target tumor antigens at the gene level, and to help to unravel the complexities of immune mechanisms required. Vaccine delivery systems can also be genetic, with DNA vaccines able to act as viral mimics and enter several antigen processing pathways. Rational vaccine designs can be rapidly tested in models and selected for pilot clinical trials. One difficulty faced by tumor antigens is that they may be weak, and therefore fail to engage the immune system. Attaching genes encoding alert signals appears to solve this problem. We have focused initially on idiotypic determinants of B-cell tumors, where the encoding variable region genes can induce protective anti-idiotypic immunity if delivered as a fusion protein with a fragment of Tetanus toxin. This model may have relevance for alternative tumor antigens. A clinical trial of patients with lymphoma is in progress, and wider application may be limited only by the ability to bring patients into clinical remission prior to vaccination.     

Gene therapy for carcinoma of the breast: Genetic immunotherapy

Advances in gene transfer technology have greatly expanded the opportunities for developing immunotherapy strategies for breast carcinoma. Genetic immunotherapy approaches include the transfer of genes encoding cytokines and costimulatory molecules to modulate immune function, as well as genetic immunization strategies which rely on the delivery of cloned tumor antigens. Improved gene transfer vectors, coupled with a better understanding of the processes that are necessary to elicit an immune response and an expanding number of target breast tumor antigens, have led to renewed enthusiasm that effective immunotherapy may be achieved. It is likely that immunotherapeutic interventions will find their greatest clinical application as adjuvants to traditional first-line therapies, targeting micrometastatic disease and thereby reducing the risk of cancer recurrence.     

Gene therapy for carcinoma of the breast: Genetic immunotherapy

Advances in gene transfer technology have greatly expanded the opportunities for developing immunotherapy strategies for breast carcinoma. Genetic immunotherapy approaches include the transfer of genes encoding cytokines and costimulatory molecules to modulate immune function, as well as genetic immunization strategies which rely on the delivery of cloned tumor antigens. Improved gene transfer vectors, coupled with a better understanding of the processes that are necessary to elicit an immune response and an expanding number of target breast tumor antigens, have led to renewed enthusiasm that effective immunotherapy may be achieved. It is likely that immunotherapeutic interventions will find their greatest clinical application as adjuvants to traditional first-line therapies, targeting micrometastatic disease and thereby reducing the risk of cancer recurrence.     

Update on cancer vaccines

PURPOSE OF REVIEW: Vaccination against cancer has had a variable history, with claims of success often fading into disappointment. The reasons for this include poor vaccine design, inadequate understanding of the nature of the immune response, and a lack of objective measures to evaluate performance. The impact of genetic technology has changed everything. We now have multiple strategies to identify candidate tumor antigens, and we understand more about activation and regulation of immunity against cancer. There are novel vaccine strategies to activate specific attack on tumor cells. We also have modern assays using surrogate markers of performance to correlate with clinical effects. It is timely to select significant relevant papers to illustrate the growing potential for patients with cancer. RECENT FINDINGS: Recent findings include tumor antigen discovery and vaccine formulation, relevant knowledge concerning mechanisms of induction of effective immunity from preclinical models, and translation into clinical trials with objective evaluation of performance. SUMMARY: The ability of the immune response to dispose of cancer cells is clear. Passive transfer of antibody or immune cells is already clinically successful. We are now in a position to harness new gene-based information to design vaccines capable of inducing effective and long-lasting immunity. Safe vaccines could be used either in patients or in transplant donors. Pilot clinical trials are the means of testing performance, with continuing vaccine design modification to target specific antigens in different cancers.     

Strategies of antigen-specific T-cell-based immunotherapy for cancer

The critical role of antigen-specific T-cells in the eradication of cancer has been demonstrated in numerous animal models, while significant challenges need to be conquered before antigen-specific T-cell immunotherapy can achieve true success in clinical practice. These challenges include: (1) weak or nonimmunogenicity of spontaneous tumors, (2) negative immune regulation mechanisms of the host immune system, (3) immune inhibition exerted by tumor cells, (4) physical barrier in solid tumor, and (5) escape or resistance to immune attack by tumor cells. Nonetheless, significant success has been achieved in several clinical trials recently, highlighting the possibility of successful manipulation of the immune system for control and elimination of tumor. We focused our study on summarizing the current knowledge and corresponding strategies for improving autologous cytotoxic T-cell (CTL)-based cancer immunotherapy, which include the following aspects: (1) the selection of tumor antigens for stimulation of CTL, (2) strategies of enhancing maturation and antigen presentation activity of dendritic cells (DC), (3) strategies of activation and maintenance of CTL response, and (4) recruitment of suitable immune effector cells to tumor sites. The successful manipulation of the immune system, based on the more and more detailed knowledge of tumor immunology, may finally reach the goal of "immune surveillance of malignancy."     

Anti-CD40 agonist antibodies: Preclinical and clinical experience

The cell-surface molecule CD40, a member of the tumor necrosis factor receptor superfamily, broadly regulates immune activation and mediates tumor apoptosis. CD40 is expressed by antigen-presenting cells (APC) and engagement of its natural ligand on T cells activates APC including dendritic cells and B cells. Agonistic CD40 antibodies have been shown to substitute for T cell help provided by CD4+ lymphocytes in murine models of T cell-mediated immunity. In tumor-bearing hosts, CD40 agonists trigger effective immune responses against tumor-associated antigens. In contrast, CD40 is also expressed on many tumor cells and its ligation in this setting mediates a direct cytotoxic effect. Engagement of CD40 on tumor cells results in apoptosis in vitro and impaired tumor growth in vivo. These observations have prompted efforts to use agonistic CD40 antibodies for the treatment of cancer patients and initial clinical results have been promising.     

therapeutic vaccines for colorectal cancer

A number of cancer vaccine strategies for the treatment of colorectal cancer have entered clinical trials. Whole tumor cell vaccines have been developed from both patients’ autologous tumor cells as well as established allogeneic tumor cell lines. A vaccine consisting of autologous tumor cells along with bacillus Calmette-Guerin (BCG) has shown a potential clinical benefit in patients with stage II colon cancer. Other approaches using autologous tumor cells have involved transfection of primary tumor cells with cytokine genes. Allogeneic tumor cell vaccines have also been modified to express cytokine genes. Vectors have been studied extensively as a means of vaccine strategy. One tumor-associated antigen (TAA) that has been extensively studied in viral vector vaccines is carcinoembryonic antigen (CEA). A recombinant vaccinia virus containing the CEA transgene (rV-CEA) has been shown to elicit CEA-specific immune responses in advanced carcinoma patients. However, patients receiving multiple vaccinations had limited increases in CEA-specific responses by the third vaccination. This problem may be overcome by the use of non-replicating poxviruses, which have been shown in clinical trials to be safe and to elicit CEA-specific responses. However, recent clinical studies have shown that the optimal use of poxviruses is to prime with vaccinia, followed by boosts with avipox vectors. A recent randomized clinical trial showed that patients primed with rV-CEA and boosted with avipox-CEA had greater immune responses compared with patients receiving three 1-monthly avipox-CEA vaccinations followed by an rV-CEA vaccination. Furthermore, a statistically significant survival advantage was noted in the prime/boost arm. Ongoing studies are now incorporating the genes for costimulatory molecules along with TAA in these vectors. Another vaccine strategy involving TAA that is currently in clinical trials for colorectal cancer is the peptide vaccine. Dendritic cells (DCs) are considered to be the most potent antigen-presenting cell, thus providing an attractive modality for cancer vaccines. In addition to using DCs for peptide-based vaccines, a number of other strategies, including transfection with messenger RNA, have produced specific T-cell responses in clinical trials. In addition, several clinical trials using murine anti-idiotype antibodies as vaccines for patients with advanced colorectal cancer have shown both immunologic responses as well as clinical responses.     

Targeting the tumor microenvironment to enhance antitumor immune responses

The identification of tumor-specific antigens and the immune responses directed against them has instigated the development of therapies to enhance antitumor immune responses. Most of these cancer immunotherapies are administered systemically rather than directly to tumors. Nonetheless, numerous studies have demonstrated that intratumoral therapy is an attractive approach, both for immunization and immunomodulation purposes. Injection, recruitment and/or activation of antigen-presenting cells in the tumor nest have been extensively studied as strategies to cross-prime immune responses. Moreover, delivery of stimulatory cytokines, blockade of inhibitory cytokines and immune checkpoint blockade have been explored to restore immunological fitness at the tumor site. These tumor-targeted therapies have the potential to induce systemic immunity without the toxicity that is often associated with systemic treatments. We review the most promising intratumoral immunotherapies, how these affect systemic antitumor immunity such that disseminated tumor cells are eliminated, and which approaches have been proven successful in animal models and patients.