Safety of intravenous administration of a canarypox virus encoding the human wild-type p53 gene in colorectal cancer patients

The search for a TNBC vaccine: the guardian vaccine

Nearly 20 million people are diagnosed with cancer each year with breast cancer being the most common among women. Triple negative breast cancer (TNBC), defined by its no/low expression of ER and PR and lack of amplification of HER2, makes up 15-20% of all breast cancer cases. While patients overall have a higher response to chemotherapy, this subgroup is associated with the lowest survival rate indicating significant clinical and molecular heterogeneity demanding alternate treatment options. Therefore, new therapies have been explored, with a large focus on utilizing the immune system. A whole host of immunotherapies have been studied including immune checkpoint inhibitors, now standard of care for eligible patients, and possibly the most exciting and promising is that of a TNBC vaccine. While currently there are no approved TNBC vaccines, this review highlights many promising studies and points to an antigen, p53, which we believe is highly relevant for TNBC.

Apoptosis: A Comprehensive Overview of Signaling Pathways, Morphological Changes, and Physiological Significance and Therapeutic Implications

Cell survival and death are intricately governed by apoptosis, a meticulously controlled programmed cell death. Apoptosis is vital in facilitating embryonic development and maintaining tissue homeostasis and immunological functioning. It is a complex interplay of intrinsic and extrinsic signaling pathways that ultimately converges on executing the apoptotic program. The extrinsic pathway is initiated by the binding of death ligands such as TNF-α and Fas to their respective receptors on the cell surface. In contrast, the intrinsic pathway leads to increased permeability of the outer mitochondrial membrane and the release of apoptogenic factors like cytochrome c, which is regulated by the Bcl-2 family of proteins. Once activated, these pathways lead to a cascade of biochemical events, including caspase activation, DNA fragmentation, and the dismantling of cellular components. Dysregulation of apoptosis is implicated in various disorders, such as cancer, autoimmune diseases, neurodegenerative disorders, and cardiovascular diseases. This article focuses on elucidating the molecular mechanisms underlying apoptosis regulation, to develop targeted therapeutic strategies. Modulating apoptotic pathways holds immense potential in cancer treatment, where promoting apoptosis in malignant cells could lead to tumor regression. This article demonstrates the therapeutic potential of targeting apoptosis, providing options for treating cancer and neurological illnesses. The safety and effectiveness of apoptosis-targeting drugs are being assessed in ongoing preclinical and clinical trials (phase I-III), opening the door for more effective therapeutic approaches and better patient outcomes.

Clinical and Immunological Effects of p53-Targeting Vaccines

Immunotherapy, including immune checkpoint blockade and chimeric antigen receptor T cells, is one of the most promising approaches to treat cancer. Vaccines have been effective in preventing cancers like liver cancer and cervical cancer with a viral etiology. Instead of preventing disease, therapeutic cancer vaccines mobilize the immune system to attack existing cancer. p53 is dysregulated in the majority of human cancers and is a highly promising target for cancer vaccines. Over twenty clinical trials have targeted p53 in malignant diseases using vaccines. In this work, we review the progress of vaccinations with p53 or its peptides as the antigens and summarize the clinical and immunological effects of p53-targeting vaccines from clinical trials. The delivery platforms include p53 peptides, viral vectors, and dendritic cells pulsed with short peptides or transduced by p53-encoding viruses. These studies shed light on the feasibility, safety, and clinical benefit of p53 vaccination in select groups of patients, implicating that p53-targeting vaccines warrant further investigations in experimental animals and human studies.

p53, cancer and the immune response

The importance of cancer-cell-autonomous functions of the tumour suppressor p53 (encoded by TP53) has been established in many studies, but it is now clear that the p53 status of the cancer cell also has a profound impact on the immune response. Loss or mutation of p53 in cancers can affect the recruitment and activity of myeloid and T cells, allowing immune evasion and promoting cancer progression. p53 can also function in immune cells, resulting in various outcomes that can impede or support tumour development. Understanding the role of p53 in tumour and immune cells will help in the development of therapeutic approaches that can harness the differential p53 status of cancers compared with most normal tissue.

The Immunogenicity of Colorectal Cancer in Relation to Tumor Development and Treatment

Although most cancer types have been viewed as immunologically silent until recently, it has become increasingly clear that the immune system plays key roles in the course of tumor development. Remarkable progress towards understanding cancer immunogenicity and tumor-immune system interactions has revealed important implications for the design of novel immune-based therapies. Natural immune responses, but also therapeutic interventions, can modulate the tumor phenotype due to selective outgrowth of resistant subtypes. This is the result of heterogeneity of tumors, with genetic instability as a driving force, and obviously changes the immunogenicity of tumors. In this review, we discuss the immunogenicity of colorectal cancer (CRC) in relation to tumor development and treatment. As most tumors, CRC activates the immune system in various ways, and is also capable of escaping recognition and elimination by the immune system. Tumor-immune system interactions underlie the balance between immune control and immune escape, and may differ in primary tumors, in the circulation, and in liver metastases of CRC. Since CRC immunogenicity varies between tumors and individuals, novel immune-based therapeutic strategies should not only anticipate the molecular profile, but also the immunological profile of a specific tumor.

Molecular mechanisms of apoptosis and roles in cancer development and treatment

Programmed cell death (PCD) or apoptosis is a mechanism which is crucial for all multicellular organisms to control cell proliferation and maintain tissue homeostasis as well as eliminate harmful or unnecessary cells from an organism. Defects in the physiological mechanisms of apoptosis may contribute to different human diseases like cancer. Identification of the mechanisms of apoptosis and its effector proteins as well as the genes responsible for apoptosis has provided a new opportunity to discover and develop novel agents that can increase the sensitivity of cancer cells to undergo apoptosis or reset their apoptotic threshold. These novel targeted therapies include those targeting anti-apoptotic Bcl-2 family members, p53, the extrinsic pathway, FLICE-inhibitory protein (c-FLIP), inhibitor of apoptosis (IAP) proteins, and the caspases. In recent years a number of these novel agents have been assessed in preclinical and clinical trials. In this review, we introduce some of the key regulatory molecules that control the apoptotic pathways, extrinsic and intrinsic death receptors, discuss how defects in apoptotic pathways contribute to cancer, and list several agents being developed to target apoptosis.

The potential role of immunotherapy to treat colorectal cancer

INTRODUCTION

Colorectal cancer (CRC) is the fourth most common cancer and the second leading cause of cancer-related death worldwide. Surgery, chemotherapy, radiation therapy and anti-angiogenic therapies form the backbone of treatment for CRC in various stages. Immunotherapy is frequently used either alone or in combination with chemotherapy for the treatment of various cancers such as melanoma, prostate cancer and renal cell cancer. Current CRC research is moving forward to discover ways to incorporate immunotherapies into the treatment of CRC.

AREAS COVERED

The aim of this review is to summarize the potential role of immunotherapy in CRC. Herein, the authors provide a brief overview of immune modulatory cells, immune surveillance and escape in CRC. They also review vaccine trials in addition to cytokines and monoclonal antibodies. This coverage includes ongoing trials and checkpoint inhibitors such as cytotoxic T lymphocyte antigen-1, programmed cell death-1, and PDL1.

EXPERT OPINION

Checkpoint inhibitors in combination with either chemotherapy or chemo-antiangiogenic-therapy may represent a future therapeutic approach for CRC incorporating immune system targeting. Given the success of immune-based therapy in other tumor types, the authors anticipate that a similar breakthrough in CRC will be forthcoming.

Synergistic anticancer effect of rAd/P53 combined with 5-fluorouracil or iodized oil in the early therapeutic response of human colon cancer in vivo

Exogenous wild-type p53 (wt-p53) tumor suppression increases the sensitivity of tumor cells to radiotherapy and chemotherapy. An iodized oil emulsion was used as a p53 vector for intra-arterial gene delivery to treat hepatic tumors. Whether the chemotherapeutic agent or the iodized oil affects exogenous wt-p53 activity remains poorly understood. In the present study, the early therapeutic response of rAd/p53, combined with 5-fluorouracil (5-FU) or with iodized oil, was observed in a human colon cancer model. Allograft models in 82 nude mice with human colon carcinoma SW480 were divided randomly into four groups and administered with physiologic saline, rAd/p53, rAd/p53+5-FU, and rAd/p53+iodized oil by intratumoral injection. At 24, 48, 72, 120, and 168 h after treatment, p53 expression, the Ki-67 index (KI), and the degree of tumor necrosis were assessed. The p53 expression and tumor necrosis in the therapeutic groups were higher than those in the control group. p53 expression reached its peak at 120 h in the rAd/p53 group, at 72 h in the rAd/p53+5-FU group, and at 48 h in the rAd/p53+iodized oil group. The p53 expression in the rAd/P53+5-FU group and the iodized oil group was significantly higher than those in the rAd/P53 group at 24 and 48 h. The results revealed that tumor necrosis is positively correlated with p53 expression. The KI of the rAd/p53+5-FU group increased significantly at 24 h. 5-FU and iodized oil increase the anticancer effect of rAd/p53, and 5-FU combined with rAd/p53 has a synergistic anticancer effect.

Immunotherapy for metastatic colorectal cancer: present status and new options

Although no immunotherapeutic treatment is approved for colorectal cancer (CRC) patients, promising results from clinical trials suggest that several immunotherapeutic strategies may prove efficacious and applicable to this group of patients. This review describes the immunogenicity of CRC and presents the most interesting strategies investigated so far: cancer vaccination including antigen-defined vaccination and dendritic cell vaccination, chemo-immunotherapy, and adoptive cell transfer. Future treatment options as well as the possibility of combining existing therapies will be discussed along with the challenges presented by tumor escape mechanisms.

Vaccine-based clinical trials in ovarian cancer

Ovarian cancer vaccines are one of the new treatment strategies under investigation in epithelial ovarian cancer. This article discusses the results of different immunization strategies, points out potential pitfalls in study designs and provides possible solutions for augmentation of clinical efficacy. Most ovarian cancer vaccines have not yet evolved beyond Phase I/II studies, which do not primarily evaluate clinical efficacy. Although different approaches of antigen-specific immunization generally result in antigen-specific immune responses, clinical benefit is not consistently observed. Based on the currently available results, we emphasize the necessity of multimodal treatment of ovarian cancer, combining classical cytoreductive surgery, (neo)adjuvant chemotherapy, immunotherapy and/or targeted therapy.

Colorectal cancer vaccines in clinical trials

This article elucidates current strategies of active immunotherapy for colorectal cancer patients with a focus on T-cell mediated immunotherapy. Poor prognosis of especially stage III and IV colorectal cancer patients emphasizes the need for advanced therapeutic intervention. Here, we refer to clinical trials using either tumor cell-derived vaccines or tumor antigen vaccines with a special interest on safety, induced immune responses, clinical benefit and efforts to improve the clinical impact of these vaccines in the context of colorectal cancer treatment.

Recombinant modified vaccinia virus ankara (MVA) expressing wild-type human p53 induces specific antitumor CTL expansion

The p53 gene product is an attractive target for tumor immunotherapy. The present study aims to understand the potential of MVAp53 vaccine to induce expansion of p53-specific cytotoxic T lymphocyte ex vivo in cancer patients. The result indicated that 14 of 23 cancer patients demonstrated p53-specific IFN-γ production, degranulation, cell proliferation, and lysis of p53 overexpressed human tumor cell lines. These experiments show that MVAp53 stimulation has the potential to induce the expansion of p53-specific cytotoxic T lymphocyte from the memory T cell repertoire. The data suggest that MVAp53 vaccine is an ideal candidate for cancer immunotherapy.

Immunological and clinical effects of vaccines targeting p53-overexpressing malignancies

Approximately 50% of human malignancies carry p53 mutations, which makes it a potential antigenic target for cancer immunotherapy. Adoptive transfer with p53-specific cytotoxic T-lymphocytes (CTL) and CD4⁺ T-helper cells eradicates p53-overexpressing tumors in mice. Furthermore, p53 antibodies and p53-specific CTLs can be detected in cancer patients, indicating that p53 is immunogenic. Based on these results, clinical trials were initiated. In this paper, we review immunological and clinical responses observed in cancer patients vaccinated with p53 targeting vaccines. In most trials, p53-specific vaccine-induced immunological responses were observed. Unfortunately, no clinical responses with significant reduction of tumor-burden have occurred. We will elaborate on possible explanations for this lack of clinical effectiveness. In the second part of this paper, we summarize several immunopotentiating combination strategies suitable for clinical use. In our opinion, future p53-vaccine studies should focus on addition of these immunopotentiating regimens to achieve clinically effective therapeutic vaccination strategies for cancer patients.

Clinical outcomes of active specific immunotherapy in advanced colorectal cancer and suspected minimal residual colorectal cancer: a meta-analysis and system review

BACKGROUND

To evaluate the objective clinical outcomes of active specific immunotherapy (ASI) in advanced colorectal cancer (advanced CRC) and suspected minimal residual colorectal cancer (suspected minimal residual CRC).

METHODS

A search was conducted on Medline and Pub Med from January 1998 to January 2010 for original studies on ASI in colorectal cancer (CRC). All articles included in this study were assessed with the application of predetermined selection criteria and were divided into two groups: ASI in advanced CRC and ASI in suspected minimal residual CRC. For ASI in suspected minimal residual CRC, a meta-analysis was executed with results regarding the overall survival (OS) and disease-free survival (DFS). Regarding ASI in advanced colorectal cancer, a system review was performed with clinical outcomes.

RESULTS

1375 colorectal carcinoma patients with minimal residual disease have been enrolled in Meta-analysis. A significantly improved OS and DFS was noted for suspected minimal residual CRC patients utilizing ASI (For OS: HR = 0.76, P = 0.007; For DFS: HR = 0.76, P = 0.03). For ASI in stage II suspected minimal residual CRC, OS approached significance when compared with control (HR = 0.71, P = 0.09); however, the difference in DFS of ASI for the stage II suspected minimal residual CRC reached statistical significance (HR = 0.66, P = 0.02). For ASI in stage III suspected minimal residual CRC compared with control, The difference in both OS and DFS achieved statistical significance (For OS: HR = 0.76, P = 0.02; For DFS: HR = 0.81, P = 0.03). 656 advanced colorectal patients have been evaluated on ASI in advanced CRC. Eleven for CRs and PRs was reported, corresponding to an overall response rate of 1.68%. No serious adverse events have been observed in 2031 patients.

CONCLUSIONS

It is unlikely that ASI will provide a standard complementary therapeutic approach for advanced CRC in the near future. However, the clinical responses to ASI in patients with suspected minimal residual CRC have been encouraging, and it has become clear that immunotherapy works best in situations of patients with suspected minimal residual CRC.

Potential target antigens for a universal vaccine in epithelial ovarian cancer

The prognosis of epithelial ovarian cancer (EOC), the primary cause of death from gynaecological malignancies, has only modestly improved over the last decades. Immunotherapeutic treatment using a cocktail of antigens has been proposed as a "universal" vaccine strategy. We determined the expression of tumor antigens in the context of MHC class I expression in 270 primary tumor samples using tissue microarray. Expression of tumor antigens p53, SP17, survivin, WT1, and NY-ESO-1 was observed in 120 (48.0%), 173 (68.9%), 208 (90.0%), 129 (56.3%), and 27 (11.0%) of 270 tumor specimens, respectively. In 93.2% of EOC, at least one of the investigated tumor antigens was (over)expressed. Expression of MHC class I was observed in 78.1% of EOC. In 3 out 4 primary tumors, (over)expression of a tumor antigen combined with MHC class I was observed. These results indicate that a multiepitope vaccine, comprising these antigens, could serve as a universal therapeutic vaccine for the vast majority of ovarian cancer patients.

p53 autoantibodies, cytokine levels and ovarian carcinogenesis

OBJECTIVE

To address the hypothesis that type II ovarian carcinoma, mutation of p53 and plasma levels of particular cytokines are associated with the generation of p53-specific serum autoantibody (AAb) responses in patients.

METHODS

Levels of CA125, 17 cytokines and AAbs to tumor-associated antigens including p53 were measured in plasma of 130 gynecologic tumor patients and 84 healthy controls. TP53 exons 4-9 were sequenced in tumor specimens.

RESULTS

p53 AAbs are associated with high grade, but not low grade ovarian carcinoma. Seropositivity for p53 AAb occurred only in those ovarian carcinoma patients whose tumors contained mutated TP53, regardless of the exon targeted. Higher p53 AAb levels were detected in ovarian carcinoma patients who had higher stage disease, but p53 AAb levels were not correlated with CA125 levels. Among high-grade carcinoma patients, there was no relationship between p53 AAb seropositivity and seropositivity to other tumor-associated antigens tested, CA125 level or survival outcome. Both high and low grade ovarian carcinoma patients exhibited elevated levels of IL6, IL8 and IL10 as compared to healthy volunteers, although increased levels of IL5, MCP1, MIP1 and TNFalpha were associated only with high grade and advanced disease. Higher levels of p53AAb responses were correlated with elevated circulating IL4 and IL12, but reduced IL8 levels.

CONCLUSION

Type II, but not type I, ovarian carcinoma patients had elevated serum levels of p53 AAb. P53 AAb is associated with mutation of TP53, higher plasma IL4 and IL12 but lower plasma IL8 levels and no survival advantage.

Survival of ovarian cancer patients overexpressing the tumour antigen p53 is diminished in case of MHC class I down-regulation

OBJECTIVES

The adaptive immune system seems to play an essential role in the natural course of ovarian cancer. Aim of this study was to establish whether disease-specific survival for patients expressing the tumour antigen p53 is influenced by MHC class I expression or the presence of p53 autoantibodies (p53-Aab).

METHODS

P53 and MHC class I expression were analysed in ovarian cancer tissue of 329 patients by immunohistochemistry using tissue microarrays. For 233 patients, pre-treatment serum samples were available to study the presence of p53 autoantibodies by ELISA. Data were linked to clinicopathological parameters and disease-specific survival.

RESULTS

P53 overexpression, MHC class I down-regulation in neoplastic cells and serum p53 autoantibodies were observed in 49.4, 38.9 and 15.9% of patients, respectively. MHC class I down-regulation in p53-overexpressing tumours correlated with a 10-month reduced disease-specific survival in univariate analysis (log-rank 4.10; p=0.043). p53-Aab were strongly correlated with p53 overexpression (p<0.001), but did not influence disease-specific survival.

CONCLUSIONS

As the prognosis of patients with p53-overexpressing ovarian cancer is affected by the MHC class I status of tumour cells and ovarian cancer patients can generate immune responses to the p53 tumour antigen, the further development of immunotherapy should evaluate strategies to improve MHC class I expression by tumour cells to facilitate antigen presentation in an attempt to increase clinical responses.

Current immunotherapeutic strategies in colon cancer

Because chemotherapy is standard in the treatment of colorectal cancer, it is important to demonstrate whether immunizations may be given to patients receiving systemic chemotherapy. Although some studies have demonstrated immune responses in patients with metastatic colorectal carcinoma who failed standard chemotherapy, the setting of minimal residual disease may be the preferred setting for cancer vaccines. It may be important to choose antigens that have functions important to the cancer cell. The best adjuvant is not well established and may depend on the type of immune response desired. The immune system is "programmed" to down-regulate immune responses once they have become activated to avoid the development of autoimmune disease.

Gene therapy in The Netherlands: highlights from the Low Countries

Gene therapy is an active research area in The Netherlands and Dutch scientists involved in fundamental and clinical gene therapy research significantly contribute to the progresses made in this field. This ranges from the establishment of the 293, 911 and PER.C6 cell lines, which are used worldwide for the production of replication‐defective adenoviral vectors, to the development of targeted viral vectors and T lymphocytes as well as of non‐viral vectors. Several milestones have been achieved in Dutch clinical gene therapy trials, including the first treatment worldwide of patients with adenosine deaminase deficiency with genetically corrected hematopoietic stem cells in collaboration with French and British scientists. Until now, about 230 patients with various diseases have been treated with viral and non‐viral gene therapy in this country. Ongoing and upcoming Dutch clinical trials focus on the translation of new developments in gene therapy research, including the restoration of genetic defects other than SCID, and the use of oncolytic adenoviruses and targeted T cells for the treatment of cancer. The growing commercial interest in Dutch clinical gene therapy is reflected by the involvement of two Dutch companies in ongoing trials as well as the participation of Dutch clinical centres in large phase III international multicenter immuno‐gene therapy trials on prostate cancer sponsored by an American company. Translational gene therapy research in The Netherlands is boosted at a governmental level by the Dutch Ministry of Health via a dedicated funding programme. This paper presents an overview on milestones in Dutch basic gene therapy research as well as on past, present and future clinical gene therapy trials in The Netherlands. Copyright © 2007 John Wiley & Sons, Ltd.

Vaccination with p53 peptide-pulsed dendritic cells is associated with disease stabilization in patients with p53 expressing advanced breast cancer; monitoring of serum YKL-40 and IL-6 as response biomarkers

p53 Mutations are found in up to 30% of breast cancers and peptides derived from over-expressed p53 protein are presented by class I HLA molecules and may act as tumor-associated epitopes in cancer vaccines. A dendritic cell (DC) based p53 targeting vaccine was analyzed in HLA-A2+ patients with progressive advanced breast cancer. DCs were loaded with 3 wild-type and 3 P2 anchor modified HLA-A2 binding p53 peptides. Patients received up to 10 sc vaccinations with 5 x 10(6) p53-peptide loaded DC with 1-2 weeks interval. Concomitantly, 6 MIU/m(2) interleukine-2 was administered sc. Results from a phase II trial including 26 patients with verified progressive breast cancer are presented. Seven patients discontinued treatment after only 2-3 vaccination weeks due to rapid disease progression or death. Nineteen patients were available for first evaluation after 6 vaccinations; 8/19 evaluable patients attained stable disease (SD) or minor regression while 11/19 patients had progressive disease (PD), indicating an effect of p53-specific immune therapy. This was supported by: (1) a positive correlation between p53 expression of tumor and observed SD, (2) therapy induced p53 specific T cells in 4/7 patients with SD but only in 2/9 patients with PD, and (3) significant response associated changes in serum YKL-40 and IL-6 levels identifying these biomarkers as possible candidates for monitoring of response in connection with DC based cancer immunotherapy. In conclusion, a significant fraction of breast cancer patients obtained SD during p53-targeting DC therapy. Data encourage initiation of a randomized trial in p53 positive patients evaluating the impact on progression free survival.

P53-specific T cell responses in patients with malignant and benign ovarian tumors: implications for p53 based immunotherapy

Despite intensive treatment, 70% of the ovarian cancer patients will develop recurrent disease, emphasizing the need for new approaches such as immunotherapy. A promising antigenic target for immunotherapy in ovarian cancer is the frequently overexpressed p53 protein. The aim of the study was to evaluate the nature and magnitude of the baseline anti-p53 immune response in ovarian cancer patients. P53-specific T cell responses were detected in both half of the ovarian cancer patients as in the group of control subjects, consisting of women with benign ovarian tumors and healthy controls. Importantly, while in the control group p53-specific immunity was detected among the CD45RA(+) naïve subset of T cells only, the p53-specific T-cell responses in ovarian cancer patients were also present in the CD45RO(+) memory T-cell subset, suggesting that in the cancer patients sufficient amounts of cancer-derived p53 was presented to induce the formation of a p53-specific memory T-cell response. Further characterization of the p53-specific memory T-cell responses revealed that in addition to the type 1 cytokine IFN-gamma also the type 2 cytokines IL-4 and IL-5, as well as the immunosuppressive cytokine IL-10 were produced. Notably, p53-specific T cells were not only detected in the peripheral blood, but also among tumor infiltrating lymphocytes and in tumor-draining lymph nodes. In conclusion, the existence of a weak mixed T-helper type 1 and 2 p53-specific T-cell repertoire supports the rationale of using p53 long peptides in vaccination strategies aiming at the induction of p53-specific Th1/CTL immunity.

Addition of TAT protein transduction domain and GrpE to human p53 provides soluble fusion proteins that can be transduced into dendritic cells and elicit p53-specific T-cell responses in HLA-A*0201 transgenic mice

The protein p53 has been shown to be an efficient tumour antigen in both murine and human cancer vaccine studies and cancer vaccines targeting p53 based on major histocompatibility complex (MHC) class I binding p53-derived peptides that induce cytotoxic T lymphocytes (CTLs) without p53-specific CD4(+) T-cell help have been tested by several research groups including ours. To obtain such CD4(+) T-cell help and cover a broader repertoire of MHC haplotypes we have previously attempted to produce recombinant human p53 for vaccination purposes. However, attempts to refold a hexahis-tagged p53 protein in our laboratory were unsuccessful. Here, we show that fusion of an 11-amino-acid region of the human immunodeficiency virus TAT protein transduction domain (PTD) to human p53 increases the solubility of the otherwise insoluble p53 protein and this rTAT-p53 protein can be transduced into human monocyte-derived dendritic cells (DCs). The induction of a p53-specific HLA-A*0201 immune response was tested in HLA-A*0201/K(b) transgenic mice after immunization with rTAT-p53-transduced bone-marrow-derived DCs. In these mice, p53-specific CD4(+) and CD8(+) T-cell proliferation was observed and immunization resulted in the induction of HLA-A*0201-restricted CTLs specific for two human p53-derived HLA-A*0201-binding peptides, p53(65-73) and p53(149-157). Addition of GrpE to generate rTAT-GrpE-p53 led to a further increase in protein solubility and to a small increase in DC maturation but did not increase the observed p53-specific T-cell responses. The use of rTAT-p53 in ongoing clinical protocols should be applicable and offers advantages to current strategies omitting the use of HLA-typed patients.

Development and registration of recombinant veterinary vaccines

The canarypox vaccine vector (ALVAC) technology has been used to develop and license several vaccines for companion animals and horses in the European Union and USA. ALVAC is a ubiquitous vector with high biosafety since it is non-replicative in mammalians, is genetically and physically stable, and able to induce both humoral and cell-mediated immune responses against the expressed transgene product. Specific rules apply for the development and registration of recombinant vector vaccines. The biology of the vector as well as the recombinant virus must be thoroughly documented to allow the risk assessment of its use in the target species. In particular, its safety for the host and the environment must be extensively demonstrated before field trials can be authorized.

Plasmid DNA and viral vector-based vaccines for the treatment of cancer

Plasmid DNA and viral vector-based cancer vaccines have many inherent features that make them promising cancer vaccine candidates. This review focuses on the use of plasmid DNA and viral vector vaccines to deliver tumour-specific antigens to induce a tumour-specific immune response. Examples of different antigen delivery systems that have been tested in recent clinical trials are summarised and advantages and disadvantages of a number of delivery systems and approaches are discussed. Finally, an outlook on how plasmid DNA and viral vectors might be developed further as cancer vaccines is provided.

Clinical results of vaccine therapy for cancer: learning from history for improving the future

Active, specific immunotherapy for cancer holds the potential of providing an approach for treating cancers, which have not been controlled by conventional therapy, with very little or no associated toxicity. Despite advances in the understanding of the immunological basis of cancer vaccine therapy as well as technological progress, clinical effectiveness of this therapy has often been frustratingly unpredictable. Hundreds of preclinical and clinical studies have been performed addressing issues related to the generation of a therapeutic immune response against tumors and exploring a diverse array of antigens, immunological adjuvants, and delivery systems for vaccinating patients against cancer. In this chapter, we have summarized a number of clinical trials performed in various cancers with focus on the clinical outcome of vaccination therapy. We have also attempted to draw objective inferences from the published data that may influence the clinical effectiveness of vaccination approaches against cancer. Collectively the data indicate that vaccine therapy is safe, and no significant autoimmune reactions are observed even on long term follow-up. The design of clinical trials have not yet been optimized, but meaningful clinical effects have been seen in B-cell malignancies, lung, prostate, colorectal cancer, and melanoma. It is also obvious that patients with limited disease or in the adjuvant settings have benefited most from this targeted therapy approach. It is imperative that future studies focus on exploring the relationship between immune and clinical responses to establish whether immune monitoring could be a reliable surrogate marker for evaluating the clinical efficacy of cancer vaccines.

Towards therapeutic vaccines for colorectal carcinoma: a review of clinical trials

Colorectal carcinoma is a leading cause of cancer-related mortality. Despite the introduction of new cytotoxic drugs, improved surgical and radiotherapeutic techniques, a large proportion of colorectal carcinomas remain incurable. New targeted therapeutic strategies, including immunotherapy, are being explored as complementary treatments. Recent advances in immunology and molecular biology have opened new avenues for the clinical testing of rationally designed vaccination strategies against cancer. The present report reviews the results of therapeutic vaccine trials in colorectal carcinoma, published mainly in the past 6 years. Tumor-associated antigens (self-antigens) have been targeted by therapeutic vaccination in more than 2000 colorectal carcinoma patients. The results demonstrate that tumor antigen-specific immune responses are reproducibly induced; that is, tolerance can be reversed, without the induction of serious adverse events or autoimmune disorders. No long-term autoimmune side effects have been observed after a minimum follow-up of 4 years in over 700 patients. Over 1300 colorectal carcinoma patients with minimal residual disease have been enrolled in randomized controlled Phase II/III trials using autologous tumor cell vaccines. A significantly improved overall survival was noted for Stages I-IV colorectal carcinoma patients utilizing Newcastle-disease virus as an adjuvant. Autologous tumor cells mixed with bacillus Calmette-Guerin (BCG) were of significant clinical benefit for patients with Stage II colon cancer. Results of randomized controlled trials targeting Ep-CAM have shown clinical benefit in subgroups of patients. Several new generation vaccines have demonstrated excellent safety profile and immunogenicity. Some studies have also demonstrated a statistically significant correlation between the induced immune response and prolonged overall survival, which should be confirmed in enlarged trials. Although it is unlikely that active specific immunotherapy will provide a standard complementary therapeutic approach for colorectal carcinoma in the near future, the results so far are encouraging. Randomized controlled vaccine trials targeting molecularly defined tumor antigens are warranted, particularly in colon carcinoma with minimal residual disease.

Tumoral and Immunologic Response After Vaccination of Melanoma Patients With an ALVAC Virus Encoding MAGE Antigens Recognized by T Cells

Purpose

To evaluate the toxicity, antitumoral effectiveness, and immunogenicity of repeated vaccinations with ALVAC miniMAGE-1/3, a recombinant canarypox virus containing a minigene encoding antigenic peptides MAGE-3168-176and MAGE-1161-169, which are presented by HLA-A1 and B35 on tumor cells and can be recognized by cytolytic T lymphocytes (CTLs).

Materials and Methods

The vaccination schedule comprised four sequential injections of the recombinant virus, followed by three booster vaccinations with the MAGE-3168-176and MAGE-1161-169peptides. The vaccines were administered, both intradermally and subcutaneously, at 3-week intervals.

Results

Forty patients with advanced cancer were treated, including 37 melanoma patients. The vaccines were generally well tolerated with moderate adverse events, consisting mainly of transient inflammatory reactions at the virus injection sites. Among the 30 melanoma patients assessable for tumor response, a partial response was observed in one patient, and disease stabilization in two others. The remaining patients had progressive disease. Among the patients with stable or progressive disease, five showed evidence of tumor regression. A CTL response against the MAGE-3 vaccine antigen was detected in three of four patients with tumor regression, and in only one of 11 patients without regression.

Conclusion

Repeated vaccination with ALVAC miniMAGE-1/3 is associated with tumor regression and with a detectable CTL response in a minority of melanoma patients. There is a significant correlation between tumor regression and CTL response. The contribution of vaccine-induced CTL in the tumor regression process is discussed in view of the immunologic events that could be analyzed in detail in one patient.

Targeted therapy for colorectal cancer: mapping the way

In spite of the significant advances in conventional therapeutic approaches to colorectal cancer (CRC), most patients ultimately die of their disease. Dissecting the molecular mechanisms underlying CRC progression will not only accelerate the development of novel cancer-selective drugs but will also enable the therapeutic regimen to be personalized according to the molecular features of individual patients and tumors. Here, we report on the novel insights into CRC biology that are paving the way to the development of molecular therapies and summarize the results from recent clinical trials demonstrating that agents targeting tumor-specific molecular derangements can significantly improve the therapeutic efficacy of conventional chemotherapy. Only a broader clinical implementation of these concepts will provide patients with CRC the best chance of a cure.

Immunologic aspect of ovarian cancer and p53 as tumor antigen

Ovarian cancer represents the fifth leading cause of death from all cancers for women. During the last decades overall survival has improved due to the use of new chemotherapy schedules. Still, the majority of patients die of this disease. Research reveals that ovarian cancer patients exhibit significant immune responses against their tumor. In this review the knowledge obtained thus far on the interaction of ovarian cancer tumor cells and the immune system is discussed. Furthermore the role of p53 as tumor antigen and its potential role as target antigen in ovarian cancer is summarized. Based on the increased knowledge on the role of the immune system in ovarian cancer major improvements are to be expected of immunotherapy based treatment of this disease.

Therapeutic vaccination in patients with gastrointestinal malignancies. A review of immunological and clinical results

Gastrointestinal (GI) malignancies are the most common types of human cancers. Despite the introduction of new cytotoxic drugs, a large proportion remains incurable. There is a great need to develop new complementary therapeutic modalities. Strategies exploiting targeted therapies are expanding. The focus of the present article is to review active specific immunotherapy (vaccination) in patients with GI malignancies. The review comprises a description of the immunogenicity of GI malignancies, various types of tumour antigens and mechanisms of action of cancer vaccines. Tumour escape from immune surveillance, vaccine strategies and adjuvants are also described. Clinical and immunological endpoints of cancer immunotherapy are outlined. Results of therapeutic vaccine trials published mainly during the last 5 years in PubMed enrolling a minimum of six patients with GI malignancies are included. Studies presented at the two last annual meetings of the American Society of Clinical Oncology are also covered. More than 2000 patients have been vaccinated with tumour antigens (self antigens). The procedure is safe and no autoimmune disorders have been observed after >4 years follow-up in a substantial number of patients. Humoral and cellular tumour antigen-specific immune responses were induced. A correlation between immune responses and prolonged overall survival was seen in several studies. The most encouraging results were noted in randomised controlled phase II/III trials including over 1300 colorectal carcinoma patients with minimal residual disease. A statistically significantly improved disease-free or overall survival was shown either in all vaccinated or in sub-groups of patients. Promising results were also reported in pancreatic and hepatocellular carcinoma. If the results of the randomised controlled trials hold true, active specific immunotherapy may provide a new promising targeted therapeutic approach in GI malignancies with minimal toxicity. Further enlarged randomised controlled studies are warranted to confirm the results, particularly in colon carcinoma with minimal residual disease.

Intratumoral Administration of a Recombinant Canarypox Virus Expressing Interleukin 12 in Patients with Metastatic Melanoma

The aim of this study was to evaluate the tolerability and activity of intratumoral administered human interleukin 12 encoded by a vector derived from the canarypox virus (ALVAC-IL-12). Nine patients with surgically incurable metastatic melanoma who had subcutaneous nodules available for injection were enrolled. ALVAC-IL-12 was administered by intratumoral injection on days 1, 4, 8, and 11. Tumor nodules greater than 2 cm in diameter were injected with 2 x 10(6) median tissue culture infectious doses (TCID(50)), and smaller tumors were injected with 1 x 10(6) TCID(50). The total dose per patient per time point ranged from 1 x 10(6) to 4 x 10(6) TCID(50). Toxicity was mild to moderate and consisted of inflammatory reactions at the injection site and fever associated with chills, myalgia, and fatigue. No dose-limiting toxicities occurred. Increases in IL-12 mRNA, and also increases in interferon gamma mRNA, were observed in ALVAC-IL-12-injected tumors compared with saline-injected control tumors in four of the nine patients. ALVAC-IL-12-injected tumors were also characterized by T cell infiltration. Three patients demonstrated increases in serum IL-12 and in interferon gamma levels. All patients developed neutralizing IgG antibody to the canarypox vector. One patient manifested a complete response of injected subcutaneous metastases and uninjected in-transit metastases. The intratumoral injection of ALVAC-IL-12 at these dose levels and according to this schedule was well tolerated and resulted in measurable biologic response in patients with metastatic melanoma.

Colorectal cancer vaccines: principles, results, and perspectives

In the search for novel therapeutic approaches to treat patients with colorectal carcinoma, anticancer vaccination holds promise. A large body of preclinical and clinical evidence has demonstrated that the immune system can be polarized against malignant cells by means of several active specific immunotherapy strategies. Although no vaccination regimen can be currently recommended outside clinical trials, tumor response and immunologic findings observed in animal models and humans prompt researchers to explore further the antitumor potential of such biotherapy in an effort to reproduce in a larger set of patients the cascade of molecular events that characterizes the successful tumor immune rejection currently observed in a minority of vaccinated subjects. In this work, we summarize the principles and the main results of cancer vaccine strategies so far implemented for the treatment of patients with colorectal carcinoma. We also discuss the most recent preclinical tumor immunology insights that might change the way to design the next generation of cancer vaccines, hopefully improving the effectiveness of such a biotherapeutic approach.

Recent advances in tumour antigen-specific therapy:In vivo veritas

Modern cancer therapies should strive not only to eliminate malignant tissues but also to preserve healthy tissues and the patient's quality of life. Antigen-specific immunotherapy approaches are promising for either aspect since they are designed to only act against tissues expressing 1 or more specified tumour antigens. In order to develop successful vaccine and adoptive transfer protocols, longitudinal monitoring of cancer patients taking part in clinical trials is mandatory. Here, in vivo expansion of antigen-specific cells, as well as their ex vivo functional status represent important parameters to be analysed. To obtain results that most closely reflect the cells' in vivo status, functional assays must be carried out with as little in vitro culturing as possible. The present minireview discusses recent advances in these domains.