Mannan-MUC1-pulsed dendritic cell immunotherapy: a phase I trial in patients with adenocarcinoma

Past, present and future targets for immunotherapy in ovarian cancer

Ovarian cancer is the leading cause of death from gynecologic malignancy in the US. Treatments have improved with conventional cytotoxic chemotherapy and advanced surgical techniques but disease recurrence is common and fatal in nearly all cases. Current evidence suggests that the immune system and its ability to recognize and eliminate microscopic disease is paramount in preventing recurrence. Ovarian cancer immunotherapy is targeting tumors through active, passive and adoptive approaches. The goal of immunotherapy is to balance the activation of the immune system against cancer while preventing the potential for tremendous toxicity elicited by immune modulation. In this paper we will review the different immunotherapies available for ovarian cancer as well as current ongoing studies and potential future directions.

MUC1 as a potential target in anticancer therapies

MUC1 is a glycoprotein that is overexpressed in tumor cells. In normal cells it forms a protective layer against microbes and toxic chemicals, besides providing lubrication on ductal surfaces. Oversecretion of MUC1 provide cancer cells with invasiveness, metastasis, and resistance to death induced by reactive oxygen species. MUC1 is made up of 2 heterodimers, MUC1-N and MUC1-C. MUC1-N is heavily glycosylated at 5 regions of the variable N-tandem repeats. MUC1-C is divisible into extracellular, intracellular, and cytoplasmic domain (MUC1-C/CD). The extracellular domain serves as a docking site for epidermal growth factor receptors and other receptor kinases; the transmembrane domain serves to relay messages from extracellular to MUC1-C/CD. The MUC1-C/CD has 5 phosphorylating sites that on interacting with the SH2 domain of specific proteins can stimulate tumor growth. Therapies targeting MUC1 consists of monoclonal antibodies (MAb), vaccines, or small molecules (aptamers). MAb therapies are mainly aimed at MUC1-N with little success, however, new generation of MAb are being developed for MUC1-C. Vaccines (peptide, carbohydrate, glycopeptide, DNA, and dendritic cell) have been developed that recognizes the aberrant glycosylated region of the variable N-tandem repeats in MUC1-N, whereas new generation vaccines are aimed at the cytoplasmic region of MUC1-C. Aptamers (peptides that resemble DNA, RNA) have been used for blocking the dimerization of CQC region and the 5 phosphorylating region of MUC1-C. In addition, aptamers have been used as cytotoxic drug carriers. However, none of the therapies for MUC1 are currently in clinical application, as they need further refinement and evaluation.

Mannan adjuvants intranasally administered inactivated influenza virus in mice rendering low doses inductive of strong serum IgG and IgA in the lung

BACKGROUND

H1N1 influenza viruses mutate rapidly, rendering vaccines developed in any given year relatively ineffective in subsequent years. Thus it is necessary to generate new vaccines every year, but this is time-consuming and resource-intensive. Should a highly virulent influenza strain capable of human-to-human transmission emerge, these factors will severely limit the number of people that can be effectively immunised against that strain in time to prevent a pandemic. An adjuvant and mode of administration capable of rendering ordinarily unprotective vaccine doses protective would thus be highly advantageous.

METHODS

The carbohydrate mannan was conjugated to whole inactivated H1N1 influenza virus at a range of ratios, and mixed with it at a range of ratios, and various doses of the resulting preparations were administered to mice via the intranasal (IN) route. Serum immunity was assessed via antigen-specific IgG ELISA and the haemagglutination-inhibition (HI) assay, and mucosal immunity was assessed via IgA ELISA of bronchio-alveolar lavages.

RESULTS

IN-administered inactivated H1N1 mixed with mannan induced higher serum IgG and respiratory-tract IgA than inactivated H1N1 conjugated to mannan, and HIN1 alone. Adjuvantation was mannan-dose-dependent, with 100 μg of mannan adjuvanting 1 μg of H1N1 more effectively than 10 or 50 μg of mannan. Serum samples from mice immunised with 1 μg H1N1 adjuvanted with 10 μg mannan did not inhibit agglutination of red blood cells (RBCs) at a dilution factor of 10 in the HI assay, but samples resulting from adjuvantation with 50 and 100 μg mannan inhibited agglutination at dilution factors of ≥ 40. Both serum IgG1 and IgG2a were induced by IN mannan-adjuvanted H1N1 vaccination, suggesting the induction of humoral and cellular immunity.

CONCLUSIONS

Mixing 100 μg of mannan with 1 μg of inactivated H1N1 adjuvanted the vaccine in mice, such that IN immunisation induced higher serum IgG and respiratory tract IgA than immunisation with virus alone. The serum from mice thus immunised inhibited H1N1-mediated RBC agglutination strongly in vitro. If mannan similarly adjuvants low doses of influenza vaccine in humans, it could potentially be used for vaccine 'dose-sparing' in the event that a vaccine shortage arises from an epidemic involving a highly virulent human-to-human transmissable influenza strain.

Targeted Immunotherapy Designed to Treat MUC1-Expressing Solid Tumour

Several approaches to antigen-specific immunotherapy of cancer antigen-specific immunotherapy of cancer have been tested clinically. In this chapter, we will describe studies done with the antigen MUC1. Tested MUC1 therapeutic vaccines include the following: monoclonal antibodies (MAbs) specific for MUC1; synthetic and recombinant polypeptides from the protein sequence of MUC1; dendritic cells carrying MUC1; RNA and DNA vaccinations; and recombinant viruses carrying the MUC1 DNA sequence. Chemotherapy of cancer aims to be toxic to the cancer cells with manageable side effects to the patient. In contrast, antigen-specific immunotherapy of cancer aims to treat the patient, such that the patient is then able to control and eventually eliminate their cancer cells. It is therefore important to know the immune status of each cancer patient prior to therapy.

Trial watch: Dendritic cell-based interventions for cancer therapy

Dendritic cells (DCs) occupy a central position in the immune system, orchestrating a wide repertoire of responses that span from the development of self-tolerance to the elicitation of potent cellular and humoral immunity. Accordingly, DCs are involved in the etiology of conditions as diverse as infectious diseases, allergic and autoimmune disorders, graft rejection and cancer. During the last decade, several methods have been developed to load DCs with tumor-associated antigens, ex vivo or in vivo, in the attempt to use them as therapeutic anticancer vaccines that would elicit clinically relevant immune responses. While this has not always been the case, several clinical studies have demonstrated that DC-based anticancer vaccines are capable of activating tumor-specific immune responses that increase overall survival, at least in a subset of patients. In 2010, this branch of clinical research has culminated with the approval by FDA of a DC-based therapeutic vaccine (sipuleucel-T, Provenge^®) for use in patients with asymptomatic or minimally symptomatic metastatic hormone-refractory prostate cancer. Intense research efforts are currently dedicated to the identification of the immunological features of patients that best respond to DC-based anticancer vaccines. This knowledge may indeed lead to personalized combination strategies that would extend the benefit of DC-based immunotherapy to a larger patient population. In addition, widespread enthusiasm has been generated by the results of the first clinical trials based on in vivo DC targeting, an approach that holds great promises for the future of DC-based immunotherapy. In this Trial Watch, we will summarize the results of recently completed clinical trials and discuss the progress of ongoing studies that have evaluated/are evaluating DC-based interventions for cancer therapy.

Antigen-specific active immunotherapy for ovarian cancer

BACKGROUND

Despite advances in chemotherapy, prognosis of ovarian cancer remains poor. Antigen-specific active immunotherapy aims to induce tumour-antigen-specific anti-tumour immune responses as an alternative treatment for ovarian cancer.

OBJECTIVES

To assess the feasibility of antigen-specific active immunotherapy for ovarian cancer. Primary outcomes are clinical efficacy and antigen-specific immunogenicity with carrier-specific immunogenicity and side effects as secondary outcomes.

SEARCH METHODS

For the previous version of this review, a systematic search of the Cochrane Central Register of Controlled Trials (CENTRAL) 2009, Issue 3, Cochrane Gynaecological Cancer Group Specialized Register, MEDLINE and EMBASE databases and clinicaltrials.gov was performed (1966 to July 2009). We conducted handsearches of the proceedings of relevant annual meetings (1996 to July 2009).For this update of the review the searches were extended to October 2013.

SELECTION CRITERIA

Randomised controlled trials (RCTs), as well as non-randomised non-controlled studies that included participants with epithelial ovarian cancer, irrespective of stage of disease, and treated with antigen-specific active immunotherapy, irrespective of type of vaccine, antigen used, adjuvant used, route of vaccination, schedule, and reported clinical or immunological outcomes.

DATA COLLECTION AND ANALYSIS

Two reviews authors independently performed the data extraction. Risk of bias was evaluated for RCTs according to standard methodological procedures expected by The Cochrane Collabororation or for non-RCTs using a selection of quality domains deemed best applicable to the non-randomised non-controlled studies.

MAIN RESULTS

Fifty-five studies were included (representing 3051 women with epithelial ovarian cancer). Response definitions showed substantial variation between trials, which makes comparison of trial results unreliable. Information on adverse events was frequently limited. Furthermore, reports of both RCTs and non-RCTs frequently lacked the relevant information necessary to assess risk of bias. Serious biases in most of the included trials can therefore not be ruled out.The largest body of evidence is currently available for CA-125 targeted antibody therapy (16 studies: 2339 participants). Non-RCTs of CA-125 targeted antibody therapy suggests increased survival in humoral and/or cellular responders. However, four large randomised placebo-controlled trials did not show any clinical benefit despite induction of immune responses in approximately 60% of participants.Other small studies targeting many different tumour antigens showed promising immunological results. As these strategies have not yet been tested in RCTs, no reliable inferences about clinical efficacy can be made. Given the promising immunological results, limited side effects and toxicity exploration of clinical efficacy in large well-designed RCTs may be worthwhile.

AUTHORS' CONCLUSIONS

We conclude that despite promising immunological responses, no clinically effective antigen-specific active immunotherapy is yet available for ovarian cancer. Results should be interpreted cautiously as there was a significant lack of relevant information for the assessment of risk of bias in both RCTs and non-RCTs.

Dendritic cell immunotherapy: clinical outcomes

The use of tumour-associated antigens for cancer immunotherapy studies is exacerbated by tolerance to these self-antigens. Tolerance may be broken by using ex vivo monocyte-derived dendritic cells (DCs) pulsed with self-antigens. Targeting tumour-associated antigens directly to DCs in vivo is an alternative and simpler strategy. The identification of cell surface receptors on DCs, and targeting antigens to DC receptors, has become a popular approach for inducing effective immune responses against cancer antigens. Many years ago, we demonstrated that targeting the mannose receptor on macrophages using the carbohydrate mannan to DCs led to appropriate immune responses and tumour protection in animal models. We conducted Phase I, I/II and II, clinical trials demonstrating the effectiveness of oxidised mannan-MUC1 in patients with adenocarcinomas. Here we summarise DC targeting approaches and their efficacy in human clinical trials.

A phase 2, single-arm study of an autologous dendritic cell treatment against mucin 1 in patients with advanced epithelial ovarian cancer

BACKGROUND

Mucin 1 antigen, highly expressed by epithelial ovarian cancer (EOC), is a potential target for immunotherapy. A previous successful phase 1 trial was conducted in patients with adenocarcinoma who were injected with Cvac, autologous monocyte-derived dendritic cells (DCs) incubated with mannosylated mucin 1 protein (M-FP). The present study was a phase 2 trial of Cvac in patients with advanced EOC.

METHODS

Eligible patients had EOC with progressive disease, defined as an increase in CA125 of ≥ 25% in 1 month. The primary endpoint was CA125 response or stabilization. Peripheral blood mononuclear cells were collected by leukapheresis and cultured to generate DCs. The DC were incubated with M-FP, and after washing were prepared for injection into the patient intradermally every 4 weeks for 3 doses, then every 10 weeks for up to 12 months.

RESULTS

All 28 patients recruited were evaluable for safety and 26 for efficacy. All had undergone surgery and platinum-based chemotherapy, and 57% of patients received ≥ 3 chemotherapy regimens. There were no Grade 3 or 4 toxicities considered related to Cvac. Four patients showed CA125 response or stabilization (2 patients with major responses, 1 minor response, 1 stabilization) of median duration 10.3 months (5.3-16.3 months). An additional patient had > 25% CA125 reduction (not confirmed).

CONCLUSIONS

Cvac immunotherapy was well tolerated. Clinical activity in EOC was evident based on decline or stabilization of CA125 in some patients, supporting ongoing development of Cvac in ovarian carcinoma and planning of additional trials of patients in remission is currently underway.

Ovarian cancer biology and immunotherapy

Ovarian cancer is the most lethal malignancy of the female reproductive system and the fifth leading cause of cancer death in women. In the year 2012 alone, United States had 22,280 new ovarian cancer cases and 15,500 deaths were reported. About 7%-10% of ovarian cancers result from an inherited tendency to develop the disease. Ovarian cancer has the ability to escape the immune system because of its pathological interactions between cancer cells and host immune cells in the tumor microenvironment create an immunosuppressive network that promotes tumor growth, protects the tumor from immune system. The levels of immune suppressive elements like regulatory T cells, plasmacytoid dendritic cells and cytokines such as IL-10, IL-6, TNF-α, and TGF-β are elevated in the tumor microenvironment. Vascular endothelial growth factor is known to have an immune suppressing role besides its angiogenic role in the tumor microenvironment. Ovarian cancer is associated with high mortality partly due to difficulties in early diagnosis and development of metastases. These problems may overcome by developing accurate mouse models that should mimic the complexity of human ovarian cancer. Such animal models are better suited to understand pathophysiology, metastases, and also for preclinical testing of targeted molecular therapeutics. Immunotherapy is an area of active investigation and off late many clinical trials is ongoing to prevent disease progression. The main aim of dendritic cells vaccination is to stimulate tumor specific effector T cells that can reduce tumor size and induce immunological memory to prevent tumor relapse.

Up to 15-year clinical follow-up of a pilot Phase III immunotherapy study in stage II breast cancer patients using oxidized mannan-MUC1

BACKGROUND

Targeting antigens to dendritic cell receptors has recently become a popular approach to inducing effective immune responses against cancer antigens. Almost 20 years ago, however, we demonstrated that targeting the mannose receptor on macrophages and dendritic cells leads to strong cellular immune responses. We conducted numerous human clinical trials demonstrating the effectiveness of oxidized mannan-MUC1 (M-FP) in MUC1(+) adenocarcinoma patients. In one trial, the 5-8-year follow-up of breast cancer patients vaccinated with M-FP was published previously; we now report here the 12-15-year follow-up. Details regarding the preparation of the vaccine, inclusion and exclusion criteria, immunotherapy and follow-up schedule, were published previously.

RESULTS

The follow-up at 12-15 years showed that the recurrence rate in patients receiving placebo was 60% (nine of 15). In those receiving immunotherapy (M-FP), the rate was 12.5% (two of 16). The time of recurrence in the placebo group ranged from 7 to 180 months (mean: 65.8 months) and in the two patients of the vaccine group, the recurrence appeared at 95 and 141 months (mean: 118 months) after surgery. These findings are statistically significant (p = 0.02 for survival and p = 0.009 for percentage of patients cancer-free). All patients injected with M-FP showed no evidence of toxic effects or signs of autoimmunity during the 12-15-year follow-up.

DISCUSSION

The preliminary evidence indicates that M-FP is beneficial in the overall survival of early-stage breast cancer patients. This long-term clinical follow-up of patients strongly supports the necessity for a large Phase III study of direct M-FP injection in early-stage breast cancer patients, to evaluate immunotherapy as an adjuvant treatment for breast cancer.

A review of dendritic cell therapy for cancer: progress and challenges

Dendritic cells are the professional antigen-presenting cells of the innate immune system with the potential to generate robust antigen-specific T cell immune responses. Immunotherapeutic strategies have attempted to monopolize on this ability of dendritic cells to deliver antigens as a means of therapeutic vaccination in individuals with advanced malignancies. Since the publication of the first clinical trial in melanoma patients in 1995, therapeutic dendritic cell cancer vaccines have been extensively studied in numerous phase I and II trials. While advances have been encountered (especially with prostate cancer), there are still considerable challenges that need to be addressed in future clinical trials. In this review, we describe the current methodology and highlight trials which have contributed to the development of dendritic cell vaccines. We then review strategies to optimize dendritic cell vaccines in order to improve antitumor responses in cancer patients.

Targeting antigens to dendritic cell receptors for vaccine development

Dendritic cells (DCs) are highly specialized antigen presenting cells of the immune system which play a key role in regulating immune responses. Depending on the method of antigen delivery, DCs stimulate immune responses or induce tolerance. As a consequence of the dual function of DCs, DCs are studied in the context of immunotherapy for both cancer and autoimmune diseases. In vaccine development, a major aim is to induce strong, specific T-cell responses. This is achieved by targeting antigen to cell surface molecules on DCs that efficiently channel the antigen into endocytic compartments for loading onto MHC molecules and stimulation of T-cell responses. The most attractive cell surface receptors, expressed on DCs used as targets for antigen delivery for cancer and other diseases, are discussed.

Identification of putative immunologic targets for colon cancer prevention based on conserved gene upregulation from preinvasive to malignant lesions

The length of time required for preinvasive adenoma to progress to carcinoma, the immunogenicity of colorectal cancer (CRC), and the identification of high-risk populations make development and testing of a prophylactic vaccine for the prevention of CRC possible. We hypothesized that genes upregulated in adenoma relative to normal tissue, which maintained increased expression in CRC, would encode proteins suitable as putative targets for immunoprevention. We evaluated existing adenoma and CRC microarray datasets and identified 160 genes that were ≥2-fold upregulated in both adenoma and CRC relative to normal colon tissue. We further identified 23 genes that showed protein overexpression in colon adenoma and CRC based on literature review. Silencing the most highly upregulated genes, CDH3, CLDN1, KRT23, and MMP7, in adenoma and CRC cell lines resulted in a significant decrease in viability (P < 0.0001) and proliferation (P < 0.0001) as compared to controls and an increase in cellular apoptosis (P < 0.05 for CDH3, KRT23). Results were duplicated across cell lines representing microsatellite instability, CpG island methylator, and chromosomal instability phenotypes, suggesting immunologic elimination of cells expressing these proteins could impact the progression of all CRC phenotypes. To determine whether these proteins were immunogens, we interrogated sera from early stage CRC patients and controls and found significantly elevated CDH3 (P = 0.006), KRT23 (P = 0.0007), and MMP7 (P < 0.0001) serum immunoglobulin G in cases as compared to controls. These data show a high throughput approach to the identification of biologically relevant putative immunologic targets for CRC and identified three candidates suitable for vaccine development.

Dendritic cell-based tumor vaccinations in epithelial ovarian cancer: a systematic review

After decades of extensive research, epithelial ovarian cancer still remains a lethal disease. Multiple new studies have reported that the immune system plays a critical role in the growth and spread of ovarian carcinoma. This review summarizes the development of dendritic cell (DC) vaccinations specific for ovarian cancer. So far, DC-based vaccines have induced effective antitumor responses in animal models, but only limited results from human clinical trials are available. Although DC-based immunotherapy has proven to be clinically safe and efficient at inducing tumor-specific immune responses, its clear role in the therapy of ovarian cancer still needs to be clarified. The relatively disappointing low-response rates in early clinical trials point to the need for the development of more effective and personalized DC-based anticancer vaccines. This article reviews the basic mechanisms, limitations and future directions of DC-based anti-ovarian cancer vaccine development.

Role of α-gal epitope/anti-Gal antibody reaction in immunotherapy and its clinical application in pancreatic cancer

Pancreatic cancer is one of the most common causes of death from cancer. Despite the availability of various treatment modalities, such as surgery, chemotherapy and radiotherapy, the 5-year survival remains poor. Although gemcitabine-based chemotherapy is typically offered as the standard care, most patients do not survive longer than 6 months. Therefore, new therapeutic approaches are needed. The α-gal epitope (Galα1-3Galβ1-4GlcNAc-R) is abundantly synthesized from glycoproteins and glycolipids in non-primate mammals and New World monkeys, but is absent in humans, apes and Old World monkeys. Instead, they produce anti-Gal antibody (Ab) (forming approximately 1% of circulating immunoglobulins), which specifically interacts with α-gal epitopes. Anti-Gal Ab can be exploited in cancer immunotherapy as vaccines that target antigen-presenting cells (APC) to increase their immunogenicity. Tumor cells or tumor cell membranes from pancreatic cancer are processed to express α-gal epitopes. Subsequent vaccination with such processed cell membranes results in in vivo opsonization by anti-Gal IgG in cancer patients. The interaction of the Fc portion of the vaccine-bound anti-Gal with Fcγ receptors of APC induces effective uptake of the vaccinating tumor cell membranes by the APC, followed by effective transport of the vaccinating tumor membranes to the regional lymph nodes, and processing and presentation of the tumor-associated antigens. Activation of tumor-specific B and T cells could elicit an immune response that in some patients is potent enough to eradicate the residual cancer cells that remain after completion of standard therapy. This review addresses these topics and new avenues of clinical importance related to this unique antigen/antibody system (α-gal epitope/anti-Gal Ab) and advances in immunotherapy in pancreatic cancer.

MUC1 vaccine for individuals with advanced adenoma of the colon: a cancer immunoprevention feasibility study

Cancer vaccines based on human tumor-associated antigens (TAA) have been tested in patients with advanced or recurrent cancer, in combination with or following standard therapy. Their immunogenicity and therapeutic efficacy has been difficult to properly evaluate in that setting characterized by multiple highly suppressive effects of the tumor and the standard therapy on the patient's immune system. In animal models of human cancer, vaccines administered in the prophylactic setting are most immunogenic and effectively prevent cancer development and progression. We report results of a clinical study that show that in patients without cancer but with a history of premalignant lesions (advanced colonic adenomas, precursors to colon cancer), a vaccine based on the TAA MUC1 was highly immunogenic in 17 of 39 (43.6%) of vaccinated individuals, eliciting high levels of anti-MUC1 immunoglobulin G (IgG) and long-lasting immune memory. Lack of response in 22 of 39 individuals was correlated with high levels of circulating myeloid-derived suppressor cells (MDSC) prevaccination. Vaccine-elicited MUC1-specific immune response and immune memory were not associated with significant toxicity. Our study shows that vaccines based on human TAAs are immunogenic and safe and capable of eliciting long-term memory that is important for cancer prevention. We also show that in the premalignant setting, immunosuppressive environment (e.g., high levels of MDSC) might already exist in some individuals, suggesting an even earlier premalignant stage or preselection of nonimmunosuppressed patients for prophylactic vaccination.

Cell therapy: a safe and efficacious therapeutic treatment for Alzheimer's disease in APP+PS1 mice

Previously, our lab was the first to report the use of antigen-sensitized dendritic cells as a vaccine against Alzheimer's disease (AD). In preparation of this vaccine, we sensitized the isolated dendritic cells ex vivo with Aβ peptide, and administered these sensitized dendritic cells as a therapeutic agent. This form of cell therapy has had success in preventing and/or slowing the rate of cognitive decline when administered prior to the appearance of Aβ plaques in PDAPP mice, but has not been tested in 2 × Tg models. Herein, we test the efficacy and safety of this vaccine in halting and reversing Alzheimer's pathology in 9-month-old APP + PS1 mice. The results showed that administration of this vaccine elicits a long-lasting antibody titer, which correlated well with a reduction of Aβ burden upon histological analysis. Cognitive function in transgenic responders to the vaccine was rescued to levels similar to those found in non-transgenic mice, indicating that the vaccine is capable of providing therapeutic benefit in APP+PS1 mice when administered after the onset of AD pathology. The vaccine also shows indications of circumventing past safety problems observed in AD immunotherapy, as Th1 pro-inflammatory cytokines were not elevated after long-term vaccine administration. Moreover, microhemorrhaging and T-cell infiltration into the brain are not observed in any of the treated subjects. All in all, this vaccine has many advantages over contemporary vaccines against Alzheimer's disease, and may lead to a viable treatment for the disease in the future.

YB-1 immunization combined with regulatory T-cell depletion induces specific T-cell responses that protect against neuroblastoma in the early stage

Neuroblastoma is the most common extracranial solid cancer in childhood and the most common cancer in infancy. Currently, no effective clinical treatments are available for advanced neuroblastoma. In a previous study, we screened Y Box protein 1 (YB-1) as a potential neuroblastoma-associated antigen from sera of AGN2a-immunized mice by serological analysis of recombinant cDNA expression libraries technique. The aim of this study is to explore if YB-1 immunization in the context of Treg depletion could induce protective immune response against the neuroblastoma in mice. YB-1 was expressed and purified by pET-15b prokaryotic expression system. It was demonstrated that anti-YB-1 CD8(+) T-cell responses could be induced by AGN2a immunization, and the strongest CD8(+) T-cell responses against AGN2a were induced by YB-1-immunized mice in the context of Treg depletion compared with YB-1 only immunization group and control group. Importantly, the survival rate of mice treated with YB-1 immunization combined with Treg depletion was 80% when challenged by 1 × 10(4) AGN2a cells, significantly higher than that of mice immunized with YB-1 alone (P < 0.01). Furthermore, T-cell adoptive therapy showed that the neuroblastoma growth was inhibited when T cells or splenic cells from YB-1-immunized mice with Treg depletion were transferred to AGN2a bearing mice. Both CD4(+) and CD8(+) T cells were involved in the anti-neuroblastoma responses induced by YB-1 immunization combined with Treg depletion. These results indicated that YB-1 immunization combined with Treg depletion could induce specific T-cell responses against neuroblastoma and could be a potential strategy for the prevention and treatment of neuroblastoma in the early stage.

Cancer associated aberrant protein O-glycosylation can modify antigen processing and immune response

Aberrant glycosylation of mucins and other extracellular proteins is an important event in carcinogenesis and the resulting cancer associated glycans have been suggested as targets in cancer immunotherapy. We assessed the role of O-linked GalNAc glycosylation on antigen uptake, processing, and presentation on MHC class I and II molecules. The effect of GalNAc O-glycosylation was monitored with a model system based on ovalbumin (OVA)-MUC1 fusion peptides (+/- glycosylation) loaded onto dendritic cells co-cultured with IL-2 secreting OVA peptide-specific T cell hybridomas. To evaluate the in vivo response to a cancer related tumor antigen, Balb/c or B6.Cg(CB)-Tg(HLA-A/H2-D)2Enge/J (HLA-A2 transgenic) mice were immunized with a non-glycosylated or GalNAc-glycosylated MUC1 derived peptide followed by comparison of T cell proliferation, IFN-γ release, and antibody induction. GalNAc-glycosylation promoted presentation of OVA-MUC1 fusion peptides by MHC class II molecules and the MUC1 antigen elicited specific Ab production and T cell proliferation in both Balb/c and HLA-A2 transgenic mice. In contrast, GalNAc-glycosylation inhibited the presentation of OVA-MUC1 fusion peptides by MHC class I and abolished MUC1 specific CD8+ T cell responses in HLA-A2 transgenic mice. GalNAc glycosylation of MUC1 antigen therefore facilitates uptake, MHC class II presentation, and antibody response but might block the antigen presentation to CD8+ T cells.

Generation of hypoallergenic neoglycoconjugates for dendritic cell targeted vaccination: a novel tool for specific immunotherapy

The incidence of allergic disorders and asthma continuously increased over the past decades, consuming a considerable proportion of the health care budget. Allergen-specific subcutaneous immunotherapy represents the only intervention treating the underlying causes of type I allergies, but still suffers from unwanted side effects and low compliance. There is an urgent need for novel approaches improving safety and efficacy of this therapy. In the present study we investigated carbohydrate-mediated targeting of allergens to dermal antigen-presenting cells and its influence on immunogenicity and allergenicity. Mannan, high (40 kDa) and low (6 kDa) molecular weight dextran, and maltodextrin were covalently attached to ovalbumin and papain via mild carbohydrate oxidation resulting in neoglycocomplexes of various sizes. In particular, mannan-conjugates were efficiently taken up by dendritic cells in vivo leading to elevated humoral immune responses against the protein moiety and a shift from IgE to IgG. Beyond providing an adjuvant effect, papain glycocomplexes also proved to mask B-cell epitopes, thus rendering the allergen derivative hypoallergenic.

The present data demonstrate that carbohydrate-modified allergens combine targeting of antigen presenting cells with hypoallergenicity, offering the potential for low dose allergen-specific immunotherapy while concomitantly reducing the risk of side effects.

Pre-clinical assessment of autologous DC-based therapy in ovarian cancer patients with progressive disease

Dendritic cell-based vaccines offer promise for therapy of ovarian cancer. Previous studies have demonstrated that oxidation of several antigens, including ovarian cancer cells, using hypochlorous acid strongly enhances their immunogenicity and their uptake and presentation by dendritic cells. The response of T cells and dendritic cells to autologous tumour from patients with active disease has not previously been investigated. Monocyte-derived dendritic cells were generated from patients with active disease and activated by co-culture with oxidised tumour cells and the TLR agonist poly I:C. The dendritic cells showed an activated phenotype, but secreted high levels of TGFβ. Co-culture of the antigen-loaded dendritic cells with autologous T cells generated a population of effector T cells that showed a low level of specific lytic activity against autologous tumour, as compared to autologous mesothelium. The addition of neutralising antibody to TGFβ in DC/T cell co-cultures increased the levels of subsequent tumour killing in three samples tested. Co-culture of monocytes from healthy volunteers with the ovarian cell line SKOV-3 prior to differentiation into dendritic cells reduced the ability of dendritic cells to stimulate cytotoxic effector cells. The study suggests that co-culture of dendritic cells with oxidised tumour cells can generate effector cells able to kill autologous tumour, but that the high tumour burden in patients with active disease may compromise dendritic cell and/or T cell function.

The androgen receptor: a biologically relevant vaccine target for the treatment of prostate cancer

The androgen receptor (AR) plays an essential role in the development and progression of prostate cancer. However, while it has long been the primary molecular target of metastatic prostate cancer therapies, it has not been explored as an immunotherapeutic target. In particular, the AR ligand-binding domain (LBD) is a potentially attractive target, as it has an identical sequence among humans as well as among multiple species, providing a logical candidate for preclinical evaluation. In this report, we evaluated the immune and anti-tumor efficacy of a DNA vaccine targeting the AR LBD (pTVG-AR) in relevant rodent preclinical models. We found immunization of HHDII-DR1 mice, which express human HLA-A2 and HLA-DR1, with pTVG-AR augmented AR LBD HLA-A2-restricted peptide-specific, cytotoxic immune responses in vivo that could lyse human prostate cancer cells. Using an HLA-A2-expressing autochthonous model of prostate cancer, immunization with pTVG-AR augmented HLA-A2-restricted immune responses that could lyse syngeneic prostate tumor cells and led to a decrease in tumor burden and an increase in overall survival of tumor-bearing animals. Finally, immunization decreased prostate tumor growth in Copenhagen rats that was associated with a Th1-type immune response. These data show that the AR is as a prostate cancer immunological target antigen and that a DNA vaccine targeting the AR LBD is an attractive candidate for clinical evaluation.

MUC1 immunotherapy is here to stay

INTRODUCTION

Success of HBV vaccines in reducing the incidence of liver cancer, and HPV vaccines in reducing preneoplastic cervical lesions, demonstrate the potential of cancer reduction by harnessing the immune system. For most human cancers, infectious etiology is not known but other tumor antigens, candidates for vaccines, have been identified.

AREAS COVERED

The authors discuss knowledge accumulated the last two decades on the tumor antigen MUC1 that has put it at the top of the list as an immunotherapy reagent. They examine evidence that anti-MUC1 immunity affects tumor development and prognosis. Finally, they review two decades of immunotherapy trials targeting MUC1, focusing primarily on vaccines but also adoptive antibody and T-cell therapies.

EXPERT OPINION

Most approaches targeting MUC1 have been immunotherapies administered to date to more than 1200 patients in clinical trials. Even though these trials focused on advanced cancer, encouraging results were reported particularly for less immunosuppressed patients. Furthermore, spontaneous anti-MUC1 immune responses are associated with better prognosis or with a reduced lifetime risk of developing MUC1+ cancers. MUC1 is abnormally expressed in over 80% of all cancers. Successfully targeting this molecule could benefit over a million patients diagnosed yearly with MUC1+ tumors just in the USA.

Aberrantly glycosylated MUC1 is expressed on the surface of breast cancer cells and a target for antibody-dependent cell-mediated cytotoxicity

Protein glycosylation often changes during cancer development, resulting in the expression of cancer-associated carbohydrate antigens. In particular mucins such as MUC1 are subject to these changes. We previously identified an immunodominant Tn-MUC1 (GalNAc-α-MUC1) cancer-specific epitope not covered by immunological tolerance in MUC1 humanized mice and man. The objective of this study was to determine if mouse antibodies to this Tn-MUC1 epitope induce antibody-dependent cellular cytotoxicity (ADCC) pivotal for their potential use in cancer immunotherapy. Binding affinity of mAb 5E5 directed to Tn-MUC1 was investigated using BiaCore. The availability of Tn-MUC1 on the surface of breast cancer cells was evaluated by immunohistochemistry, confocal microscopy, and flow cytometry, followed by in vitro assessment of antibody-dependent cellular cytotoxicity by mAb 5E5. Biacore analysis demonstrated high affinity binding (KD = 1.7 nM) of mAb 5E5 to its target, Tn-MUC1. Immunolabelling with mAb 5E5 revealed surface expression of the Tn-MUC1 epitope in breast cancer tissue and cell lines, and mAb 5E5 induced ADCC in two human breast cancer cell lines, MCF7 and T47D. Aberrantly glycosylated MUC1 is expressed on the surface of breast cancer cells and a target for antibody-dependent cell-mediated cytotoxicity suggesting that antibodies targeting glycopeptide epitopes on mucins are strong candidates for cancer-specific immunotherapies.

Efficacy of a therapeutic vaccine using mutated β-amyloid sensitized dendritic cells in Alzheimer's mice

Despite FDA suspension of Elan's AN-1792 amyloid beta (Aβ) vaccine in phase IIb clinical trials, the implications of this study are the guiding principles for contemporary anti-Aβ immunotherapy against Alzheimer's disease (AD). AN-1792 showed promising results with regards to Aβ clearance and cognitive function improvement, but also exhibited an increased risk of Th1 mediated meningoencephalitis. As such, vaccine development has continued with an emphasis on eliciting a notable anti-Aβ antibody titer, while avoiding the unwanted Th1 pro-inflammatory response. Previously, we published the first report of an Aβ sensitized dendritic cell vaccine as a therapeutic treatment for AD in BALB/c mice. Our vaccine elicited an anti-Aβ titer, with indications that a Th1 response was not present. This study is the first to investigate the efficacy and safety of our dendritic cell vaccine for the prevention of AD in transgenic mouse models (PDAPP) for AD. We also used Immunohistochemistry to characterize the involvement of LXR, ABCA1, and CD45 in order to gain insight into the potential mechanisms through which this vaccine may provide benefit. The results indicate that (1) the use of mutant Aβ1-42 sensitized dendritic cell vaccine results in durable antibody production, (2) the vaccine provides significant benefits with regards to cognitive function without the global (Th1) inflammation seen in prior Aβ vaccines, (3) histological studies showed an overall decrease in Aβ burden, with an increase in LXR, ABCA1, and CD45, and (4) the beneficial results of our DC vaccine may be due to the LXR/ABCA1 pathway. In the future, mutant Aβ sensitized dendritic cell vaccines could be an efficacious and safe method for the prevention or treatment of AD that circumvents problems associated with traditional anti-Aβ vaccines.

Cytotoxic T-lymphocyte immunotherapy for ovarian cancer: a pilot study

The objective was to evaluate the toxicity and feasibility of intraperitoneal infusion of tumor-specific cytotoxic T lymphocytes (CTL) as therapy for recurrent ovarian cancer, and to determine if repetitive cycles of CTL generation and infusion measurably increases the host's ovarian cancer immune response. In this study, 7 subjects with recurrent ovarian cancer confined to the peritoneal cavity underwent up to 4 cycles, each cycle beginning with a leukapheresis for collection of precursor lymphocytes, which were stimulated in vitro with mucin 1, a tumor-specific antigen found commonly in ovarian cancer cells. The resulting new CTL for each cycle were reintroduced into the host by intraperitoneal infusion. Immunologic parameters (killer cells, cytokine production, memory T lymphocytes, and natural killer cells) were studied. Toxicity, CA-125, and survival data were also evaluated. The tumor marker CA-125 was nonstatistically significantly reduced after the first month of immunotherapy. However, after that it rose. Killer cells, cytokine production, and memory T lymphocytes increased after the first cycle of stimulation, but plateaued or reduced thereafter. The percent of natural killer cells inversely correlated with other immune parameters. Median survival was 11.5 months. One subject is free of disease since December, 2000. Multiple cycles, beyond 1 cycle, of T-cell stimulation followed by adoptive T-cell infusion, may not enhance the in vivo immune response.

The immunomodulating roles of glycoproteins in epithelial ovarian cancer

The complexity of the immune system demands an intricate defense mechanism by tumors. Ovarian and other tumors employ specific glycoproteins and the associated glycan sequences to modulate immune responses. Glycoproteins enable tumor cells that express or secrete these molecules to evade immune cell attack and induce the immune system to promote tumor growth. This review focuses first on the immune environment in ovarian cancer, and the mechanisms of activation and inhibition that immune cells undergo in order to either attack or ignore a target cell. Next we illustrate the immunomodulatory roles of ovarian cancer-associated glycans and glycoproteins in 1. preventing immune synapse formation, 2. serving as ligands of immune cell receptors, 3. scavenging cytokines and chemokines, and 4. participating in the formation of autoantibodies against the tumor. The importance of these immunomodulating strategies from the view points of understanding the tumor immunology of ovarian tumors, potential origin of such mechanisms, and specific strategies to circumvent the glycoconjugate-mediated suppression of immune responses is discussed in this review.

Clinical trials of vaccines for immunotherapy in pancreatic cancer

A greater understanding of the molecular events that trigger oncogenesis and events that negatively regulate immune responses has allowed for the development of targeted therapies with specific vaccines to match tumor antigens coupled with immunotherapy specifically directed against that tumor's immunosuppressive microenvironment. In order to be effective, vaccine therapies need to both expand the immune response to tumors and overcome immunosuppressive microenvironments therein. Specifically, targeted therapy must be personalized for each cancer patient. While the idea of personalized targeted therapy may seem like a daunting task, it may not be that difficult as it could involve a relatively simple genetic test to identify gene mutations and additional immunohistochemical staining of tumors with antibodies directed against markers of negative immune regulation. The additional cost to personalize cancer therapy with these diagnostic tests is relatively small in comparison to the cost afforded to our healthcare system when inappropriate targeting therapies are administered to patients whose tumors do not express the targets of either the vaccine or the immune modulator. Despite the large cost, cancer patients whose tumors lack the targets of these therapies often receive no benefit from the therapy. The most illogical approach is to develop a study design and perform clinical trials of potential novel targeting drugs without knowledge or confirmation that the patients' tumors express the targets. Current cancer trials for pancreatic cancer patients are discussed in this article.

A phase I pilot trial of MUC1-peptide-pulsed dendritic cells in the treatment of advanced pancreatic cancer

The objectives of this study were to assess the toxicity and immunological response induced by the intra-dermal (i.d.) administration of MUC1-peptide-pulsed dendritic cells (DCs) in advanced pancreatic cancer patients. Patients with recurrent lesions or metastasis after surgery, and immunohistochemistry positive for MUC1 were treated in cohorts that received 3-6 × 10(6) DCs i.d. for three or four vaccines. Each vaccine was composed of autologus DCs pulsed with MUC1-peptide. Peripheral blood mononuclear cells (PBMCs) that harvested 2 weeks after the second immunization were compared with PBMCs obtained before treatment for immunological response. Serial ELISPOT assays of PBMCs for antitumor reactivity were performed. Three patients received all four vaccines, and four patients received three vaccines. These patients were evaluable for toxicity and immunological monitoring. There were no grade 3 or 4 toxicities associated with the vaccines or major evidence of autoimmunity. Interferon-γ and granzyme B ELISPOT assay reactivity increased significantly in 2 of 7 patients (P < 0.05). The administration of MUC1-peptide-pulsed DCs is non-toxic and capable of inducing immunological response to tumor antigen MUC1 in advanced pancreatic cancer patients. Additional studies are necessary to improve tumor rejection responses.

Immunotherapy in prostate cancer: emerging strategies against a formidable foe

Recent clinical trials have shown therapeutic vaccines to be promising treatment modalities against prostate cancer. Unlike preventive vaccines that teach the immune system to fight off specific microorganisms, therapeutic vaccines stimulate the immune system to recognize and attack certain cancer-associated proteins. Additional strategies are being investigated that combine vaccines and standard therapeutics, including radiation, chemotherapy, targeted therapies, and hormonal therapy, to optimize the vaccines' effects. Recent vaccine late-phase clinical trials have reported evidence of clinical benefit while maintaining excellent quality of life. One such vaccine, sipuleucel-T, was recently FDA-approved for the treatment of metastatic prostate cancer. Another vaccine, PSA-TRICOM, is also showing promise in completed and ongoing randomized multicenter clinical trials in both early- and late-stage prostate cancer. Clinical results available to date indicate that immune-based therapies could play a significant role in the treatment of prostate and other malignancies.

Natural and Induced Humoral Responses to MUC1

MUC1 is a membrane-tethered mucin expressed on the ductal cell surface of glandular epithelial cells. Loss of polarization, overexpression and aberrant glycosylation of MUC1 in mucosal inflammation and in adenocarcinomas induces humoral immune responses to the mucin. MUC1 IgG responses have been associated with a benefit in survival in patients with breast, lung, pancreatic, ovarian and gastric carcinomas. Antibodies bound to the mucin may curb tumor progression by restoring cell-cell interactions altered by tumor-associated MUC1, thus preventing metastatic dissemination, as well as counteracting the immune suppression exerted by the molecule. Furthermore, anti-MUC1 antibodies are capable of effecting tumor cell killing by antibody-dependent cell-mediated cytotoxicity. Although cytotoxic T cells are indispensable to achieve anti-tumor responses in advanced disease, abs to tumor-associated antigens are ideally suited to address minimal residual disease and may be sufficient to exert adequate immune surveillance in an adjuvant setting, destroying tumor cells as they arise or maintaining occult disease in an equilibrium state. Initial evaluation of MUC1 peptide/glycopeptide mono and polyvalent vaccines has shown them to be immunogenic and safe; anti-tumor responses are scarce. Progress in carbohydrate synthesis has yielded a number of sophisticated substrates that include MUC1 glycopeptide epitopes that are at present in preclinical testing. Adjuvant vaccination with MUC1 glycopeptide polyvalent vaccines that induce strong humoral responses may prevent recurrence of disease in patients with early stage carcinomas. Furthermore, prophylactic immunotherapy targeting MUC1 may be a strategy to strengthen immune surveillance and prevent disease in subjects at hereditary high risk of breast, ovarian and colon cancer.

Therapeutic cancer vaccines: are we there yet?

Enthusiasm for therapeutic cancer vaccines has been rejuvenated with the recent completion of several large, randomized phase III clinical trials that in some cases have reported an improvement in progression free or overall survival. However, an honest appraisal of their efficacy reveals modest clinical benefit and a frequent requirement for patients with relatively indolent cancers and minimal or no measurable disease. Experience with adoptive cell transfer-based immunotherapies unequivocally establishes that T cells can mediate durable complete responses, even in the setting of advanced metastatic disease. Further, these findings reveal that the successful vaccines of the future must confront: (i) a corrupted tumor microenvironment containing regulatory T cells and aberrantly matured myeloid cells, (ii) a tumor-specific T-cell repertoire that is prone to immunologic exhaustion and senescence, and (iii) highly mutable tumor targets capable of antigen loss and immune evasion. Future progress may come from innovations in the development of selective preparative regimens that eliminate or neutralize suppressive cellular populations, more effective immunologic adjuvants, and further refinement of agents capable of antagonizing immune check-point blockade pathways.

Enhancement of dendritic cells as vaccines for cancer

Dendritic cells are the most potent antigen-presenting cells known; owing to their ability to stimulate antigen-specific cytolytic and memory T-cell responses, their use as cancer vaccines is rapidly increasing. While clinical trials provide evidence that dendritic cells vaccines are safe and elicit immunological responses in most patients, few complete tumor remissions have been reported and further technological advances are required. An effective dendritic cell vaccine must possess and maintain several characteristics: it must migrate to lymph nodes, have a mature, Th1-polarizing phenotype expressed stably after infusion and present antigen for sufficient time to produce a T-cell response capable of eliminating a tumor. While dendritic cells are readily matured ex vivo, their phenotype and fate after infusion are rarely evaluable; therefore, strategies to ensure that dendritic cells access lymphoid tissues and retain an immunostimulatory phenotype are required. In order to best exploit dendritic cells as vaccines, they may require genetic modification and combination with other strategies including adoptive T-cell transfer, inhibition of regulatory T cells or modulation of inflammatory pathways.

Expression of aberrantly glycosylated Mucin-1 in ovarian cancer

AIMS

  Mucin 1 (MUC1) is an important tumour-associated antigen (TAA), both overexpressed and aberrantly glycosylated in adenocarcinomas. The aim of this study was to examine the MUC1-glycosylation status of primary ovarian adenocarcinomas and metastatic lesions.

METHODS AND RESULTS

  Paraffin-embedded tissue sections of 37 primary ovarian adenocarcinomas representing all histotypes (22 serous, five mucinous, two clear-cell, eight endometrioid), four serous borderline tumours with intraepithelial carcinoma, seven sections of ovarian endometriosis and 13 metastatic lesions were analysed by immunohistochemistry. Non-neoplastic ovarian surface epithelium and serous cystadenomas were used as controls. All epithelia expressed MUC1 protein. Of primary tumours, 76% expressed the differentiation-dependent glycoform and 84% the cancer-associated glycoform (Tn/Sialyl-Tn-epitopes). In metastatic lesions this was 77% and 85%, respectively. Notably, in 57% of ovarian endometriosis and 75% of intraepithelial lesions, the cancer-associated MUC1 epitopes were expressed, whereas normal ovarian surface epithelium and serous cystadenomas did not express these epitopes.

CONCLUSIONS

  The underglycosylated MUC1 epitopes are expressed by all histotypes of primary ovarian adenocarcinomas, by the vast majority of metastatic lesions and by possible ovarian cancer precursor lesions, but not by normal ovarian tissue. These results indicate that MUC1-associated Tn/STn-epitopes are important targets for immunotherapy and diagnostic imaging in ovarian cancer patients.

MUC1 immunotherapy

The overexpression and aberrant glycosylation of MUC1 is associated with a wide variety of cancers, making it an ideal target for immunotherapeutic strategies. This review highlights the main avenues of research in this field, focusing on adenocarcinomas, from the preclinical to clinical; the problems and possible solutions associated with each approach; and speculates on the direction of MUC1 immunotherapeutic research over the next 5-10 years.

MUC1-based recombinant Bacillus Calmette-Guerin vaccines as candidates for breast cancer immunotherapy

IMPORTANCE OF THE FIELD

The challenge in breast cancer vaccine development is to find the best combination of antigen, adjuvant and delivery system to produce a strong and long-lasting immune response. Mucin 1 (MUC1) is a potential candidate target for breast cancer immunotherapy. Bacillus Calmette-Guerin (BCG) is used widely in human vaccines. Furthermore, it can potentially offer unique advantages for developing a safe and effective multi-vaccine vehicle. Due to these properties, the development of MUC1 based recombinant BCG (rBCG) vaccines for breast cancer immunotherapy has gained great momentum in recent years.

AREAS COVERED IN THIS REVIEW

Our aim is to discuss the recent progress in MUC1-based breast cancer immunotherapy and to highlight the advantages of MUC1-based rBCG vaccines as the new breast cancer vaccines.

WHAT THE READER WILL GAIN

Several promising MUC1-based rBCG vaccines have been shown to induce MUC1-specific antitumor immune responses in pre-clinical studies. This review updates and evaluates this very important and rapidly developing field, and provides a critical perspective and information source for its potential clinical applications.

TAKE HOME MESSAGE

MUC1-based rBCG vaccines have been shown to elicit an effective anti-tumor immune response in vivo demonstrating its potential utility in breast cancer treatment.

Analysis of a cholera toxin B subunit (CTB) and human mucin 1 (MUC1) conjugate protein in a MUC1-tolerant mouse model

Since epithelial mucin 1 (MUC1) is associated with several adenocarcinomas at the mucosal sites, it is pertinent to test the efficacy of a mucosally targeted vaccine formulation. The B subunit of the Vibrio cholerae cholera toxin (CTB) has great potential to act as a mucosal carrier for subunit vaccines. In the present study we evaluated whether a MUC1 tandem repeat (TR) peptide chemically linked to CTB would break self-antigen tolerance in the transgenic MUC1-tolerant mouse model (MUC1.Tg) through oral or parenteral immunizations. We report that oral immunization with the CTB-MUC1 conjugate along with mucosal adjuvant, unmethylated CpG oligodeoxynucleotide (ODN) and interleukin-12 (IL-12) did not break self-antigen tolerance in MUC1.Tg mice, but induced a strong humoral response in wild-type C57BL/6 mice. However, self-antigen tolerance in the MUC1.Tg mouse model was broken after parenteral immunizations with different doses of the CTB-MUC1 conjugate protein and with the adjuvant CpG ODN co-delivered with CTB-MUC1. Importantly, mice immunized systemically with CpG ODN alone and with CTB-MUC1 exhibited decreased tumor burden when challenged with a mammary gland tumor cell line that expresses human MUC1.

Therapeutic cancer vaccines in prostate cancer: the paradox of improved survival without changes in time to progression

Therapeutic cancer vaccines represent a new class of agents in the treatment of cancer. Sipuleucel-T is an antigen-presenting cell-based vaccine that recently demonstrated a significant 4.8-month improvement in overall survival in advanced prostate cancer patients and was well tolerated. The findings of that study have been met with skepticism, primarily because the agent did not change initial disease progression and yet led to longer survival. Although the commonly accepted treatment paradigm suggests that treatments should initially decrease tumor volume, perhaps vaccines work differently. Vaccines may induce delayed responses not seen in the first few months of therapy or they may initiate a dynamic immune response that ultimately slows the tumor growth rate, resulting in longer survival. Subsequent therapies may also combine with the induced immune response, resulting in a combination that is more effective than conventional treatments alone. Also, other treatments may alter tumor-associated antigen expression, enhancing the immune response. Future trials are currently planned to investigate these hypotheses; however, the results of the sipuleucel-T vaccine in prostate cancer should not be dismissed. Results with another vaccine in prostate cancer are similar, perhaps suggesting a class effect. In a broader context, clinicians may need to reconsider how they measure success. Several agents have been approved that produce superior disease progression results, but do not affect overall survival. Given the toxicity and costs of cancer therapies, perhaps studies should put more weight on long-term survival endpoints than on short-term endpoints that may be less consequential.

Purification of clinical-grade recombinant HSP65-MUCI fusion protein

HSP65-MUCI is a fusion protein between BCG (Bacille Calmette-Guerin)-derived HSP65 (heat-shock protein 65) and human MUCI (mucin I) VNTR (variable number of tandem repeats)-domain peptides that has shown antitumour efficacy. China's Food and Drug Administration has recently approved a Phase I clinical trial using HSP65-MUCI for the treatment of MUCI-positive breast cancer. In order to produce sufficient quantities of clinical-grade HSP65-MUCI, we established a pilot-scale purification scheme comprising two steps of column chromatography: HIC (hydrophobic-interaction chromatography) and IEX (ion-exchange chromatography). The pH values of the buffers used in homogenization and HIC were adjusted to pH 9.0 to maintain protein stability and prevent protein degradation. Using this manufacturing process, we obtained clinical-grade HSP65-MUCI with a yield of 400 mg per 70 g of wet cell pellet and >96% purity.

Therapeutic vaccines in metastatic castration-resistant prostate cancer: principles in clinical trial design

Although docetaxel was approved for the treatment of metastatic castration-resistant prostate cancer in 2004, additional therapies are still required. Prostate cancer is often slow-growing and expresses many tumor-associated antigens, making it a feasible target for immunotherapy. Several therapeutic cancer vaccines have been developed for prostate cancer, including antigen-presenting-cell-based, vector-based, and whole tumor cell vaccines. Initial trials demonstrated that vaccine approaches have limited toxicity. Clinical trials of targeted biologic therapies have demonstrated that patient selection is vital, and there is preliminary evidence that clinical parameters can be used to encompass metastatic prostate cancer patients who will more probably respond to vaccine treatment. In addition to appropriate patient selection, a successful clinical trial must have an appropriate primary endpoint as well. Three randomized, 'placebo'-controlled studies in metastatic castration-resistant prostate cancer have suggested a clinically significant survival advantage in spite of a lack of improvement in time to progression, implying that overall survival is the ideal endpoint for such trials. Careful examination of data from completed immunotherapy clinical trials in prostate cancer has identified appropriate patient populations and endpoints. Those principles need to be applied to future trial design to properly evaluate prostate cancer vaccines.

Increased immunogenicity of tumor-associated antigen, mucin 1, engineered to express alpha-gal epitopes: a novel approach to immunotherapy in pancreatic cancer

Mucin 1 (MUC1), a bound mucin glycoprotein, is overexpressed and aberrantly glycosylated in >80% of human ductal pancreatic carcinoma. Evidence suggests that MUC1 can be used as a tumor marker and is a potential target for immunotherapy of pancreatic cancer. However, vaccination with MUC1 peptides fails to stimulate the immune response against cancer cells because immunity toward tumor-associated antigens (TAA), including MUC1, in cancer patients is relatively weak, and the presentation of these TAAs to the immune system is poor due to their low immunogenicity. We investigated whether vaccination with immunogenetically enhanced MUC1 (by expressing alpha-gal epitopes; Galalpha1-3Galbeta1-4GlcNAc-R) can elicit effective antibody production for MUC1 itself as well as certain TAAs derived from pancreatic cancer cells and induced tumor-specific T-cell responses. We also used alpha1,3galactosyltransferase (alpha1,3GT) knockout mice that were preimmunized with pig kidney and transplanted with B16F10 melanoma cells transfected with MUC1 expression vector. Vaccination of these mice with alpha-gal MUC1 resulted in marked inhibition of tumor growth and significant improvement of overall survival time compared with mice vaccinated with MUC1 alone (P = 0.003). Furthermore, vaccination with pancreatic cancer cells expressing alpha-gal epitopes induced immune responses against not only differentiated cancer cells but also cancer stem cells. The results suggested that vaccination using cells engineered to express alpha-gal epitopes is a novel strategy for treatment of pancreatic cancer.

Antigen-specific active immunotherapy for ovarian cancer

BACKGROUND

Despite advances in chemotherapy, prognosis of ovarian cancer remains poor. Antigen-specific active immunotherapy aims to induce a tumour-antigen-specific anti-tumour immune responses as an alternative treatment for ovarian cancer.

OBJECTIVES

To assess feasibility of antigen-specific active immunotherapy for ovarian cancer. Primary outcomes are clinical efficacy and antigen-specific immunogenicity with carrier-specific immunogenicity and side-effects as secondary outcomes.

SEARCH STRATEGY

A systematic search of the Cochrane Central Register of Controlled Trials (CENTRAL) Issue 3, 2009, Cochrane Gynaecological Cancer Group Specialized Register, MEDLINE and EMBASE databases and clinicaltrials.gov was performed (1966 to July 2009). Hand searches were conducted of the proceedings of relevant annual meetings (1996 to July 2009).

SELECTION CRITERIA

Randomised controlled trials (RCTs), as well as non-randomised non-controlled studies that included patients with epithelial ovarian cancer, irrespective of stage of disease, and treated with antigen-specific active immunotherapy, irrespective of type of vaccine, antigen used, adjuvant used, route of vaccination, schedule, and reported clinical or immunological outcomes.

DATA COLLECTION AND ANALYSIS

Data extraction was performed independently by two review authors. Risk of bias was evaluated with the Delphi-list for RCTs or a selection of quality domains pivotal to the assessment of non-RCTs and deemed best applicable to the non-randomised non-controlled studies.

MAIN RESULTS

Thirty-six studies were included. Response definitions showed substantial variation between trials, which makes comparison of trial results unreliable. Information on adverse events was frequently limited. Furthermore, reports of both RCTs and non-RCTs frequently lacked information necessary to assess risk of bias. Serious biases in these trials can thus not be ruled out.The largest body of evidence is currently available for CA-125 targeted antibody therapy (15 studies: 1505 patients). Non-RCTs of this CA-125 targeted antibody therapy suggest increased survival in humoral and/or cellular responders. However, three large randomised placebo-controlled trials did not show any clinical benefit despite induction of immune responses in approximately 60% of patients.Other small studies targeting many different tumour antigens showed promising immunological results. As these strategies have not yet been tested in RCTs, no reliable inferences about clinical efficacy can be made. Given the promising immunological results, limited side effects and toxicity exploration of clinical efficacy in large well-designed RCTs may be worthwhile.

AUTHORS' CONCLUSIONS

We conclude that despite promising immunological responses no clinically effective antigen-specific active immunotherapy is yet available for ovarian cancer. Furthermore, the adoption of guidelines to ensure uniformity in trial conduct, response definitions and trial reporting is recommended to improve quality and comparability of immunotherapy trials.

Current status of mucins in the diagnosis and therapy of cancer

Mucins are the most abundant high molecular weight glycoproteins in mucus. Their nature and glycosylation content dictates the biochemical and biophysical properties of viscoelastic secretions, pointing out an important role in diverse biological functions, such as differentiation, cell adhesions, immune responses, and cell signaling. Mucins are expressed in tubular organs by specialized epithelial cells in the body. Their aberrant expression is well documented in a variety of inflammatory or malignant diseases. From a prognosis point of view, their expression and alterations in glycosylation are associated with the development and progression of malignant diseases. Therefore, mucins can be used as valuable markers to distinguish between normal and disease conditions. Indeed, this alteration in glycosylation patterns generates several epitopes in the oligosaccharide side chains that can be used as diagnostic and/or prognostic markers. Furthermore, these characteristic tumor-associated epitopes are extensively used as appropriate immunotargets of malignant epithelial cells. Therefore, in an effort to detect and treat cancer at the earliest stage possible, mucins are analyzed as potential markers of disease for diagnosis, progression, and for therapeutic purposes. In this review, we focused on the current status of the distribution of mucins in normal and pathologic conditions and their clinical use both in cancer diagnosis and therapeutics treatments.

Progression of pancreatic adenocarcinoma is significantly impeded with a combination of vaccine and COX-2 inhibition

With a 5-year survival rate of <5%, pancreatic cancer is one of the most rapidly fatal malignancies. Current protocols for the treatment of pancreas cancer are not as effective as we desire. In this study, we show that a novel Mucin-1 (MUC1)-based vaccine in combination with a cyclooxygenase-2 inhibitor (celecoxib), and low-dose chemotherapy (gemcitabine) was effective in preventing the progression of preneoplastic intraepithelial lesions to invasive pancreatic ductal adenocarcinomas. The study was conducted in an appropriate triple transgenic model of spontaneous pancreatic cancer induced by the KRAS(G12D) mutation and that expresses human MUC1 as a self molecule. The combination treatment elicited robust antitumor cellular and humoral immune responses and was associated with increased apoptosis in the tumor. The mechanism for the increased immune response was attributed to the down-regulation of circulating prostaglandin E(2) and indoleamine 2, 3,-dioxygenase enzymatic activity, as well as decreased levels of T regulatory and myeloid suppressor cells within the tumor microenvironment. The preclinical data provide the rationale to design clinical trials with a combination of MUC1-based vaccine, celecoxib, and gemcitabine for the treatment of pancreatic cancer.

Interaction of current cancer treatments and the immune system: implications for breast cancer therapeutics

Early diagnosis and treatment of breast cancer may account for the current improvement in the mortality of breast cancer. However, achieving a complete 'cure' is the holy grail of cancer medicine and, in many cases, cancer patients still succumb to their ultimate fate. There is therefore a need to devise innovative therapies to overcome this problem. To this end, many emerging therapies utilizing the immune system to eradicate the residues of disease have been described in the preclinical and clinical arenas. However, there is very little work examining the impact of immunotherapy on the existing natural immunity. The relationship between antitumor immunity, in the form of immunotherapy (either passive or active), and current strategies of treatment also needs to be explored. If we are to improve the success of cancer treatment, we must understand how current therapies interact with the immune system and with the emerging immunotherapies. For breast-cancer treatment to be successful, therapeutics should be tailored towards antitumor immunity; they should also avoid tumor-specific tolerance. The sources of information used to prepare this paper were obtained through published work on Pubmed/Medline and materials published on the US/UK governmental agencies' websites.

Clinical potential of mucins in diagnosis, prognosis, and therapy of ovarian cancer

Knowledge of mucins and their multiple roles in various normal and pathological processes has improved greatly in the past two decades. Mucins belong to a family of glycoproteins characterised by densely O-glycosylated repetitive domains and expressed by various surface epithelial cells. Altered expression of mucins is present in various diseases, including cancer. Ovarian cancer is the sixth most common cancer worldwide and the seventh leading cause of cancer-related deaths in women. The most common ovarian cancer is epithelial ovarian carcinoma, which is characterised by few early symptoms, widespread peritoneal dissemination, and ascites at advanced stages that result in poor prognosis. After diagnosis, 5 year survival is only 35-45%. Therefore, improved strategies for early diagnosis and treatment are needed. Because of the surface epithelial origin of epithelial ovarian cancer, mucins are obvious biomolecules for investigation as markers for early diagnosis and as therapeutic targets. We discuss the potential role and clinical usefulness of mucins in early diagnosis, prognosis, and treatment of ovarian cancer.