Cancer vaccines: between the idea and the reality

The use of signal peptide domains as vaccine candidates

Signal peptide (SP) domains have a common motif but also sequence specific features. This knowledge was mainly ignored by immunologists who considered SP as generic, short-lived, targeting sequences. Consequently, while SP-derived MHC class I, class II and HLA-E epitopes have been isolated, their use as antigen-specific vaccine candidates (VCs) was mostly neglected. Recently we demonstrated the rational of selecting entire SP domains as multi-epitope long peptide VCs based on their high T and B-cell epitope densities. This review summarizes preclinical and clinical results demonstrating the various advantages of human SP domain VCs derived from both bacterial and tumor antigens. Such vaccine design provides for a straightforward, yet unique immunotherapeutic means of generating robust, non-toxic, diversified, combined antigen-specific CD4+/CD8+ T/B-cell immunity, irrespective of patient HLA repertoire also in disease associated transporter-associated with antigen processing (TAP) deficiencies. Subsequent clinical trials will further assess the full potential of this approach.

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.

Current status of autologous breast tumor cell-based vaccines

Approximately nine out of ten breast cancer-related deaths are attributable to metastasis. Yet, less than 4% of breast cancer patients are initially diagnosed with metastatic cancer. Therefore, the majority of breast cancer-related deaths are due to recurrence and progression of non-metastatic disease. There is tremendous clinical opportunity for novel adjuvant strategies, such as immunotherapies, that have the potential to prevent progressive recurrences. In particular, autologous tumor cell-based vaccines (ATCVs) can train a patient's immune system to recognize and eliminate occult disease. ATCVs have several advantages including safety, multivalency and patient specificity. Furthermore, because lumpectomy or mastectomy is indicated for the vast majority of breast cancer patients, resected tumors offer a readily available, patient-specific source of tumor antigen. Disadvantages of ATCVs include poor immunogenicity and production inconsistencies. This review summarizes recent progress in the development of autologous breast tumor vaccines and offers insight for overcoming existing limitations.

Hydrogels and scaffolds for immunomodulation

For over two decades, immunologists and biomaterials scientists have co-existed in parallel world with the rationale of understanding the molecular profile of immune responses to vaccination, implantation, and treating incurable diseases. Much of the field of biomaterial-based immunotherapy has relied on evaluating model antigens such as chicken egg ovalbumin in mouse models but their relevance to humans has been point of much discussion. Nevertheless, such model antigens have provided important insights into the mechanisms of immune regulation and served as a proof-of-concept for plethora of biomaterial-based vaccines. After years of extensive development of numerous biomaterials for immunomodulation, it is only recently that an experimental scaffold vaccine implanted beneath the skin has begun to use the human model to study the immune responses to cancer vaccination by co-delivering patient-derived tumor lysates and immunomodulatory proteins. If successful, this scaffold vaccine will change the way we approached untreatable cancers, but more importantly, will allow a faster and more rational translation of therapeutic regimes to other cancers, chronic infections, and autoimmune diseases. Most materials reviews have focused on immunomodulatory adjuvants and micro-nano-particles. Here we provide an insight into emerging hydrogel and scaffold based immunomodulatory approaches that continue to demonstrate efficacy against immune associated diseases.

The future of glioblastoma therapy: synergism of standard of care and immunotherapy

The current standard of care for glioblastoma (GBM) is maximal surgical resection with adjuvant radiotherapy and temozolomide (TMZ). As the 5-year survival with GBM remains at a dismal <10%, novel therapies are needed. Immunotherapies such as the dendritic cell (DC) vaccine, heat shock protein vaccines, and epidermal growth factor receptor (EGFRvIII) vaccines have shown encouraging results in clinical trials, and have demonstrated synergistic effects with conventional therapeutics resulting in ongoing phase III trials. Chemoradiation has been shown to have synergistic effects when used in combination with immunotherapy. Cytotoxic ionizing radiation is known to trigger pro-inflammatory signaling cascades and immune activation secondary to cell death, which can then be exploited by immunotherapies. The future of GBM therapeutics will involve finding the place for immunotherapy in the current treatment regimen with a focus on developing strategies. Here, we review current GBM therapy and the evidence for combination of immune checkpoint inhibitors, DC and peptide vaccines with the current standard of care.

Cross-sectional and longitudinal analysis of cancer vaccination trials registered on the US Clinical Trials Database demonstrates paucity of immunological trial endpoints and decline in registration since 2008

Introduction

Cancer vaccination has been researched as a means of treating and preventing cancer, but successful translational efforts yielding clinical therapeutics have been limited. Numerous reasons have been offered in explanation, pertaining both to the vaccine formulation, and the clinical trial methodology used. This study aims to characterize the tumor vaccine clinical trial landscape quantitatively, and explore the possible validity of the offered explanations including the translational obstacles posed by the current common endpoints.

Methods

We performed a detailed cross-sectional and longitudinal analysis of tumor vaccine trials (n=955) registered in the US Clinical Trials database.

Results

The number of tumor vaccine trials initiated per annum has declined 30% since a peak in 2008. In terms of vaccine formulation, 25% of trials use tumor cell/lysate preparations; whereas, 73% of trials vaccinate subjects against defined protein/peptide antigens. Also, 68% of trials do not use vectors for antigen delivery. Both these characteristics of tumor vaccines have remained unchanged since 1996. The top five types of cancer studied are: melanoma (22.6%); cervical cancer (13.0%); breast cancer (11.3%); lung cancer (9.5%); and prostate cancer (9.4%). In addition, 86% of the trials are performed where there is established disease rather than prophylactically, of which 67% are performed exclusively in the adjuvant setting. Also, 42% of Phase II trials do not measure any survival-related endpoint, and only 23% of Phase III trials assess the immune response to vaccination.

Conclusion

The clinical trial effort in tumor vaccination is declining, necessitating a greater urgency in identifying and removing the obstacles to clinical translation. These obstacles may include: 1) vaccination against a small range of antigens; 2) naked delivery of antigen; 3) investigation of less immunogenic cancer types; and 4) investigation in the setting of established disease. In addition, the prevalence of late phase failure may be due to inadequate assessment of survival-related endpoints in Phase II trials. The clinical trial development of tumor vaccines should include mechanism-based translational endpoints, as well as the discovery of immune biomarkers with which to stratify, monitor, and prognosticate patients.

Different immunogenicity but similar antitumor efficacy of two DNA vaccines coding for an antigen secreted in different membrane vesicle-associated forms

The induction of an active immune response to control or eliminate tumours is still an unfulfilled challenge. We focused on plasmid DNA vaccines using an innovative approach whereby the antigen is expressed in association with extracellular vesicles (EVs) to facilitate antigen cross-presentation and improve induced immunity. Our two groups had independently shown previously that DNA vaccines encoding EV-associated antigens are more efficient at inducing cytotoxic T-cell responses than vaccines encoding the non-EV-associated antigen. Here, we compared our two approaches to associate the ovalbumin (OVA) antigen to EVs: (a) by fusion to the lipid-binding domain C1C2 of MFGE8(=lactadherin), which is exposed on the surface of secreted membrane vesicles; and (b) by fusion to retroviral Gag capsid protein, which is incorporated inside membrane-enclosed virus-like particles. Plasmids encoding either form of modified OVA were used as DNA-based vaccines (i.e. injected into mice to allow in vivo expression of the antigen associated to EVs). We show that both DNA vaccines induced, with similar efficiency, OVA-specific CD8(+) T cells and total IgG antibodies. By contrast, each vaccine preferentially stimulated different isotypes of immunoglobulins, and the OVA-C1C2-encoding vaccine favoured antigen-specific CD4(+) T lymphocyte induction as compared to the Gag-OVA vaccine. Nevertheless, both OVA-C1C2 and Gag-OVA vaccines efficiently prevented in vivo outgrowth of OVA-expressing tumours and reduced tumour progression when administered to tumour-bearing mice, although with variable efficacies depending on the tumour models. DNA vaccines encoding EV-associated antigens are thus promising immunotherapy tools in cancer but also potentially other diseases.

The effect of adjuvanting cancer vaccines with herpes simplex virus glycoprotein D on melanoma-driven CD8+ T cell exhaustion

Two vaccines expressing CD4(+) and CD8(+) T cell epitopes of melanoma-associated Ags (MAAs) by a chimpanzee-derived replication-defective AdC68 vector were compared in a mouse model of melanoma. In one vaccine, termed AdC68-gDMelapoly, the epitopes were expressed as a fusion protein within HSV-1 glycoprotein D (gD), which blocks immunoinhibitory signaling through the herpes virus entry mediator pathway. The other vaccine, termed AdC68-Melapoly, expressed only the MAA epitopes. AdC68-gDMelapoly induced more potent MAA-specific CD8(+) T cell responses especially to the subdominant MAA epitopes. Upon prophylactic vaccination, mice that developed CD8(+) T cell responses to the two vaccines that were comparable in magnitude showed equal protection against tumor challenge. When mice were first challenged with tumor cells and then vaccinated results differed. In animals with comparable CD8(+) T cell responses, the AdC68-gDMelapoly vaccine was more efficacious compared with the AdC68-Melapoly vaccine in delaying tumor growth. This effect was linked to reduced expression of 2B4, LAG-3, and programmed death-1 on tumor-infiltrating MAA-specific CD8(+) T cells elicited by the gD-adjuvanted vaccine, suggesting that CD8(+) T cells induced in presence of gD are less susceptible to tumor-driven exhaustion.

Polymer blend particles with defined compositions for targeting antigen to both class I and II antigen presentation pathways

Defense against many persistent and difficult-to-treat diseases requires a combination of humoral, CD4(+) , and CD8(+) T-cell responses, which necessitates targeting antigens to both class I and II antigen presentation pathways. In this study, polymer blend particles are developed by mixing two functionally unique polymers, poly(lactide-co-glycolide) (PLGA) and a pH-responsive polymer, poly(dimethylaminoethyl methacrylate-co-propylacrylic acid-co-butyl methacrylate) (DMAEMA-co-PAA-co-BMA). Polymer blend particles are shown to enable the delivery of antigens into both class I and II antigen presentation pathways in vitro. Increasing the ratio of the pH-responsive polymer in blend particles increases the degree of class I antigen presentation, while maintaining high levels of class II antigen presentation. In a mouse model, it is demonstrated that a significantly higher and sustained level of CD4(+) and CD8(+) T-cell responses, and comparable antibody responses, are elicited with polymer blend particles than PLGA particles and a conventional vaccine, Alum. The polymer blend particles offer a potential vaccine delivery platform to generate a combination of humoral and cell-mediated immune responses that insure robust and long-lasting immunity against many infectious diseases and cancers.

Activated cytotoxic lymphocytes promote tumor progression by increasing the ability of 3LL tumor cells to mediate MDSC chemoattraction via Fas signaling

The Fas/FasL system transmits intracellular apoptotic signaling, inducing cell apoptosis. However, Fas signaling also exerts non-apoptotic functions in addition to inducing tumor cell apoptosis. For example, Fas signaling induces lung cancer tumor cells to produce prostaglandin E2 (PGE2) and recruit myeloid-derived suppressor cells (MDSCs). Activated cytotoxic T lymphocytes (CTLs) induce and express high levels of FasL, but the effects of Fas activation initiated by FasL in CTLs on apoptosis-resistant tumor cells remain largely unclear. We purified activated CD8(+) T cells from OT-1 mice, evaluated the regulatory effects of Fas activation on tumor cell escape and investigated the relevant mechanisms. We found that CTLs induced tumor cells to secrete PGE2 and increase tumor cell-mediated chemoattraction of MDSCs via Fas signaling, which was favorable to tumor growth. Our results indicate that CTLs may participate in the tumor immune evasion process. To the best of our knowledge, this is a novel mechanism by which CTLs play a role in tumor escape. Our findings implicate a strategy to enhance the antitumor immune response via reduction of negative immune responses to tumors promoted by CTLs through Fas signaling.

Various ways to improve whole cancer cell vaccines

Immunotherapy based on whole cancer cell vaccines is regarded as a promising avenue for cancer treatment. However, limited efficacy in the first human clinical trials calls for more optimized whole cancer cell vaccines and better patient selection. It is suggested that whole cancer cell vaccines consist preferably of immunogenically killed autologous cancer stem cells associated with dendritic cells. Adjuvants should stimulate both immune effector cells and memory cells, which could be achieved through their correct dosage and timing of administration. There are indications that whole cancer cell vaccination is less effective in patients who are immunocompromised, who have specific genetic defects in their immune or cancer cells, as well as in patients in an advanced cancer stage. However, such patients form the bulk of enrolled patients in clinical trials, prohibiting an objective evaluation of the true potential of whole cancer cell immunotherapy. Each key point will be discussed.

Carbohydrate antigen delivery by water soluble copolymers as potential anti-cancer vaccines

Tumor associated carbohydrate antigens (TACAs) are overexpressed on tumor cells, which renders them attractive targets for anti-cancer vaccines. To overcome the poor immunogenicity of TACAs, we designed a polymer platform for antigen presentation by co-delivering TACA and helper T (Th) cell epitope on the same chain. The block copolymer was synthesized by cyanoxyl-mediated free radical polymerization followed by conjugation with a TACA Tn antigen and a mouse Th-cell peptide epitope derived from polio virus (PV) to afford the vaccine construct. The glycopolymer vaccine elicited an anti-Tn immune response with significant titers of IgG antibodies, which recognized Tn-expressing tumor cells.

Viral nanoparticles as antigen carriers: influence of shape on humoral immune responses in vivo

Rod-shaped viral nanoparticles serve as effective carriers for small molecular haptens with improved humoral immune responses in vivo.

A vision for vaccines built from fully synthetic tumor-associated antigens: from the laboratory to the clinic

Cancer cells may be distinguished from normal cells by cell surface displays of aberrant levels and types of carbohydrate domains. Accordingly, these tumor-associated carbohydrate antigens (TACAs) represent promising target structures for the design of anticancer vaccines. Over the past 20 years, our laboratory has sought to use the tools of chemical synthesis to develop TACA-based anticancer vaccine candidates. We provide herein a personal accounting of our laboratory's progress toward the long-standing goal of developing clinically viable fully synthetic carbohydrate-based anticancer vaccines.

Trial watch: Dendritic cell-based interventions for cancer therapy

Dendritic cells (DCs) occupy a privileged position at the interface between innate and adaptive immunity, orchestrating a large panel of responses to both physiological and pathological cues. In particular, whereas the presentation of antigens by immature DCs generally results in the development of immunological tolerance, mature DCs are capable of priming robust, and hence therapeutically relevant, adaptive immune responses. In line with this notion, functional defects in the DC compartment have been shown to etiologically contribute to pathological conditions including (but perhaps not limited to) infectious diseases, allergic and autoimmune disorders, graft rejection and cancer. Thus, the possibility of harnessing the elevated immunological potential of DCs for anticancer therapy has attracted considerable interest from both researchers and clinicians over the last decade. Alongside, several methods have been developed not only to isolate DCs from cancer patients, expand them, load them with tumor-associated antigens and hence generate highly immunogenic clinical grade infusion products, but also to directly target DCs in vivo. This intense experimental effort has culminated in 2010 with the approval by the US FDA of a DC-based preparation (sipuleucel-T, Provenge®) for the treatment of asymptomatic or minimally symptomatic metastatic castration-refractory prostate cancer. As an update to the latest Trial Watch dealing with this exciting field of research (October 2012), here we summarize recent advances in DC-based anticancer regimens, covering both high-impact studies that have been published during the last 13 mo and clinical trials that have been launched in the same period to assess the antineoplastic potential of this variant of cellular immunotherapy.

The relationship between KRAS gene mutations and HLA class I antigen downregulation in the metastasis of non-small cell lung cancer

OBJECTIVE

To investigate the association between v-Ki-ras2 Kirsten rat sarcoma viral oncogene homologue (KRAS) gene mutations and levels of human leucocyte antigen (HLA) class I antigen in primary lung tumours and metastatic lymph nodes of patients with non-small cell lung cancer (NSCLC).

METHODS

Patients with NSCLC undergoing tumour resection were enrolled. KRAS codon 12 mutations were analysed in normal lung and lymph node tissue, primary lung tumours and metastatic lymph nodes using polymerase chain reaction-restriction fragment length polymorphism analysis. HLA class I antigen immunostaining was examined using flow cytometry.

RESULTS

A total of 65 patients participated in the study. All normal lung tissues had positive HLA class I antigen immunostaining. The majority of primary lung tumours (56/65) and all of the metastatic lymph nodes (31/31) had downregulated HLA class I antigen immunostaining. There was a positive correlation between downregulated HLA class I antigen in primary tumours and metastatic lymph nodes. There was a negative correlation between KRAS codon 12 mutations and the level of HLA class I antigen in primary and metastatic tumours.

CONCLUSIONS

KRAS codon 12 mutations appear to be important in the downregulation of HLA class I antigen in NSCLC. Abnormal activation of the oncogenic KRAS pathway might provide a new treatment target for NSCLC.

Tumor-induced endothelial cell surface heterogeneity directly affects endothelial cell escape from a cell-mediated immune response in vitro

Immune-mediated damage to tumor vessels is a potential means of preventing solid tumor progression. Antiangiogenic cancer vaccines capable of inducing this kind of damage include formulations comprised of endothelial cell-specific antigens. Identification of antigens capable of eliciting efficient vaccination is difficult because the endothelial cell phenotype is affected by surrounding tissues, including angiogenic stimuli received from surrounding tumor cells. Therefore, phenotype endothelial cell variations (heterogeneity) were examined in the context of the development of an efficient vaccine using mass spectrometry-based cell surface profiling. This approach was applied to primary human microvascular endothelial cell (HMEC) cultures proliferated under growth stimuli provided by either normal tissues (growth supplement from human hypothalamus) or cancer cells (MCF-7, LNCap and HepG2). It was found that tumors induced pronounced, tumor type-dependent changes to HMEC surface targets that in an in vitro model of human antiangiogenic vaccination directly facilitated HMEC escape from cytotoxic T cell-mediated cell death. Furthermore, it was found that tumors influenced the HMEC phenotype unidirectionally and that HMEC imunogenicity was reciprocal to the intensity of tumor-induced changes to the HMEC surface. These findings provide data for the design of tumor-specific endothelial cell based vaccines with sufficient immunogenicity without posing a risk to the elicitation of autoimmunity if administered in vivo.

Combination of radiofrequency ablation and sequential cellular immunotherapy improves progression-free survival for patients with hepatocellular carcinoma

Hepatocellular carcinoma (HCC) recurs frequently after minimally invasive therapy. The aim of our study was to observe the efficiency and safety of the combined treatment of radiofrequency ablation (RFA) with cellular immunotherapy (CIT) for HCC patients. In our study, 62 patients with HCC who were treated with radical RFA were divided into two groups: RFA alone (32 patients) and RFA/CIT (30 patients). Autologous mononuclear cells were collected from the peripheral blood and separated by apheresis, and then induced into natural killer (NK) cells, γδT cells and cytokine-induced killer (CIK) cells. These cells were identified by flow cytometry with their specific antibodies and then were infused intravenously to RFA/CIT patients for three or six courses. The tumor recurrent status of these patients was evaluated with computed tomography or magnetic resonance imaging every 3 months after RFA. Progression-free survival (PFS), liver function, viral load and adverse effects were examined. The results implied that PFS was higher in RFA/CIT group than that in RFA group. In RFA/CIT group, six courses had better survival prognosis than three courses. Viral load of hepatitis C was decreased in two of three patients without antiviral therapy in RFA/CIT group, but was increased in RFA group. No significant adverse reaction was found in the patients with CIT. In summary, these preliminary results suggest that combination of sequential CIT with RFA for HCC patients was efficient and safe, and may be helpful in the prevention of the recurrence for the patients with HCC after RFA.

Modeling tumor response after combined administration of different immune-stimulatory agents

The aims of this work were as follows: 1) to develop a semimechanistic pharmacodynamic model describing tumor shrinkage after administration of a previously developed antitumor vaccine (CyaA-E7) in combination with CpG (a TLR9 ligand) and/or cyclophosphamide (CTX), and 2) to assess the translational capability of the model to describe tumor effects of different immune-based treatments. Population approach with NONMEM version 7.2 was used to analyze the previously published data. These data were generated by injecting 5 × 10(5) tumor cells expressing human papillomavirus (HPV)-E7 proteins into C57BL/6 mice. Large and established tumors were treated with CpG and/or CTX administered alone or in combination with CyaA-E7. Applications of the model were assessed by comparing model-based simulations with preclinical and clinical outcomes obtained from literature. CpG effects were modeled: 1) as an amplification of the immune signal triggered by the vaccine and 2) by shortening the delayed response of the vaccine. CTX effects were included through a direct decrease of the tumor-induced inhibition of vaccine efficacy over time, along with a delayed induction of tumor cell death. A pharmacodynamic model, built based on plausible biologic mechanisms known for the coadjuvants, successfully characterized tumor response in all experimental scenarios. The model developed was satisfactory applied to reproduce clinical outcomes when CpG or CTX was used in combination with different vaccines. The results found after simulation exercise indicated that the contribution of the coadjuvants to the tumor response elicited by vaccines can be predicted for other immune-based treatments.

Mesothelin virus-like particle immunization controls pancreatic cancer growth through CD8+ T cell induction and reduction in the frequency of CD4+ foxp3+ ICOS- regulatory T cells

Our previous study has shown that mesothelin (MSLN) is a potential immunotherapeutic target for pancreatic cancer. Here, we further studied the immunogenicity of chimeric murine MSLN-virus-like particles (mMSLN-VLPs), their ability to break tolerance to mMSLN, a self-antigen, and deciphered the mechanism of immune responses elicited by mMSLN-VLP immunization using a pancreatic cancer (PC) mouse model. In addition to what we have found with xenogeneic human MSLN-VLP (hMSLN-VLP), mMSLN-VLP immunization was able to break the tolerance to intrinsic MSLN and mount mMSLN-specific, cytotoxic CD8⁺ T cells which led to a significant reduction in tumor volume and prolonged survival in an orthotopic PC mouse model. Furthermore, CD4⁺foxp3⁺ regulatory T cells (Tregs) were progressively decreased in both spleen and tumor tissues following mMSLN-VLP immunization and this was at least partly due to elevated levels of IL-6 production from activated plasmocytoid dendritic cell (pDC)-like cells following mMSLN-VLP immunization. Moreover, mMSLN-VLP treatment mainly reduced the frequency of the CD4⁺foxp3⁺ICOS⁻ Treg subset. However, mMSLN-VLP induced IL-6 production also increased ICOSL expression on pDC-like cells which supported the proliferation of immunosuppressive CD4⁺foxp3⁺ICOS⁺ Treg cells. This study reveals that mMSLN-VLP immunization is capable of controlling PC progression by effectively mounting an immune response against mMSLN, a tumor self-antigen, and altering the immunosuppressive tumor microenvironment via activation of pDCs-like cells and reduction in the frequency of CD4⁺foxp3⁺ICOS⁻ Treg cells. However, combination therapies will likely need to be used in order to target residual CD4⁺foxp3⁺ICOS⁺ Treg cells.

Immunotherapy of radioresistant mammary tumors with early metastasis using molecular chaperone vaccines combined with ionizing radiation

In the current study, exposure of mammary tumor cells derived from mice transgenic for the polyomavirus middle T oncogene to ionizing radiation resulted in the generation of a tumor cell population that preferentially expressed cancer stem cell markers. In addition, these cells were more resistant to subsequent radiation treatments and appeared to acquire an enhanced capacity for dissemination to the lungs of mice. Therefore, we tested an immunotherapy approach to the treatment of local and disseminated mammary tumor cells in a murine model using a recently developed molecular chaperone-based vaccine that specifically targets the radioresistant subpopulation of tumor cells. Heat shock protein 70-peptide complexes (Hsp70.PC-F) were extracted from fusions of dendritic cells and radiation-enriched tumor cells, and the resulting chaperone vaccines were used to treat mice with pre-existing lung metastases. Immunization of mice with the Hsp70.PC-F vaccine resulted in a T cell-mediated immune response, including a significant increase in CD4 and CD8 T cell proliferation and the induction of effector T cells capable of targeting radioresistant tumor cells. Importantly, the growth of primary tumors was inhibited, and the number of tumor cells metastasizing to lung was reduced significantly by combining chaperone vaccine with radiotherapy. These results indicate that Hsp70.PC-F vaccine can induce specific immunity to radioresistant populations of mammary tumor cells and, thus, can complement radiotherapy, leading to synergistic killing.

Tailoring DNA Vaccines: Designing Strategies Against HER2-Positive Cancers

The crucial role of HER2 in epithelial transformation and its selective overexpression on cancer tissues makes it an ideal target for cancer immunotherapies such as passive immunotherapy with Trastuzumab. There are, however, a number of concerns regarding the use of monoclonal antibodies which include resistance, repeated treatments, considerable costs, and side effects that make active immunotherapies against HER2 desirable alternative approaches. The efficacy of anti-HER2 DNA vaccination has been widely demonstrated in transgenic cancer-prone mice, which recapitulate several features of human breast cancers. Nonetheless, the rational design of a cancer vaccine able to trigger a long-lasting immunity, and thus prevent tumor recurrence in patients, would require the understanding of how tolerance and immunosuppression regulate antitumor immune responses and, at the same time, the identification of the most immunogenic portions of the target protein. We herein retrace the findings that led to our most promising DNA vaccines that, by encoding human/rat chimeric forms of HER2, are able to circumvent peripheral tolerance. Preclinical data obtained with these chimeric DNA vaccines have provided the rationale for their use in an ongoing Phase I clinical trial (EudraCT 2011-001104-34).

Universal cancer vaccine: an update on the design of cancer vaccines generated from endothelial cells

Among the potential cancer immunotherapies, vaccination against antigens expressed by endothelial cells lining the tumor vasculature represents one of the most attractive options because this approach may prevent the growth of any solid tumor. Therefore, endothelial cells can be used as a source of antigens for developing a so-called "universal" cancer vaccine. Unfortunately, efficient endothelial cell-based cancer vaccines have not yet been developed because previous approaches utilized direct endothelial cell immunizations which is not effective and can result in the elicitation of autoimmune responses associated with systemic autoimmune vasculitis. Recently, the heterogeneity of the endothelial cell surface was defined using an in vitro system as a means of developing antiangiogenic cancer vaccines. This analysis demonstrated that tumors induced specific changes to the microvascular of human endothelial cell (HMEC) surface thereby providing a basis for the design of endothelial cell-based vaccines that directly target the tumor endothelium. (1) This commentary further describes HMEC heterogeneity from the perspective of designing an endothelial cell-based universal (for the treatment of all solid tumors) cancer vaccine with high immunogenicity that does not pose the risk of eliciting autoimmunity.

Boosting immunity to small tumor-associated carbohydrates with bacteriophage qβ capsids

The development of an effective immunotherapy is an attractive strategy toward cancer treatment. Tumor associated carbohydrate antigens (TACAs) are overexpressed on a variety of cancer cell surfaces, which present tempting targets for anticancer vaccine development. However, such carbohydrates are often poorly immunogenic. To overcome this challenge, we show here that the display of a very weak TACA, the monomeric Tn antigen, on bacteriophage Qβ virus-like particles elicits powerful humoral responses to the carbohydrate. The effects of adjuvants, antigen display pattern, and vaccine dose on the strength and subclasses of antibody responses were established. The local density of antigen rather than the total amount of antigen administered was found to be crucial for induction of high Tn-specific IgG titers. The ability to display antigens in an organized and high density manner is a key advantage of virus-like particles such as Qβ as vaccine carriers. Glycan microarray analysis showed that the antibodies generated were highly selective toward Tn antigens. Furthermore, Qβ elicited much higher levels of IgG antibodies than other types of virus-like particles, and the IgG antibodies produced reacted strongly with the native Tn antigens on human leukemia cells. Thus, Qβ presents a highly attractive platform for the development of carbohydrate-based anticancer vaccines.

Nanomaterials and autophagy: new insights in cancer treatment

Autophagy represents a cell’s response to stress. It is an evolutionarily conserved process with diversified roles. Indeed, it controls intracellular homeostasis by degradation and/or recycling intracellular metabolic material, supplies energy, provides nutrients, eliminates cytotoxic materials and damaged proteins and organelles. Moreover, autophagy is involved in several diseases. Recent evidences support a relationship between several classes of nanomaterials and autophagy perturbation, both induction and blockade, in many biological models. In fact, the autophagic mechanism represents a common cellular response to nanomaterials. On the other hand, the dynamic nature of autophagy in cancer biology is an intriguing approach for cancer therapeutics, since during tumour development and therapy, autophagy has been reported to trigger both an early cell survival and a late cell death. The use of nanomaterials in cancer treatment to deliver chemotherapeutic drugs and target tumours is well known. Recently, autophagy modulation mediated by nanomaterials has become an appealing notion in nanomedicine therapeutics, since it can be exploited as adjuvant in chemotherapy or in the development of cancer vaccines or as a potential anti-cancer agent. Herein, we summarize the effects of nanomaterials on autophagic processes in cancer, also considering the therapeutic outcome of synergism between nanomaterials and autophagy to improve existing cancer therapies.

Higher frequencies of GARP(+)CTLA-4(+)Foxp3(+) T regulatory cells and myeloid-derived suppressor cells in hepatocellular carcinoma patients are associated with impaired T-cell functionality

The extent to which T-cell-mediated immune surveillance is impaired in human cancer remains a question of major importance, given its potential impact on the development of generalized treatments of advanced disease where the highest degree of heterogeneity exists. Here, we report the first global analysis of immune dysfunction in patients with advanced hepatocellular carcinoma (HCC). Using multi-parameter fluorescence-activated cell sorting analysis, we quantified the cumulative frequency of regulatory T cells (Treg), exhausted CD4(+) helper T cells, and myeloid-derived suppressor cells (MDSC) to gain concurrent views on the overall level of immune dysfunction in these inoperable patients. We documented augmented numbers of Tregs, MDSC, PD-1(+)-exhausted T cells, and increased levels of immunosuppressive cytokines in patients with HCC, compared with normal controls, revealing a network of potential mechanisms of immune dysregulation in patients with HCC. In dampening T-cell-mediated antitumor immunity, we hypothesized that these processes may facilitate HCC progression and thwart the efficacy of immunotherapeutic interventions. In testing this hypothesis, we showed that combined regimens to deplete Tregs, MDSC, and PD-1(+) T cells in patients with advanced HCC restored production of granzyme B by CD8(+) T cells, reaching levels observed in normal controls and also modestly increased the number of IFN-γ producing CD4(+) T cells. These clinical findings encourage efforts to restore T-cell function in patients with advanced stage disease by highlighting combined approaches to deplete endogenous suppressor cell populations that can also expand effector T-cell populations.

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.

Materials based tumor immunotherapy vaccines

Immunotherapy is a promising approach for treating cancer. However, there are limitations inherent to current approaches which may be addressed by integrating them with biomaterial-based strategies. Material platforms have been fabricated to interact with immune cells through spatially controlled and temporally controlled delivery of immune modulators and to promote immune cell crosstalk. Particle vaccines have been developed to specifically target and deliver agents to organs, cells and subcellular compartments. These strategies have been shown to generate antigen-specific CTL responses and, in some cases, tumor regression. Therefore, collaboration between immunology and materials engineering is likely to result in the creation of strong vaccines to combat cancer in the future.

Glycodendrimers: versatile tools for nanotechnology

Combining nanotechnology with glycobiology has triggered an exponential growth of research activities in the design of novel functional bionanomaterials (glyconanotechnology). More specifically, recent synthetic advances towards the tailored and versatile design of glycosylated nanoparticles namely glyconanoparticles, considered as synthetic mimetics of natural glycoconjugates, paved the way toward diverse biomedical applications. The accessibility of a wide variety of these structured nanosystems, in terms of shapes, sizes, and organized around stable nanoparticles have readily contributed to their development and applications in nanomedicine. In this context, glycosylated gold-nanoparticles (GNPs), glycosylated quantum dots (QDs), fullerenes, single-wall natotubes (SWNTs), and self-assembled glycononanoparticles using amphiphilic glycopolymers or glycodendrimers have received considerable attention to afford powerful imaging, therapeutic, and biodiagnostic devices. This review will provide an overview of the most recent syntheses and applications of glycodendrimers in glycoscience that have permitted to deepen our understanding of multivalent carbohydrate-protein interactions. Together with synthetic breast cancer vaccines, inhibitors of bacterial adhesions to host tissues including sensitive detection devices, these novel bionanomaterials are finding extensive relevance.

Clustered carbohydrates in synthetic vaccines

Are there general rules to obtain efficient immunization against carbohydrate antigens? Thanks to technological advances in glycobiology and glycochemistry we entered a new era in which the rational design of carbohydrate vaccines has become an achievable goal. The aim of this Tutorial Review is to present the most recent accomplishments in the field of semi and fully synthetic carbohydrate vaccines against viruses, bacteria and cancer. It is also pointed out that the understanding of the chemical and biochemical processes related to immunization allows the modern chemist to rationally design carbohydrate vaccines with improved efficiency.

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.

Preventive evolutionary medicine of cancers

Evolutionary theory predicts that once an individual reaches an age of sufficiently low Darwinian fitness, (s)he will have reduced chances of keeping cancerous lesions in check. While we clearly need to better understand the emergence of precursor states and early malignancies as well as their mitigation by the microenvironment and tissue architecture, we argue that lifestyle changes and preventive therapies based in an evolutionary framework, applied to identified high-risk populations before incipient neoplasms become clinically detectable and chemoresistant lineages emerge, are currently the most reliable way to control or eliminate early tumours. Specifically, the relatively low levels of (epi)genetic heterogeneity characteristic of many if not most incipient lesions will mean a relatively limited set of possible adaptive traits and associated costs compared to more advanced cancers, and thus a more complete and predictable understanding of treatment options and outcomes. We propose a conceptual model for preventive treatments and discuss the many associated challenges.

DNA vaccination for prostate cancer, from preclinical to clinical trials - where we stand?

Development of various vaccines for prostate cancer (PCa) is becoming an active research area. PCa vaccines are perceived to have less toxicity compared with the available cytotoxic agents. While various immune-based strategies can elicit anti-tumour responses, DNA vaccines present increased efficacy, inducing both humoural and cellular immunity. This immune activation has been proven effective in animal models and initial clinical trials are encouraging. However, to validate the role of DNA vaccination in currently available PCa management paradigms, strong clinical evidence is still lacking. This article provides an overview of the basic principles of DNA vaccines and aims to provide a summary of preclinical and clinical trials outlining the benefits of this immunotherapy in the management of PCa.

Amino acid metabolism related to immune tolerance by MDSCs

Myeloid-derived suppressor cells (MDSCs) are present in most cancer patients. Due to their significant role in blocking immune responses, MDSCs are strategic obstacles to immunotherapy that require activation of the host's cell-mediated and innate immune responses. Following a brief description of the immunosuppressive MDSCs, the authors review the discovered mechanisms of amino acid metabolism that MDSCs use to suppress the activation of T cells. Given the heterogeneity of MDSCs and the variety of suppressive mechanisms employed by MDSCs, it is essential to understand which group of these cells and mechanisms are dominant.

Novel targeted agents for the treatment of advanced breast cancer

The discovery of the molecular processes involved in cancer development has led to the design of an array of targeted agents. These agents, directed to specific proteins in the machinery of cancer cells, interfere with vital cascades involved in cell invasion, metastasis, apoptosis, cell-cycle control and angiogenesis. In breast cancer, the main pathways studied and targeted by drugs are the HER2 pathway, EGFR, VEGF, PI3K/Akt/mammalian target of rapamycin (PI3K-M-Tor), IGF/IGFR, poly(ADP ribose) polymerase 1, HDAC and many others. In this review, we present the most promising studies of these new targeted therapies and novel combination of targeted therapies with cytotoxic agents for the treatment of breast cancer patients.

The sweet side of tumor immunotherapy

Carbohydrate signatures on tumor cells have functional implications in tumor growth and metastasis and constitute valuable tools in cancer diagnosis and immunotherapy. Increasing data regarding the mechanisms by which they are recognized by the immune system are facilitating the design of more efficient immunotherapeutic protocols based on cancer-associated glycan structures. Recent molecular and proteomic studies revealed that carbohydrates are recognized, not only by B cells and antibodies, but also by cells from the innate arm of immunity, as well as by T cells, and are able to induce specific T-cell immunity and cytotoxicity. In this review, we discuss and update the different strategies targeting tumor-associated carbohydrate antigens that are being evaluated for antitumor immunotherapy, an approach that will be highly relevant, especially when combined with other strategies, in the future fight against cancer.

Trial Watch: Adoptive cell transfer immunotherapy

During the last two decades, several approaches for the activation of the immune system against cancer have been developed. These include rather unselective maneuvers such as the systemic administration of immunostimulatory agents (e.g., interleukin-2) as well as targeted interventions, encompassing highly specific monoclonal antibodies, vaccines and cell-based therapies. Among the latter, adoptive cell transfer (ACT) involves the selection of autologous lymphocytes with antitumor activity, their expansion/activation ex vivo, and their reinfusion into the patient, often in the context of lymphodepleting regimens (to minimize endogenous immunosuppression). Such autologous cells can be isolated from tumor-infiltrating lymphocytes or generated by manipulating circulating lymphocytes for the expression of tumor-specific T-cell receptors. In addition, autologous lymphocytes can be genetically engineered to prolong their in vivo persistence, to boost antitumor responses and/or to minimize side effects. ACT has recently been shown to be associated with a consistent rate of durable regressions in melanoma and renal cell carcinoma patients and holds great promises in several other oncological settings. In this Trial Watch, we will briefly review the scientific rationale behind ACT and discuss the progress of recent clinical trials evaluating the safety and effectiveness of adoptive cell transfer as an anticancer therapy.

Enhancement of DNA vaccine efficacy by targeting the xenogeneic human chorionic gonadotropin, survivin and vascular endothelial growth factor receptor 2 combined tumor antigen to the major histocompatibility complex class II pathway

BACKGROUND

A number of strategies have been used to improve the efficacy of the DNA vaccine for the treatment of tumors. These strategies, ranging from activating CD4+ T cell, manipulating antigen presentation and/or processing to anti-angiogenesis, focus on one certain aspect in the functioning of the vaccine. Therefore, their combination is necessary for rational DNA vaccines design by synergizing different regimens and overcoming the limitations of each strategy.

METHODS

A DNA fragment (HSV) encoding the C terminal 37 amino acids of human chorionic gonadotropin β chain (hCGβ), 5 different HLA-restricted cytotoxic T lymphocyte epitopes from human survivin and the third and fourth extracellular domains of vascular endothelial growth factor receptor 2 (VEGFR2) was inserted into the sequence between the luminal and transmembrane domain of human lysosome-associated membrane protein-1 cDNA for the construction of a novel DNA vaccine.

RESULTS

This novel vaccine, named p-L/HSV, has a potent antitumor effect on the LL/2 lung carcinoma model in syngeneic C57BL/6 mice. The immunologic mechanism involved in the antitumor effect referred to the activation of both cellular and humoral immune response. In addition, the tumor vasculature was abrogated as observed by immunohistochemistry in p-L/HSV immunized mice. Furthermore, the immunized mice received an additional boost with p-L/HSV 6 months later and showed a strong immune recall response.

CONCLUSIONS

The present study indicates that the strategies of combining antitumor with antiangiogenesis and targeting the tumor antigen to the major histocompatibility complex class II pathway cooperate well. Such a study may shed new light on designing vaccine for cancer in the future.

Enhanced T Cell Immunity by B7-H4 Downregulation in Nonsmall-Cell Lung Cancer Cell Lines

OBJECTIVES: T cell immunity plays a critical role in host immune surveillance of tumour cell growth and metastatic spread. This study used small hairpin (sh)RNA-mediated gene silencing to target VTCN1 (B7-H4) expression in a nonsmall-cell lung cancer (NSCLC) cell line (A549) and evaluated the effects on T cell immune activity using an in vitro coculture system. METHODS: VTCN1-specific shRNA-expressing plasmid was transfected into A549 cells. Mock transfected and empty plasmid-transfected A549 cells served as controls. VTCN1 expression in A549 cells was determined by reverse transcription– polymerase chain reaction (RT—PCR) for VTCN1 mRNA and Western blotting for B7-H4 protein. Transfected A549 cells were cocultured with Jurkat cells. Jurkat cells were examined for proliferation, apoptosis, cell cycle distribution and intracellular cytokine mRNA and protein levels. RESULTS: VTCN1-specific shRNA efficiently knocked down VTCN1 mRNA and B7-H4 protein levels in A549 cells. This downregulation led to enhanced Jurkat cell proliferation, decreased apoptosis, stimulated cell cycle progression and elevated production of interferon-γ, interleukin (IL)-10 and IL-2. CONCLUSIONS: B7-H4 negatively regulates T cell-mediated antitumour immunity in NSCLC.

IL-13 receptor-directed cancer vaccines and immunotherapy

Many immunotherapy approaches including therapeutic cancer vaccines targeting specific tumor-associated antigens are at various stages of development. Although the significance of overexpression of (IL-13Rα2) in cancer is being actively investigated, we have reported that IL-13Rα2 is a novel tumor-associated antigen. The IL-13Rα2-directed cancer vaccine is one of the most promising approaches to tumor immunotherapy, because of the selective expression of IL-13Rα2 in various solid tumor types but not in normal tissues. In this article, we will summarize its present status and potential strategies to improve IL-13Rα2-directed cancer vaccines for an optimal therapy of cancer.