Vaccination with autologous endothelium inhibits angiogenesis and metastasis of colon cancer through autoimmunity

Vaccines targeting angiogenesis in melanoma

Angiogenesis has a significant role in metastasis and progression of melanoma. Even small tumors may be susceptible to metastasis and hence lead to a worse outcome in patients with melanoma. One of the anti-angiogenic treatment approaches that is undergoing comprehensive study is specific immunotherapy. While tumor cells are challenging targets for immunotherapy due to their genetic instability and heterogeneity, endothelial cells (ECs) are genetically stable. Therefore, vaccines targeting angiogenesis in melanoma are appropriate choices that target both tumor cells and ECs while capable of inducing strong, anti-tumor immune responses with limited toxicity. The main targets of angiogenesis are VEGFs and their receptors but other potential targets have also been investigated, especially in preclinical studies. Various types of vaccines that target angiogenesis in melanoma have been studied including DNA, peptide, protein, dendritic cell-based, and endothelial cell vaccines. This review outlines a number of target antigens that are important for potential progress in developing vaccines for targeting angiogenesis in melanoma. We also discuss different types of vaccines that have been investigated, delivery mechanisms and popular adjuvants, and suggest ways to improve future clinical outcomes.

Antigenic Essence: Upgrade of Cellular Cancer Vaccines

Simple Summary

Early cancer vaccines include whole-cell formulations, which operate on the principle that you should vaccinate with what you want to develop protection against. Such vaccines have been widely tested in various cancers and their advantages described but have not yet managed to pass clinical trials. Antigenic essence technology offers the possibility to revitalize the field of whole-cell-based vaccination, as the essence comprises the entire diversity of native cellular antigens. At the same time, the technology allows for precise control and purposeful change of essence composition as well as purification of essence from ballast cellular substances and also addresses issues of major histocompatibility complex restriction. Antigenic essence technology makes it possible to update many cellular vaccines that have already been developed, as well as to develop new ones, therefore introducing a new direction for anticancer vaccination research.

Abstract

The development of anticancer immunotherapy is characterized by several approaches, the most recognized of which include cellular vaccines, tumor-associated antigens (TAAs), neoantigens, and chimeric antigen receptor T cells (CAR-T). This paper presents antigenic essence technology as an effective means for the production of new antigen compositions for anticancer vaccination. This technology is developed via proteomics, cell culture technology, and immunological assays. In terms of vaccine development, it does not fit into any of the above-noted approaches and can be considered a new direction. Here we review the development of this technology, its main characteristics, comparison with existing approaches, and the features that distinguish it as a novel approach to anticancer vaccination. This review will also highlight the benefits of this technology over other approaches, such as the ability to control composition, optimize immunogenicity and similarity to target cells, and evade major histocompatibility complex restriction. The first antigenic essence products, presented under the SANTAVAC brand, are also described.

Combination of vasculature targeting, hypofractionated radiotherapy, and immune checkpoint inhibitor elicits potent antitumor immune response and blocks tumor progression

Background

Tumor endothelial marker 1 (TEM1) is a protein expressed in the tumor-associated endothelium and/or stroma of various types of cancer. We previously demonstrated that immunization with a plasmid-DNA vaccine targeting TEM1 reduced tumor progression in three murine cancer models. Radiation therapy (RT) is an established cancer modality used in more than 50% of patients with solid tumors. RT can induce tumor-associated vasculature injury, triggering immunogenic cell death and inhibition of the irradiated tumor and distant non-irradiated tumor growth (abscopal effect). Combination treatment of RT with TEM1 immunotherapy may complement and augment established immune checkpoint blockade.

Methods

Mice bearing bilateral subcutaneous CT26 colorectal or TC1 lung tumors were treated with a novel heterologous TEM1-based vaccine, in combination with RT, and anti-programmed death-ligand 1 (PD-L1) antibody or combinations of these therapies, tumor growth of irradiated and abscopal tumors was subsequently assessed. Analysis of tumor blood perfusion was evaluated by CD31 staining and Doppler ultrasound imaging. Immunophenotyping of peripheral and tumor-infiltrating immune cells as well as functional analysis was analyzed by flow cytometry, ELISpot assay and adoptive cell transfer (ACT) experiments.

Results

We demonstrate that addition of RT to heterologous TEM1 vaccination reduces progression of CT26 and TC1 irradiated and abscopal distant tumors as compared with either single treatment. Mechanistically, RT increased major histocompatibility complex class I molecule (MHCI) expression on endothelial cells and improved immune recognition of the endothelium by anti-TEM1 T cells with subsequent severe vascular damage as measured by reduced microvascular density and tumor blood perfusion. Heterologous TEM1 vaccine and RT combination therapy boosted tumor-associated antigen (TAA) cross-priming (ie, anti-gp70) and augmented programmed cell death protein 1 (PD-1)/PD-L1 signaling within CT26 tumor. Blocking the PD-1/PD-L1 axis in combination with dual therapy further increased the antitumor effect and gp70-specific immune responses. ACT experiments show that anti-gp70 T cells are required for the antitumor effects of the combination therapy.

Conclusion

Our findings describe novel cooperative mechanisms between heterologous TEM1 vaccination and RT, highlighting the pivotal role that TAA cross-priming plays for an effective antitumor strategy. Furthermore, we provide rationale for using heterologous TEM1 vaccination and RT as an add-on to immune checkpoint blockade as triple combination therapy into early-phase clinical trials.

Allogenic mouse cell vaccine inhibits lung cancer progression by inhibiting angiogenesis

Aim: This research investigated the therapeutic effect of an allogeneic mouse brain microvascular endothelial cell vaccine on lung cancer and further elucidated its potential anti-angiogenic mechanism. Materials & methods: The immune effect of the allogeneic bEnd.3 vaccine and DC vaccine loaded with bEnd.3 antigen on the subcutaneous transplantation of Lewis lung cancer (LLC) was assessed by ELISA, the CCK test and the CTL killing test. The mechanism was preliminarily revealed by immunohistochemistry and immunoblot analysis. Results: This study revealed that tumor volume was decreased (p < .01) and the survival was prolonged significantly (p < .05) by the bEnd.3 vaccine in subcutaneous LLC transplantation in the vaccine prevention group. In contrast, both tumor volume in the serum therapeutic group and survival of bEnd.3 vaccine were not significantly different from those of the control group (p > .05). Importantly, tumor volume and survival of the T lymphocyte therapeutic group were decreased and prolonged (p < .05). In addition, both tumor volume and survival of DC vaccine loaded with bEnd.3 in the vaccine prevention group were decreased and prolonged significantly (p < .01). Furthermore, bEnd.3 vaccine and DC vaccine loaded with bEnd.3 both produced the activity of killing bEnd.3 target cells in vitro.The reason may induce the immune mice to produce anti-VEGFR-II, anti-endoglin and anti-integrin αν antibodies to have an anti-angiogenesis function. Conclusion: The allogeneic mouse bEnd.3 cell vaccine can block angiogenesis and prevent the development of lung cancer transplantation tumors.

Low-dose docetaxel enhances the anti-tumour efficacy of a human umbilical vein endothelial cell vaccine

Our previous studies have indicated that human umbilical vein endothelial cell (HUVEC) vaccination appears to be a potentially promising anti-angiogenesis therapy, but the modest therapeutic anti-tumour efficiency limits its clinical use. This highlights the importance of identifying more potent therapeutic HUVEC vaccine strategies for clinical testing. In the present study, the immune-modulating doses of docetaxel (DOC) was combined with 1 × 10⁶ viable HUVECs as a means to enhance the therapeutic anti-tumour efficiency of the HUVEC vaccine. Our results demonstrated that 5 mg/kg DOC administrated prior to HUVEC vaccine could most effectively assist HUVEC vaccine to display a remarkable suppression of tumour growth and metastasis as wells as a prolongation of survival time in a therapeutic procedure. CD31 immunohistochemical analysis of the excised tumours confirmed a significant reduction in vessel density after treatment with the HUVEC vaccine with 5 mg/kg DOC. Additionally, an increased HUVEC-specific antibody level, activated CTLs and an elevated IFN-γ level in cultured splenocytes were revealed after treatment with HUVEC vaccine with 5 mg/kg DOC. Finally, 5 mg/kg DOC coupled with the HUVEC vaccine led to induction of significant increases in CD8⁺T cells and decrease in Tregs in the tumour microenvironment. Taken together, all the results verified that 5 mg/kg DOC could assist HUVEC vaccine to elicit strong HUVEC specific humoral and cellular responses, which could facilitate the HUVEC vaccine-mediated inhibition of cancer growth and metastasis. These findings provide the immunological rationale for the combined use of immune-modulating doses of DOC and HUVEC vaccines in patients with cancer.

SANTAVACTM: Summary of Research and Development

SANTAVAC is an antigen composition developed via proteomics and cell culture technology that is intended for the development of cancer vaccines against various solid tumors. Its mechanism of action is based on the heterogeneity of endothelial cells, the polypeptides of which are similar to the surface antigens of tumor-vessel cells, allowing targeted destruction by vaccination. While research and development work with SANTAVAC is ongoing, the existing data provide strong evidence that allogeneic SANTAVAC is an ideal candidate for the development of cancer vaccines with significant efficacy and safety. The SANTAVAC compositions described here demonstrated the ability to inhibit the growth of tumor vessel-specific endothelial cells up to 60 fold, with minimal effect on normal vasculature. Innovation, background, description of product development, and summary of nonclinical studies with SANTAVAC to date are presented in this review.

Improved Antitumor Efficacy of Combined Vaccine Based on the Induced HUVECs and DC-CT26 Against Colorectal Carcinoma

Angiogenesis is essential for the development, growth, and metastasis of solid tumors. Vaccination with viable human umbilical vein endothelial cells (HUVECs) has been used for antitumor angiogenesis. However, the limited immune response induced by HUVECs hinders their clinical application. In the present study, we found that HUVECs induced by a tumor microenvironment using the supernatant of murine CT26 colorectal cancer cells exerted a better antiangiogenic effect than HUVECs themselves. The inhibitory effect on tumor growth in the induced HUVEC group was significantly better than that of the HUVEC group, and the induced HUVEC group showed a strong inhibition in CD31-positive microvessel density in the tumor tissues. Moreover, the level of anti-induced HUVEC membrane protein antibody in mouse serum was profoundly higher in the induced HUVEC group than in the HUVEC group. Based on this, the antitumor effect of a vaccine with a combination of induced HUVECs and dendritic cell-loading CT26 antigen (DC-CT26) was evaluated. Notably, the microvessel density of tumor specimens was significantly lower in the combined vaccine group than in the control groups. Furthermore, the spleen index, the killing effect of cytotoxic T lymphocytes (CTLs), and the concentration of interferon-γ in the serum were enhanced in the combined vaccine group. Based on these results, the combined vaccine targeting both tumor angiogenesis and tumor cells may be an attractive and effective cancer immunotherapy strategy.

Assessment of in vivo anti-tumor activity of human umbilical vein endothelial cell vaccines prepared by various antigen forms

Human umbilical vein endothelial cell (HUVEC) vaccine has been proved as an effective whole-cell vaccine, but the modest therapeutic anti-tumor efficiency limits its clinical use. Various antigen forms, including paraformaldehyde-fixed HUVEC, glutaraldehyde-fixed HUVEC, HUVEC lysate and live HUVEC, have been intensively used in HUVEC vaccine preparation, however, the most effective antigen form has not yet been identified. In the present study, these four commonly used antigen forms were used to prepare vaccines named Para-Fixed-EC, Glu-Fixed-EC, Lysate-EC, and Live-EC respectively, and the anti-tumor efficacy of these four vaccines was investigated. Results showed that Live-EC exhibited the most favorable anti-tumor growth and metastasis effects among the four vaccines in both H22 hepatocellular carcinoma and Lewis lung cancer models. High titer anti-HUVEC antibodies were detected in Live-EC immunized mice sera, and the immune sera of Live-EC group could significantly inhibit HUVEC proliferation and tube formation. Moreover, T cells isolated from Live-EC immunized mice exhibited strong cytotoxicity against HUVEC cells, with an increasing IFN-γ and decreasing Treg production in Live-EC immunized mice. Finally, CD31 immunohistochemical analysis of the excised tumors verified a significant reduction in vessel density after Live-EC vaccination, which was in accordance with the anti-tumor efficiency. Taken together, all the results proved that live HUVEC was the most effective antigen form to induce robust HUVEC specific antibody and CTL responses, which could lead to the significant inhibition of tumor growth and metastasis. We hope the present findings would provide a rationale for the further optimization of HUVEC vaccine.

SANTAVAC ™: A Novel Universal Antigen Composition for Developing Cancer Vaccines

Background:

Development of a universal cancer vaccine for the prevention of all cancers has been under development for many years. Antiangiogenic cancer vaccines elicit immune responses with the potential of destroying tumor vasculature endothelial cells without affecting vasculature integrity in normal tissues. The methods used in the development of antigen compositions comprising these vaccines have been recently improved and described in this report in the context of SANTAVAC ™ development - the first cancer vaccine based on endothelial cell heterogeneity.

Methods:

The present report summarizes data related to SANTAVAC™ development, including technical key points associated with optimal SANTAVAC™ production, a description of the composition required for preparing cancer vaccines with the highest predicted efficacy and safety, and a strategy for SANTAVAC™ large-scale implementation. Patents related to SANTAVAC™ and other universal cancer vaccines are also described.

Results:

SANTAVAC ™ was shown to be the most promising antigen composition for anti-cancer vaccination, allowing for immune targeting of the tumor vasculature in experimental models with a high predicted efficacy (up to 60), where efficacy represents the fold decrease in the number of endothelial cells with a tumor-induced phenotype and directly related to predicted arrest of tumor growth.

Conclusion:

The use of SANTAVAC ™ as a universal antigenic composition may spur vaccine development activities resulting in a set of therapeutic or prophylactic vaccines against different types of solid cancers.

Dendritic cells loading autologous tumor lysate promote tumor angiogenesis

Dendritic cells (DC) have been exploited for vaccination against cancer for years. DC loading autologous tumor lysate (ATL-DC) have been assessed in ongoing clinical trials, but frequently do not meet expectation. In this study, we found that mice immunized with ATL-DC induced less protective anti-tumor effect than immunized with DC alone. The percentage of CD8+ T cells and the lysis efficiency of CTLs to auto tumor cells in ATL-DC vaccination group was less than that of DC group. Moreover, vaccination of mice with ATL-DC also promoted tumor angiogenesis by analyzing the CD31 positive microvessel density and hemoglobin content of tumor specimens. Human umbilical vein endothelial cells (HUVEC) have been proved effective in the anti-angiogenesis immunity against cancer. However, in the following research we found that the anti-tumor effect was attenuated while immunized mice with HUVEC combined with ATL-DC (HUVEC + ATL-DC). Furthermore, immunized mice with HUVEC + ATL-DC profoundly increased the tumor angiogenesis by analyzing the microvessel density and hemoglobin content of tumor specimens. These data suggest that vaccination using ATL-DC antagonized HUVEC induced anti-angiogenesis effect. Our research for the first time indicated that ATL-DC have the potential to promote the process of tumor angiogenesis in vivo. As vaccines based on DC loading autologous tumor lysate have been used in clinical, this find warned that the safety of this kind of vaccine should be taken into consideration seriously.

Bone marrow stromal cells inhibits HMGB1-mediated inflammation after stroke in type 2 diabetic rats

High-mobility group box 1 (HMGB1), a ligand of receptor for advanced glycation endproducts (RAGE), functions as a proinflammatory factor. It is mainly involved in inflammatory activation and contributes to the initiation and progression of stroke. By using a model of transient middle cerebral artery occlusion (MCAo) in type 2 diabetic rats, we investigated the changes of pro-inflammation mediators, blood-brain barrier (BBB) leakage and functional outcome after stroke. Type 2 diabetic rats did not show an increased lesion volume, but exhibited significantly increased expression of HMGB1 and RAGE, BBB leakage, as well as decreased functional outcome after stroke compared with control rats. Injection of bone marrow stromal cells (BMSCs) into type 2 diabetic rats significantly reduced the expression of HMGB1 and RAGE, attenuated BBB leakage, and improved functional outcome after stroke. BMSCs-treated type 2 diabetic rats inhibited inflammation and improved functional outcome after stroke. Furthermore, in vitro data support the hypothesis that BMSCs-induced reduction of HMGB1 and RAGE in T2DM-MCAo rats contributed to attenuated inflammatory response in the ischemic brain, which may lead to the beneficial effects of BMSCs treatment. Further investigation of BMSCs treatment in type 2 diabetic stroke is warranted.

Insight to drug delivery aspects for colorectal cancer

Colorectal cancer (CRC) is the third most common cancer diagnosed worldwide in human beings. Surgery, chemotherapy, radiotherapy and targeted therapies are the conventional four approaches which are currently used for the treatment of CRC. The site specific delivery of chemotherapeutics to their site of action would increase effectiveness with reducing side effects. Targeted oral drug delivery systems based on polysaccharides are being investigated to target and deliver chemotherapeutic and chemopreventive agents directly to colon and rectum. Site-specific drug delivery to colon increases its concentration at the target site, and thus requires a lower dose and hence abridged side effects. Some novel therapies are also briefly discussed in article such as receptor (epidermal growth factor receptor, folate receptor, wheat germ agglutinin, VEGF receptor, hyaluronic acid receptor) based targeting therapy; colon targeted proapoptotic anticancer drug delivery system, gene therapy. Even though good treatment options are available for CRC, the ultimate therapeutic approach is to avert the incidence of CRC. It was also found that CRCs could be prevented by diet and nutrition such as calcium, vitamin D, curcumin, quercetin and fish oil supplements. Immunotherapy and vaccination are used nowadays which are showing better results against CRC.

Design of universal cancer vaccines using natural tumor vessel-specific antigens (SANTAVAC)

Vaccination against endothelial cells (ECs) lining the tumor vasculature represents one of the most attractive potential cancer immunotherapy options due to its ability to prevent solid tumor growth. Using this approach, target antigens can be derived from ECs and used to develop a universal cancer vaccine. Unfortunately, direct immunization with EC preparations can elicit autoimmune vasculitis in normal tissues. Recently, tumor-induced changes to the human EC surface were described that provided a basis for designing efficient EC-based vaccines capable of eliciting immune responses that targeted the tumor endothelium directly. This review examines these data from the perspective of designing EC-based cancer vaccines for the treatment of all solid tumors, including the antigen composition of vaccine formulations, the selection ECs for antigen derivation, the production and control of antigens, and the method for estimating vaccine efficacy and safety. As the vaccine preparation requires a specifically derived set of natural cell surface antigens, a new vaccine preparation concept was formulated. Antigen compositions prepared according to this concept were named SANTAVAC (Set of All Natural Target Antigens for Vaccination Against Cancer).

Cancer anti-angiogenesis vaccines: Is the tumor vasculature antigenically unique?

Angiogenesis is essential for the growth and metastasis of solid tumors. The tumor endothelium exists in a state of chronic activation and proliferation, fueled by the tumor milieu where angiogenic mediators are aberrantly over-expressed. Uncontrolled tumor growth, immune evasion, and therapeutic resistance are all driven by the dysregulated and constitutive angiogenesis occurring in the vasculature. Accordingly, great efforts have been dedicated toward identifying molecular signatures of this pathological angiogenesis in order to devise selective tumor endothelium targeting therapies while minimizing potential autoimmunity against physiologically normal endothelium. Vaccination with angiogenic antigens to generate cellular and/or humoral immunity against the tumor endothelium has proven to be a promising strategy for inhibiting or normalizing tumor angiogenesis and reducing cancer growth. Here we review tumor endothelium vaccines developed to date including active immunization strategies using specific tumor endothelium-associated antigens and whole endothelial cell-based vaccines designed to elicit immune responses against diverse target antigens. Among the novel therapeutic options, we describe a placenta-derived endothelial cell vaccine, ValloVax™, a polyvalent vaccine that is antigenically similar to proliferating tumor endothelium and is supported by pre-clinical studies to be safe and efficacious against several tumor types.

Targeting the tumor vasculature to enhance T cell activity

T cells play a critical role in tumor immune surveillance as evidenced by extensive mouse-tumor model studies as well as encouraging patient responses to adoptive T cell therapies and dendritic cell vaccines. It is well established that the interplay of tumor cells with their local cellular environment can trigger events that are immunoinhibitory to T cells. More recently it is emerging that the tumor vasculature itself constitutes an important barrier to T cells. Endothelial cells lining the vessels can suppress T cell activity, target them for destruction, and block them from gaining entry into the tumor in the first place through the deregulation of adhesion molecules. Here we review approaches to break this tumor endothelial barrier and enhance T cell activity.

Vaccination approach to anti-angiogenic treatment of cancer

Improvement of patient survival by anti-angiogenic therapy has proven limited. A vaccination approach inducing an immune response against the tumor vasculature combines the benefits of immunotherapy and anti-angiogenesis, and may overcome the limitations of current anti-angiogenic drugs. Strategies to use whole endothelial cell vaccines and DNA- or protein vaccines against key players in the VEGF signaling axis, as well as specific markers of tumor endothelial cells, have been tested in preclinical studies. Current clinical trials are now testing the promise of this specific anti-cancer vaccination approach. This review will highlight the state-of-the-art in this exciting field of cancer research.

Tumor endothelial marker 1-specific DNA vaccination targets tumor vasculature

Tumor endothelial marker 1 (TEM1; also known as endosialin or CD248) is a protein found on tumor vasculature and in tumor stroma. Here, we tested whether TEM1 has potential as a therapeutic target for cancer immunotherapy by immunizing immunocompetent mice with Tem1 cDNA fused to the minimal domain of the C fragment of tetanus toxoid (referred to herein as Tem1-TT vaccine). Tem1-TT vaccination elicited CD8+ and/or CD4+ T cell responses against immunodominant TEM1 protein sequences. Prophylactic immunization of animals with Tem1-TT prevented or delayed tumor formation in several murine tumor models. Therapeutic vaccination of tumor-bearing mice reduced tumor vascularity, increased infiltration of CD3+ T cells into the tumor, and controlled progression of established tumors. Tem1-TT vaccination also elicited CD8+ cytotoxic T cell responses against murine tumor-specific antigens. Effective Tem1-TT vaccination did not affect angiogenesis-dependent physiological processes, including wound healing and reproduction. Based on these data and the widespread expression of TEM1 on the vasculature of different tumor types, we conclude that targeting TEM1 has therapeutic potential in cancer immunotherapy.

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.

Glioma immunotherapy with combined autologous tumor cell and endothelial cell vaccine in vivo

Combined vaccines containing GL261 murine glioma cells and F-2 murine endothelial cells fixed with glutaraldehyde-phosphate buffered saline were injected into the intradermal tissue of the tail base of C57BL/6 mice. After the vaccination, GL261 cells were injected subcutaneously into the left flank of the mice. Vaccination with fixed F-2 cells induced the development of relatively high amounts of interferon-gamma-releasing cells after in vitro re-stimulation with vascular endothelial growth factor-receptor 2 peptide. Tumor growth was inhibited after preventive use of the combined vaccine, prepared from GL261 and F-2 cells. Tumor specimens obtained from the combined vaccine group in a therapeutic experiment showed significantly decreased vessel count. Glioma immunotherapy with a combined vaccine prepared from tumor cells and endothelial cells might represent a new clinical strategy, as such combinations may theoretically affect both high-grade glioma cells and their environment.

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.

Cancer microenvironment and cancer vaccine

The cancer microenvironment is constituted of non-transformed host stromal cells such as endothelial cells, fibroblasts, various immune cells, and a complex extra-cellular matrix secreted by both the normal and neoplastic cells embedded in it. The importance of the microenvironment and its potential in cancer therapy is just being established. Among modalities that target the microenvironment, cancer vaccine is a unique strategy which is aimed to elicit specific immunity against components in the microenvironment. Most, if not all, components can be targeted by the vaccines. The most extensively studied are the endothelial cells, fibroblasts and macrophages as well as ECM. Vaccines are in development for each of them. All the vaccines were proved to be effective at providing protective or therapeutic anti-tumor effects in the pre-clinical models. A few of them have been tested in the clinical trials. The mechanisms of the vaccines were mainly related to the cellular immune response such as CD8+ cytotoxic T cells, and in some instances CD4+ Th cells were involved as well. The present review also discussed the hurdles associated with the microenvironment-based vaccines such as the selection of suitable patients with appropriate biomarkers. With the rapid increase of our knowledge in the cancer microenvironment, the proof-of-concept of microenvironment-based cancer vaccines will surely expand our armamentarium against cancer.

Therapeutic antitumor potential of endoglin-based DNA vaccine combined with immunomodulatory agents

Therapy targeting tumor blood vessels ought to inhibit tumor growth. However, tumors become refractory to antiangiogenic drugs. Therefore, therapeutic solutions should be sought to address cellular resistance to antiangiogenic therapy. In this regard, reversal of the proangiogenic and immunosuppressive phenotype of cancer cells, and the shift of the tumor microenvironment towards more antiangiogenic and immune-stimulating phenotype may hold some promise. In our study, we sought to validate the effects of a combination therapy aimed at reducing tumor blood vessels, coupled with the abrogation of the immunosuppressive state. To achieve this, we developed an oral DNA vaccine against endoglin. This antigen was carried by an attenuated Salmonella Typhimurium and applied before or after tumor cell inoculation into immunocompetent mice. Our results show that this DNA vaccine effectively inhibited tumor growth, in both the prophylactic and therapeutic settings. It also activated both specific and nonspecific immune responses in immunized mice. Activated cytotoxic T-lymphocytes were directed specifically against endothelial and tumor cells overexpressing endoglin. The DNA vaccine inhibited angiogenesis but did not affect wound healing. In combination with interleukin-12-mediated gene therapy, or with cyclophosphamide administration, the DNA vaccine resulted in reduced microvessel density and lowered the level of Treg lymphocytes in the experimental tumors. This effectively inhibited tumor growth and prolonged survival of the treated animals. Polarization of tumor milieu, from proangiogenic and immunosuppressive, towards an immunostimulatory and antiangiogenic profile represents a promising avenue in anticancer therapy.

Vaccines targeting tumor blood vessel antigens promote CD8(+) T cell-dependent tumor eradication or dormancy in HLA-A2 transgenic mice

We have recently shown that effective cytokine gene therapy of solid tumors in HLA-A2 transgenic (HHD) mice lacking murine MHC class I molecule expression results in the generation of HLA-A2-restricted CD8(+) T effector cells selectively recognizing tumor blood vessel-associated pericytes and/or vascular endothelial cells. Using an HHD model in which HLA-A2(neg) tumor (MC38 colon carcinoma or B16 melanoma) cells are not recognized by the CD8(+) T cell repertoire, we now show that vaccines on the basis of tumor-associated blood vessel Ags (TBVA) elicit protective Tc1-dependent immunity capable of mediating tumor regression or extending overall survival. Vaccine efficacy was not observed if (HLA-A2(neg)) wild-type C57BL/6 mice were instead used as recipient animals. In the HHD model, effective vaccination resulted in profound infiltration of tumor lesions by CD8(+) (but not CD4(+)) T cells, in a coordinate reduction of CD31(+) blood vessels in the tumor microenvironment, and in the "spreading" of CD8(+) T cell responses to alternate TBVA that were not intrinsic to the vaccine. Protective Tc1-mediated immunity was durable and directly recognized pericytes and/or vascular endothelial cells flow-sorted from tumor tissue but not from tumor-uninvolved normal kidneys harvested from these same animals. Strikingly, the depletion of CD8(+), but not CD4(+), T cells at late time points after effective therapy frequently resulted in the recurrence of disease at the site of the regressed primary lesion. This suggests that the vaccine-induced anti-TBVA T cell repertoire can mediate the clinically preferred outcomes of either effectively eradicating tumors or policing a state of (occult) tumor dormancy.

Cytotoxic T cells - stroma interactions

The tumor microenvironment is a complex system playing an important role in tumor development and progression. Besides tumor cells, the tumor microenvironment harbours a variety of host-derived cells, such as endothelial cells, fibroblasts, innate and adaptive immune cells, as well as extracellular matrix (ECM) fibers, cytokines, and other mediators. This review discusses the potential role of hypoxia and endothelial cells within tumor microenvironment and emphasizes their interaction with antigen specific killer cells.

Vaccines targeting the neovasculature of tumors

Angiogenesis has a critical role in physiologic and disease processes. For the growth of tumors, angiogenesis must occur to carry sufficient nutrients to the tumor. In addition to growth, development of new blood vessels is necessary for invasion and metastases of the tumor. A number of strategies have been developed to inhibit tumor angiogenesis and further understanding of the interplay between tumors and angiogenesis should allow new approaches and advances in angiogenic therapy. One such promising angiogenic approach is to target and inhibit angiogenesis with vaccines. This review will discuss recent advances and future prospects in vaccines targeting aberrant angiogenesis of tumors. The strategies utilized by investigators have included whole endothelial cell vaccines as well as vaccines with defined targets on endothelial cells and pericytes of the developing tumor endothelium. To date, several promising anti-angiogenic vaccine strategies have demonstrated marked inhibition of tumor growth in pre-clinical trials with some showing no observed interference with physiologic angiogenic processes such as wound healing and fertility.

Intratumoral IL-12 gene therapy results in the crosspriming of Tc1 cells reactive against tumor-associated stromal antigens

HLA-A2 transgenic mice bearing established HLA-A2(neg) B16 melanomas were effectively treated by intratumoral (i.t.) injection of syngeneic dendritic cells (DCs) transduced to express high levels of interleukin (IL)-12, resulting in CD8(+) T cell-dependent antitumor protection. In this model, HLA-A2-restricted CD8(+) T cells do not directly recognize tumor cells and therapeutic benefit was associated with the crosspriming of HLA-A2-restricted type-1 CD8(+) T cells reactive against antigens expressed by stromal cells [i.e., pericytes and vascular endothelial cells (VEC)]. IL-12 gene therapy-induced CD8(+) T cells directly recognized HLA-A2(+) pericytes and VEC flow-sorted from B16 tumor lesions based on interferon (IFN)-γ secretion and translocation of the lytic granule-associated molecule CD107 to the T cell surface after coculture with these target cells. In contrast, these CD8(+) T effector cells failed to recognize pericytes/VEC isolated from the kidneys of tumor-bearing HHD mice. The tumor-associated stromal antigen (TASA)-derived peptides studied are evolutionarily conserved and could be recognized by CD8(+) T cells harvested from the blood of HLA-A2(+) normal donors or melanoma patients after in vitro stimulation. These TASA and their derivative peptides may prove useful in vaccine formulations against solid cancers, as well as, in the immune monitoring of HLA-A2(+) cancer patients receiving therapeutic interventions, such as IL-12 gene therapy.

Cellular cancer vaccines: an update on the development of vaccines generated from cell surface antigens

A recent advance in anti-cancer therapies has been the use of cancer cells to develop vaccines. However, immunization with cancer cell-based vaccines has not resulted in significant long-term therapeutic benefits. A possible reason for this is that while cancer cells provide surface antigens that are targets for a desired immune response, they also contain a high abundance of housekeeping proteins, carbohydrates, nucleic acids, lipids, and other intracellular contents that are ubiquitous in all mammalian cells. These ubiquitous molecules are not the intended targets of this therapy approach, and thus, the immune response generated is not sufficient to eliminate the cancer cells present. In this review, a discussion of the cell surface of cancer cells is presented in relation to the goals of improving antigen composition of cancer cell-based vaccines. Strategies to enrich vaccines for cancer-specific antigens are also discussed.

Catechin inhibits adhesion and migration of peripheral blood B cells by blocking CD11b

CONTEXT

Previously, we demonstrated that CD11b is expressed on peripheral blood memory B cells, and it plays an important role in the migration of B cells. And epigallocatechin gallate (EGCG), a bioactive component of green tea, by binding to CD11b, expressed on CD8(+) cytotoxic T cells, inhibited their migratory ability, one possible mechanism of the antiallergic activity of EGCG.

OBJECTIVE

Here, we investigated whether EGCG also affected CD11b expressed on B cells, similar to cytotoxic T cells.

MATERIALS AND METHODS

Isolated peripheral blood CD19(+) B cells were treated with EGCG and the change in the expression of CD11b was analyzed using flow cytometry. The effects of EGCG on the ability of B cells to adhere to and to transmigrate through the endothelial cell layer were evaluated using the transwell assay.

RESULTS

EGCG significantly suppressed the apparent expression of CD11b on B cells, in the flow-cytometric analysis, and this apparent suppression was speculated to be dependent on the competitive binding of EGCG to CD11b. EGCG also significantly suppressed CD11b-mediated migration and adhesion of B cells to endothelial cells.

DISCUSSION AND CONCLUSION

EGCG has a strong suppressive activity on the adhesive and migratory abilities of peripheral blood B cells. This suppressive activity was mediated by the binding of EGCG to CD11b on B cells, and the consequent suppression of B-cell extravasation to the extravascular space. Because B cell plays an important role in the humoral immunity, EGCG could be a promising drug for the prevention and/or treatment of allergic and/or autoimmune diseases.

The inhibition of autophagy potentiates anti-angiogenic effects of sulforaphane by inducing apoptosis

BACKGROUND

Sulforaphane (SUL), a kind of isothiocyanate, has recently been focused due to its strong pro-apoptotic effect on cancer cells as well as tumor vascular endothelial cells (ECs). And recently, we demonstrated the induction of autophagy by colon cancer cells as a protective mechanism against SUL. In the present study, we aimed to investigate the possible role of autophagy induction by ECs as a defense mechanism against SUL.

METHODS

Human umbilical vein endothelial cells (HUVECs) were used as the in vitro model of angiogenic ECs. The induction of autophagy was evaluated by the detection of acidic vesicular organelles (AVOs) by flow-cytometry, after the staining with acridine orange, as well as the detection of light chain 3(LC3) by Western blot. Finally, the functional implication of autophagy inhibition and SUL treatment in ECs was investigated by their ability to form vascular-like structures on Matrigel.

RESULTS

Treatment of HUVECs with relatively low concentrations of SUL for 16 h resulted in the evident formation of AVOs and the recruitment of LC3 to autophagosomes, the pathognomonic features of autophagy. Co-treatment of cells with the specific autophagy inhibitor (3-methyladenine) potentiated the proapoptotic effect of SUL. And inhibition of autophagy potentiated the inhibitory effect of SUL on the ability of ECs to form capillary-like structures.

CONCLUSION

Similar to cancer cells, ECs induced autophagy in response to the pro-apoptotic agent, SUL, and the inhibition of autophagy potentiated the pro-apoptotic effect. These findings open premises for the use of autophagy inhibitors in combination with anti-angiogenic agents.

Vaccination with xenogeneic tumor endothelial proteins isolated in situ inhibits tumor angiogenesis and spontaneous metastasis

Angiogenesis is critical for tumor growth and metastasis. Tumor tissues induce the expression of angiogenesis-associated proteins on endothelial surface that can be targeted for tumor immunotherapy. In our study, the rat tumor endothelial proteins (EP) were isolated in situ via biotinylation of tumor vascular endothelial luminal surface followed by streptavidin affinity chromatography. The isolated tumor EP contained numerous up-regulated angiogenesis-associated endothelial proteins. The administration of these tumor EP as a vaccine to mice reduced the microvessel density in subcutaneous primary LLC tumors, delayed spontaneous LLC tumor metastasis and prolonged post-surgery life span. T lymphocytes from tumor EP-vaccinated mice lysed human umbilical vascular endothelial cells, but not tumor cells in vitro, in a dose-dependent manner. Furthermore, adoptive transfer of antitumor EP antibodies in vivo targeted to tumor endothelium and inhibited spontaneous LLC tumor metastasis. This study provides a successful preclinical exploration of the active immunotherapy for tumor by targeting tumor angiogenesis.

Inhibition of B16 melanoma growth and metastasis in C57BL mice by vaccination with a syngeneic endothelial cell line

Background

Key role of angiogenesis in tumor growth and metastasis based on accumulating evidence and recent progress of immunotherapy have led us to investigate vaccine therapy targeting tumor angiogenesis.

Methods

C57BL/6J mice were vaccinated with a syngeneic endothelial cell line Tpit/E by subcutaneous injection once a week. Prior to ninth vaccination, the mice were challenged with B16/F10 melanoma cells by subcutaneous inoculation on the back for the tumor growth model or by tail venous injection for the lung metastasis model. Development of subcutaneous tumor and lung metastasis was monitored by computed tomography scanning, which enabled accurate evaluation with the minimized sacrifice of mice.

Results

Vaccination with Tpit/E cells inhibited subcutaneous tumor growth and appearance of lung metastasis compared to control. Survival period was elongated in the Tpit/E vaccination in both of the two models. We also obtained hybridomas secreting specific antibodies to Tpit/E cells from a mouse vaccinated with the cells, indicating that specific immune response to the syngeneic endothelial cells was elicited.

Conclusion

These results suggest that vaccination with an autologous endothelial cell line may be effective against melanoma.

Anti-tumoral effect of active immunotherapy in C57BL/6 mice using a recombinant human VEGF protein as antigen and three chemically unrelated adjuvants

Following the clinical success of Bevacizumab, a humanized monoclonal antibody that affects the interaction between vascular endothelial growth factor (VEGF) and its receptors, blocking tumor-induced angiogenesis has become one of the most important targets for the development of new cancer therapeutic drugs and procedures. Among the latter, therapeutic vaccination using VEGF as antigen presents itself as very attractive, with the potential of generating not only a growth factor blocking antibody response but also a cellular response against tumor cells and stromal elements, which appear to be a major source of tumor VEGF. In this paper, we report the development of a protein vaccine candidate, based on a human modified VEGF antigen that is expressed at high levels in E. coli. With respect to controls, immunization experiments in C57BL/6 mice using weekly doses of this antigen and three adjuvants of different chemical natures show that time for tumor development after subcutaneous injection of Melanoma B16-F10 cells increases, tumors that develop grow slower, and overall animal survival is higher. Immunization also prevents tumor development in some mice, making them resistant to second tumor challenges. Vaccination of mice with the human modified VEGF recombinant antigen produces antibodies against the human antigen and the homologous mouse VEGF molecule. We also show that sera from immunized mice block human VEGF-induced HUVEC proliferation. Finally, a possible contribution of T cell cytotoxicity to the overall anti-tumor effect is suggested from the results of vaccination experiments where CD8+ lymphocytes were impaired using neutralizing rat antibodies.

An effective vaccine against colon cancer in mice: Use of recombinant adenovirus interleukin-12 transduced dendritic cells

AIM: To investigate the effect of a vaccine with recombinant adenovirus interleukin-12 (AdVIL-12) transduced dendritic cells (DCs) against colon cancer in mice.

METHODS: DCs and AdVIL-12 were incubated together at different time intervals and at different doses. Supernatant was collected and tested for IL-12 by enzyme-linked immunosorbent assay (ELISA). In order to determine whether tumor cell lysate-pulsed (TP) AdVIL-12/DCs enhance therapeutic potential in the established tumor model, CT26 colon tumor cells were implanted subcutaneously (s.c.) in the midflank of naïve BALB/c mice. Tumor-bearing mice were injected with a vaccination of CT26 TP AdVIL-12/DCs on d 3 and 10. As a protective colon tumor model, naïve BALB/c mice were immunized s.c. in their abdomens with CT26 TP AdVIL-12/DCs twice at seven day intervals. After the immunization on d 7, the mice were challenged with a lethal dose of CT26 tumor cells and survival times were evaluated. Subsequently, cytotoxic T lymphocyte (CTL) activity and interferon gamma (IFNγ) secretion was evaluated in the immunized mice, and assayed CTL ex vivo.

RESULTS: Murine DCs were retrovirally transduced with AdVIL-12 efficiency, and the AdVIL-12 transduced DCs secreted a high level of IL-12 (AdVIL-12/DCs, 615.27 ± 42.3 pg/mL vs DCs, 46.32 ± 7.29 pg/mL, P < 0.05). Vaccination with CT26 TP AdVIL-12/DCs could enhance anti-tumor immunity against CT26 colon tumor in murine therapeutic models (tumor volume on d 19: CT26 TP AdVIL-12/DCs 107 ± 42 mm³vs CT26 TP DCs 383 ± 65 mm³, P < 0.05) and protective models. Moreover, the CT26 TP AdVIL-12/DC vaccination enhances tumor-specific CTL activity, producing high levels of IFNγ in immunized mice. Ex vivo primed T cells with AdVIL-12/DCs were able to induce more effective CTL activity than in primed T cells with CT26 TP/DCs (E:T = 100:1, 69.49% ± 6.11% specific lysis vs 37.44% ± 4.32% specific lysis, P < 0.05).

CONCLUSION: Vaccination with recombinant AdVIL-12 transduced DC pulsed tumor cell lysate enhance anti-tumor immunity specific to colon cancer in mice.

A study of dendritic and endothelial cell interactions in colon cancer in a cell line and small mammal model

AIM

Historically, cancer therapy directly targeting tumor cells have yielded suboptimal clinical results, and therefore anti-angiogenic therapy that targets tumor cells indirectly through impairing tumor vasculature is now considered to be one of the novel approaches potentially effective against various types of cancer. In this study, we evaluated whether lysates of endothelium could be effectively pulsed in dendritic cells (DCs), to enhance their anti-tumor effects.

METHODS

For this purpose, we prepared DCs of BALB/c mouse, incubated them with lysates of autologous or xenogeneic endothelium, and tested their anti-tumor effects in two syngeneic models of colon cancer.

RESULTS

DCs pulsed with the respective endothelium lysates significantly inhibited the growth of subcutaneous tumors as well as pulmonary metastases in mice, and their anti-tumor effect was superior to that of unpulsed DCs. Immunohistopathological analysis showed significant decrease in the mean vascular density of tumors, correlating well with the extent of tumor inhibition. In vitro analysis of splenocytes isolated from immunized mice revealed an induction of cytotoxic T lymphocytes and activation of natural killer cells, with a lytic activity against activated endothelium but not tumor cells. In addition, antibodies reacting with activated endothelium, but not tumor cells, were detected in murine sera by ELISA, and their function was confirmed by complement-dependent cytotoxicity assay.

CONCLUSIONS

Our present results suggest that lysates of endothelium can be effectively pulsed in DCs and enhance their anti-tumor effects through induction of anti-angiogenesis, and therefore should have important clinical implications for adjuvant cancer therapy.

Evaluation of a xenogeneic VEGF vaccine in dogs with soft tissue sarcoma

Active immunization against pro-angiogenic growth factors or their receptors is an emerging strategy for controlling tumor growth and angiogenesis. Previous studies in rodent tumor models have indicated that immunization against xenogeneic growth factors is more likely to induce effective anti-tumor responses than immunization against the autologous growth factor. However, the effectiveness or safety of the xenogeneic vaccination approach has not been previously assessed in a clinically relevant outbred, spontaneous tumor model. Therefore, we investigated the safety and anti-tumor and anti-angiogenic effects of a xenogeneic vascular endothelial cell growth factor (VEGF) vaccine in pet dogs with spontaneous cancer. Nine dogs with soft tissue sarcoma were immunized with a recombinant human VEGF vaccine over a 16-week period. The effects of immunization on antibodies to human and canine VEGF, circulating VEGF concentrations, tumor microvessel density (MVD), and tumor growth were assessed. The xenogeneic VEGF vaccine was well-tolerated by all dogs and resulted in induction of humoral responses against both human and canine VEGF in animals that remained in the study long enough to receive multiple immunizations. Three of five multiply immunized dogs also experienced sustained decreases in circulating plasma VEGF concentrations and two dogs had a significant decrease in tumor MVD. The overall tumor response rate was 30% for all treated dogs in the study. We conclude therefore that a xenogeneic VEGF vaccine may be a safe and effective alternative means of controlling tumor growth and angiogenesis.

Vaccination with Viable Human Umbilical Vein Endothelial Cells Prevents Metastatic Tumors by Attack on Tumor Vasculature with Both Cellular and Humoral Immunity

PURPOSE

Because tumor endothelium is rarely targeted by immunity but is critically important for tumor growth, the immunity against tumor endothelium is to be developed as a novel antitumor strategy.

EXPERIMENTAL DESIGN

First, viable human umbilical vein endothelial cells (HUVEC) were immunized to C57BL/6 and BALB/c mice to evoke specific CTLs as well as antibodies against tumor endothelium. Lewis lung carcinoma or myeloma cells were subsequently inoculated to evaluate the effect on tumor growth by vaccination. Second, the effect on tumor metastasis by vaccination was studied using tumor-resected mice receiving HUVEC immunization 3 days after excision. Third, the immune sera and T lymphocytes from HUVEC-immunized mice were transferred to tumor-bearing mice and added to cultured HUVECs to investigate their antiproliferative effect.

RESULTS

Viable HUVEC immunization showed potent antitumor effects in Lewis lung carcinoma and myeloma tumor models. Both immune sera and CTL inhibited tumor growth and specifically suppressed proliferation of HUVECs. Particularly, tumors entirely disappeared on day 90 after tumor inoculation in four of six tumor-bearing mice receiving CTL therapy. In a metastatic tumor model, we found that the HUVEC vaccination prolonged life span from 30.9 to 41.5 days after tumor resection compared with PBS-treated mice without apparent side effects.

CONCLUSIONS

Vaccination with viable HUVECs evoked both humoral and cellular immunity against tumor microvasculature, and therefore significantly inhibited tumor growth and prolonged life span of tumor-resected mice. This may provide with a novel treatment for metastatic tumors. Moreover, we have established a convenient method to evoke specific CTL against tumor angiogenesis.

Induction of antitumor immunity through xenoplacental immunization

Historically cancer vaccines have yielded suboptimal clinical results. We have developed a novel strategy for eliciting antitumor immunity based upon homology between neoplastic tissue and the developing placenta. Placenta formation shares several key processes with neoplasia, namely: angiogenesis, activation of matrix metalloproteases, and active suppression of immune function. Immune responses against xenoantigens are well known to break self-tolerance. Utilizing xenogeneic placental protein extracts as a vaccine, we have successfully induced anti-tumor immunity against B16 melanoma in C57/BL6 mice, whereas control xenogeneic extracts and B16 tumor extracts where ineffective, or actually promoted tumor growth, respectively. Furthermore, dendritic cells were able to prime tumor immunity when pulsed with the placental xenoantigens. While vaccination-induced tumor regression was abolished in mice depleted of CD4 T cells, both CD4 and CD8 cells were needed to adoptively transfer immunity to naïve mice. Supporting the role of CD8 cells in controlling tumor growth are findings that only freshly isolated CD8 cells from immunized mice were capable of inducing tumor cell caspases-3 activation ex vivo. These data suggest feasibility of using xenogeneic placental preparations as a multivalent vaccine potently targeting not just tumor antigens, but processes that are essential for tumor maintenance of malignant potential.

Vaccines targeting tumour angiogenesis--a novel strategy for cancer immunotherapy

AIMS

To review the concept of tumour angiogenesis and anti-angiogenic therapy, limitations of recently used anti-angiogenic therapeutics; provide an up-to-date overview of the growing number of reports on vaccines targeting tumour angiogenesis; and finally discuss potential complications and future directions in the development of more potent and specific vaccines.

METHODS

A literature search was carried out from PubMed for indexed articles. The most important articles were analysed and discussed.

FINDINGS

The search yielded a large number of important indexed published articles that were reviewed, screened and tracked for other relevant publications. The most relevant articles, including those previously published by authors, were analysed and discussed.

CONCLUSIONS

Recently, different vaccine strategies have been reported to inhibit tumour growth and metastasis by induction of specific cellular and/or humoral immunity against angiogenesis-associated antigens in pre-clinical models, suggesting effective combination of anti-angiogenesis and cancer immunotherapy. Evaluation of tumour endothelial cells and clinical phase I study of the vaccines are recently ongoing, and should give us better insight into the possibilities of this novel strategy for cancer immunotherapy.

T cell-mediated immunotherapy of metastases: state of the art in 2005

Advances in cellular and molecular immunology have led to the development of strategies for effective augmentation of antitumour immune responses in cancer patients. This review focuses on the manipulation of T cell immunity either by active specific immunotherapy (ASI) using tumour vaccines, or by adoptive immunotherapy (ADI) with immune T cells. Such therapies offer exquisite specificity of tumour recognition based on the ability of the T cell to distinguish single amino acid differences in any protein from any compartment of the tumour cell. Examples are presented of clinical survival benefits for cancer patients by postoperative ASI with a modified autologous tumour vaccine of high quality. Furthermore, clinical studies employing ADI with T cells activated and expanded ex vivo have demonstrated 'proof of principle' that tumour-specific T cells are capable of mediating anticancer activity in vivo, as measured by regression of metastatic tumours. Translation of these findings into a standardised immunotherapy is, however, not easy and will require coordination and cooperation among academic, private and federal sectors.