Pilot study of anti-angiogenic vaccine using fixed whole endothelium in patients with progressive malignancy after failure of conventional therapy

Next-generation antigen-presenting cell immune therapeutics for gliomas

Antigen presentation machinery and professional antigen-presenting cells (APCs) are fundamental for an efficacious immune response against cancers, especially in the context of T cell-centric immunotherapy. Dendritic cells (DCs), the gold standard APCs, play a crucial role in initiating and maintaining a productive antigen-specific adaptive immunity. In recent decades, ex vivo-differentiated DCs from circulating CD14+ monocytes have become the reference for APC-based immunotherapy. DCs loaded with tumor-associated antigens, synthetic peptides, or RNA activate T cells with antitumor properties. This strategy has paved the way for the development of alternative antigen-presenting vaccination strategies, such as monocytes, B cells, and artificial APCs, that have shown effective therapeutic outcomes in preclinical cancer models. The search for alternative APC platforms was initiated by the overall limited clinical impact of DC vaccines, especially in indications such as gliomas, a primary brain tumor known for resistance to any immune intervention. In this Review, we navigate the APC immune therapeutics' past, present, and future in the context of primary brain tumors.

Changing Landscape of Cancer Vaccines-Novel Proteomics Platform for New Antigen Compositions

The creation of cancer vaccines is a constant priority for research and biotechnology. Therefore, the emergence of any new technology in this field is a significant event, especially because previous technologies have not yielded results. Recently, the development of a cancer vaccine has been complemented by a new proteomics technology platform that allows the creation of antigen compositions known as antigenic essences. Antigenic essence comprises a target fraction of cellular antigens, the composition of which is precisely controlled by peptide mass spectrometry and compared to the proteomic footprint of the target cells to ensure similarity. This proteomics platform offers potential for a massive upgrade of conventional cellular cancer vaccines. Antigenic essences have the same mechanism of action, but without the disadvantages, and with notable advantages such as precise targeting of the immune response, safety, controlled composition, improved immunogenicity, addressed MHC restriction, and extended range of vaccination doses. The present paper calls attention to this novel platform, stimulates discussion of the role of antigenic essence in vaccine development, and consolidates academic science with biotech capabilities. A brief description of the platform, list of cellular cancer vaccines suitable for the upgrade, main recommendations, limitations, and legal and ethical aspects of vaccine upgrade are reported here.

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.

Current Immunotherapeutic Strategies for the Treatment of Glioblastoma

Glioblastoma (GBM) is a lethal primary brain tumor. Despite extensive effort in basic, translational, and clinical research, the treatment outcomes for patients with GBM are virtually unchanged over the past 15 years. GBM is one of the most immunologically "cold" tumors, in which cytotoxic T-cell infiltration is minimal, and myeloid infiltration predominates. This is due to the profound immunosuppressive nature of GBM, a tumor microenvironment that is metabolically challenging for immune cells, and the low mutational burden of GBMs. Together, these GBM characteristics contribute to the poor results obtained from immunotherapy. However, as indicated by an ongoing and expanding number of clinical trials, and despite the mostly disappointing results to date, immunotherapy remains a conceptually attractive approach for treating GBM. Checkpoint inhibitors, various vaccination strategies, and CAR T-cell therapy serve as some of the most investigated immunotherapeutic strategies. This review article aims to provide a general overview of the current state of glioblastoma immunotherapy. Information was compiled through a literature search conducted on PubMed and clinical trials between 1961 to 2021.

Architecture of Cancer-Associated Fibroblasts in Tumor Microenvironment: Mapping Their Origins, Heterogeneity, and Role in Cancer Therapy Resistance

The tumor stroma, a key component of the tumor microenvironment (TME), is a key determinant of response and resistance to cancer treatment. The stromal cells, extracellular matrix (ECM), and blood vessels influence cancer cell response to therapy and play key roles in tumor relapse and therapeutic outcomes. Of the stromal cells present in the TME, much attention has been given to cancer-associated fibroblasts (CAFs) as they are the most abundant and important in cancer initiation, progression, and therapy resistance. Besides releasing several factors, CAFs also synthesize the ECM, a key component of the tumor stroma. In this expert review, we examine the role of CAFs in the regulation of tumor cell behavior and reveal how CAF-derived factors and signaling influence tumor cell heterogeneity and development of novel strategies to combat cancer. Importantly, CAFs display both phenotypic and functional heterogeneity, with significant ramifications on CAF-directed therapies. Principal anti-cancer therapies targeting CAFs take the form of: (1) CAFs' ablation through use of immunotherapies, (2) re-education of CAFs to normalize the cells, (3) cellular therapies involving CAFs delivering drugs such as oncolytic adenoviruses, and (4) stromal depletion via targeting the ECM and its related signaling. The CAFs' heterogeneity could be a result of different cellular origins and the cancer-specific tumor microenvironmental effects, underscoring the need for further multiomics and biochemical studies on CAFs and the subsets. Lastly, we present recent advances in therapeutic targeting of CAFs and the success of such endeavors or their lack thereof. We recommend that to advance global public health and personalized medicine, treatments in the oncology clinic should be combinatorial in nature, strategically targeting both cancer cells and stromal cells, and their interactions.

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.

Viral therapies for glioblastoma and high-grade gliomas in adults: a systematic review

OBJECTIVE

High-grade gliomas (HGGs) inevitably recur and progress despite resection and standard chemotherapies and radiation. Viral therapies have emerged as a theoretically favorable adjuvant modality that might overcome intrinsic factors of HGGs that confer treatment resistance.

METHODS

The authors present the results of systematic searches of the MEDLINE and ClinicalTrials.gov databases that were performed for clinical trials published or registered up to July 15, 2020.

RESULTS

Fifty-one completed clinical trials were identified that made use of a virus-based therapeutic strategy to treat HGG. The two main types of viral therapies were oncolytic viruses and viral vectors for gene therapy. Among clinical trials that met inclusion criteria, 20 related to oncolytic viruses and 31 to gene therapy trials. No oncolytic viruses have progressed to phase III clinical trial testing, although there have been many promising early-phase results and no reported cases of encephalitis or death due to viral therapy. Three phase III trials in which viral gene therapy was used have been completed but have not resulted in any FDA-approved therapy. Recent efforts in this area have been focused on the delivery of suicide genes such as herpes simplex virus thymidine kinase and cytosine deaminase.

CONCLUSIONS

Decades of research efforts and an improving understanding of the immunomodulatory effects of viral therapies for gliomas are informing ongoing clinical efforts aimed at improving outcomes in patients with HGG. The available clinical data reveal varied efficacy among different virus-based treatment strategies.

The Gastrointestinal Tumor Microenvironment: An Updated Biological and Clinical Perspective

Gastrointestinal cancers are still responsible for high numbers of cancer-related deaths despite advances in therapy. Tumor-associated cells play a key role in tumor biology, by supporting or halting tumor development through the production of extracellular matrix, growth factors, cytokines, and extracellular vesicles. Here, we review the roles of these tumor-associated cells in the initiation, angiogenesis, immune modulation, and resistance to therapy of gastrointestinal cancers. We also discuss novel diagnostic and therapeutic strategies directed at tumor-associated cells and their potential benefits for the survival of these patients.

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.

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.

The revival of cancer vaccines - The eminent need to activate humoral immunity

In light of the increasing number of approved monoclonal antibodies for the treatment of cancer, it seems peculiar that the development of antibody inducing vaccines gets so little attention. In our view there is a tremendous opportunity in the development of cancer vaccines inducing humoral immune responses, involving a couple of major advantages. Firstly, the effectivity of a polyclonal antibody response is expected to exceed the one of monoclonal antibodies. This is supported by preclinical data that show pronounced anti-tumor responses and early clinical trials in which benefit is observed in patients with advanced cancer. Secondly, vaccination strategies are expected to reduce hospital visits, resulting in enhanced quality of life. And last but not least, vaccination strategies are extremely cost effective, alleviating the socioeconomic problems of prohibitively high drug costs. To reach further clinical success, efforts should focus on target identification, optimization of vaccination strategies and adjuvant development.

Vaccination strategies for neuro-oncology

Vaccination against cancer-associated antigens has long held the promise of inducting potent antitumor immunity, targeted cytotoxicity while sparing normal tissues, and long-lasting immunologic memory that can provide surveillance against tumor recurrence. Evaluation of vaccination strategies in preclinical brain tumor models has borne out the capacity for the immune system to effectively and safely eradicate established tumors within the central nervous system. Early phase clinical trials have established the feasibility, safety, and immunogenicity of several vaccine platforms, predominantly in patients with glioblastoma. Definitive demonstration of clinical benefit awaits further study, but initial results have been encouraging. With increased understanding of the stimulatory and regulatory pathways that govern immunologic responses and the enhanced capacity to identify novel antigenic targets using genomic interrogation of tumor cells, vaccination platforms for patients with malignant brain tumors are advancing with increasing personalized complexity and integration into combinatorial treatment paradigms.

Safety of targeting tumor endothelial cell antigens

The mechanisms underlying discrimination between "self" and "non-self", a central immunological principle, require careful consideration in immune oncology therapeutics where eliciting anti-cancer immunity must be weighed against the risk of autoimmunity due to the self origin of tumors. Whole cell vaccines are one promising immunotherapeutic avenue whereby a myriad of tumor antigens are introduced in an immunogenic context with the aim of eliciting tumor rejection. Despite the possibility collateral damage to healthy tissues, cancer immunotherapy can be designed such that off target autoimmunity remains limited in scope and severity or completely non-existent. Here we provide an immunological basis for reconciling the safety of cancer vaccines, focusing on tumor endothelial cell vaccines, by discussing the following topics: (a) Antigenic differences between neoplastic and healthy tissues that can be leveraged in cancer vaccine design; (b) The layers of tolerance that control T cell responses directed against antigens expressed in healthy tissues and tumors; and, (c) The hierarchy of antigenic epitope selection and display in response to whole cell vaccines, and how antigen processing and presentation can afford a degree of selectivity against tumors. We conclude with an example of early clinical data utilizing ValloVax™, an immunogenic placental endothelial cell vaccine that is being advanced to target the tumor endothelium of diverse cancers, and we report on the safety and efficacy of ValloVax™ for inducing immunity against tumor endothelial antigens.

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.

Fusion with human lung cancer cells elongates the life span of human umbilical endothelial cells and enhances the anti-tumor immunity

PURPOSE

Human umbilical endothelial cells (HUVECs) have been proved as an effective whole-cell vaccine inhibiting tumor angiogenesis. However, HUVECs divide a very limited number of passages before entering replicative senescence, which limits its application for clinical situation. Here, we fused HUVECs with human pulmonary adenocarcinoma cell line A549s and investigated the anti-tumor immunity of the hybrids against mice Lewis lung cancer.

METHODS

HUVECs were fused with A549s using polyethylene glycol and were sorted by flow cytometry. The fusion cells (HUVEC-A549s) were confirmed by testing the expression of telomerase and VE-cadherin, the senescence-associated β-galactosidase activity, and tube formation ability. HUVEC-A549s were then irradiated and injected into the C57BL/6 mice of protective, therapeutic, and metastatic models. The mechanism of the anti-tumor immunity was explored by analyzing mice sera, spleen T lymphocytes, tumor microenvironment, and histological changes.

RESULTS

HUVEC-A549s coexpressed tumor and endothelial markers and maintained the vascular function of tube forming at passage 30 without showing signs of senescence. HUVEC-A549s could induce protective and therapeutic anti-tumor activity for LL(2) model and presented stronger activity against metastasis than HUVECs. Both humoral and cellular immunity were participated in the anti-angiogenic activity, as HUVECs-neutralizing IgG and HUVECs-toxic lymphocytes were increased. Angiogenic mediators (VEGF and TGF-β) and tumor microenvironment cells MDSCs and Tregs were also diminished.

CONCLUSIONS

Our findings might provide a novel strategy for HUVECs-related immunotherapy, and this vaccine requires lower culture condition than primary HUVECs while enhancing the anti-tumor immunity.

Induction of tumor inhibitory anti-angiogenic response through immunization with interferon Gamma primed placental endothelial cells: ValloVax™

BACKGROUND

While the concept of angiogenesis blockade as a therapeutic intervention for cancer has been repeatedly demonstrated, the full promise of this approach has yet to be realized. Specifically, drugs such as VEGF-blocking antibodies or kinase inhibitors suffer from the drawbacks of resistance development, as well as off-target toxicities. Previous studies have demonstrated feasibility of specifically inducing immunity towards tumor endothelium without consequences of systemic autoimmunity in both animal models and clinical settings.

METHOD

Placenta-derived endothelial cells were isolated and pretreated with interferon gamma to enhance immunogenicity. Syngeneic mice received subcutaneous administration of B16 melanoma, 4 T1 mammary carcinoma, and Lewis Lung Carcinoma (LLC), followed by administration of control saline, control placental endothelial cells, and interferon gamma primed endothelial cells (ValloVax™). Tumor volume was quantified. An LLC metastasis model was also established and treated under similar conditions. Furthermore, a safety analysis in non-tumor bearing mice bracketing the proposed clinical dose was conducted.

RESULTS

ValloVax™ immunization led to significant reduction of tumor growth and metastasis as compared to administration of non-treated placental endothelial cells. Mitotic inactivation by formalin fixation or irradiation preserved tumor inhibitory activity. Twenty-eight day evaluation of healthy male and female mice immunized with ValloVax™ resulted in no abnormalities or organ toxicities.

CONCLUSION

Given the established rationale behind the potential therapeutic benefit of inhibiting tumor angiogenesis as a treatment for cancer, immunization against a variety of endothelial cell antigens may produce the best clinical response, enhancing efficacy and reducing the likelihood of the development of treatment resistance. These data support the clinical evaluation of irradiated ValloVax™ as an anti-angiogenic cancer vaccine.

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.

Specific active immunotherapy with a VEGF vaccine in patients with advanced solid tumors. results of the CENTAURO antigen dose escalation phase I clinical trial

CIGB-247 is a novel cancer therapeutic vaccine that uses a human VEGF variant molecule as antigen, in combination with a bacterial adjuvant. In mice, CIGB-247 has anti-tumor and anti-metastatic effects. The vaccine induces anti-VEGF blocking antibodies and a cellular response targeting tumor cells producing VEGF, and has proven to be safe in mice, rats, rabbits and non-human primates. Herein we report the results of a Phase I clinical trial (code name CENTAURO) where safety, tolerance, and immunogenicity of CIGB-247 were studied in 30 patients with advanced solid tumors, at three antigen dose levels. Individuals were subcutaneously immunized for 8 consecutive weeks with 50, 100 or 400 μg of antigen, and re-immunized on week twelve. On week sixteen, evaluations of safety, tolerance, clinical status, and immunogenicity (seroconversion for anti-VEGF IgG, serum VEGF/KDR-Fc blocking ability, and gamma-IFN ELISPOT with blood cells stimulated in vitro with mutated VEGF) were done. Surviving patients were eligible for off-trial additional 4-week re-immunizations with 400 μg of antigen. Immunogenicity and clinical status were again studied on weeks 25 and 49. Vaccination was shown to be safe at the three dose levels, with only grade 1-2 adverse events. CIGB-247 was immunogenic and higher numbers of individuals positive to the three immune response tests were seen with increasing antigen dose. Off-protocol long-term vaccination produced no additional adverse events or negative changes in immunogenicity. Eleven patients are still alive, with overall survivals ranging from 20 to 24 months. Twelve of the thirty patients exhibited objective clinical benefits, and two individuals have complete responses. Most patients with higher survivals are positive in the three immune response tests. In summary, this is the first clinical testing report of a cancer therapeutic vaccine based on a human VEGF related molecule as antigen. The CIGB-247 vaccine is safe, immunogenic, and merits further clinical development.

REGISTRATION NUMBER AND NAME OF TRIAL REGISTRY

RPCEC00000102. Cuban Public Clinical Trial Registry (WHO accepted Primary Registry). Available from: http://registroclinico.sld.cu/.

CXCL12 secreted from glioma stem cells regulates their proliferation

Emerging evidence suggests that the chemokine CXCL12 and its receptor CXCR4, which are expressed by glioma stem cells (GSCs), play an important role in tumorigenesis. To provide evidence for establishing a new therapy targeting the CXCL12/CXCR4 pathway, we investigated whether CXCL12 secreted from GSCs contributed to their proliferation and promoted angiogenesis in murine GSCs. Angiogenetic functions and proliferation of GSCs with or without CXCL12 inhibitors were evaluated in an in vitro model using tube formation assays, RT-PCR, and proliferation, as well as in an in vivo syngenic model. In endothelial culture, the morphology and gene expression of GSCs changed from stem cell-like characteristics to endothelial cell-like features. CXCL12 expression increased in endothelial cell-like GSCs. CXCL12 blockage with siRNA or shRNA markedly inhibited cell proliferation in vitro. CXCL12 knockdown with shRNA also inhibited tumor growth in vivo. On the other hand, CXCL12/CXCR4 blockage affected neither tube formation in vitro nor angiogenesis in vivo. The CXCL12 secreted from GSCs (autocrine/paracrine CXCL12) regulates their proliferation, but probably not angiogenesis.

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.

Human umbilical vein endothelial cell vaccine therapy in patients with recurrent glioblastoma

We aimed to assess the clinical efficacy of glutaraldehyde-fixed human umbilical vein endothelial cell (HUVEC) vaccine for the treatment of patients with recurrent glioblastoma. Patients of a HUVEC vaccine group received intradermal injections of 5 × 10(7) HUVEC weekly during the first month, and every 2 weeks from the second month, until progression of the disease was observed. Salvage treatment consisted of multimodal chemotherapy, radiation, including gamma-knife therapy, and/or repeated surgery, when feasible. Hazard ratios for death were calculated using a Cox model. A total of 17 patients with recurrent glioblastoma were enrolled in this study. All the patients received the initial treatment consisting of maximal safe surgical resection, followed by radiotherapy of 50-80 Gy or more, with concomitant and adjuvant chemotherapy consisting of temozolomide or nimustine (ACNU). A total of 352 vaccinations were performed for the patients of the HUVEC vaccine group (median number of vaccination = 11 doses; range 3-122 doses). The median progression-free survival and overall survival were 5.5 and 11.4 months, respectively. The median overall survival from the diagnosis was 24.3 months. The HUVEC vaccine therapy significantly prolonged the tumor doubling time and contributed to reducing the tumor growth rate. Hematological adverse reactions due to chemotherapy were recognized: one patient experienced grade III leukocytopenia and one showed grade II lymphocytopenia. Associated with the HUVEC vaccine therapy, a delayed-type hypersensitivity-like skin reaction developed at the injection site. The HUVEC vaccine therapy effectively controlled disease progression, without evident adverse effects, except for a delayed-type hypersensitivity-like skin reaction at the injection site.

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.

Antigen dose escalation study of a VEGF-based therapeutic cancer vaccine in non human primates

CIGB-247 is a cancer therapeutic, based on recombinant modified human vascular endothelial growth factor (VEGF) as antigen, in combination with the oil free adjuvant VSSP (very small sized proteoliposomes of Neisseria meningitidis outer membrane). Our previous experimental studies in mice with CIGB-247 have shown that the vaccine has both anti-tumoral and anti-metastatic activity, and produces both antibodies that block VEGF-VEGF receptor interaction, and a specific T-cell cytotoxic response against tumor cells. CIGB-247, with an antigen dose of 100 μg, has been characterized by an excellent safety profile in mice, rats, rabbits, and non human primates. In this article we extend the immunogenicity and safety studies of CIGB-247 in non human primates, scaling the antigen dose from 100 μg to 200 and 400 μg/vaccination. Our results indicate that such dose escalation did not affect animal behavior, clinical status, and blood parameters and biochemistry. Also, vaccination did not interfere with skin deep skin wound healing. Anti-VEGF IgG antibodies and specific T-cell mediated responses were documented at all three studied doses. Antigen dose apparently did not determine differences in maximum antibody titer during the 8 weekly immunization induction phase, or the subsequent increase in antibodies seen for monthly boosters delivered afterwards. Higher antigen doses had a positive influence in antibody titer maintenance, after cessation of immunizations. Boosters were important to achieve maximum antibody VEGF blocking activity, and specific T-cell responses in all individuals. Purified IgG from CIGB-247 immunized monkey sera was able to impair proliferation and formation of capillary-like structures in Matrigel, for HMEC cells in culture. Altogether, these results support the further clinical development of the CIGB-247 therapeutic cancer vaccine, and inform on the potential mechanisms involved in its effect.

Therapeutic cancer vaccines: are we there yet?

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

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.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Experimental approaches for the treatment of malignant gliomas

Malignant gliomas, which include glioblastomas and anaplastic astrocytomas, are the most common primary tumors of the brain. Over the past 30 years, the standard treatment for these tumors has evolved to include maximal safe surgical resection, radiation therapy and temozolomide chemotherapy. While the median survival of patients with glioblastomas has improved from 6 months to 14.6 months, these tumors continue to be lethal for the vast majority of patients. There has, however, been recent substantial progress in our mechanistic understanding of tumor development and growth. The translation of these genetic, epigenetic and biochemical findings into therapies that have been tested in clinical trials is the subject of this review.

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.

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.

Antiangiogenic therapy in brain tumors

Angiogenesis, the recruitment of new blood vessels, is an essential component of tumor progression. Malignant brain tumors are highly vascularized and their growth is angiogenesis-dependent. As such, inhibition of the sprouting of new capillaries from pre-existing blood vessels is one of the most promising antiglioma therapeutic approaches. Numerous classes of molecules have been implicated in regulating angiogenesis and, thus, novel agents that target and counteract angiogenesis are now being developed. The therapeutic trials of a number of angiogenesis inhibitors as antiglioma drugs are currently under intense investigation. Preliminary studies of angiogenic blockade in glioblastoma have been promising and several clinical trials are now underway to develop optimum treatment strategies for antiangiogenic agents. This review will cover state-of-the-art antiangiogenic targets for brain tumor treatment and discuss future challenges. An increased understanding of the angiogenic process, the diversity of its inducers and mediators, appropriate drug schedules and the use of these agents with other modalities may lead to radically new treatment regimens to achieve maximal efficacy.

Targeted therapy for neuro-oncology: reviewing the menu

Targeted therapy against cancer shows not only promise, but also limits. No matter how specific the target, many pathways and cell types can be affected, some unexpectedly. A tumor is heterogeneous and plastic; it can evade a targeting agent or an attack mechanism. Local regulatory factors contribute to site-specific effects. In the brain, widely disseminated tumor, including microscopic tumor; local regulatory differences and impediments to brain-wide delivery can all limit the efficacy of any single agent or approach. Provocatively, precedents for both problems and solutions are seen in the original targeted therapy, the immune response.