Enhanced antimetastatic effect of fetal liver kinase 1 extracellular domain and interferon-gamma fusion gene-modified dendritic cell vaccination

Tumor vaccines: Toward multidimensional anti-tumor therapies

For decades, immunotherapies have offered hope for patients with advanced cancer. However, they show distinct benefits and limited clinical effects. Tumor vaccines have the potential to prime tumor-antigen-specific T cells and induce broad subsets of immune responses, ultimately eradicating tumor cells. Here, we classify tumor vaccines by their anti-tumor mechanisms, which include boosting the immune system, overcoming tumor immunosuppression, and modulating tumor angiogenesis. We focus on multidimensional tumor vaccine strategies using combinations of two or three of the above mechanisms, as these are superior to single-dimensional treatments. This review offers a perspective on tumor vaccine strategies and the future role of vaccine therapies in cancer treatment.

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.

Antitumor immunity induced by VE-cadherin modified DC vaccine

Dendritic cells (DCs) are the most potent antigen-presenting cells. A strong interest has been developed in DC vaccines for cancer immunotherapy. Besides, angiogenesis is essential for tumor growth. VE-cadherin has a crucial function in various aspects of vascular biological functions. Here, we produced the full VE-cadherin gene modified DC vaccine (DC-VEC). Its antitumor immunity and chief mechanism driving antitumor effect was evaluated. Analyses were performed including test of antitumor antibody, CTL-mediated cytotoxicity experiment, vascular density, evaluation of the variation of cells and cytokines in immunoregulation. Its damage to the major organs was also evaluated. DC-VEC vaccine resulted in retarded tumor progression and prolonged survival in mice. In DC-VEC group, large amount of immunoglobulin was generated, T cells exhibited greater cytotoxicity against VE-cadherin, and tumor angiogenesis was suppressed. Besides, a decrease of VEGF-A and TGF-β1, and an increase of IL-4 and IFN-γ were observed. CD4⁺ and CD8⁺ T cells were higher, with increased IFN-γ secretion. The percentage of myeloid-derived suppressor cells and regulatory T cells decreased mildly. Also, it had no pathologic changes in major organs. DC-VEC vaccine represents a promising antitumor immunotherapy. The main mechanism is associated with its anti-angiogenesis and immunoregulation response.

Anti-metastatic effects of DNA vaccine encoding single-chain trimer composed of MHC I and vascular endothelial growth factor receptor 2 peptide

Vascular endothelial growth factor receptor 2 (VEGFR2)-mediated signaling is the key rate-limiting step in angiogenesis. VEGFR2 serves as the most important target of anti-angiogenic therapy for cancers. Single-chain trimer (SCT) comprising antigen peptide, β2-microglobulin (β2m), and major histocompatibility complex (MHC) class I heavy chain was a particularly powerful strategy involved in the increase of the potency of DNA vaccine against tumors and infections. In the present study, we constructed an SCT-encoding VEGFR2 antigen peptide [aa400-408, also known as kinase insert domain-containing receptor (KDR2)], β2m, and mouse MHC class I heavy chain H-2Db [pcDNA3.1(+)-KDR2-β2m-H-2Db, or SCT-KDR2]. The constructed SCT-KDR2 DNA was efficiently expressed in the human A293 embryonic kidney cell line. Intradermal immunization of C57BL/6 mice with SCT-KDR2 DNA was able to successfully break self-immunological tolerance and induce robust cytotoxic T‑lymphocyte (CTL) response to VEGFR2, leading to marked suppression of tumor cell‑induced angiogenesis and metastasis in murine models of B16 melanoma and 3LL Lewis lung carcinoma. Taken together, the results showed that VEGFR2-targeted SCT vaccination is an effective modality that can be utilized in anti-angiogenic active immunotherapy for various types of cancer.

Enhanced effect of soluble transforming growth factor-beta receptor II and IFN-gamma fusion protein in reversing hepatic fibrosis

Objective

To examine the in vivo anti-fibrotic effect of rat soluble transforming growth factor β receptor II (RsTβRII) and IFN-γ fusion protein (RsTβRII-IFN-γ) in rat hepatic fibrosis model.

Methods

Model rats were divided into five groups and treated i.m. for 8 weeks: 1) fibrotic model group (each rat, 100 μl of 0.9% NaCl day^-1); 2) RsTβRII-IFN-γ treatment group (each rat, 0.136 mg· day^-1); 3) IFN-γ treatment group (each rat, 7.5 MU· day^-1); 4) RsTβRII treatment group (each rat, 0.048 mg· day^-1); and 5) mixture of IFN-γ and RsTβRII treatment group (each rat, IFN-γ 7.5 MU· day^-1+ RsTβRII 0.048 mg· day^-1). After treatment, hepatic fibrogenesis was evaluated by histopathological analysis and measurement of collagen III, α-smooth muscle actin (α-SMA), TGF-β1, TGF-βRII and their mRNA.

Results

Immunohistochemistry, Western blot and real-time RT-PCR showed that RsTβRII-IFN-γ treatment significantly inhibited liver expression of collagen III, α-SMA, TGF-β1 and TGF-βRII at both protein and mRNA levels. Histopathological analysis also showed that the enhanced anti-fibrotic effects were achieved in model rats treated with RsTβRII-IFN-γ.

Conclusion

Our results confirmed that RsTβRII-IFN-γ has the enhanced effects in reversing hepatic fibrosis.

Expression and identification of immunological activities of the HIV-gp120N-human interferon gamma fusion protein

The human immunodeficiency virus type 1 (HIV-1) envelope glycoprotein gp120 is a vaccine immunogen that has been studied extensively. To enhance the immune response of cells against HIV-1 gp120, we tested the coexpression of gp120N with interferon-gamma (IFN-gamma) as an immune adjuvant. Two recombinant prokaryotic plasmids were constructed: the pET44b-HIV-1-gp120N plasmid construct carried the HIV-1 gp120N gene (pET44-gp120N), whereas the pET44b-HIV-1-gp120N-IFN-gamma plasmid construct carried a fusion gp120N-IFN-gamma gene (pET44b-gp120N-IFN-gamma). Target protein expression was achieved in E. coli BL21 (DE3) cells by chemical induction. To test the immunological activity of the proteins, mice were injected with a control, gp120N, or the fusion gp120N-IFN-gamma protein. The serum and spleen cells of the mice were collected for immunological detection. Results showed that specific T lymphocyte proliferation and the expression of the Th1-type cytokines (IL-2 and IFN-gamma) were higher in the gp120N-IFN-gamma group than the other two groups (P < 0.05). No difference was observed in the expression levels of the Th2-type cytokines (IL-4 and IL-10; P > 0.05). These results suggest that IFN-gamma plays a prominent role as an immune adjuvant when coexpressed with HIV-1 gp120N. IFN-gamma enhances the specific cell immune response of mice against HIV-1 gp120.

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.

Anti-angiogenic active immunotherapy: a new approach to cancer treatment

Tumor angiogenesis plays an important role in tumor growth, aggression and metastasis. Many molecules have been demonstrated as positive regulators of angiogenesis, including vascular endothelial growth factor (VEGF), fibroblast growth factor (FGF), epidermal growth factor (EGF), and others. In recent years, significant progress has been made in the research on anti-angiogenic strategies for tumor therapies. In this review, anti-angiogenic active immunotherapies for tumors based on vaccination with xenogeneic homologous molecules and non-xenogeneic homologous molecules are discussed.

Inhibition of angiogenesis by a Semliki Forest virus vector expressing VEGFR-2 reduces tumour growth and metastasis in mice

Inhibition of tumour angiogenesis has been shown to restrict primary tumour growth and metastatic spread. This study examines the active induction of immune responses against tumour endothelial cells following immunization with recombinant Semliki Forest virus (rSFV) particles encoding murine vascular endothelial growth factor receptor-2 (VEGFR-2). This approach was tested in two murine tumour models, CT26 colon carcinoma and 4T1 metastasizing mammary carcinoma. Tumour growth and metastatic spread were shown to be significantly inhibited in mice that were prophylactically vaccinated or therapeutically treated with rSFV particles coding for VEGFR-2. Microvessel density analysis showed that immunization with rSFV led to significant inhibition of tumour angiogenesis. Therapeutic efficacy was found to be associated with the induction of an antibody response against VEGFR-2. Co-immunization of mice with rSFV particles encoding VEGFR-2 and interleukin (IL)-12 completely abrogated both the antibody response and the antitumour effect. However, co-immunization of mice with VEGFR-2 and IL-4 encoding particles was shown both to induce higher titres of anti-VEGFR-2 antibodies and lead to enhanced survival following tumour challenge when compared to mice vaccinated with VEGFR-2 particles alone. These findings indicate that active immunization with rSFV particles coding for VEGFR-2 can break immunological tolerance and could potentially be used as part of a novel treatment for cancer.

The kinase insert domain-containing receptor is an angiogenesis-associated antigen recognized by human cytotoxic T lymphocytes

Antigen-specific cancer immunotherapy directed toward tumor-nourishing angiogenic blood vessels holds the promise of high efficacy, low toxicity, and ease of application. To evaluate whether the human angiogenic kinase insert domain-containing receptor (KDR) can serve as a target for cellular immunotherapy, 19 peptide sequences with HLA-A*0201 motifs were selected by computer-based algorithms. Five peptides (KDR82-90, KDR288-297, KDR766-774, KDR1093-1101, KDR1035-1044) stimulated specific cytotoxic T lymphocytes (CTLs) from peripheral-blood mononuclear cells (PBMCs) of 3 HLA-A*0201 donors. The decapeptide KDR288-297 was efficient in sensitizing target cells for recognition by a CTL clone at a concentration of 10 nM. More important, KDR288-297-specific CTLs lysed target cells transfected with HLA-A2/KDR cDNAs and a range of HLA-matched KDR+ angiogenic endothelial cells (aECs) and also recognized CD34+ endothelial progenitor cells. The specificity of CTLs was further confirmed by tetramer assay and cold-target inhibition assay. In addition, ex vivo exposure of aECs to the inflammatory cytokines enhanced CTL reactivity, which is in keeping with up-regulated KDR and HLA class 1 expression. In Matrigel assays, recognition of aECs by specific CTLs triggered an antivascular effect. These findings provide the first proof of the antigenic property of KDR protein and may be useful for devising new immunotherapeutic approaches to human cancers.