Successful tumor eradication was achieved by collaboration of augmented cytotoxic activity and anti-angiogenic effects following therapeutic vaccines containing helper-activating analog-loaded dendritic cells and tumor antigen DNA

Tumor rim cells: From resistance to vascular targeting agents to complete tumor ablation

Current vascular targeting strategies pursue two main goals: anti-angiogenesis agents aim to halt sprouting and the formation of new blood vessels, while vascular disrupting agents along with coaguligands seek to compromise blood circulation in the vessels. The ultimate goal of such therapies is to deprive tumor cells out of oxygen and nutrients long enough to succumb cancer cells to death. Most of vascular targeting agents presented promising therapeutic potential, but the final goal which is cure is rarely achieved. Nevertheless, in both preclinical and clinical settings, tumors tend to grow back, featuring a highly invasive, metastatic, and extremely resistant form. This review highlights the critical significance of tumor rim cells as the main factor, determining therapy success with vascular targeting agents. We present an overview of different single and combination treatments with vascular targeting agents that enable efficient targeting of tumor rim cells and long-lasting tumor cure. Understanding the nature of tumor rim cells, how they establish, how they manage to survive of vascular targeting agents, and how they contribute in tumor refractoriness, may open new avenues to the development of beneficial strategies, capable to eliminate residual rim cells, and enable tumor ablation once and forever.

The present status and future prospects of peptide-based cancer vaccines

Tumor cells commonly express several antigens, such as tumor-associated antigens (TAAs) or mutation-derived antigens (neoantigens), that can be regarded as foreign antigens and elicit anti-tumor immune responses in cancer patients. Various TAAs or neoantigens expressed in cancer cells have been identified and utilized as targets for cancer vaccines. One approach to elicit tumor-specific immune responses is termed peptide-based cancer vaccination; it involves administrating TAAs or neoantigen-derived peptide for treatment of cancers. There have been several forms of peptide-based cancer vaccines depending on which effector cells, such as CTLs or CD4(+) T-helper cells, are targeted to be activated. Many phase I and II clinical trials of peptide-based cancer vaccines using TAA-derived CTL epitopes, T-helper cell epitopes or dendritic cells loaded with TAA-derived peptides for various malignant tumors have been conducted and provide clinical benefits in a small fraction of patients. Nowadays, to improve the efficiency of peptide-based cancer vaccines, combination immunotherapy of peptide-based cancer vaccines with the immune-checkpoint blockade therapies using mAbs specific for CTLA-4, programmed cell death 1 (PD-1), or PD-1 ligand 1 (PD-L1) have been developed for clinical application. Furthermore, along with the recent technological progress in genetic and bioinformatic analysis, it has become easier to identify neoantigens from individual cancer patients. It is expected that peptide-based cancer vaccines targeting neoantigens as a personalized cancer immunotherapy will be developed.

An oncofetal antigen, IMP-3-derived long peptides induce immune responses of both helper T cells and CTLs

Insulin-like growth factor II mRNA-binding protein 3 (IMP-3), an oncofetal antigen identified using genome-wide cDNA microarray analyses, is overexpressed in several malignancies. IMP-3-derived cytotoxic T lymphocyte (CTL) epitopes have been used for peptide-based immunotherapies against various cancers. In addition to CTLs, induction of tumor-associated antigen (TAA)-specific helper T (Th) cells is crucial for establishment of effective antitumor immunity. In this study, we aimed to identify IMP-3-derived long peptides (IMP-3-LPs) carrying CTL and promiscuous Th-cell epitopes for use in cancer immunotherapy. IMP-3-derived Th-cell epitopes that bind to multiple HLA-class II molecules were predicted by in silico analysis, and their immunogenicity was determined by utilizing human T cells. We identified two highly immunogenic IMP-3-LPs presented by multiple HLA-class II molecules. One of the IMP-3-LPs encompassed two CTL epitopes that have been used for peptide-vaccine immunotherapy in ongoing clinical trials. IMP-3-LPs-specific Th cells responded to autologous dendritic cells (DCs) loaded with the recombinant IMP-3 proteins, suggesting that these s (LPs) can be naturally processed and presented. The IMP-3-LPs and specific Th cells augmented the expansion of IMP-3-specific CTLs, which was further enhanced by programmed cell death-1 (PD-1) blockade. In addition, IMP-3-LP encapsulated in liposomes was efficiently cross-presented in vitro, and this LP successfully cross-primed CTLs in HLA-A2 transgenic mice (Tgm) in vivo. Furthermore, one of the IMP-3-LPs induced IMP-3-specific Th cells from peripheral blood mononuclear cells (PBMCs) of head-and-neck malignant tumor (HNMT) patients. These findings suggest the potential usefulness of IMP-3-LPs in propagating both Th cells and CTLs and may have implications for IMP-3-LPs-based cancer immunotherapy.

Cancer-associated fibroblast-targeted strategy enhances antitumor immune responses in dendritic cell-based vaccine

Given the close interaction between tumor cells and stromal cells in the tumor microenvironment (TME), TME-targeted strategies would be promising for developing integrated cancer immunotherapy. Cancer-associated fibroblasts (CAFs) are the dominant stromal component, playing critical roles in generation of the pro-tumorigenic TME. We focused on the immunosuppressive trait of CAFs, and systematically explored the alteration of tumor-associated immune responses by CAF-targeted therapy. C57BL/6 mice s.c. bearing syngeneic E.G7 lymphoma, LLC1 Lewis lung cancer, or B16F1 melanoma were treated with an anti-fibrotic agent, tranilast, to inhibit CAF function. The infiltration of immune suppressor cell types, including regulatory T cells and myeloid-derived suppressor cells, in the TME was effectively decreased through reduction of stromal cell-derived factor-1, prostaglandin E2 , and transforming growth factor-β. In tumor-draining lymph nodes, these immune suppressor cell types were significantly decreased, leading to activation of tumor-associated antigen-specific CD8(+) T cells. In addition, CAF-targeted therapy synergistically enhanced multiple types of systemic antitumor immune responses such as the cytotoxic CD8(+) T cell response, natural killer activity, and antitumor humoral immunity in combination with dendritic cell-based vaccines; however, the suppressive effect on tumor growth was not observed in tumor-bearing SCID mice. These data indicate that systemic antitumor immune responses by various immunologic cell types are required to bring out the efficacy of CAF-targeted therapy, and these effects are enhanced when combined with effector-stimulatory immunotherapy such as dendritic cell-based vaccines. Our mouse model provides a novel rationale with TME-targeted strategy for the development of cell-based cancer immunotherapy.

Simultaneous activation of T helper function can augment the potency of dendritic cell-based cancer immunotherapy

PURPOSE

Simultaneous activation of T helper 1 (Th1) cell function has crucial roles in induction of potent cytotoxic T lymphocyte (CTL) responses in cancer immunotherapy. Here, we investigated whether dendritic cell (DC)-based vaccines loaded with both tumor-associated antigen (TAA)-derived MHC class I and pan-MHC class II peptides could elicit more potent CTL responses through simultaneous activation of Th1 function and reduction in CD4(+) regulatory T (Treg) cell proliferation.

METHODS

C57BL/6 mice bearing LLC1, a mouse Lewis lung cancer cell line, were subcutaneously administered DCs loaded with both LLC-derived MHC class I (MUT1&2) and LLC-unrelated pan-MHC class II (PADRE) peptides (DC-MUT1&2-PADRE). In assays using samples from advanced lung cancer patients, peripheral blood mononuclear cells were stimulated with autologous DCs loaded with both MUC1 MHC class I and PADRE peptides (DC-MUC1-PADRE) in vitro. Subsequently, TAA-specific CTL responses and the population of CD4(+) Treg cells were analyzed.

RESULTS

The population of spleen CD4(+) PADRE-specific cells producing interferon-gamma (IFNγ) was significantly increased by DC-MUT1&2-PADRE administration. Vaccinations with DC-MUT1&2-PADRE decreased the population of CD4(+) Treg cells in spleen and augmented CTL responses, effectively leading to suppression of tumor growth. In assays with human samples, CD4(+) Treg cells were induced less frequently, and MUC1-specific cytotoxicity was enhanced by stimulation with DC-MUC1-PADRE compared with that by stimulation with DC-MUC1 alone.

CONCLUSIONS

Simultaneous activation of Th1 function by DCs loaded with both TAA-derived MHC class I and PADRE peptides augments TAA-specific CTL responses while reducing Treg cell proliferation.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Targeting the tumor microenvironment with anti-neu/anti-CD40 conjugated nanoparticles for the induction of antitumor immune responses

Clinical and preclinical data indicate that immunotherapeutic interventions could induce immune responses capable of controlling or retard the tumor growth. However, immunotherapies need to be further optimized. We hypothesized that a more effective strategy for tumor eradication is to directly target the tumor microenvironment in order to generate a proinflammatory response and induce a localized antitumor immune response capable of eliminating the tumor cells. Nanoparticles have been proven to be an effective delivery system. In these studies we evaluated conjugated anti-RNEU and anti-CD40 antibodies onto PLA-(poly dl-lactic acid)-biodegradable nanoparticles (PLA-NP) for the induction of antitumor immune responses. The anti-neu/anti-CD40-NP were functional in vitro recognizing RNEU(+) tumors and activating dendritic cells. The delivery of anti-neu/anti-CD40-NP but not anti-neu-NP or anti-CD40-NP induced an antitumor response resulting in complete tumor elimination and generation of protective memory responses. The anti-neu/anti-CD40-NP specifically activated an antitumor response against RNEU(+) tumors but not against RNEU(-) tumors. The antitumor immune responses correlate with the induction of a Th1-proinflammatory response, reduction in the number of Tregs within the tumor and activation of a specific cytotoxic response. These results indicate that anti-neu/anti-CD40-NP with immunomodulatory properties are safe and can be used effectively as cancer vaccines strategy for the specific induction of antitumor immune responses.

Activation of tumor-specific T cells by dendritic cells expressing the NY-ESO-1 antigen after transfection with the cationic lipophosphoramide KLN5

BACKGROUND

Genetic modification of human monocyte-derived dendritic cells (DC) with cDNA sequences encoding tumor-associated antigens (TAA) is a promising strategy for cancer immunotherapy. The present study aimed to develop a nonviral gene transfer method based on the use of the cationic lipophosphoramide reagent, KLN-5, as an alternative to the commonly used viral vectors.

METHODS

First, the efficiency of KLN5 for gene transfection into DC was investigated using the green fluorescent protein (GFP) reporter gene. The highest transfection efficiency/cell viability ratio was determined by flow cytometry. Next, DC were transfected with a plasmid encoding NY-ESO-1, a TAA expressed in numerous cancers, according to the transfection protocol previously established with the GFP reporter. Transfected DC were then co-cultured with a CD8+ NY-ESO-1 specific HLA-A*02.01 T cell clone to control their ability to correctly process and present the corresponding epitope in the HLA-A*02.01 context. Finally, T cell activation was assessed via flow cytometry-based detection of interferon-gamma production.

RESULTS

An optimal KLN5/plasmid DNA ratio allowing both significant transgene expression and high viability of DC could be determined. Under the established experimental conditions, antigen processing and presentation of the immunodominant (SLLMWITQC(157-165)) epitope in the HLA-A*0201 context was demonstrated by activation of the NY-ESO-1-specific CD8+ T cell clone.

CONCLUSIONS

KLN5-based gene transfection into DC allows the efficient induction of TAA presentation and may thus represent a novel attractive nonviral approach for cancer vaccination.

Anti-angiogenetic effects of immune-reconstituted influenza virosomes assembled with parathyroid hormone-related protein derived peptide vaccine

BACKGROUND

C-IRIV/PTR-4 is a novel anticancer vaccine construct composed of immune-reconstituted influenza virosomes (IRIV) assembled with the PTH-rP derived peptide (PTR)-4, a synthetic CTL epitope with HLA-A(*)02.01 amino acid binding motifs. This peptide is able to generate a human PTH-rP specific CTL response with anti-tumor activity in vitro and in mice.

MATERIALS AND METHODS

We have investigated the immunological and preventive anti-tumor activity of C-IRIV/PTR-4 compared with the soluble PTR-4 peptide, in HHD mice inoculated with autologous PTH-rP+ tumor cells.

RESULTS

Peptide vaccination with either a soluble and an IRIV formulation showed similar immunological activity and the ability to purge the tumor tissue of tumor cell clones able to produce the target antigen (PTR-rP). The most efficient protection from tumor growth was however observed in animals vaccinated with C-IRIV/PTR-4 in which an additional IRIV related anti-angiogenetic effect was detected in the tumor tissue.

CONCLUSIONS

These results confirm the immunological activity of PTR-4 vaccination and suggest a more efficacious therapeutic potential of C-IRIV/PTR-4 against bone metastases and malignancies like breast, prostate and lung which very often over-express PTH-rP.

Problems and emerging approaches in HIV/AIDS vaccine development

According to recent estimates, 39.5 million people have been infected with HIV and 2.9 million have already died. The effect of HIV infection on individuals and communities is socially and economically devastating. Although antiretroviral drugs have had a dramatically beneficial impact on HIV-infected individuals who have access to treatment, it has had a negligible impact on the global epidemic. Therefore, the need for an efficacious HIV/AIDS vaccine remains the highest priority of the world HIV/AIDS agenda. The generation of a vaccine against HIV/AIDS has turned out to be extremely challenging, as indicated by > 20 years of unsuccessful attempts. This review discusses the major challenges in the field and key experimental evidence providing a rationale for the use of non-structural HIV proteins, such as Rev, Tat and Nef, either in the native form or expressed by viral vectors such as a replicating adeno-vector. These non-structural proteins alone or in combination with modified structural HIV-1 Env proteins represent a novel strategy for both preventative and therapeutic HIV/AIDS vaccine development.