Active antimetastatic immunotherapy in Lewis lung carcinoma with self EGFR extracellular domain protein in VSSP adjuvant

Sodium acetate increases the productivity of HEK293 cells expressing the ECD-Her1 protein in batch cultures: experimental results and metabolic flux analysis

Human Embryonic Kidney cells (HEK293) are a popular host for recombinant protein expression and production in the biotechnological industry. This has driven within both, the scientific and the engineering communities, the search for strategies to increase their protein productivity. The present work is inserted into this search exploring the impact of adding sodium acetate (NaAc) into a batch culture of HEK293 cells. We monitored, as a function of time, the cell density, many external metabolites, and the supernatant concentration of the heterologous extra-cellular domain ECD-Her1 protein, a protein used to produce a candidate prostate cancer vaccine. We observed that by adding different concentrations of NaAc (0, 4, 6 and 8 mM), the production of ECD-Her1 protein increases consistently with increasing concentration, whereas the carrying capacity of the medium decreases. To understand these results we exploited a combination of experimental and computational techniques. Metabolic Flux Analysis (MFA) was used to infer intracellular metabolic fluxes from the concentration of external metabolites. Moreover, we measured independently the extracellular acidification rate and oxygen consumption rate of the cells. Both approaches support the idea that the addition of NaAc to the culture has a significant impact on the metabolism of the HEK293 cells and that, if properly tuned, enhances the productivity of the heterologous ECD-Her1 protein.

Aspects of Phage-Based Vaccines for Protein and Epitope Immunization

Because vaccine development is a difficult process, this study reviews aspects of phages as vaccine delivery vehicles through a literature search. The results demonstrated that because phages have adjuvant properties and are safe for humans and animals, they are an excellent vaccine tool for protein and epitope immunization. The phage genome can easily be manipulated to display antigens or create DNA vaccines. Additionally, they are easy to produce on a large scale, which lowers their manufacturing costs. They are stable under various conditions, which can facilitate their transport and storage. However, no medicine regulatory agency has yet authorized phage-based vaccines despite the considerable preclinical data confirming their benefits. The skeptical perspective of phages should be overcome because humans encounter bacteriophages in their environment all the time without suffering adverse effects. The lack of clinical trials, endotoxin contamination, phage composition, and long-term negative effects are some obstacles preventing the development of phage vaccines. However, their prospects should be promising because phages are safe in clinical trials; they have been authorized as a food additive to avoid food contamination and approved for emergency use in phage therapy against difficult-to-treat antibiotic-resistant bacteria. Therefore, this encourages the use of phages in vaccines.

Polyclonal antibody-induced downregulation of HER1/EGFR and HER2 surpasses the effect of combinations of specific registered antibodies

Background

Antitumor therapies targeting HER1/EGFR and HER2, such as monoclonal antibodies (MAbs) and tyrosine-kinase inhibitors (TKIs), have demonstrated a significant clinical benefit, but the emergence of resistance limits long-term efficacy. While secondary HER1 mutations confer tolerance to TKI, compensatory upregulation of HER2 drives resistance to anti-HER1 MAbs, which identifies MAb combinations targeting both receptors as an attractive therapeutic strategy. Nevertheless, toxicity hampers the clinical validation of this approach. Alternatively, cancer vaccines may induce antibodies directed against several antigens with less concern about induced toxicity.

Methods

Polyclonal antibodies (PAbs) targeting HER1 and HER2 were induced in mice or rabbits through immunization. Recognition of different epitopes on targets by PAbs was validated by phage-display technology. Receptor downregulation was evaluated by flow cytometry, immunofluorescence, and Western blot. MTT assays assessed cytotoxicity, while the antitumor effect of PAbs was assayed in nude mice.

Results

PAbs promoted degradation of HER1 and HER2 regarding clinical MAbs or their combinations. As a result, inhibition of cytotoxicity on tumor cell lines was improved, even in the presence of oncogenic mutations in HER1, as well as in cetuximab-insensitive cells. Accordingly, the antitumor effect of vaccination-induced PAbs was observed in lung tumor lines representative of sensitivity or resistance to HER1 targeting therapies.

Conclusions

Immunization against HER1 and HER2 receptors offers an alternative to passive administration of combinations of MAbs, since vaccination-induced PAbs promote the downregulation of both receptors and they have a higher impact on the survival of tumor cells.

VSSP abrogates murine ovarian tumor-associated myeloid cell-driven immune suppression and induces M1 polarization in tumor-associated macrophages from ovarian cancer patients

The ovarian tumor microenvironment (TME) is characterized by the accumulation of immunosuppressive tumor-associated macrophages (TAMs) and granulocytic cells. Very small size particles (VSSP), comprised of the ganglioside NAcGM3 and Neisseria meningitidis derived outer membrane vesicles, is being developed as a nanoparticulated modulator of innate immunity. Prior studies have shown that VSSP enhanced antigen-specific cytotoxic T cell responses and reduced the suppressive phenotype of splenic granulocytic cells in tumor-bearing mice. Here, we hypothesized that intraperitoneal VSSP would modify myeloid cell accumulation and phenotypes in the ovarian TME and abrogate suppressor function of TAMs and tumor-associated granulocytic cells. In the ID8 syngeneic model of epithelial ovarian cancer, VSSP reduced peritoneal TAMs and induced M1-like polarization in TAMs. In addition, VSSP stimulated peritoneal inflammation characterized by increased granulocytes and monocytes, including inflammatory monocytic cells. VSSP treatment resulted in peritoneal TAMs and granulocytic cells being less suppressive of ex vivo stimulated CD8+ T cell responses. VSSP alone and combined with anti-PD-1 modestly but significantly prolonged survival in tumor-bearing mice. In addition, ex vivo treatment with VSSP induced M1-like polarization in TAMs from patients with metastatic ovarian cancer and variably abrogated their suppressor phenotype. VSSP treatment also partially abrogated the induction of suppressor function in healthy donor neutrophils exposed to ascites supernatants from patients with ovarian cancer. Together, these results point to VSSP reprogramming myeloid responses resulting in abrogation of suppressive pathways and raise the potential for administration of VSSP into the TME to enhance anti-tumor immunity.

Mitigating the prevalence and function of myeloid-derived suppressor cells by redirecting myeloid differentiation using a novel immune modulator

BACKGROUND

Immune suppression is common in neoplasia and a major driver is tumor-induced myeloid dysfunction. Yet, overcoming such myeloid cell defects remains an untapped strategy to reverse suppression and improve host defense. Exposure of bone marrow progenitors to heightened levels of myeloid growth factors in cancer or following certain systemic treatments promote abnormal myelopoiesis characterized by the production of myeloid-derived suppressor cells (MDSCs) and a deficiency in antigen-presenting cell function. We previously showed that a novel immune modulator, termed 'very small size particle' (VSSP), attenuates MDSC function in tumor-bearing mice, which was accompanied by an increase in dendritic cells (DCs) suggesting that VSSP exhibits myeloid differentiating properties. Therefore, here, we addressed two unresolved aspects of the mechanism of action of this unique immunomodulatory agent: (1) does VSSP alter myelopoiesis in the bone marrow to redirect MDSC differentiation toward a monocyte/macrophage or DC fate? and (2) does VSSP mitigate the frequency and suppressive function of human tumor-induced MDSCs?

METHODS

To address the first question, we first used a murine model of granulocyte-colony stimulating factor-driven emergency myelopoiesis following chemotherapy-induced myeloablation, which skews myeloid output toward MDSCs, especially the polymorphonuclear (PMN)-MDSC subset. Following VSSP treatment, progenitors and their myeloid progeny were analyzed by immunophenotyping and MDSC function was evaluated by suppression assays. To strengthen rigor, we validated our findings in tumor-bearing mouse models. To address the second question, we conducted a clinical trial in patients with metastatic renal cell carcinoma, wherein 15 patients were treated with VSSP. Endpoints in this study included safety and impact on PMN-MDSC frequency and function.

RESULTS

We demonstrated that VSSP diminished PMN-MDSCs by shunting granulocyte-monocyte progenitor differentiation toward monocytes/macrophages and DCs with heightened expression of the myeloid-dependent transcription factors interferon regulatory factor-8 and PU.1. This skewing was at the expense of expansion of granulocytic progenitors and rendered the remaining MDSCs less suppressive. Importantly, these effects were also demonstrated in a clinical setting wherein VSSP monotherapy significantly reduced circulating PMN-MDSCs, and their suppressive function.

CONCLUSIONS

Altogether, these data revealed VSSP as a novel regulator of myeloid biology that mitigates MDSCs in cancer patients and reinstates a more normal myeloid phenotype that potentially favors immune activation over immune suppression.

Domain-level epitope mapping of polyclonal antibodies against HER-1 and HER-2 receptors using phage display technology

HER-1 and HER-2 are tumor-associated antigens overexpressed in several epithelial tumors, and successfully targeted by therapeutic approaches against cancer. Vaccination with their recombinant extracellular domains has had encouraging results in the pre-clinical setting. As complex humoral responses targeting multiple epitopes within each antigen are the ultimate goal of such active immunotherapy strategies, molecular dissection of the mixture of antibody specificities is required. The current work exploits phage display of antigenic versions of HER-1 and HER-2 domains to accomplish domain-level epitope mapping. Recognition of domains I, III and IV of both antigens by antibodies of immunized mice was shown, indicating diverse responses covering a broad range of antigenic regions. The combination of phage display and site-directed mutagenesis allowed mutational screening of antigen surface, showing polyclonal antibodies' recognition of mutated receptor escape variants known to arise in patients under the selective pressure of the anti-HER-1 antibody cetuximab. Phage-displayed HER domains have thus the potential to contribute to fine specificity characterization of humoral responses during future development of anti-cancer vaccines.

Immuno-toxicological evaluation of her1 cancer vaccine in non-human primates: a 6-month subcutaneous study

Purpose: A vaccine composition based on the extracellular domain of the human epidermal growth factor receptor 1 (HER1-ECD) and the combination of VSSP (very small size proteoliposomes) and Montanide ISA 51 adjuvants when used by intramuscular route, demonstrated promising results in preclinical studies. However, in order to avoid potential adverse events due to the use of Montanide, it is proposed to modify the vaccine formulation by using VSSP (very small size proteoliposomes) adjuvant alone, and to evaluate the quality of subcutaneously induced immune response. This study aimed to assess the immunotoxicological effects of HER1 vaccine in Cercopithecus aethiops.Materials and methods: Fifteen monkeys were randomized into four groups: Negative Control (Tris/NaCl, s.c.), Positive Control (200 µg HER1-ECD/VSSP/Montanide ISA-51 VG, i.m), Low Dose (200 µg HER1-ECD/VSSP/Tris NaCl, s.c.) and High Dose (800 µg HER1-ECD/VSSP/Tris NaCl, s.c). All monkeys received 7 doses and were daily inspected for clinical signs. Body weight, rectal temperature, cardiac and respiratory rates were measured during the study, and electrocardiographical and ophthalmological studies were performed. Humoral and cellular immune response and clinical pathology parameters were analyzed.Results: Animal's survival in the study was 100% (n = 15). Administration site reactions were observed in the Positive Control animals (n = 4). HER1 vaccine administered subcutaneously (High Dose Group) achieved good IgG antibody titers although lower than the Positive Control group, but with higher ability to inhibit HER1 phosphorylation. Conclusions: This suggests that the alternative of eliminating the use of Montanide in the HER1 vaccine preparation and the using subcutaneous route is feasible.

Phage Display-Based Nanotechnology Applications in Cancer Immunotherapy

Phage display is a nanotechnology with limitless potential, first developed in 1985 and still awaiting to reach its peak. Awarded in 2018 with the Nobel Prize for Chemistry, the method allows the isolation of high-affinity ligands for diverse substrates, ranging from recombinant proteins to cells, organs, even whole organisms. Personalized therapeutic approaches, particularly in oncology, depend on the identification of new, unique, and functional targets that phage display, through its various declinations, can certainly provide. A fast-evolving branch in cancer research, immunotherapy is now experiencing a second youth after being overlooked for years; indeed, many reports support the concept of immunotherapy as the only non-surgical cure for cancer, at least in some settings. In this review, we describe literature reports on the application of peptide phage display to cancer immunotherapy. In particular, we discuss three main outcomes of this procedure: (i) phage display-derived peptides that mimic cancer antigens (mimotopes) and (ii) antigen-carrying phage particles, both as prophylactic and/or therapeutic vaccines, and (iii) phage display-derived peptides as small-molecule effectors of immune cell functions. Preclinical studies demonstrate the efficacy and vast potential of these nanosized tools, and their clinical application is on the way.

HER1-based vaccine: Simultaneous activation of humoral and cellular immune response

The human epidermal growth factor receptor 1 (HER1) is a tumor-associated antigen that has been validated as a clinical target for several passive, non-immune therapies currently approved for the treatment of epithelial tumors. HER1 is an oncogene that not only promotes tumor progression and survival, but also immune escape. Its overexpression in some epithelial malignancies has been correlated with a poor prognosis. We developed an approach to target HER1 by specific active immunotherapy, recognizing the extracellular domain of the receptor, using a combination of VSSP and Montanide ISA 51 as adjuvants. We summarize the results obtained with this vaccine in both the preclinical and clinical settings, emphasizing the importance of the induction of both humoral and cellular responses for the success of cancer vaccines as safe therapeutic alternatives for the treatment of cancer.

Bacterial components as naturally inspired nano-carriers for drug/gene delivery and immunization: Set the bugs to work?

Drug delivery is a rapidly growing area of research motivated by the nanotechnology revolution, the ideal of personalized medicine, and the desire to reduce the side effects of toxic anti-cancer drugs. Amongst a bewildering array of different nanostructures and nanocarriers, those examples that are fundamentally bio-inspired and derived from natural sources are particularly preferred. Delivery of vaccines is also an active area of research in this field. Bacterial cells and their components that have been used for drug delivery, include the crystalline cell-surface layer known as "S-layer", bacterial ghosts, bacterial outer membrane vesicles, and bacterial products or derivatives (e.g. spores, polymers, and magnetic nanoparticles). Considering the origin of these components from potentially pathogenic microorganisms, it is not surprising that they have been applied for vaccines and immunization. The present review critically summarizes their applications focusing on their advantages for delivery of drugs, genes, and vaccines.

Targeting Myeloid-Derived Suppressor Cells in Cancer

Myeloid derived suppressor cells (MDSC) represent only a minor fraction of circulating blood cells but play an important role in tumor formation and progression. They are a heterogeneous group of cells that influence the tumor microenvironment by depletion of amino acids, oxidative stress, decreased trafficking of antitumor effector cells, and increased regulatory T and regulatory dendritic cell responses. Investigational treatment strategies targeting MDSCs have attempted to inhibit MDSC development and expansion (stem cell factor blockade, modulate of cell signaling, and target MDSC migration and recruitment), inhibit MDSC function (nitric oxide inhibition and reactive oxygen and nitrogen species inhibition), differentiate MDSCs into more mature cells (Vitamins A and D, all-trans retinoic acid, interleukin-2, toll-like receptor 9 inhibitors, taxanes, beta-glucan particles, tumor-derived exosome inhibition, and very small size proteoliposomes), and destroy MDSCs (cytotoxic agents, ephrin A2 degradation, anti-interleukin 13, and histamine blockers). To date, there are no Food and Drug Administration approved therapies selectively targeting MDSCs, but such therapies are likely to be implemented in the future, due to the key role of MDSCs in antitumor immunity.

Cancer-induced systemic myeloid dysfunction: Implications for treatment and a novel nanoparticle approach for its correction

Unlike other regulatory circuits, cancer-induced myeloid dysfunction involves more than an accumulation of impaired dendritic cells, protumoral macrophages, and myeloid derived suppressor cells in the tumor microenvironment. It is also characterized by "aberrant" myelopoiesis that results in the accumulation and expansion of immature myeloid precursors with a suppressive phenotype in the systemic circulation. The first part of this review briefly describes the evidence for and consequences of this systemic dysfunctional myelopoiesis and the possible reinforcement of this phenomenon by conventional treatments used in patients with cancer, in particular chemotherapy and granulocyte-colony stimulating factor. The second half of this review describes very small size particles, a novel immune-modulatory nanoparticle, and the evidence indicating a possible role of this agent in correcting or re-programming the dysfunctional myelopoiesis in different scenarios.

A novel recombinant anti-epidermal growth factor receptor peptide vaccine capable of active immunization and reduction of tumor volume in a mouse model

Over-expression of epidermal growth factor receptor (EGFR) has been reported in a number of human malignancies. Strong expression of this receptor has been associated with poor survival in many such patients. Active immunizations that elicit antibodies of the desired type could be an appealing alternative to conventional passive immunization. In this regard, a novel recombinant peptide vaccine capable of prophylactic and therapeutic effects was constructed. A novel fusion recombinant peptide base vaccine consisting of L2 domain of murine extra-cellular domain-EGFR and EGFR mimotope (EM-L2) was constructed and its prophylactic and therapeutic effects in a Lewis lung carcinoma mouse (C57/BL6) model evaluated. Constructed recombinant peptide vaccine is capable of reacting with anti-EGFR antibodies. Immunization of mice with EM-L2 peptide resulted in antibody production against EM-L2. The constructed recombinant peptide vaccine reduced tumor growth and increased the survival rate. Designing effective peptide vaccines could be an encouraging strategy in contemporary cancer immunotherapy. Investigating the efficacy of such cancer immunotherapy approaches may open exciting possibilities concerning hyperimmunization, leading to more promising effects on tumor regression and proliferation.

Anti-proliferative and pro-apoptotic effects induced by simultaneous inactivation of HER1 and HER2 through endogenous polyclonal antibodies

The human epidermal growth factor receptor (HER1) and its partner HER2 are extensively described oncogenes and validated targets for cancer therapy. However, the effectiveness of monospecific therapies targeting these receptors is hampered by resistance emergence, which is frequently associated with the upregulation of other members of HER family. Combined therapies using monoclonal antibodies or tyrosine kinase inhibitors have been suggested as a promising strategy to circumvent this resistance mechanism. We propose an alternative approach based on simultaneous inactivation of HER1 and HER2 by multi-epitope blockade with specific polyclonal antibodies induced by vaccination. Elicited antibodies impaired both receptors activation and induced their degradation, which caused the inhibition of down-signaling cascades. This effect was translated into cell cycle arrest and apoptosis induction of human tumor cells. Elicited antibodies were able to reduce the viability of a panel of human tumor lines with differential expression levels of HER1 and HER2. The most significant effects were obtained in the tumor lines with lower expression levels of both receptors. These new insights would contribute to the rational design of HER receptors targeting multivalent vaccines, as an encouraging approach for the treatment of cancer patients.

Safety and Immunogenicity of a Human Epidermal Growth Factor Receptor 1 (HER1)-Based Vaccine in Prostate Castration-Resistant Carcinoma Patients: A Dose-Escalation Phase I Study Trial

Metastatic castration-resistant prostate cancer (CRPC) remains incurable due to the lack of effective therapies. Activation of the human epidermal growth factor receptor 1 (HER1) in prostate cancer contributes to metastatic progression as well as to disease relapse. Here, we determined the toxicity and immunogenicity of a HER1-based cancer vaccine in CRPC patients included in a phase I clinical trial. CRPC patients (n = 24) were intramuscularly vaccinated with HER1 vaccine consisting of the extracellular domain of HER1 molecule (ECD) and very small size proteoliposome from Neisseria meningitidis (VSSP) and Montanide ISA-51 VG as adjuvants. Patients were included in five groups according to the vaccine dose (100, 200, 400, 600, and 800 μg). The primary endpoints were safety and immunogenicity. The anti-HER1 antibodies were measured by an ELISA, the recognition of an HER1 positive tumor cell line and the inhibition of HER1 phosphorylation by sera were determined by flow cytometry and western blot analysis, respectively. The HER1-specific T cell response was assessed by determination of IFN-γ-producing T cells using ELISpot assay. The vaccine was well tolerated. No grade III or IV adverse events were reported. High titers of anti-HER1 antibodies were observed in most of the evaluated patients. There were no significant differences regarding the geometric means of the anti-HER1 titers among the dose groups except the group of 100 μg in which antibody titers were significantly lower. A Th1-type IgG subclasses pattern was predominant in most patients. Only patients receiving the higher doses of vaccine showed significant tumor cell recognition and HER1 phosphorylation inhibition by hyperimmune sera. Forty two percent of the patients showed a specific T cell response against HER1 peptides pool in post-treatment samples. There was a trend toward survival benefit in those patients showing high anti-HER1 specific antibody titers and a significant association between cellular immune response and clinical outcome.

Cancer immunotherapy by a recombinant phage vaccine displaying EGFR mimotope: an in vivo study

To date, several small molecule inhibitors and monoclonal-antibodies (like ICR-62) have been used to treat tumors over-expressing epidermal growth factor receptor (EGFR). However, the limitations associated with these conventional applications accentuate the necessity of alternative approaches. Mimotopes as compelling molecular tools could rationally be employed to circumvent these drawbacks. In the present study, an M13 phage displaying ICR-62 binding peptide mimotope is exploited as a vaccine candidate. It exhibited high affinity towards ICR62 and polyclonal anti-P-BSA antibodies. Following the mice immunization, phage-based mimotope vaccine induced humoral immunity. Elicited anti-EGFR mimotope antibodies were detected using ELISA method. Moreover, the phage vaccine was tested on the Lewis lung carcinoma mice model to investigate the prophylactic and therapeutic effects. The tumor volume was measured and recorded in different animal groups to evaluate the anti-tumor effects of the vaccine. Our data indicate that the reported phage-based mimotope could potentially elicit specific antibodies resulting in low titers of EGFR-specific antibodies and reduced tumor growth. However, in vivo experiments of prophylactic or therapeutic vaccination showed no specific advantage. Furthermore, phage-mimotope vaccine might be a promising approach in the field of cancer immunotherapy.

GM3-containing nanoparticles in immunosuppressed hosts: Effect on myeloid-derived suppressor cells

Cancer vaccines to date have not broadly achieved a significant impact on the overall survival of patients. The negative effect on the immune system of the tumor itself and conventional anti-tumor treatments such as chemotherapy is, undoubtedly, a key reason for these disappointing results. Myeloid-derived suppressor cells (MDSCs) are considered a central node of the immunosuppressive network associated with tumors. These cells inhibit the effector function of natural killer and CD8⁺ T cells, expand regulatory T cells and can differentiate into tumor-associated macrophages within the tumor microenvironment. Thus, overcoming the suppressive effects of MDSCs is likely to be critical for cancer immunotherapy to generate effective anti-tumor immune responses. However, the capacity of cancer vaccines and particularly their adjuvants to overcome this inhibitory population has not been well characterized. Very small size proteoliposomes (VSSP) is a nanoparticulated adjuvant specifically designed to be formulated with vaccines used in the treatment of immunocompromised patients. This adjuvant contains immunostimulatory bacterial signals together with GM3 ganglioside. VSSP promotes dendritic cell maturation, antigen cross-presentation to CD8⁺ T cells, Th1 polarization, and enhances CD8⁺ T cell response in tumor-free mice. Currently, four cancer vaccines using VSSP as the adjuvant are in Phase I and II clinical trials. In this review, we summarize our work characterizing the unique ability of VSSP to stimulate antigen-specific CD8⁺ T cell responses in two immunocompromised scenarios; in tumor-bearing mice and during chemotherapy-induced leukopenia. Particular emphasis has been placed on the interaction of these nanoparticles with MDSCs, as well as comparison with other cancer vaccine adjuvants currently in preclinical or clinical studies.

Delineating the functional map of the interaction between nimotuzumab and the epidermal growth factor receptor

Molecular details of epidermal growth factor receptor (EGFR) targeting by nimotuzumab, a therapeutic anti-cancer antibody, have been largely unknown. The current study delineated a functional map of their interface, based on phage display and extensive mutagenesis of both the target antigen and the Fv antibody fragment. Five residues in EGFR domain III (R353, S356, F357, T358, and H359T) and the third hypervariable region of nimotuzumab heavy chain were shown to be major functional contributors to the interaction. Fine specificity differences between nimotuzumab and other anti-EGFR antibodies were revealed. Mapping information guided the generation of a plausible in silico binding model. Knowledge about the epitope/paratope interface opens new avenues for the study of tumor sensitivity/resistance to nimotuzumab and for further engineering of its binding site. The developed mapping platform, also validated with the well-known cetuximab epitope, allows a comprehensive exploration of antigenic regions and could be expanded to map other anti-EGFR antibodies.

Very small size proteoliposomes abrogate cross-presentation of tumor antigens by myeloid-derived suppressor cells and induce their differentiation to dendritic cells

Background

Myeloid-derived suppressor cells (MDSCs) are among the major obstacles that adjuvants for cancer vaccines have to overcome. These cells cross-present tumor-associated antigens (TAA) to naive T lymphocytes with a tolerogenic outcome. Very Small Size Proteoliposomes (VSSP) is used as adjuvant by four therapeutic cancer vaccines currently in Phase I and II clinical trials. We previously found that VSSP reduces the suppressive function of MDSCs, then activating antigen-specific CTL responses in tumor-bearing (TB) mice, with the consequent reduction of tumor growth. However the mechanistic explanation for the immunomodulatory effect of this adjuvant in TB hosts has not been addressed before.

Methods

TB mice were inoculated with VSSP and MDSCs isolated and characterized by their expression of Arg1 and Nos2 genes by RT-PCR. The effect of VSSP on antigen cross-presentation by MDSCs, regulatory T cells (Tregs) expansion and MDSCs differentiation towards dendritic cells (DCs) was analyzed by FACS. Student’s t test or ANOVA and Tukey’s tests were used for statistical analyses.

Results

After inoculating VSSP into TB mice, a significant reduction of Arg1 and Nos2 gene expression was observed in recovered MDSCs. Concurrently the ability of these cells to induce down-regulation of CD3ζ chain on T cells was lost. Likewise in mice inoculated with the adjuvant lower percentages of Tregs were detected. In vitro, VSSP treatment was enough to differentiate MDSCs into phenotypically mature DCs, eliminating the former suppressive effect. Noteworthy, in vivo administration of VSSP to OVA-expressing (EG.7) TB mice abrogated this model antigen cross-presentation by splenic MDSCs. Similar results were obtained even when OVA antigen was administered into these TB mice formulated in VSSP. On the contrary, immunization with the same protein in polyI:C did not change the percentage of MDSCs expressing SIINFEKL/H-2K^b complexes, whereas a concomitant injection of VSSP aborted the limitations of polyI:C in this setting.

Conclusions

Altogether, these results indicate that VSSP has the peculiar capacity of inhibiting TAA cross-presentation and certain suppressive mechanisms on MDSCs which in turn, combined with the ability to induce differentiation of these cells into antigen-presenting cells (APCs), sustains this adjuvant as an ideal immunomodulator for cancer immunotherapy.

A view on EGFR-targeted therapies from the oncogene-addiction perspective

Tumor cell growth and survival can often be impaired by inactivating a single oncogen– a phenomenon that has been called as “oncogene addiction.” It is in such scenarios that molecular targeted therapies may succeed. among known oncogenes, the epidermal growth factor receptor (EGFR) has become the target of different cancer therapies. So far, however, the clinical benefit from EGFR-targeted therapies has been rather limited. a critical review of the large amount of clinical data obtained with anti-EGFR agents, carried out from the perspective of the oncogene addiction concept, may help to understand the causes of the unsatisfactory results. In this article we intend to do such an exercise taking as basis for the analysis a few case studies of anti-EGFR agents that are currently in the clinic. There, the “EGFR addiction” phenomenon becomes apparent in high-responder patients. We further discuss how the concept of oncogene addiction needs to be interpreted on the light of emerging experimental evidences and ideas; in particular, that EGFR addiction may reflect the interconnection of several cellular pathways. In this regard we set forth several hypotheses; namely, that requirement of higher glucose uptake by hypoxic tumor cells may reinforce EGFR addiction; and that chronic use of EGFR-targeted antibodies in EGFR-addicted tumors would induce stable disease by reversing the malignant phenotype of cancer stem cells and also by sustaining an anti-tumor T cell response. Finally, we discuss possible reasons for the failure of certain combinatorial therapies involving anti-EGFR agents, arguing that some of these agents might produce either a negative or a positive trans-modulation effect on other oncogenes. It becomes evident that we need operational definitions of EGFR addiction in order to determine which patient populations may benefit from treatment with anti-EGFR drugs, and to improve the design of these therapies.

Comparative in vitro and experimental in vivo studies of the anti-epidermal growth factor receptor antibody nimotuzumab and its aglycosylated form produced in transgenic tobacco plants

A broad variety of foreign genes can be expressed in transgenic plants, which offer the opportunity for large-scale production of pharmaceutical proteins, such as therapeutic antibodies. Nimotuzumab is a humanized anti-epidermal growth factor receptor (EGFR) recombinant IgG1 antibody approved in different countries for the treatment of head and neck squamous cell carcinoma, paediatric and adult glioma, and nasopharyngeal and oesophageal cancers. Because the antitumour mechanism of nimotuzumab is mainly attributed to its ability to interrupt the signal transduction cascade triggered by EGF/EGFR interaction, we have hypothesized that an aglycosylated form of this antibody, produced by mutating the N(297) position in the IgG(1) Fc region gene, would have similar biochemical and biological properties as the mammalian-cell-produced glycosylated counterpart. In this paper, we report the production and characterization of an aglycosylated form of nimotuzumab in transgenic tobacco plants. The comparison of the plantibody and nimotuzumab in terms of recognition of human EGFR, effect on tyrosine phosphorylation and proliferation in cells in response to EGF, competition with radiolabelled EGF for EGFR, affinity measurements of Fab fragments, pharmacokinetic and biodistribution behaviours in rats and antitumour effects in nude mice bearing human A431 tumours showed that both antibody forms have very similar in vitro and in vivo properties. Our results support the idea that the production of aglycosylated forms of some therapeutic antibodies in transgenic plants is a feasible approach when facing scaling strategies for anticancer immunoglobulins.

Pharmacokinetics and Biodistribution Study of 7A7 Anti-Mouse Epidermal Growth Factor Receptor Monoclonal Antibody and Its F(ab')(2) Fragment in an Immunocompetent Mouse Model

Immunocompetent mice, Fc receptor γ-chain deficient mice (Fcer1g^−/−), and molecular tools as F(ab′)₂ bivalent fragments appear as the most suitable biological models to study the mechanisms of the action of anti-epidermal growth factor receptor (EGFR) monoclonal antibodies (mAbs). In vivo experiments contrasting antitumor effects of whole Abs and their bivalent fragments commonly involve a previous comparative pharmacokinetics study. In this paper, pharmacokinetics and biodistribution of an anti-mouse EGFR Ab were assessed using immunocompetent mice. ¹²⁵I-labeled 7A7 mAb holds an elimination half-life (t_1/2β) of 23.1 h in C57BL/6 mice. Accumulation of mAb was found in liver, spleen, kidneys, and mostly in lungs. We used an ELISA method to determine the t_1/2β of a 7A7 mAb using the same experimental setting. Results from this new analysis revealed a t_1/2β of 23.9 h, supporting this method as a safer and easier system to evaluate pharmacokinetics parameters of mAbs targeting mouse EGFR. Using this system we also studied pharmacokinetics of 7A7 F(ab′)₂ fragment. A tenfold difference between the mAb and fragment t_1/2β was found. These data support the use of the 7A7 F(ab′)₂ fragment in in vivo studies to explore the contribution of the EGFR signaling blockade and the Fc region to the antitumor effect of 7A7 mAb in this autologous scenario.

Antitumor activity and immunomodulatory effects of the intraperitoneal administration of Kanglaite in vivo in Lewis lung carcinoma

AIMS OF THE STUDY

Kanglaite (KLT) is a useful antitumor drug with proven effects when combined with chemotherapy, radiotherapy or surgery. We hypothesize that KLT has antitumor activity and immunomodulatory effects in Lewis lung carcinoma.

MATERIALS AND METHODS

C57BL/6 mice with Lewis lung carcinoma were divided into four groups: the control group (C), cisplatin group (1 mg/kg, DDP), low KLT group (6.25 ml/kg body weight [L]), and high KLT group (12.5 ml/kg body weight [H]). T cell proliferation was determined by the MTT assay. Nuclear factor-kappa B (NF-κB), inhibitor kappa B alpha (IκBα), IκB kinase (IKK) and epidermal growth factor receptor (EGFR) levels were measured by western blotting. An enzyme-linked immunosorbent assay was used to analyze the expression of interleukin-2 (IL-2).

RESULTS

Intraperitoneal KLT significantly inhibited the growth of Lewis lung carcinoma, and the spleen index was significantly higher in the L and H groups than in the C group. KLT stimulated T cell proliferation in a dose-dependent manner. Treatment with KLT at either 6.25 or 12.5 ml/kg decreased the level of NF-κB in the nucleus in a dose-dependent manner, and KLT markedly decreased the expression of IκBα, IKK and EGFR in the cytoplasm of tumor cells and overall. IL-2 was significantly increased in the supernatant of splenocytes in the H group.

CONCLUSIONS

These results demonstrate that KLT has pronounced antitumor and immunostimulatory activities in C57BL/6 mice with Lewis lung carcinoma. These may affect the regulation of NF-κB/IκB expression, in addition to cytokines such as IL-2 and EGFR. Further work needs to investigate the relevant signaling pathway effects, but our findings suggest that KLT may be a promising antitumor drug for clinical use.

Effects of an epidermal growth factor receptor-based cancer vaccine on wound healing and inflammation processes in murine experimental models

Anti-epidermal growth factor receptor (EGFR) therapies have been proven clinically effective for a variety of epithelial tumours. Vaccination of mice with the extracellular domain (ECD) of autologous EGFR overcomes the tolerance to self-EGFR and has antimetastatic effect on EGFR+ tumour. Because EGF/EGFR-signalling plays an important role in the inflammation stage of wound healing, the main objective of this study was to explore the possible role of murine (m) EGFR-ECD vaccine in the croton-oil-induced ear oedema and wound healing process in mice as autologous experimental models, mimicking the possible post-surgical wound complication in patients treated with human EGFR-ECD/VSSP vaccine. Mice were intramuscularly immunised four times; biweekly with the mEGFR-ECD/VSSP/Mont. Seven days later, an 8 mm diameter, full-thickness skin wound was created on the back of each animal. Immunisation induced a strong specific humoral response against the mEGFR-ECD protein and a DTH dose-response curve but interestingly, animals treated with mEGFR-ECD/VSSP/Mont had similar inflammatory and healing speed responses compared to control ones. These data suggest that application of mEGFR-ECD/VSSP vaccine as a therapeutic approach in cancer patients could not elicit a poor healing process after surgery.

Lentiviral vector followed by protein immunisation breaks tolerance against the self-antigen Her1 and results in lung cancer immunotherapy

BACKGROUND

Lung cancer remains a leading cause of cancer mortality, and so the aim of the present study was to develop a therapeutic vaccine protocol.

METHODS

We constructed a lentiviral vector (LV) expressing the extracellular domain (ECD) of murine Her1, an antigen associated with poor prognosis in lung cancer.

RESULTS

A single LV injection, followed by two Her1 protein boosts, was effective in reducing the metastatic burden of Lewis lung carcinoma in mice. The Her1 LV immunisation generated CD8+ T cells that recognised Her1 ECD presented by dendritic cells, and that also homed to Her1-expressing tumours. Protein boosting further increased the CD8+ T cell response and generated anti-Her1 antibodies; in the antibody response, Her1 LV priming increased Th1-dependent immunoglobulin G2c production.

CONCLUSIONS

The ability of this vaccine protocol to break both T cell and B cell tolerance to a self-antigen likely explains its effectiveness.

Inhibition of tumor angiogenesis in lung cancer by T4 phage surface displaying mVEGFR2 vaccine

Vascular endothelial growth factor (VEGF) has been known as a potential vasculogenic and angiogenic factor and its receptor (VEGFR2) is a major receptor to response to the angiogenic activity of VEGF. The technique that to break the immune tolerance of "self-antigens" associated with angiogenesis is an attractive approach for cancer therapy with T4 phage display system. In this experiment, mouse VEGFR2 was constructed on T4 phage nanometer-particle surface as a recombinant vaccine. T4-mVEGFR2 recombinant vaccine was identified by PCR and western blot assay. Immunotherapy with T4-mVEGFR2 was confirmed by protective immunity against Lewis lung carcinoma (LLC) in mice. The antibody against mVEGFR2 was detected by ELISPOT, ELISA and Dot ELISA. The inhibitive effects against angiogenesis were studied using CD31 and CD105 via histological analysis. VEGF-mediated endothelial cells proliferation and tube formation were inhibited in vitro by immunoglobulin induced by T4-mVEGFR2. The antitumor activity was substantiated from the adoptive transfer of the purified immunoglobulin. Antitumor activity and autoantibody production of mVEGFR2 could be neutralized by the depletion of CD4+T lymphocytes. These studies strongly suggest that T4-mVEGFR2 recombinant vaccine might be a promising antitumor approach.

Inhibition of tumor-induced myeloid-derived suppressor cell function by a nanoparticulated adjuvant

The interaction between cancer vaccine adjuvants and myeloid-derived suppressor cells (MDSCs) is currently poorly understood. Very small size proteoliposomes (VSSP) are a nanoparticulated adjuvant under investigation in clinical trials in patients with renal carcinoma, breast cancer, prostate cancer, and cervical intraepithelial neoplasia grade III. We found that VSSP adjuvant induced a significant splenomegaly due to accumulation of CD11b(+)Gr-1(+) cells. However, VSSP-derived MDSCs showed a reduced capacity to suppress both allogeneic and Ag-specific CTL response compared with that of tumor-induced MDSCs. Moreover, splenic MDSCs isolated from tumor-bearing mice treated with VSSP were phenotypically more similar to those isolated from VSSP-treated tumor-free mice and much less suppressive than tumor-induced MDSCs, both in vitro and in vivo. Furthermore, different from dendritic cell vaccination, inoculation of VSSP-based vaccine in EG.7-OVA tumor-bearing mice was sufficient to avoid tumor-induced tolerance and stimulate an immune response against OVA Ag, similar to that observed in tumor-free mice. This effect correlated with an accelerated differentiation of MDSCs into mature APCs that was promoted by VSSP. VSSP used as a cancer vaccine adjuvant might thus improve antitumor efficacy not only by stimulating a potent immune response against tumor Ags but also by reducing tumor-induced immunosuppression.

Antitumor activity of endogenous mFlt4 displayed on a T4 phage nanoparticle surface

AIM

Flt4 plays a key role in promoting tumor metastasis by stimulating solid tumor lymphangiogenesis. In this study, mouse Flt4 (mFlt4) was displayed on T4 phage in order to explore the feasibility of breaking immune tolerance to "self-antigens" and to evaluate the phage's antitumor activity.

METHODS

A T4 phage nanometer particle expressing mFlt4 on the surface was constructed for evaluation as a recombinant vaccine. The presence of the mFlt4 gene in the T4-mFlt4 recombinant vaccine was verified by PCR and Western blot analysis. The immunotherapeutic potential of T4-mFlt4 was tested in mice injected with Lewis lung carcinoma (LLC) cells. Anti-Flt4 antibody producing B cells were detected by ELISPOT. The effects of T4-mFlt4 on lymphatic metastasis and lymphangiogenesis were investigated in a mouse antimetastasis assay and by Flt4 and CD105 immunohistochemistry.

RESULTS

The T4-mFlt4 recombinant vaccine demonstrated antitumor activity and elicited autoantibodies against mFlt4. Mice carrying LLC-derived tumors exhibited prolonged survival when given the vaccine compared with control-treated animals. The vaccine also inhibited lymphangiogenesis and tumor metastasis in the mouse models. However, T4-mFlt4 was not observed to inhibit tumor growth.

CONCLUSION

The T4-mFlt4 recombinant vaccine induced protective antitumor immunity and antimetastasis against LLC. Induction of an autoimmune response directed against tumor progression merits further study as a new strategy for immunotherapy in cancer.

Targeting toll-like receptor 9 with CpG oligodeoxynucleotides enhances anti-tumor responses of peripheral blood mononuclear cells from human lung cancer patients

CpG-oligonucleotides (CpG-ODN), which induce signaling through Toll-like receptor 9 (TLR9), are currently under investigation as adjuvants in therapy against infections and cancer. However, whether the CpG-ODN alone could enhance the anti-tumor immunity and the underlying mechanisms remains unclear. Here, we investigated that stimulation of peripheral blood mononuclear cells (PBMCs) from human lung cancer patients with CpG-ODN induced proliferation responses of the PBMCs, accompanied by the elevated cytokine secretion, including IFN-alpha, IL-12 and TNF-alpha. In addition, after treatment with CpG-ODN, the cytotoxic activity of the PBMCs and the production of IFN-gamma in CD8(+) T cells were dramatically enhanced. Furthermore, we found that adoptive transfer of CpG-ODN treated PBMCs significantly inhibited the tumor progression in nude mice, which were challenged with the autologuous tumor cells from human lung cancer patients. Finally, we demonstrated that the inhibitory CpG ODN or chloroquine could dramatically abrogate the enhanced anti-tumor responses of the CpG ODN treated PBMCs. Our findings suggest that the CpG-ODN is promising as a preventive and therapeutic anti-tumor measure against pulmonary carcinoma.

T cells are crucial for the anti-metastatic effect of anti-epidermal growth factor receptor antibodies

Experimental evidences supporting the epidermal growth factor receptor (EGFR) as an important molecule for tumor metastasis had been accumulated. Currently, anti-EGFR monoclonal antibodies (mAbs) constitute a promising approach for the treatment of patients with metastatic tumors. However, the mechanisms associated with the potent anti-metastatic effect of these mAbs have not been completely elucidated due to the lack of appropriate syngeneic preclinical models. In this paper, we have investigated the effects of 7A7, an antibody specific to murine EGFR, on the metastatic properties of D122 murine lung carcinoma. 7A7 mAb significantly impaired metastatic spread of D122 cells in C57BL/6 mice by direct anti-proliferative and pro-apoptotic effects on tumor metastasis. 7A7 mAb capacity to inhibit EGFR activation on D122 cells could contribute to its anti-metastatic effect. In addition, 7A7 mAb was able to induce in vitro antibody-dependent cell-mediated cytotoxicity on D122 cells. Interestingly, 7A7 mAb treatment increased the number of natural killer cells, T lymphocytes and dendritic cells infiltrating the metastatic sites. More strikingly, depletion of CD8(+) and CD4(+) T cells in vivo completely abrogated the 7A7 mAb anti-metastatic activity whereas function of natural killer cells was irrelevant. This study supports an in vivo role for T cell response in the mechanism of action of anti-EGFR mAbs, suggesting the induction of an adjuvant effect.

Inhibition of Lewis lung carcinoma growth by Toxoplasma gondii through induction of Th1 immune responses and inhibition of angiogenesis

Toxoplasma gondii is an obligate intracellular protozoan parasite that induces antitumor activity against certain types of cancers. However, little information is available regarding the immunologic mechanisms that regulate these effects. For this purpose, C57BL/6 mice were administered either the T. gondii Me49 strain orally or Lewis lung carcinoma (LLC) cells intramuscularly. Survival rates, tumor size, histopathology, and immune responses were determined for each group, and angiogenesis was evaluated by in vivo Matrigel plug assay. Toxoplasma-infected (TG-injected) mice survived the entire experimental period, whereas cancer cell-bearing (LLC-injected) mice died within six weeks. Mice injected with both T. gondii and cancer cells (TG/LLC-injected group) showed significantly increased survival rates, CD8+ T-cell percentages, IFN-gamma mRNA expression levels, serum IgG2a titers, and CTL responses as compared to the LLC-injected mice. In addition, angiogenesis in the TG/LLC-injected mice was notably inhibited. These effects in TG/LCC-injected mice were similar or were increased by the addition of an adjuvant, Quil-A. However, TG/LLC-injected mice showed decreased percentages of CD4+ and CD8+ T cells, IFN-gamma mRNA expression levels, and serum IgG1 and IgG2a titers as compared to TG-injected mice. Taken together, our results demonstrate that T. gondii infection inhibits tumor growth in the Lewis lung carcinoma mouse model through the induction of Th1 immune responses and antiangiogenic activity.