Yeast whole glucan particle (WGP) beta-glucan in conjunction with antitumour monoclonal antibodies to treat cancer

Extraction, purification, structural characteristics, bioactivity and potential applications of polysaccharides from Avena sativa L.: A review

Avena sativa L. (A. sativa L.), commonly known as oat, is a significant cereal grain crop with excellent edible and medicinal value. Oat polysaccharides (OPs), the major bioactive components of A. sativa L., have received considerable attention due to their beneficial bioactivities. However, the isolation and purification methods of OPs lack innovation, and the structure-activity relationship remains unexplored. This review emphatically summarized recent progress in the extraction and purification methods, structural characteristics, biological activities, structure-to-function associations and the potential application status of OPs. Different materials and isolation methods can result in the differences in the structure and bioactivity of OPs. OPs are mainly composed of various monosaccharide constituents, including glucose, arabinose and mannose, along with galactose, xylose and rhamnose in different molar ratios and types of glycosidic bonds. OPs exhibited a broad molecular weight distribution, ranging from 1.34 × 105 Da to 4.1 × 106 Da. Moreover, structure-activity relationships demonstrated that the monosaccharide composition, molecular weight, linkage types, and chemical modifications are closely related to their multiple bioactivities, including immunomodulatory activity, antioxidant effect, anti-inflammatory activity, antitumor effects etc. This work can provide comprehensive knowledge, update information and promising directions for future exploitation and application of OPs as therapeutic agents and multifunctional food additives.

Immunomodulatory Effect and Biological Significance of β-Glucans

β-glucan, one of the homopolysaccharides composed of D-glucose, exists widely in cereals and microorganisms and possesses various biological activities, including anti-inflammatory, antioxidant, and anti-tumor properties. More recently, there has been mounting proof that β-glucan functions as a physiologically active "biological response modulator (BRM)", promoting dendritic cell maturation, cytokine secretion, and regulating adaptive immune responses-all of which are directly connected with β-glucan-regulated glucan receptors. This review focuses on the sources, structures, immune regulation, and receptor recognition mechanisms of β-glucan.

The role of neutrophils in trained immunity

The principle of trained immunity represents innate immune memory due to sustained, mainly epigenetic, changes triggered by endogenous or exogenous stimuli in bone marrow (BM) progenitors (central trained immunity) and their innate immune cell progeny, thereby triggering elevated responsiveness against secondary stimuli. BM progenitors can respond to microbial and sterile signals, thereby possibly acquiring trained immunity-mediated long-lasting alterations that may shape the fate and function of their progeny, for example, neutrophils. Neutrophils, the most abundant innate immune cell population, are produced in the BM from committed progenitor cells in a process designated granulopoiesis. Neutrophils are the first responders against infectious or inflammatory challenges and have versatile functions in immunity. Together with other innate immune cells, neutrophils are effectors of peripheral trained immunity. However, given the short lifetime of neutrophils, their ability to acquire immunological memory may lie in the central training of their BM progenitors resulting in generation of reprogrammed, that is, "trained", neutrophils. Although trained immunity may have beneficial effects in infection or cancer, it may also mediate detrimental outcomes in chronic inflammation. Here, we review the emerging research area of trained immunity with a particular emphasis on the role of neutrophils and granulopoiesis.

The role and regulation of Maf proteins in cancer

The Maf proteins (Mafs) belong to basic leucine zipper transcription factors and are members of the activator protein-1 (AP-1) superfamily. There are two subgroups of Mafs: large Mafs and small Mafs, which are involved in a wide range of biological processes, such as the cell cycle, proliferation, oxidative stress, and inflammation. Therefore, dysregulation of Mafs can affect cell fate and is closely associated with diverse diseases. Accumulating evidence has established both large and small Mafs as mediators of tumor development. In this review, we first briefly describe the structure and physiological functions of Mafs. Then we summarize the upstream regulatory mechanisms that control the expression and activity of Mafs. Furthermore, we discuss recent studies on the critical role of Mafs in cancer progression, including cancer proliferation, apoptosis, metastasis, tumor/stroma interaction and angiogenesis. We also review the clinical implications of Mafs, namely their potential possibilities and limitations as biomarkers and therapeutic targets in cancer.

Evaluation of Immune Modulation by β-1,3; 1,6 D-Glucan Derived from Ganoderma lucidum in Healthy Adult Volunteers, A Randomized Controlled Trial

Fungi-derived β-glucan, a type of glucopolysaccharide, has been shown to possess immune-modulatory properties in clinical settings. Studies have indicated that β-glucan derived from Ganoderma lucidum (commonly known as Reishi) holds particular promise in this regard, both in laboratory and in vivo settings. To further investigate the efficacy and safety of Reishi β-glucan in human subjects, a randomized, double-blinded, placebo-controlled clinical trial was conducted among healthy adult volunteers aged 18 to 55. Participants were instructed to self-administer the interventions or placebos on a daily basis for 84 days, with bloodwork assessments conducted at the beginning and end of the study. The results of the trial showed that subjects in the intervention group, who received Reishi β-glucan, exhibited a significant enhancement in various immune cell populations, including CD3⁺, CD4⁺, CD8⁺ T-lymphocytes, as well as an improvement in the CD4/CD8 ratio and natural killer cell counts when compared to the placebo group. Additionally, a statistically significant difference was observed in serum immunoglobulin A levels and natural killer cell cytotoxicity between the intervention and placebo groups. Notably, the intervention was found to be safe and well tolerated, with no statistically significant changes observed in markers of kidney or liver function in either group. Overall, the study provides evidence for the ability of Reishi β-glucan to modulate immune responses in healthy adults, thereby potentially bolstering their defense against opportunistic infections.

Beta-Glucan from S. cerevisiae Protected AOM-Induced Colon Cancer in cGAS-Deficient Mice Partly through Dectin-1-Manipulated Macrophage Cell Energy

Although the impacts of Saccharomyces cerevisiae on cancers are mentioned, data on its use in mice with cyclic GMP-AMP synthase deficiency (cGAS-/-) are even rarer. Here, 12 weeks of oral administration of S. cerevisiae protected cGAS-/- mice from azoxymethane (AOM)-induced colon cancers, partly through dysbiosis attenuation (fecal microbiome analysis). In parallel, a daily intralesional injection of a whole glucan particle (WGP; the beta-glucan extracted from S. cerevisiae) attenuated the growth of subcutaneous tumor using MC38 (murine colon cancer cell line) in cGAS-/- mice. Interestingly, the incubation of fluorescent-stained MC38 with several subtypes of macrophages, including M1 (using Lipopolysaccharide; LPS), M2 (IL-4), and tumor-associated macrophages (TAM; using MC38 supernatant activation), could not further reduce the tumor burdens (fluorescent intensity) compared with M0 (control culture media). However, WGP enhanced tumoricidal activities (fluorescent intensity), the genes of M1 pro-inflammatory macrophage polarization (IL-1β and iNOS), and Dectin-1 expression and increased cell energy status (extracellular flux analysis) in M0, M2, and TAM. In M1, WGP could not increase tumoricidal activities, Dectin-1, and glycolysis activity, despite the upregulated IL-1β. In conclusion, S. cerevisiae inhibited the growth of colon cancers through dysbiosis attenuation and macrophage energy activation, partly through Dectin-1 stimulation. Our data support the use of S. cerevisiae for colon cancer protection.

More Prominent Inflammatory Response to Pachyman than to Whole-Glucan Particle and Oat-β-Glucans in Dextran Sulfate-Induced Mucositis Mice and Mouse Injection through Proinflammatory Macrophages

(1→3)-β-D-glucans (BG) (the glucose polymers) are recognized as pathogen motifs, and different forms of BGs are reported to have various effects. Here, different BGs, including Pachyman (BG with very few (1→6)-linkages), whole-glucan particles (BG with many (1→6)-glycosidic bonds), and Oat-BG (BG with (1→4)-linkages), were tested. In comparison with dextran sulfate solution (DSS) alone in mice, DSS with each of these BGs did not alter the weight loss, stool consistency, colon injury (histology and cytokines), endotoxemia, serum BG, and fecal microbiome but Pachyman-DSS-treated mice demonstrated the highest serum cytokine elicitation (TNF-α and IL-6). Likewise, a tail vein injection of Pachyman together with intraperitoneal lipopolysaccharide (LPS) induced the highest levels of these cytokines at 3 h post-injection than LPS alone or LPS with other BGs. With bone marrow-derived macrophages, BG induced only TNF-α (most prominent with Pachyman), while LPS with BG additively increased several cytokines (TNF-α, IL-6, and IL-10); inflammatory genes (iNOS, IL-1β, Syk, and NF-κB); and cell energy alterations (extracellular flux analysis). In conclusion, Pachyman induced the highest LPS proinflammatory synergistic effect on macrophages, followed by WGP, possibly through Syk-associated interactions between the Dectin-1 and TLR-4 signal transduction pathways. Selection of the proper form of BGs for specific clinical conditions might be beneficial.

Increasing the Production of β-Glucan from Saccharomyces carlsbergensis RU01 by Using Tannic Acid

In this study, we increased β-glucan production from brewer’s yeast, Saccharomyces carlsbergensis RU01, by using tannic acid. High-pressure freezing and transmission electron microscopy (HPF-TEM) revealed that the yeast cell wall obtained from yeast malt (YM) medium supplemented with 0.1% w/v tannic acid was thicker than that of yeast cultured in YM medium alone. The production of β-glucan from S. carlsbergensis RU01 was optimized in 3% w/v molasses and 0.1% w/v diammonium sulfate (MDS) medium supplemented with 0.1% w/v tannic acid. The results showed that MDS medium supplemented with 0.1% w/v tannic acid significantly increased the dry cell weight (DCW), and the β-glucan production was 0.28±0.01% w/v and 11.99±0.04% w/w. Tannic acid enhanced the β-glucan content by up to 42.23%. β-Glucan production in the stirred tank reactor (STR) was 1.4-fold higher than that in the shake flask (SF) culture. Analysis of the β-glucan composition by Fourier transform infrared (FTIR) spectroscopy showed that the β-glucan of S. carlsbergensis RU01 cultured in MDS medium supplemented with 0.1% w/v tannic acid had a higher proportion of polysaccharide than that of the control. In addition, β-glucans from brewer’s yeast can be used as prebiotic and functional foods for human health and in animal feed.

β-glucan therapy converts the inhibition of myeloid-derived suppressor cells in oral cancer patients

OBJECTIVES

The myeloid-derived suppressor cells (MDSCs) frequently have a high expansion in cancer patients. This research explored whether administration of β-glucan could increase anti-tumor immunity in oral squamous cell carcinoma (OSCC) patients.

MATERIALS AND METHODS

This study evaluated the MDSC level of circulating blood as CD33⁺ /CD11b⁺ /HLA-DR^-/low by flow cytometry in 30 healthy donors (HDs, group I), in 48 oral squamous cell carcinoma (OSCC) patients before and after 14-day preoperative administration of β-glucan (group II), and in 52 OSCC patients without taking β-glucan (group III).

RESULTS

A significantly higher mean MDSC level was observed in 100 OSCC patients than in 30 HDs (p < .001). There was a significant reduction of the mean MDSC level in group II patients after taking β-glucan (p < .001). Moreover, we discovered a significantly higher recurrence-free survival (RFS) in group II than in group III patients (p = .026). Finally, the multivariate Cox regression further identified the MDSC level ≤1% and administration of β-glucan as more favorable prognostic factors for OSCC patients.

CONCLUSION

Preoperative administration of β-glucan can augment anti-tumor immunity and increase RFS rate via subversion of suppressive function of MDSC in OSCC patients.

Spent Brewer's Yeast as a Source of Insoluble β-Glucans

In the brewing process, the consumption of resources and the amount of waste generated are high and due to a lot of organic compounds in waste-water, the capacity of natural regeneration of the environment is exceeded. Residual yeast, the second by-product of brewing is considered to have an important chemical composition. An approach with nutritional potential refers to the extraction of bioactive compounds from the yeast cell wall, such as β-glucans. Concerning the potential food applications with better textural characteristics, spent brewer’s yeast glucan has high emulsion stability and water-holding capacity fitting best as a fat replacer in different food matrices. Few studies demonstrate the importance and nutritional role of β-glucans from brewer’s yeast, and even less for spent brewer’s yeast, due to additional steps in the extraction process. This review focuses on describing the process of obtaining insoluble β-glucans (particulate) from spent brewer’s yeast and provides an insight into how a by-product from brewing can be converted to potential food applications.

Recent advances in the application of probiotic yeasts, particularly Saccharomyces, as an adjuvant therapy in the management of cancer with focus on colorectal cancer

Today, the increasing rate of cancer-related mortality, has rendered cancer a major global challenge, and the second leading cause of death worldwide. Conventional approaches in the treatment of cancer mainly include chemotherapy, surgery, immunotherapy, and radiotherapy. However, these approaches still come with certain disadvantages, including drug resistance, and different side effects such as gastrointestinal (GI) irritation (e.g., diarrhea, mucositis). This has encouraged scientists to look for alternative therapeutic methods and adjuvant therapies for a more proper treatment of malignancies. Application of probiotics as an adjuvant therapy in the clinical management of cancer appears to be a promising strategy, with several notable advantages, e.g., increased safety, higher tolerance, and negligible GI side effects. Both in vivo and in vitro analyses have indicated the active role of yeast probiotics in mitigating the rate of cancer cell proliferation, and the induction of apoptosis through regulating the expression of cancer-related genes and cellular pathways. Strain-specific anti-cancer activities of yeast probiotics strongly suggest that their administration along with the current cancer therapies may be an efficient method to reduce the side effects of these approaches. The main purpose of this article is to evaluate the efficacy of yeast probiotics in alleviating the adverse effects associated with cancer therapies.

Barley beta-Glucan and Zymosan induce Dectin-1 and Toll-like receptor 2 co-localization and anti-leishmanial immune response in Leishmania donovani-infected BALB/c mice

Toll-like receptors (TLRs), TLR2 in particular, are shown to recognize various glycans and glycolipid ligands resulting in various immune effector functions. As barley β-glucan and zymosan are the glycans implicated in immunomodulation, we examined whether these ligands interact with Dectin-1, a lectin-type receptor for glycans, and TLR2 and induce immune responses that can be used against Leishmania infection in a susceptible host. The binding affinity of barley β-glucan and zymosan with Dectin-1 and TLR2 was studied in silico. Barley β-glucan- and zymosan-induced dectin-1 and TLR2 co-localization was studied by confocal microscopy and co-immunoprecipitation. These ligands-induced signalling and effector functions were assessed by Western blot analyses and various immunological assays. Finally, the anti-leishmanial potential of barley β-glucan and zymosan was tested in Leishmania donovani -infected macrophages and in L. donovani-infected BALB/c mice. Both barley β-glucan and zymosan interacted with TLR2 and dectin-1, but with a much stronger binding affinity for the latter, and therefore induced co-localization of these two receptors on BALB/c-derived macrophages. Both ligandsactivated MyD88- and Syk-mediated downstream pathways for heightened inflammatory responses in L. donovani-infected macrophages. These two ligands induced T cell-dependent host protection in L. donovani-infected BALB/c mice. These results establish a novel modus operandi of β-glucans through dectin-1 and TLR2 and suggest an immuno-modulatory potential against infectious diseases.

Simultaneous Nanoscale Imaging of Chemical and Architectural Heterogeneity on Yeast Cell Wall Particles

Particles extracted from yeast cell walls are naturally occurring immunomodulators with significant therapeutic applications. Their biological function has been thought to be a consequence of the overall chemical composition. In contrast, here we achieve direct nanoscale visualization of the compositional and structural heterogeneity of yeast cell wall particles and demonstrate that such nanoscale heterogeneity directly influences the receptor function of immune cells. By combining peak force infrared (PFIR) microscopy with super-resolution fluorescence microscopy, we achieve simultaneous chemical, topographical, and mechanical mapping of cell wall particles extracted from the yeast Saccharomyces cerevisiae with ≈6 nm resolution. We show that polysaccharides (β-glucan and chitin) and proteins are organized in specific nonuniform structures, and their heterogeneous spatial organization leads to heterogeneous recruitment of receptors on immune cell membranes. Our findings indicate that the biological function of yeast cell wall particles depends on not only their overall composition but also the nanoscale distribution of the different cell wall components.

Oral treatment with T6-loaded yeast cell wall particles reduces the parasitemia in murine visceral leishmaniasis model

Yeast cell wall particles isolated from Saccharomyces cerevisiae (scYCWPs) have a rich constitution of β-glucan derived from the cell wall. After removing intracellular contents, β-glucan molecules are readily recognized by dectin-1 receptors, present on the cytoplasmic membrane surface of the mononuclear phagocytic cells and internalized. Leishmania spp. are obligate intracellular parasites; macrophages are its primary host cells. An experimental murine model of visceral leishmaniasis caused by L. infantum was used to evaluate the antileishmanial activity of oral administration of these particles. A low-water soluble thiophene previously studied in vitro against L. infantum was entrapped into scYCWPs to direct it into the host cell, in order to circumvent the typical pharmacokinetic problems of water-insoluble compounds. We found that scYCWPs + T6 reduced the parasitic burden in the liver and spleen. There was an increase in IFN-γ levels related to nitric oxide production, explaining the reduction of the L. infantum burden in the tissue. Histological analysis did not show signals of tissue inflammation and biochemical analysis from plasma did not indicate signals of cytotoxicity after scYCWPs + T6 treatment. These findings suggested that scYCWPs + T6 administered through oral route reduced the parasitic burden without causing toxic effects, satisfying requirements for development of new strategies to treat leishmaniasis.

Hemicellulose from Plant Biomass in Medical and Pharmaceutical Application: A Critical Review

BACKGROUND

Due to the non-toxicity, abundance and biodegradability, recently more and more attention has been focused on the exploration of hemicellulose as the potential substrate for the production of liquid fuels and other value-added chemicals and materials in different fields. This review aims to summarize the current knowledge on the promising application of nature hemicellulose and its derivative products including its degradation products, its new derivatives and hemicellulosebased medical biodegradable materials in the medical and pharmaceutical field, especially for inmmune regulation, bacteria inhibition, drug release, anti-caries, scaffold materials and anti-tumor.

METHODS

We searched the related papers about the medical and pharmaceutical application of hemicellulose and its derivative products, and summarized their preparation methods, properties and use effects.

RESULTS

Two hundred and twenty-seven papers were included in this review. Forty-seven papers introduced the extraction and application in immune regulation of nature hemicellulose, such as xylan, mannan, xyloglucan (XG) and β-glucan. Seventy-seven papers mentioned the preparation and application of degradation products of hemicellulose for adjusting intestinal function, maintaining blood glucose levels, enhancing the immunity and alleviating human fatigue fields such as xylooligosaccharides, xylitol, xylose, arabinose, etc. The preparation of hemicellulose derivatives were described in thirty-two papers such as hemicellulose esters, hemicellulose ethers and their effects on anticoagulants, adsorption of creatinine, the addition of immune cells and the inhibition of harmful bacteria. Finally, the preparations of hemicellulose-based materials such as hydrogels and membrane for the field of drug release, cell immobilization, cancer therapy and wound dressings were presented using fifty-five papers.

CONCLUSION

The structure of hemicellulose-based products has the significant impact on properties and the use effect for the immunity, and treating various diseases of human. However, some efforts should be made to explore and improve the properties of hemicellulose-based products and design the new materials to broaden hemicellulose applications.

Curcumin encapsulation in yeast glucan particles promotes its anti-inflammatory potential in vitro

Glucan particles (GPs) from Saccharomyces cerevisiae are hollow shells that are composed mainly of β-1,3-d-glucan, which has demonstrated immunomodulatory and anti-inflammatory potential both in vitro and in vivo. Curcumin is a natural hydrophobic phenolic compound, which possesses a significant anti-inflammatory effect and is used as supportive therapy in the treatment of many inflammatory diseases. The aim of this study is to evaluate the possible synergic effect and other benefits of the co-application of GPs and curcumin in the form of pharmaceutical composites. GP/curcumin composites were prepared using controlled evaporation of the organic solvent and their anti-oxidative effect and anti-inflammatory potential were tested on THP1‑XBlue™‑MD2‑CD14 human monocytes cell line. The anti-oxidative effect was measured on pyocyanin-stimulated cells in vitro and the NF-κB/AP-1 signaling pathway on lipopolysaccharide pre-treated monocytes was chosen for anti-inflammatory assays. The secretion of pro-inflammatory cytokines TNF-α and IL-1β was evaluated as well. Results mostly showed a pro-oxidative activity of empty GPs, however, pharmaceutical composites demonstrated an anti-oxidative effect. The activity of NF-κB/AP-1 was substantially decreased by the tested GP/curcumin composites, which also caused the attenuation of cytokines secretion. The obtained results indicate a beneficial effect of the incorporation of curcumin into GPs.

Activity and Cell-Death Pathway in Leishmania infantum Induced by Sugiol: Vectorization Using Yeast Cell Wall Particles Obtained From Saccharomyces cerevisiae

Visceral leishmaniasis, caused by Leishmania infantum, is a neglected tropical disease, to which efforts in the innovation of effective and affordable treatments remain limited, despite the rising incidence in several regions of the world. In this work, the antileishmanial effects of sugiol were investigated in vitro. This compound was isolated from the bark of Cupressus lusitanica and showed promising activity against L. infantum. In spite of the positive results, it is known that the compound is a poorly water-soluble diterpene molecule, which hinders further investigation, especially in preclinical animal studies. Thus, in an alternative delivery method, sugiol was entrapped in glucan-rich particles obtained from Saccharomyces cerevisiae yeast cell walls (YCWPs). To evaluate the activity of sugiol, the experiments were divided into two parts: (i) the in vitro investigation of antileishmanial activity of free sugiol against L. infantum promastigotes after 24, 48, and 72 h of treatment and (ii) the evaluation of antileishmanial activity of sugiol entrapped in glucan-rich particles against intracellular L. infantum amastigotes. Free sugiol induced the cell-death process in promastigotes, which was triggered by enhancing cytosolic calcium level and promoting the autophagy up to the first 24 h. Over time, the presence of autophagic vacuoles became rarer, especially after treatment with lower concentrations of sugiol, but other cellular events intensified, like ROS production, cell shrinkage, and phosphatidylserine exposure. Hyperpolarization of mitochondrial membrane potential was found at 72 h, induced by the mitochondria calcium uptake, causing an increase in ROS production and lipid peroxidation as a consequence. These events resulted in the cell death of promastigotes by secondary necrosis. Sugiol entrapped in glucan-rich particles was specifically recognized by dectin-1 receptor on the plasma membrane of macrophages, the main host cell of Leishmania spp. Electron micrographs revealed particles containing sugiol within the infected macrophages and these particles were active against the intracellular L. infantum amastigotes without affecting the host cell. Therefore, the YCWPs act like a Trojan horse to successfully deliver sugiol into the macrophage, presenting an interesting strategy to deliver water-insoluble drugs to parasitized cells.

Glucan Particles Are a Powerful Adjuvant for the HBsAg, Favoring Antiviral Immunity

The lack of vaccine adjuvants that are able to induce robust T cell responses fosters the search for more powerful options. Pathogen-like particles are a promising approach. The adjuvant activity of pathogen-like particles is highly influenced by size and surface composition. This study aimed to evaluate the adjuvant potential of two different β-glucan-based particles, blend chitosan/β-glucan particles (ChiGluPs), which are positively charged and have mean size of 1276 nm, and neutral yeast-derived glucan particles (GPs), with a mean size of 3 μm. Additionally, chitosan particles (ChiPs) were used to understand the effect of β-glucan addition (ChiGluPs). Mouse spleen cells responded through the production of either TNF-α or RANTES, following in vitro stimulation with particles containing either β-glucan (ChiGluPs and GPs) or chitosan (ChiGluPs and ChiPs). Human monocytes responded to all particles through TNF-α secretion. Subcutaneous vaccination of mice with the hepatitis B surface antigen (HBsAg) showed increased serum IgG for all particles compared to HBsAg alone (435-, 4500-, or 2500-fold increase for either ChiPs, ChiGluPs, or GPs). Interestingly, only GPs elicited the secretion of HBsAg-specific Th1, Th2, Th9, Th17, Th22, and Treg-related cytokines. This study demonstrates, for the first time, that GPs can have a significant role against the hepatitis B virus by favoring antiviral immunity.

Synthesis and Evaluation of 1,5-Dithia-d-laminaribiose, Triose, and Tetraose as Truncated β-(1→3)-Glucan Mimetics

The preparation and characterization of a series of di-, tri-, and tetrasaccharide analogues of β-(1→3)-glucans is described in which each pyranoside ring is replaced by a 5-thiopyranosyl ring and each glycosidic oxygen by a thioether. These oligomeric 1,5-dithio-d-glucopyranose derivatives were shown to inhibit the staining of human neutrophils and of mouse macrophages by fluorescent anti-CR3 and anti-Dectin-1 antibodies, respectively. The compounds were also demonstrated to stimulate phagocytosis and pinocytosis indicative of binding to the carbohydrate binding domains of complement receptor 3 (CR3) and Dectin-1. Activity in all three assays was optimum at the level of the trisaccharide mimic, suggesting that, while the replacement of ethereal oxygens by thioethers results in a greater affinity for the aromatic lined hydrophobic binding pockets, the presence of multiple longer C-S bonds eventually results in a mismatch and a loss of affinity.

Candida albicans β-Glucan-Containing Particles Increase HO-1 Expression in Oral Keratinocytes via a Reactive Oxygen Species/p38 Mitogen-Activated Protein Kinase/Nrf2 Pathway

Oral keratinocytes provide the first line of host defense against oral candidiasis. We speculated that interactions of fungal cell wall components with oral keratinocytes regulate the stress response against Candida infection and examined the expression of genes induced by heat-killed Candida albicans in oral immortalized keratinocytes using a cDNA microarray technique. Of 24,000 genes revealed by that analysis, we focused on HO-1, a stress-inducible gene, as its expression was increased by both heat-killed and live C. albicans In histological findings, HO-1 expression in the superficial layers of the oral epithelium following Candida infection was elevated compared to that in healthy epithelium. We then investigated fungal cell wall components involved in induction of HO-1 expression and found that β-glucan-containing particles (β-GPs) increased its expression. Furthermore, β-glucan was observed on the surface of both heat-killed C. albicans and Candida cells that had invaded the oral epithelium. Fungal β-GPs also promoted induction of intracellular reactive oxygen species (ROS), NADPH oxidase activation, and p38 mitogen-activated protein kinase (MAPK) phosphorylation, while those specific inhibitors inhibited the HO-1 expression induced by fungal β-GPs. Moreover, fungal β-GPs induced Nrf2 translocation into nuclei via p38 MAPK signaling, while the HO-1 expression induced by fungal β-GPs was inhibited by Nrf2-specific small interfering RNA (siRNA). Finally, knockdown of cells by HO-1- and Nrf2-specific siRNAs resulted in increased β-GP-mediated ROS production compared to that in the control cells. Our results show that the HO-1 induced by fungal β-GPs via ROS/p38 MAPK/Nrf2 from oral keratinocytes may have important roles in host defense against the stress caused by Candida infection in the oral epithelium.

Characterization of nuclear factor of activated T-cells-c3 (NFATc3) and gene expression of upstream-downstream signaling molecules in response to immunostimulants in Pacific red snapper cells

The nuclear factor of activated T cells (NFAT) proteins have crucial roles in the development and function of the immune system since they not only regulate activation of T cells but are also involved in the control of thymocyte development and T-cell differentiation. In this study, NFATc3 was characterized from the Pacific red snapper, Lutjanus peru. LpNFAtc3, which contains an open reading of 3300 bp frame coding for a protein of 1100 aa with a predicted molecular weight of 118.52 kDa. The predicted protein showed a conserved NFAT family structure with signature motifs and domains, sharing high identity (up to 76%) compared to other fish sequences. NFATc3 gene expression was analyzed by real time-PCR in head-kidney cells (leukocytes and lymphocytes) following yeast, zymosan and Vibrio parahaemolyticus stimulation along with the expression of upstream (ILF2, ILF3 and CaN) and downstream (CD3, TCRβ, IL-6 and IL-12) molecules. This study revealed a broad expression of NFATc3 with a relative strong expression in intestine and lymphocytes. The expression of NFATc3 was differentially up-regulated after stimulation with yeast in head-kidney leukocytes and after bacterial infection in lymphocytes at 24 h. Interestingly, the yeast and zymosan were able to activate ILF2, ILF3 and CaN mRNA gene expression in both kinds of cells. On the other hand, NFAT downstream genes such as CD3, TCRβ, IL-6 and IL-12 were significantly up-regulated in leukocytes stimulated with yeast or zymosan at 12 h; however in lymphocytes, this up-regulation was detected when cells reacted to V. parahaemolyticus stimuli at 24 h. Stimulating Pacific red snapper leukocytes with immunostimulants as yeast significantly up-regulated the expression of NFATc3, and up- and down-stream molecular genes and NFATc3 lymphocytes expression were potentially involved in responses to invasion of bacterial pathogens in an early immune response.

Systemic administration of β-glucan of 200 kDa modulates melanoma microenvironment and suppresses metastatic cancer

Converting an immunosuppressive melanoma microenvironment into one that favors the induction of antitumor immunity is indispensable for effective cancer immunotherapy. In the current study we demonstrate that oat-derived β-(1-3)-(1-4)-glucan of 200 kDa molecular size (BG34-200) previously shown to mediate direct interaction with macrophages could alter the immune signature within melanoma microenvironment. Systemic administration of BG34-200 resulted in reversion of tolerant melanoma microenvironment to an immunogenic one that allows M1-type activation of macrophages, the induction of pro-inflammatory cytokines/chemokines including IFN-γ, TNF-α, CXCL9, and CXCL10, and enhanced IRF1 and PD-L1 expression. In turn, BG34-200 induced a superior antitumor response against primary and lung metastatic B16F10 melanoma compared to untreated controls. The enhanced tumor destruction was accompanied with significantly increased tumor infiltration of CD4⁺ and CD8⁺ T cells as well as elevated IFN-γ in the tumor sites. Systemic administration of BG34-200 also provoked systemic activation of tumor draining lymph node T cells that recognize antigens naturally expressing in melanoma (gp100/PMEL). Mechanistic studies using CD11b-knockout (KO), CD11 c-DTR transgenic mice and nude mice revealed that macrophages, DCs, T cells and NK cells were all required for the BG34-200-induced therapeutic benefit. Studies using IFN-γ-KO transgenic mice showed that IFN-γ was essential for the BG34-200-elicited antitumor response. Beyond melanoma, the therapeutic efficacy of BG34-200 and its immune stimulating activity were demonstrated in a mouse model of osteosarcoma. Together, BG34-200 is highly effective in modulating antitumor immunity. Our data support the potential therapeutic use of this novel immune modulator in the treatment of metastatic melanoma.

Gamma-irradiated β-glucan modulates signaling molecular targets of hepatocellular carcinoma in rats

β-glucans are one of the most abundant forms of polysaccharides known as biological response modifiers which influence host's biological response and stimulate immune system. Accordingly, this study was initiated to evaluate irradiated β-glucan as a modulator for cellular signaling growth factors involved in the pathogenesis of hepatocellular carcinoma in rats. Hepatocellular carcinoma was induced with 20 mg diethylnitrosamine/kg BW. Rats received daily by gastric gavage 65 mg irradiated β-glucan/kg BW. It was found that treatment of rats with diethylnitrosamine induced hepatic injury and caused significant increase in liver injury markers with a concomitant significant increase in both hepatic oxidative and inflammatory indices: alpha-fetoprotein, interferon gamma, and interleukin 6 in comparison with normal and irradiated β-glucan-treated groups. Western immunoblotting showed a significant increase in the signaling growth factors: extracellular signal-regulated kinase 1 and phosphoinositide 3-kinase proteins in a diethylnitrosamine-treated group while both preventive and therapeutic irradiated β-glucan treatments recorded significant improvement versus diethylnitrosamine group via the modulation of growth factors that encounters hepatic toxicity. The transcript levels of vascular endothelial growth factor A and inducible nitric oxide synthase genes were significantly higher in the diethylnitrosamine-treated group in comparison with controls. Preventive and therapeutic treatments with irradiated β-glucan demonstrated that the transcript level of these genes was significantly decreased which demonstrates the protective effect of β-glucan. Histological investigations revealed that diethylnitrosamine treatment affects the hepatic architecture throughout the significant severe appearance of inflammatory cell infiltration in the portal area and congestion in the portal vein in association with severe degeneration and dysplasia in hepatocytes all over hepatic parenchyma. The severity of hepatic architecture changes was significantly decreased with both β-glucan therapeutic and preventive treatments. In conclusion, irradiated β-glucan modulated signal growth factors, vascular endothelial growth factor A, extracellular signal-regulated kinase 1, and phosphatidylinositol-3-kinase, which contributed to experimental hepatocarcinogenesis.

Orally administered β-glucan attenuates the Th2 response in a model of airway hypersensitivity

β-Glucan is a polysaccharide that can be extracted from fungal cell walls. Wellmune WGP^®, a preparation of β-1,3/1,6-glucans, is a dietary supplement that has immunomodulating properties. Here we investigated the effect WGP had on a mouse model of asthma. OVA-induced asthma in mice is characterized by infiltration of eosinophils into the lung, production of Th2 cytokines and IgE. Daily oral administration of WGP (400 µg) significantly reduced the influx of eosinophils into the lungs of OVA-challenged mice compared to control mice. In addition, WGP inhibited pulmonary production of Th2 cytokines (IL-4, IL-5, IL-13), however serum IgE levels were unaffected by WGP treatment. These data indicate that WGP could potentially be useful as an oral supplement for some asthma patients, however, it would need to be combined with therapies that target other aspects of the disease such as IgE levels. As such, further studies that examine the potential of WGP in combination with other therapies should be explored.

Molecular Interactions of β-(1→3)-Glucans with Their Receptors

β-(1→3)-Glucans can be found as structural polysaccharides in cereals, in algae or as exo-polysaccharides secreted on the surfaces of mushrooms or fungi. Research has now established that β-(1→3)-glucans can trigger different immune responses and act as efficient immunostimulating agents. They constitute prevalent sources of carbons for microorganisms after subsequent recognition by digesting enzymes. Nevertheless, mechanisms associated with both roles are not yet clearly understood. This review focuses on the variety of elucidated molecular interactions that involve these natural or synthetic polysaccharides and their receptors, i.e., Dectin-1, CR3, glycolipids, langerin and carbohydrate-binding modules.

Immune gene expression profile of Penaeus monodon in response to marine yeast glucan application and white spot syndrome virus challenge

Immunostimulant potential of eight marine yeast glucans (YG) from Candida parapsilosis R20, Hortaea werneckii R23, Candida spencermartinsiae R28, Candida haemulonii R63, Candida oceani R89, Debaryomyces fabryi R100, Debaryomyces nepalensis R305 and Meyerozyma guilliermondii R340 were tested against WSSV challenge in Penaeus monodon post larvae (PL). Structural characterization of these marine yeast glucans by proton nuclear magnetic resonance (NMR) indicated structures containing (1-6)-branched (1-3)-β-D-glucan. PL were fed 0.2% glucan incorporated diet once in seven days for a period of 45 days and the animals were challenged with white spot syndrome virus (WSSV). The immunostimulatory activity of yeast glucans were assessed pre- and post-challenge WSSV by analysing the expression profile of six antimicrobial peptide (AMP) genes viz., anti-lipopolysaccharide factor (ALF), crustin-1, crustin-2, crustin-3, penaeidin-3 and penaeidin-5 and 13 immune genes viz., alpha-2-macroglobulin (α-2-M), astakine, caspase, catalase, glutathione peroxidase, glutathione-s-transferase, haemocyanin, peroxinectin, pmCathepsinC, prophenol oxidase (proPO), Rab-7, superoxide dismutase and transglutaminase. Expression of seven WSSV genes viz., DNA polymerase, endonuclease, protein kinase, immediate early gene, latency related gene, thymidine kinase and VP28 were also analysed to detect the presence and intensity of viral infection in the experimental animals post-challenge. The study revealed that yeast glucans (YG) do possess immunostimulatory activity against WSSV and also supported higher survival (40-70 %) post-challenge WSSV. Among the various glucans tested, YG23 showed maximum survival (70.27%), followed by YG20 (66.66%), YG28 (60.97%), YG89 (58.53%), YG100 (54.05%), YG63 (48.64%), YG305 (45.7%) and YG340 (43.24%).

Placebo-driven clinical trials of yeast-derived β-(1-3) glucan in children with chronic respiratory problems

BACKGROUND

The role of glucan in stimulation of immune reactions has been studied for several decades. In this report we focused on the effects of orally administered glucan in children with chronic respiratory problems.

MATERIALS AND METHODS

We measured the levels of albumin, lysozyme and CRP in saliva of 40 children aged 8-12 years and evaluate the effects of 100 mg/d oral dose of glucan.

RESULTS

We found a significant increase in production of changes in production of lysozyme and CRP in glucan-treated children. In addition, a strong improvement in general conditions was found.

CONCLUSIONS

Short-term oral application of natural immunomodulator β-glucan stimulated mucosal immunity of children with chronic respiratory problems.

Whole glucan particles as a vaccine against murine aspergillosis

Vaccination with heat-killed Saccharomyces cerevisiae (HKY) protects against experimental infection by pathogenic fungi of five genera. Here we tested whether purified Saccharomyces cell wall β-glucan could induce protection against systemic aspergillosis. CD-1 mice were given three weekly vaccine doses subcutaneously prior to intravenous infection with Aspergillus fumigatus. Mice received PBS, 2.5 mg HKY, whole glucan particles (WGP), WGP conjugated to BSA (0.06 to 12 mg per dose), a soluble medium molecular mass (MMW) β-glucan alone or MMW-BSA (≤24 mg per dose). Survival and c.f.u. were determined, and cytokine induction and anti-β-glucan antibodies were assessed in vaccinated mice. Neither soluble MMW glucan, nor MMW-BSA was effective. HKY protected in two studies (survival and c.f.u. were reduced in brain and kidney organs, P<0.004). Six or 12 mg WGP or WGP-BSA prolonged survival (P≤0.004) and reduced c.f.u. in each organ (P≤0.015) in both experiments; 0.6 mg WGP or WGP-BSA prolonged survival (P≤0.015) and reduced c.f.u. (P≤0.015) in one experiment. Cytokine profiles in serum and bronchoalveolar lavage from uninfected vaccinated mice showed an innate and adaptive immune profile (i.e. upregulation of colony stimulating factors, interferons, TNF-α, chemokines such as MCP-1, MIP-1α, RANTES and KC, and Th17-activating cytokines such as IL-6, IL-1β, IL-17). No anti-β-glucan antibodies were in the sera, suggesting an adaptive T cell-mediated, not a B cell-mediated, protective response. Vaccination with WGP or WGP-BSA proved protective against systemic aspergillosis, equivalent to that of HKY, supporting the potential of particulate β-glucans, alone or conjugated, as vaccines against aspergillosis.

Immunomodulation of Fungal β-Glucan in Host Defense Signaling by Dectin-1

During the course of evolution, animals encountered the harmful effects of fungi, which are strong pathogens. Therefore, they have developed powerful mechanisms to protect themselves against these fungal invaders. β-Glucans are glucose polymers of a linear β(1,3)-glucan backbone with β(1,6)-linked side chains. The immunostimulatory and antitumor activities of β-glucans have been reported; however, their mechanisms have only begun to be elucidated. Fungal and particulate β-glucans, despite their large size, can be taken up by the M cells of Peyer's patches, and interact with macrophages or dendritic cells (DCs) and activate systemic immune responses to overcome the fungal infection. The sampled β-glucans function as pathogen-associated molecular patterns (PAMPs) and are recognized by pattern recognition receptors (PRRs) on innate immune cells. Dectin-1 receptor systems have been incorporated as the PRRs of β-glucans in the innate immune cells of higher animal systems, which function on the front line against fungal infection, and have been exploited in cancer treatments to enhance systemic immune function. Dectin-1 on macrophages and DCs performs dual functions: internalization of β-glucan-containing particles and transmittance of its signals into the nucleus. This review will depict in detail how the physicochemical nature of β-glucan contributes to its immunostimulating effect in hosts and the potential uses of β-glucan by elucidating the dectin-1 signal transduction pathway. The elucidation of β-glucan and its signaling pathway will undoubtedly open a new research area on its potential therapeutic applications, including as immunostimulants for antifungal and anti-cancer regimens.

NFAT control of innate immunity

The calcineurin/nuclear factor of activated T cells (NFAT) signaling pathway mediates multiple adaptive T-cell functions, but recent studies have shown that calcineurin/NFAT signaling also contributes to innate immunity and regulates the homeostasis of innate cells. Myeloid cells, including granulocytes and dendritic cells, can promote inflammation, regulate adaptive immunity, and are essential mediators of early responses to pathogens. Microbial ligation of pattern-recognition receptors, such as TLR4, CD14, and dectin 1, is now known to induce the activation of calcineurin/NFAT signaling in myeloid cells, a finding that has provided new insights into the molecular pathways that regulate host protection. Inhibitors of calcineurin/NFAT binding, such as cyclosporine A and FK506, are broadly used in organ transplantation and can act as potent immunosuppressive drugs in a variety of different disorders. There is increasing evidence that these agents influence innate responses as well as inhibiting adaptive T-cell functions. This review focuses on the role of calcineurin/NFAT signaling in myeloid cells, which may contribute to the various unexplained effects of immunosuppressive drugs already being used in the clinic.

β-Glucans inhibit intracellular growth of Mycobacterium bovis BCG but not virulent Mycobacterium tuberculosis in human macrophages

The yeast polysaccharide, β-glucan, has been shown to promote both anti-microbial and anti-tumor activities through its interaction with macrophages. Here we analyzed the effects of an insoluble whole glucan particle (WGP), a 1,3/1,6-β-glucan from Saccharomyces cerevisiae, and a soluble poly-1-6-β-d-glucopyranosyl-1-3-β-d-glucopyranose (PGG), a hydrolytic product of WGP, on the anti-microbial response of human macrophages against mycobacterial infection. Treatment of macrophages with WGP and PGG significantly decreased cell association and intracellular growth of Mycobacterium bovis BCG, but not Mycobacterium tuberculosis (M.tb) when compared to untreated controls. We characterized the influence of β-glucans on the generation of macrophage oxidative products and pro-inflammatory cytokines, two important anti-microbial defense mechanisms. WGP but not PGG treatment enhanced the oxidative response of macrophages as determined by the 2',7'-dichlorofluorescin (DCF) assay. WGP treatment also induced macrophages to produce pro-inflammatory cytokines. The β-glucan receptor, Dectin-1, was found to be involved in the WGP-induced macrophage oxidative burst and intracellular growth inhibition of M. bovis BCG. This report indicates that although some forms of β-glucan are able to stimulate the respiratory burst and cytokine production in human macrophages, and exhibit anti-microbial properties against M. bovis BCG, the β-glucans tested here did not inhibit growth of M.tb within human macrophages.

Orally administered particulate beta-glucan modulates tumor-capturing dendritic cells and improves antitumor T-cell responses in cancer

PURPOSE

The beneficial properties of β-glucans have been recognized for centuries. Their proposed mechanisms of action in cancer therapy occur via stimulation of macrophages and priming of innate neutrophil complement receptor 3 for eliciting complement receptor 3-dependent cellular cytotoxicity of iC3b-opsonized tumor cells. The current study is to investigate whether β-glucan therapy has any effect on antitumor adaptive T-cell responses.

EXPERIMENTAL DESIGN

We first examined the trafficking of orally administered particulate yeast-derived β-glucan and its interaction with dendritic cells (DC) that captured tumor materials. Antigen-specific T cells were adoptively transferred into recipient mice to determine whether oral β-glucan therapy induces augmented T-cell responses. Lewis lung carcinoma and RAM-S lymphoma models were used to test oral β-glucan therapeutic effect. Further mechanistic studies including tumor-infiltrating T cells and cytokine profiles within the tumor milieu were determined.

RESULTS

Orally administered particulate β-glucan trafficked into spleen and lymph nodes and activated DCs that captured dying tumor cells in vivo, leading to the expansion and activation of antigen-specific CD4 and CD8 T cells. In addition, IFN-γ production of tumor-infiltrating T cells and CTL responses were significantly enhanced on β-glucan treatment, which ultimately resulted in significantly reduced tumor burden. Moreover, β-glucan-treated tumors had significantly more DC infiltration with the activated phenotype and significant levels of Th1-biased cytokines within the tumor microenvironment.

CONCLUSIONS

These data highlight the ability of yeast-derived β-glucan to bridge innate and adaptive antitumor immunity and suggest that it can be used as an adjuvant for tumor immunotherapy.

Effects of yeast-derived beta-glucans on blood cholesterol and macrophage functionality

The objective of this study is to investigate the effects of two different yeast-derived beta-glucans on macrophage functionality and blood cholesterol levels in mice. After establishing their ability to act as a strong stimulator of macrophages, we measured the capacities of the glucans to lower blood cholesterol. Our results showed that consumption of diets containing yeast-derived beta-glucan indicated a dose-dependent decrease in plasma cholesterol levels, with Betamune having a significantly stronger effect than WGP (Whole Glucan Particles). In hypercholesterolemic subjects, the cholesterol- and triglycerides-lowering effects of Betamune were again significantly stronger. The results of this investigation demonstrated that highly purified yeast-derived beta-glucans modify plasma cholesterol levels and other indicators associated with artherogenic progression in mice. The fact that these glucans also strongly stimulated both monocytes and macrophages supports the hypothesis that there could be a macrophage-cholesterol (metabolism) axis involvement in these outcomes.

Effect of yeast-derived beta-glucan in conjunction with bevacizumab for the treatment of human lung adenocarcinoma in subcutaneous and orthotopic xenograft models

Human lung cancer is the leading cause of cancer death worldwide. Bevacizumab, a monoclonal antibody against vascular endothelial growth factor (VEGF), in combination with chemotherapy showed significant therapeutic efficacy in human lung cancer patients. However, increased adverse effects limit its clinical utilization. Previous studies demonstrated that polysaccharide beta-glucan significantly augments antitumor monoclonal antibody-mediated efficacy via stimulation of the innate effector neutrophil complement receptor 3. Here, we explored combined beta-glucan with bevacizumab therapy for human lung cancer using murine xenograft models. To that end, human lung adenocarcinomas were screened for membrane-bound VEGF expression. Both subcutaneous and orthotopic lung cancer xenograft models were used to evaluate the combination therapy. We found that PC14PE6 adenocarcinoma cells express membrane-bound VEGF both in vitro and in vivo. Bevacizumab bound to surface VEGF on PC14PE6 cells and activated complement. In the subcutaneous PC14PE6 tumor model, beta-glucan plus bevacizumab showed augmented efficacy in terms of tumor progression and long-term survival compared with bevacizumab-treated alone. These effects were accompanied with massive complement deposition and neutrophil infiltration within tumors. However, this effect was not observed in surface-bound VEGF-negative human lung tumors. Therapeutic efficacy of beta-glucan with bevacizumab was further demonstrated in an orthotopic lung cancer model. Thus, our data suggest that beta-glucan enhances bevacizumab-mediated efficacy and may provide therapeutic benefits for lung cancers with membrane-bound VEGF expression.

Combined yeast-derived beta-glucan with anti-tumor monoclonal antibody for cancer immunotherapy

Beta-glucan is an immuno-stimulating agent that has been used to treat cancer and infectious disease for many years with varying and unpredictable efficacy. Recent studies have unraveled the action mode of yeast-derived beta-glucan in combination with anti-tumor monoclonal antibodies (mAbs) in cancer therapy. It has demonstrated that particulate or large molecular weight soluble beta-glucans are ingested and processed by macrophages. These macrophages secrete the active moiety that primes neutrophil complement receptor 3 (CR3) to kill iC3b-opsonized tumor cells. In vitro and in vivo data demonstrate that successful combination therapy requires complement activation and deposition on tumors and CR3 expression on granulocytes. Pre-clinical animal studies have demonstrated the efficacy of combined beta-glucan with anti-tumor mAb therapy in terms of tumor regression and long-term survival. Clinical trials are underway using anti-epidermal growth factor receptor mAb (cetuximab) in combination with beta-glucan for metastatic colorectal cancer. This review provides a brief overview of this combination therapy in cancer and describes in detail the beta-glucan composition and structure, mechanism of action, and preclinical studies in human carcinoma xenograft models. It is proposed that the addition of beta-glucan will further improve the therapeutic efficacy of anti-tumor mAbs in cancer patients.

A phase I/II trial of beta-(1,3)/(1,6) D-glucan in the treatment of patients with advanced malignancies receiving chemotherapy

Beta-(1,3)/(1,6) D-glucan, a component of the fungal cell wall, has been shown to stimulate the immune system, enhance hematopoiesis, amplify killing of opsonized tumor cells and increase neutrophil chemotaxis and adhesion. In view of these attributes, the beta-glucans should be studied for both their therapeutic efficacy in patients with cancer as well as an adjunctive therapy in patients receiving chemotherapy as a maneuver to limit suppression of hematopoiesis.In this study, twenty patients with advanced malignancies receiving chemotherapy were given a beta-(1,3)/(1,6) D-glucan preparation (MacroForce plus IP6, ImmuDyne, Inc.) and monitored for tolerability and effect on hematopoiesis. Our results lead us to conclude that beta-glucan is well-tolerated in cancer patients receiving chemotherapy, may have a beneficial effect on hematopoiesis in these patients and should be studied further, especially in patients with chronic lymphocytic leukemia and lymphoma.

Yeast-derived beta-glucan augments the therapeutic efficacy mediated by anti-vascular endothelial growth factor monoclonal antibody in human carcinoma xenograft models

PURPOSE

Bevacizumab is a recombinant IgG1 humanized monoclonal antibody against vascular endothelial growth factor (VEGF). Its proposed mechanism of action is independent of immune effector functions. Many human carcinomas not only secrete VEGF but also express membrane-bound VEGF. In addition, VEGF receptors are expressed on tumor cells. It is hypothesized that bevacizumab could bind membrane-bound VEGF or VEGF-VEGF receptor complexes on tumors, thereby initiating potential immunologic consequences. We previously showed that yeast-derived beta-glucan functions with antitumor antibodies that activate complement to recruit complement receptor 3-expressing leukocytes capable of mediating complement receptor 3-dependent cellular cytotoxicity of tumors opsonized with iC3b. In the current study, the therapeutic efficacy mediated by combining bevacizumab with yeast-derived beta-glucan was studied in human carcinoma xenograft models.

EXPERIMENTAL DESIGN

Human tumor cell lines were screened for membrane-bound VEGF expression both in vitro and in vivo. Complement activation mediated by bevacizumab was examined. Tumor cell lines positive or negative for membrane-bound VEGF expression were implanted in severe combined immunodeficient mice to establish xenograft models. Tumor-bearing mice were treated with different regimens. Tumor regression and long-term survival were recorded.

RESULTS

Human ovarian carcinoma SKOV-3 cells expressed membrane-bound VEGF both in vitro and in vivo. Bevacizumab was bound to membrane-bound VEGF, activated complement, and synergized with beta-glucan to elicit cellular cytotoxicity in vitro. In vivo study showed that beta-glucan could significantly augment the therapeutic efficacy mediated by bevacizumab.

CONCLUSIONS

Yeast-derived beta-glucan can synergize with anti-VEGF monoclonal antibody bevacizumab for the treatment of cancer with membrane-bound VEGF expression.

Mobilization of hematopoietic progenitor cells by yeast-derived beta-glucan requires activation of matrix metalloproteinase-9

Poly-(1,6)-beta-d-glucopyranosyl-(1,3)-beta-d-glucopyranose (PGG) beta-glucan is a soluble yeast-derived polysaccharide that has previously been shown to induce hematopoietic progenitor cell (HPC) mobilization. However, the mobilizing mechanism of action remains unknown. Here, we confirmed that PGG beta-glucan alone or in combination with granulocyte colony-stimulating factor (G-CSF) mobilizes HPC into the periphery. Optimal mobilizing effects were seen 24-48 hours after PGG beta-glucan doses of 4.8-9.6 mg/kg. Animals treated with G-CSF and PGG beta-glucan showed a collaborative effect in HPC mobilization compared with G-CSF treatment alone. Additional studies demonstrated that neither complement 3 nor complement receptor 3 played a role in this effect and that PGG beta-glucan treatment did not induce proinflammatory cytokine secretion. However, bone marrow cells from PGG beta-glucan-treated mice secreted abundant matrix metalloproteinase-9 (MMP-9), and PGG beta-glucan-induced HPC mobilization was abrogated in MMP-9 knockout mice. Moreover, we demonstrated that both hematopoietic and nonhematopoietic cells contributed to MMP-9 secretion upon PGG beta-glucan treatment. In addition, HPCs mobilized by PGG beta-glucan had similar levels of engraftment in host and lineage differentiation capability compared with those mobilized by G-CSF. Thus, PGG beta-glucan is an agent that enhances HPC mobilization and may improve the outcome of clinical stem cell transplantation.