Inhibitory effect of vitamin D-binding protein-derived macrophage activating factor on DMBA-induced hamster cheek pouch carcinogenesis and its derived carcinoma cell line

The Molecular Aspects of Functional Activity of Macrophage-Activating Factor GcMAF

Group-specific component macrophage-activating factor (GcMAF) is the vitamin D3-binding protein (DBP) deglycosylated at Thr420. The protein is believed to exhibit a wide range of therapeutic properties associated with the activation of macrophagal immunity. An original method for GcMAF production, DBP conversion to GcMAF, and the analysis of the activating potency of GcMAF was developed in this study. Data unveiling the molecular causes of macrophage activation were obtained. GcMAF was found to interact with three CLEC10A derivatives having molecular weights of 29 kDa, 63 kDa, and 65 kDa. GcMAF interacts with high-molecular-weight derivatives via Ca2+-dependent receptor engagement. Binding to the 65 kDa or 63 kDa derivative determines the pro- and anti-inflammatory direction of cytokine mRNA expression: 65 kDa-pro-inflammatory (TNF-α, IL-1β) and 63 kDa-anti-inflammatory (TGF-β, IL-10). No Ca2+ ions are required for the interaction with the canonical 29 kDa CLEC10A. Both forms, DBP protein and GcMAF, bind to the 29 kDa CLEC10A. This interaction is characterized by the stochastic mRNA synthesis of the analyzed cytokines. Ex vivo experiments have demonstrated that when there is an excess of GcMAF ligand, CLEC10A forms aggregate, and the mRNA synthesis of analyzed cytokines is inhibited. A schematic diagram of the presumable mechanism of interaction between the CLEC10A derivatives and GcMAF is provided. The principles and elements of standardizing the GcMAF preparation are elaborated.

Analysis of the Biological Properties of Blood Plasma Protein with GcMAF Functional Activity

The main problem related to the studies focusing on group-specific component protein-derived macrophage-activating factor (GcMAF) is the lack of clarity about changes occurring in different types of macrophages and related changes in their properties under the effect of GcMAF in various clinical conditions. We analyzed the antitumor therapeutic properties of GcMAF in a Lewis carcinoma model in two clinical conditions: untreated tumor lesion and tumor resorption after exposure to Karanahan therapy. GcMAF is formed during site-specific deglycosylation of vitamin D3 binding protein (DBP). DBP was obtained from the blood of healthy donors using affinity chromatography on a column with covalently bound actin. GcMAF-related factor (GcMAF-RF) was converted in a mixture with induced lymphocytes through the cellular enzymatic pathway. The obtained GcMAF-RF activates murine peritoneal macrophages (p < 0.05), induces functional properties of dendritic cells (p < 0.05) and promotes in vitro polarization of human M0 macrophages to M1 macrophages (p < 0.01). Treatment of whole blood cells with GcMAF-RF results in active production of both pro- and anti-inflammatory cytokines. It is shown that macrophage activation by GcMAF-RF is inhibited by tumor-secreted factors. In order to identify the specific antitumor effect of GcMAF-RF-activated macrophages, an approach to primary reduction of humoral suppressor activity of the tumor using the Karanahan therapy followed by macrophage activation in the tumor-associated stroma (TAS) was proposed. A prominent additive effect of GcMAF-RF, which enhances the primary immune response activation by the Karanahan therapy, was shown in the model of murine Lewis carcinoma. Inhibition of the suppressive effect of TAS is the main condition required for the manifestation of the antitumor effect of GcMAF-RF. When properly applied in combination with any chemotherapy, significantly reducing the humoral immune response at the advanced tumor site, GcMAF-RF is a promising antitumor therapeutic agent that additively destroys the pro-tumor properties of macrophages of the tumor stroma.

Improved preparation of group-specific component (Gc) protein to derive macrophage activating factor

Cancer immunotherapy has recently attracted attention as an approach for cancer treatment through the activation of the immune system. Group-specific component (Gc) protein is a precursor for macrophage activating factor (GcMAF), which has a promising immunomodulatory effect on the suppression of tumor growth and angiogenesis. In this study, we successfully purified Gc protein from human serum using anion-exchange chromatography combined with affinity chromatography using a 25-OH-D₃-immobilized column. The purity of Gc protein reached 95.0% after anion-exchange chromatography. The known allelic variants of Gc protein are classified into three subtypes-Gc1F, Gc1S and Gc2. The fragment sequence of residues 412-424 determined according to their MS/MS spectra is available to evaluate the subtypes of Gc protein. The data showed that the Gc protein purified in this study consisted of the Gc1F and Gc2 subtypes. Our method improved the purity of Gc protein, which was not affected by the treatment to convert it into GcMAF using β-galactosidase- or neuraminidase-immobilized resin, and will be useful for biological studies and/or advanced clinical uses of GcMAF, such as cancer immunotherapy.

<i>In vitro</i> assay of biological activity of a national preparation of macrophage activating factor (GcMAF-RF)

В статье сообщается о разработанном оригинальном способе получения витамин D3-связывающего белка (DBP) и его конвертации в макрофаг-активирующий фактор GcMAF-RF. Согласно разработанному регламенту, DBP получали из плазмы крови человека, применяя аффинную колоночную хроматографию, очи- щали и модифицировали до GcMAF-RF с использованием цитоиммобилизованных гликозидаз (бета-галакто- зидаза и нейраминидаза). Принадлежность полученного полипептида к Gc-группе глобулинов плазмы крови подтверждали вестерн-блотом с использованием специфических антител. Полученный полипептид по своим молекулярным свойствам соответствует описанному в литературе белку GсMAF, находящемуся на стадии кли- нических испытаний в США, Британии, Израиле и Японии (Saisei Mirai, Reno Integrative Medical Center, Immuno Biotech Ltd, Efranat, Catalytic Longevity). Биологическую активность препарата GcMAF-RF определяли по индук- ции у перитонеальных макрофагов мыши фагоцитарной активности и способности продуцировать моноок- сид азота (NO) in vitro. Фагоцитарную активность макрофагов оценивали по эффективности захвата магнитных шариков. Степень активации макрофагов рассчитывали по отношению числа захваченных шариков к общему числу макрофагов. Уровень продукции NO оценивали по накоплению монооксида азота в культуральных су- пернатантах перитонеальных макрофагов колориметрическим методом с использованием реактива Грисса. Показано, что GcMAF-RF кратно увеличивает фагоцитарную активность макрофагов и достоверно увеличивает продукцию ими монооксида азота. Выделенный оригинальным способом активатор макрофагов GcMAF-RF по своим характеристикам (согласно материалам, опубликованным в печати) соответствует препаратам GcMAF, представляемым на рынке зарубежными компаниями, и может рассматриваться как новый отечественный био- логически активный препарат с широким спектром действия. Наибольший интерес вызывает его способность через активацию макрофагов усиливать адаптивный иммунитет организма. В этой связи предполагаются два направления терапевтического применения препарата GcMAF-RF. Препарат может быть востребован в области лечения онкологических заболеваний и, кроме того, может быть использован при лечении ряда нейродегене- ративных патологий и иммунодефицитных состояний.

A thorny pathway of macrophage activating factor (GcMAF): from bench to bedside

Vitamin D3 Binding Protein (DBP) is a multifunctional glycoprotein whose main role is to transport vitamin D3 and its metabolites, but it also is the precursor of the macrophage activating factor (GcMAF). DBP is converted to GcMAF as a result of site-specific selective deglycosylation under the action of β-galactosidase and sialidase, localized on activated B and T cells, respectively. GcMAF exerts its biological activity primarily as the capability of activating macrophages by enhancing their phagocytic function and producing ROS. Activation results in elevated expression of the specific macrophageal surface receptors involved in the recognition of tumor-associated antigens, as well as in the implementation of direct anticancer activity by inducing the apoptosis or necrosis of tumor cells. Increased interest in GcMAF is associated with its potential to be used in the clinic as a new antitumor drug. Besides its anti-tumor activity, GcMAF exerts a potential against a number of viral and neurodegenerative diseases associated with increased activity of N-acetylgalactosaminidase (nagalase) in the blood serum of patients. Nagalase is an enzyme that completely (rather than selectively) deglycosylates DBP so it cannot be converted to GcMAF, leading to immunodeficiency. Circulating DBP is composed of unmodified and O-glycosylated molecules with the glycosylation degree being dependent on the allelic variants of the gene encoding DBP. The role of DBP in the resistance of organism against a number of diseases is supported by the increased risk of a variety of severe illnesses (amyotrophic lateral sclerosis, colorectal cancer etc.) in patients deficient for GcMAF due to homozygosity for defective DBP alleles. In this review, we also will examine in detail the current data i) on the structure and functions of DBP, as the main precursor of GcMAF, ii) on the main mechanisms of GcMAF anticancer effect, iii) on the tumor strategy for neutralizing GcMAF activity, iv) on the results of GcMAF clinical trials in various cancers; and will discuss the available controversies regarding the positioning of GcMAF as an effective antitumor drug. 

Is chondroitin sulfate responsible for the biological effects attributed to the GC protein-derived Macrophage Activating Factor (GcMAF)?

We hypothesize that a plasma glycosaminoglycan, chondroitin sulfate, may be responsible for the biological and clinical effects attributed to the Gc protein-derived Macrophage Activating Factor (GcMAF), a protein that is extracted from human blood. Thus, Gc protein binds chondroitin sulfate on the cell surface and such an interaction may occur also in blood, colostrum and milk. This interpretation would solve the inconsistencies encountered in explaining the effects of GcMAF in vitro and in vivo. According to our model, the Gc protein or the GcMAF bind to chondroitin sulfate both on the cell surface and in bodily fluids, and the resulting multimolecular complexes, under the form of oligomers trigger a transmembrane signal or, alternatively, are internalized and convey the signal directly to the nucleus thus eliciting the diverse biological effects observed for both GcMAF and chondroitin sulfate.

A novel role for a major component of the vitamin D axis: vitamin D binding protein-derived macrophage activating factor induces human breast cancer cell apoptosis through stimulation of macrophages

The role of vitamin D in maintaining health appears greater than originally thought, and the concept of the vitamin D axis underlines the complexity of the biological events controlled by biologically active vitamin D (1,25(OH)(2)D3), its two binding proteins that are the vitamin D receptor (VDR) and the vitamin D-binding protein-derived macrophage activating factor (GcMAF). In this study we demonstrate that GcMAF stimulates macrophages, which in turn attack human breast cancer cells, induce their apoptosis and eventually phagocytize them. These results are consistent with the observation that macrophages infiltrated implanted tumors in mice after GcMAF injections. In addition, we hypothesize that the last 23 hydrophobic amino acids of VDR, located at the inner part of the plasma membrane, interact with the first 23 hydrophobic amino acids of the GcMAF located at the external part of the plasma membrane. This allows 1,25(OH)(2)D3 and oleic acid to become sandwiched between the two vitamin D-binding proteins, thus postulating a novel molecular mode of interaction between GcMAF and VDR. Taken together, these results support and reinforce the hypothesis that GcMAF has multiple biological activities that could be responsible for its anti-cancer effects, possibly through molecular interaction with the VDR that in turn is responsible for a multitude of non-genomic as well as genomic effects.