Polyphenol-rich black currant and cornelian cherry juices ameliorate metabolic syndrome induced by a high-fat high-fructose diet in Wistar rats.

Diets high in fat and sugar lead to metabolic syndrome (MetS) and related chronic diseases. We investigated the effects of commercially available, cold-pressed polyphenol-rich black currant (BC) and cornelian cherry (CC) juices on the prevention of MetS in Wistar rats induced by a 10-weeks high-fat high-fructose (HFF) diet. Juice consumption, either BC or CC, with a HFF diet resulted in lower serum triglycerides compared to only the HFF consumption. Both juices also mitigated the effects of HFF on the liver, pancreas, and adipose tissue, by preserving liver and pancreas histomorphology and reducing visceral fat and adipocyte size. Furthermore, supplementation with both juices reduced glucagon and up-regulated insulin expression in the pancreas of the rats on the HFF diet, whereas the BC also showed improved glucose regulation. BC juice also reduced the expression of IL-6 and hepatic inflammation compared to the group only on HFF diet. Both juices, especially BC, could be a convenient solution for the prevention of MetS in humans.

The involvement of Akt, mTOR, and S6K in the in vivo effect of IGF-1 on the regulation of rat cardiac Na+/K+-ATPase.

BACKGROUND: We previously demonstrated that insulin-like growth factor-1 (IGF-1) regulates sodium/potassium adenosine triphosphatase (Na+/K+-ATPase) in vascular smooth muscle cells (VSMC) via phosphatidylinositol-3 kinase (PI3K). Taking into account that others' work show that IGF-1 activates the PI3K/protein kinase B (Akt) signaling pathway in many different cells, we here further questioned if the Akt/mammalian target of rapamycin (mTOR)/ribosomal protein p70 S6 kinase (S6K) pathway stimulates Na+/K+-ATPase, an essential protein for maintaining normal heart function. METHODS AND RESULTS: There were 14 adult male Wistar rats, half of whom received bolus injections of IGF-1 (50 µg/kg) for 24 h. We evaluated cardiac Na+/K+-ATPase expression, activity, and serum IGF-1 levels. Additionally, we examined the phosphorylated forms of the following proteins: insulin receptor substrate (IRS), phosphoinositide-dependent kinase-1 (PDK-1), Akt, mTOR, S6K, and α subunit of Na+/K+-ATPase. Additionally, the mRNA expression of the Na+/K+-ATPase α1 subunit was evaluated. Treatment with IGF-1 increases levels of serum IGF-1 and stimulates Na+/K+-ATPase activity, phosphorylation of α subunit of Na+/K+-ATPase on Ser23, and protein expression of α2 subunit. Furthermore, IGF-1 treatment increased phosphorylation of IRS-1 on Tyr1222, Akt on Ser473, PDK-1 on Ser241, mTOR on Ser2481 and Ser2448, and S6K on Thr421/Ser424. The concentration of IGF-1 in serum positively correlates with Na+/K+-ATPase activity and the phosphorylated form of mTOR (Ser2448), while Na+/K+-ATPase activity positively correlates with the phosphorylated form of IRS-1 (Tyr1222) and mTOR (Ser2448). CONCLUSION: These results indicate that the Akt/mTOR/S6K signalling pathway may be involved in the IGF-1 regulating cardiac Na+/K+-ATPase expression and activity.

O-glycoprofiling of Serum Apolipoprotein C-III in Colorectal Cancer.

BACKGROUND: Aberrant glycosylation is a hallmark of cancer and thereby has an excellent potential for the discovery of novel biomarkers. Impairments in the glycan composition of lipoproteins impact their functional properties and can be associated with various diseases, including cancer. This research is still in its infancy; however, it can lead to the development of new diagnostic and disease stratification approaches as well as therapeutic strategies. Therefore, we aimed to evaluate anomalies in O-glycosylation of apolipoprotein C-III (apoC-III) in colorectal carcinoma (CRC) patients' sera, in comparison with sera from healthy individuals, and assess the disparities of O-glycoforms on apoC-III in CRC. METHODS: The choice of patients (n = 42) was based on the same tumor type (adenocarcinoma) and tumor size (T3), without or with inconsiderable lymph node infiltration. Patients with comorbidities were excluded from the study. The control healthy individuals (n = 40) were age- and sex-matched with patients. We used an approach based on the MALDI-TOF MS in linear positive ion mode, allowing simple analysis of O-glycosylation on intact apoC-III molecules in the serum samples directly, without the need for specific protein isolation. This approach enables relatively simple and high-throughput analysis. RESULTS: In CRC patients' sera samples, we observed significantly elevated apoC-III sialylation. Fully sialylated (disialylated) O-glycans had 1.26 times higher relative abundance in CRC samples compared to controls with a p-value of Mann-Whitney U test of 0.0021. CONCLUSIONS: We found altered O-glycosylation of apoC-III in the serum of CRC patients. However, it can be non-specific as it may be associated with another process such as ongoing inflammation. Therefore, to establish it as a potential novel non-invasive biomarker for CRC in suspected patients, further studies interrogating the changes in apoC-III O-glycosylation and the robustness of this biomarker need to be performed and evaluated.

Food Antioxidants and Their Interaction with Human Proteins.

Common to all biological systems and living organisms are molecular interactions, which may lead to specific physiological events. Most often, a cascade of events occurs, establishing an equilibrium between possibly competing and/or synergistic processes. Biochemical pathways that sustain life depend on multiple intrinsic and extrinsic factors contributing to aging and/or diseases. This article deals with food antioxidants and human proteins from the circulation, their interaction, their effect on the structure, properties, and function of antioxidant-bound proteins, and the possible impact of complex formation on antioxidants. An overview of studies examining interactions between individual antioxidant compounds and major blood proteins is presented with findings. Investigating antioxidant/protein interactions at the level of the human organism and determining antioxidant distribution between proteins and involvement in the particular physiological role is a very complex and challenging task. However, by knowing the role of a particular protein in certain pathology or aging, and the effect exerted by a particular antioxidant bound to it, it is possible to recommend specific food intake or resistance to it to improve the condition or slow down the process.

Structural changes of proteins in liver cirrhosis and consequential changes in their function.

The liver is the site of synthesis of the majority of circulating proteins. Besides initial polypeptide synthesis, sophisticated machinery is involved in the further processing of proteins by removing parts of them and/or adding functional groups and small molecules tailoring the final molecule to suit its physiological purpose. Posttranslational modifications (PTMs) design a network of molecules with the common protein ancestor but with slightly or considerably varying activity/localization/purpose. PTMs can change under pathological conditions, giving rise to aberrant or overmodified proteins. Undesired changes in the structure of proteins most often accompany undesired changes in their function, such as reduced activity or the appearance of new effects. Proper protein processing is essential for the reactions in living beings and crucial for the overall quality control. Modifications that occur on proteins synthesized in the liver whose PTMs are cirrhosis-related are oxidation, nitration, glycosylation, acetylation, and ubiquitination. Some of them predominantly affect proteins that remain in liver cells, whereas others predominantly occur on proteins that leave the liver or originate from other tissues and perform their function in the circulation. Altered PTMs of certain proteins are potential candidates as biomarkers of liver-related diseases, including cirrhosis. This review will focus on PTMs on proteins whose structural changes in cirrhosis exert or are suspected to exert the most serious functional consequences.

The Insulin-like Growth Factor System and Colorectal Cancer.

Insulin-like growth factors (IGFs) are peptides which exert mitogenic, endocrine and cytokine activities. Together with their receptors, binding proteins and associated molecules, they participate in numerous pathophysiological processes, including cancer development. Colorectal cancer (CRC) is a disease with high incidence and mortality rates worldwide, whose etiology usually represents a combination of the environmental and genetic factors. IGFs are most often increased in CRC, enabling excessive autocrine/paracrine stimulation of the cell growth. Overexpression or increased activation/accessibility of IGF receptors is a coinciding step which transmits IGF-related signals. A number of molecules and biochemical mechanisms exert modulatory effects shaping the final outcome of the IGF-stimulated processes, frequently leading to neoplastic transformation in the case of irreparable disbalance. The IGF system and related molecules and pathways which participate in the development of CRC are the focus of this review.

Lectin-Based Protein Microarray for the Glycan Analysis of Colorectal Cancer Biomarkers: The Insulin-Like Growth Factor System.

Lectin-based protein microarrays are used for glycoprofiling of various kinds of biological samples. Here we describe lectin-based microarray assay in the reverse-phase format where glycoprotein samples are spotted onto microarray slide and then are incubated with set of lectins. This configuration allows high-throughput screening of a large cohort of samples by a set of lectins without need of separation of glycans from glycoproteins. We applied the described method for glycan analysis of glycoprotein biomarkers of colorectal cancer associated with the insulin-like growth factor system.

Molecular Mechanisms of Possible Action of Phenolic Compounds in COVID-19 Protection and Prevention.

The worldwide outbreak of COVID-19 was caused by a pathogenic virus called Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2). Therapies against SARS-CoV-2 target the virus or human cells or the immune system. However, therapies based on specific antibodies, such as vaccines and monoclonal antibodies, may become inefficient enough when the virus changes its antigenicity due to mutations. Polyphenols are the major class of bioactive compounds in nature, exerting diverse health effects based on their direct antioxidant activity and their effects in the modulation of intracellular signaling. There are currently numerous clinical trials investigating the effects of polyphenols in prophylaxis and the treatment of COVID-19, from symptomatic, via moderate and severe COVID-19 treatment, to anti-fibrotic treatment in discharged COVID-19 patients. Antiviral activities of polyphenols and their impact on immune system modulation could serve as a solid basis for developing polyphenol-based natural approaches for preventing and treating COVID-19.

Association between genetic variants in DICER1 and cancer risk: An updated meta-analysis.

Dysfunctions in mechanisms of gene regulation based on RNA interference are recognized as a common feature of the molecular basis of cancer pathogenesis. Therefore, as one of the crucial components of the machinery involved in the biogenesis of both siRNAs and microRNA molecules, DICER was recognized as one of the candidates for the research in the field of carcinogenesis. Due to their potential functional properties, several genetic variants located within DICER1 gene were analyzed for their possible association with the susceptibility to cancer through case-control studies. In order to elucidate their effect on the overall cancer risk, we conducted an updated meta-analysis of all eligible association studies. The publications were selected based on PubMed database search, while OpenMeta-analyst and MetaGenyo software were used for quantitative data synthesis. Statistically significant results were found for the association of rs1057035 with the overall cancer risk under multiple genetic models (PCT vs. TT < 0.001, ORCT vs. TT = 0.870, 95% CI = 0.812-0.933; Pallelic = 0.009, ORallelic = 0.896, 95% CI = 0.825-0.973; Pdom < 0.001, ORdom = 0.874, 95% CI = 0.817-0.934; Poverdom = 0.004, ORoverdom = 0.858, 95% CI = 0.773-0.953). Other selected genetic variants within DICER1, rs13078, rs1209904 and rs3742330, did not show the association with the overall susceptibility to malignant diseases. We conclude that rs1057035 may represent a potential biomarker associated with the risk of developing cancer, which requires a confirmation in a larger set of studies.

Fibrinogen Increases Resveratrol Solubility and Prevents it from Oxidation.

The French paradox describes a lower incidence of cardiovascular problems despite a high intake of saturated fats. This phenomenon was associated with higher consumption of red wine, as it was later discovered that the presence of antioxidants, including resveratrol, have beneficial effects. We hypothesized that resveratrol may have a more direct role in protection from harmful oxidation, presumably through binding to important proteins of the blood coagulation process. Spectrofluorimetry demonstrated that resveratrol is capable of binding to fibrinogen, the main protein in the coagulation process, which is also important as a food additive. Various spectroscopic methods determined that binding does not cause fibrinogen unfolding or destabilization since protein melting temperature remains unchanged. A mutually protective effect against the free radical-induced oxidation of polyphenol and fibrinogen was found. The presence of fibrinogen caused only a negligible masking effect of the antioxidative abilities of resveratrol, measured by a reduction of hexacyanoferrate (III), while greatly increasing its solubility in an aqueous environment, thus increasing its potential bioavailability. Due to its interaction with fibrinogen, resveratrol may serve as an antioxidant at the site of injury. The antioxidative effect of resveratrol may also protect and thus keep the desired characteristics of fibrinogen during the application of this protein as a food additive.

Lectin from Laetiporus sulphureus effectively inhibits angiogenesis and tumor development in the zebrafish xenograft models of colorectal carcinoma and melanoma.

In spite of extensive usage of Laetiporus sulphureus (sulphur polypore) in traditional European and Asian ethno-medicine for centuries, its anticancer therapeutic potential and toxicity profile remained explored in animal models. Herein, using zebrafish (Danio rerio), as a preclinical animal model, we demonstrated that L. sulphureus lectin (LSL) and ethanol extract (LSE) are non-toxic at high doses up to 400-500 µg/mL, while they effectively inhibited angiogenesis and cancer development at much lower doses. Lectin showed 74-fold higher anti-angiogenic potency than the extract, and even 378-fold higher therapeutic potential than sunitinib-malate, cardiotoxic and myelosupressive anti-angiogenic drug of clinical relevance. Using wound healing and MTT assays, we proved LSL's strong antimigratory effect and selective endothelial cytotoxicity in relation to lung fibroblasts. In addition, employing the zebrafish xenograft models, we demonstrated that LSL almost completely reduced growth, neovascularization and metastasis of human colorectal carcinoma and mouse melanoma. Even more, LSL exerted 8-fold higher potency towards colorectal carcinoma than melanoma, showing markedly higher activity than cisplatin, while LSE failed to express any anticancer activity. Accompanied with non-toxic response, including neutropenia and inflammation, the results of this study strongly imply that LSL could be used as safe adjuvant in chemotherapy against colorectal carcinoma and melanoma.

Sensitive glycoprofiling of insulin-like growth factor receptors isolated from colon tissue of patients with colorectal carcinoma using lectin-based protein microarray.

Glycosylation of cell receptors influences their function and development of tumour induces changes in glycosylation. Cell growth depends on the activation of receptors which bind growth factors and the insulin-like growth factor (IGF) receptors are among the most important ones. Usually, only small quantities of isolated receptors are available thus there is a need of suitable assay to study receptors glycosylation. Therefore, we developed a lectin-based reverse-phase protein microarray method for screening the glycosylation pattern of receptors in picomolar (pM) concentrations. The method was applied to glycoprofile IGF1 and IGF2 receptors and the solubilised membrane proteins isolated from tumour and non-tumour colon tissue of patients with colorectal cancer. We found that common to both receptors was partial overlapping of the major glycan structures with those present in the entire glycome of membrane proteins. In contrast, receptors possess higher level of α2,3 sialic acid residues and lower level of tri-/tetra-antennary complex type N-glycans and terminal mannose in high-mannose structures. Increased levels of fucosylation and branched mannose structures were observed in both receptors derived from tumour tissue compared to non-tumour tissue. The described method enabling glycan analysis of receptors has a big application potential in e.g. biomarker research, biology and diagnostics.

Is There Something Fishy About Fish Oil?

BACKGROUND: Fish is consumed as food worldwide and is considered as a rich source of essential nutrients required for a healthy life. Supplementation with fish oil has been adopted as a solution to prevent or cure many pathophysiological states and diseases by both the professionals and the civil population. The beneficial effects are, however, being questioned, as some controversial results were obtained in clinical and population studies. METHODS: Critical evaluation of studies regarding known effects of fish oil, both in favour of its consumption and related controversies. RESULTS: From the literature review, contradictory allegations about the positive action of the fish oil on human health emerged, so that a clear line about its beneficial effect cannot be withdrawn. CONCLUSION: Scientific results on the application of fish oil should be taken with caution as there is still no standardised approach in testing its effects and there are significantly different baselines in respect to nutritional and other lifestyle habits of different populations.

Diagnostic Potential of Transferrin Glycoforms-A Lectin-Based Protein Microarray Approach.

PURPOSE: Disease or a specific condition may cause alteration of human transferrin (hTf) glycosylation pattern. A specific analytical platform, lectin-based protein microarray, is designed and optimized for the investigation of hTf glycans, attached to the protein core in their native form. EXPERIMENTAL DESIGN: hTf molecules isolated from healthy persons of different age, diabetes mellitus type 2 (T2DM) or colorectal carcinoma (CRC) patients are used for method validation. Reliability of the results is ensured by three criteria for the evaluation of hTf-lectin interactions: i) signal-to-noise ratio above 3, ii) signal intensity above 250 arbitrary units, and iii) hTf concentration ensuring high sensitivity of the assay. RESULTS: Six lectins, out of fourteen tested, satisfy the criteria. hTf is spotted at concentration of 50 µg mL-L . When physiological samples (isolated hTf) are analyzed, the highest potential to differentiate between population groups expresses Aleuria aurantia (AAL), Triticum vulgaris (WGA) and Phaseolus vulgaris (PHA-E) lectins. The initial amount of hTf which can be analyzed is very low (75 pg). CONCLUSION AND CLINICAL RELEVANCE: Results confirm that a very sensitive, high-throughput lectin-based protein microarray platform can be formulated to detect changes in hTf glycan structures which can be considered as biomarkers of ageing or a disease.

Changes Due to Ageing in the Glycan Structure of Alpha-2-Macroglobulin and Its Reactivity with Ligands.

Alpha-2-macroglobulin (α2M) is a molecule generally associated with inflammation, and chronic inflammation is associated with ageing and cancer. The degree of inflammation was recently proposed to be considered as a biomarker of biological ageing. In this study, glycans attached to α2M were analysed in a human population of different ages by lectin-based protein microarray. Higher reactivity of α2M with several lectins was detected in older individuals indicating an increased content of specific monosaccharides: α2,6 sialic acid, mannose and N-acetylglucosamine, and multiantennary complex type N-glycans. The increased glycosylation of α2M was accompanied by reduced binding of Zn ions and insulin-like growth factor-binding protein 2 (IGFBP-2). Glycosylation of α2M and its reactivity with IGFBP-2 is similarly affected by ageing and incidence of colon cancer, but the reactivity of α2M with Zn ions is differently affected, as the binding of Zn ions remains unaltered in patients with colon cancer compared to healthy middle-aged individuals. Thus, the binding of IGFBP-2 to α2M seems to be related to structural changes in the glycan moieties of α2M, whereas binding of Zn ions, most likely, is not.

Regulation of Insulin and Insulin-Like Activity in Malnourished Patients with Carcinoma Ventriculi Subjected to Total Gastrectomy and Personalized Nutritional Support.

BACKGROUND: Insulin and insulin-like growth factor (IGF) activities are disturbed during critical illness. Time-course changes in the concentrations of insulin, IGF-I and IGF-binding proteins (IGFBPs) were monitored in this study and their correlation with interleukin (IL)-6 was assessed in patients subjected to total gastrectomy and specific nutritional regime. METHODS: Patients were fed post-operatively according to the following scheme: parenteral nutrition on day 1, enteral nutrition combined with parenteral form from day 2 to 7, peroral nutrition from day 8 and full oral nutrition from day 14. Blood samples were taken periodically and the levels of IL-6, insulin, IGF-I and IGFBP-1 to -4 were determined. RESULTS: On day 1 post-operatively, the concentration of IL-6 reached its maximum and decreased afterwards. The concentration of insulin increased until day 3 and then started to fall. The concentration of IGF-I, already low preoperatively, continued to decrease. The concentration of IGFBP-1 peaked on day 1 post-operatively, whereas the concentration of IGFBP-3 decreased on that day. The concentration of IL-6 correlated positively with the concentration of IGFBP-1 and negatively with IGFBP-3. On day 14, the concentrations of IL-6, insulin and IGFBP-1 returned to or were close to their basal levels, whereas the concentrations of IGF-I and IGFBP-3 remained reduced. CONCLUSIONS: A 14-day post-operative recovery, which included specific nutritional support, was suitable to restore insulin concentration and re-establish IGFBP-1 regulation primarily by nutrition. Very low IGF-I level on day 14 after surgery and IGFBP-3 concentration still lower than before surgery indicated that the catabolic condition was not compensated.

Lectin-based protein microarray analysis of differences in serum alpha-2-macroglobulin glycosylation between patients with colorectal cancer and persons without cancer.

Glycosylation is co- and posttranslational modifications affecting proteins. The glycopattern changes are associated with changes in biological function and are involved in many diseases including cancer. We present the lectin-based protein microarray method enabling determination of differences in protein glycosylation. The method involves isolation of targeted protein from samples by immunoprecipitation, spotting of protein from multiple samples into arrays on a microarray slide, incubation with set of biotinylated lectins, the reaction with fluorescent conjugate of streptavidin, and detection of fluorescent intensities by microarray scanner. Lectin-based protein microarray was applied in investigation of differences in alpha-2-macroglobulin (α2M) glycosylation isolated from sera samples of healthy persons and patients with colorectal cancer (CC). From 14 lectins used in analysis, statistically significant differences (Student's t-test, P < 0.05) between two groups of samples (persons without cancer and CC patients) were found for 5 of them. α2M molecules isolated from sera of CC patients have higher content of α2,6 sialic acid, N-acetylglucosamine and mannose residues, and tri-/tetraantennary complex type high-mannose N-glycans. A novel lectin-based protein microarray developed and described can serve as a suitable analytical technique for sensitive, simple, fast, and high-throughput determination of differences in protein glycosylation isolated from serum or other samples.

Standardization and quality control in quantifying non-enzymatic oxidative protein modifications in relation to ageing and disease: Why is it important and why is it hard?

Post-translational modifications (PTM) of proteins determine the activity, stability, specificity, transportability and lifespan of a protein. Some PTM are highly specific and regulated involving various enzymatic pathways, but there are other non-enzymatic PTM (nePTM), which occur stochastically, depend on the ternary structure of proteins and can be damaging. It is often observed that inactive and abnormal proteins accumulate in old cells and tissues. The nature, site and extent of nePTM give rise to a population of that specific protein with alterations in structure and function ranging from being fully active to totally inactive molecules. Determination of the type and the amount (abundance) of nePTM is essential for establishing connection between specific protein structure and specific biological role. This article summarizes analytical demands for reliable quantification of nePTM, including requirements for the assay performance, standardization and quality control, and points to the difficulties, uncertainties and un-resolved issues.

IGFBP-3/transferrin/transferrin receptor 1 complexes as principal mediators of IGFBP-3 delivery to colon cells in non-cancer and cancer tissues.

PURPOSE: The aim of this work was to study the involvement of IGFBP-3/Tf complexes in the pathology of colorectal carcinoma (CRC), quantify them, investigate their relation to iron concentration and binding to transferrin receptor (TfR) in colon tissue (non-cancer and cancer), and to assess the priority of this pathway for internalization of IGFBP-3. METHODS: The presence of IGFBP-3/Tf complexes was analyzed in sera from healthy persons and patients with CRC, and in colon tissue by immunoblotting. Complexes were immunoprecipitated, quantified by immunoassay and structurally characterized by immunoblotting, lectin blotting and mass spectrometry. Complexes which interacted with colon cells were immunoprecipitated with anti-TfR1 antibody and studied. Colon tissue slides were subjected to immunohistochemical analysis. RESULTS: The concentration of IGFBP-3/Tf complexes was three times lower in patients with CRC. They were increasingly carbonylated, sialylated, contained more Galß4GlcNAc units, expressed altered charge density and increased affinity for metal ions. Immunoprecipitation experiments revealed more TfR1 on membranes than in cytosol of colon cells, also more in cancer than non-cancer tissue. TfR1 on membranes were less occupied with IGFBP-3/Tf complexes than in cytosol. Immunofluorescent staining indicated a remarkable degree of co-localization of IGFBP-3 and TfR1, evenly distributed in non-cancer tissue and both evenly and cell surface concentrated in cancer tissue. CONCLUSIONS: Increased expression of TfR1 on colon cell membranes in patients with CRC compensates for the reduced extracellular availability of IGFBP-3/Tf and TfR1 is the principal binding partner of extracellular IGFBP-3. IGFBP-3/Tf complexes in patients with CRC exhibit increased affinity for iron ions.

Complexes between insulin-like growth factor binding proteins and alpha-2-macroglobulin in patients with tumor.

The intention of this work was to systematically study the presence of insulin-like growth factor-binding protein 1 and 2 (IGFBP-1 and IGFBP-2) complexes with alpha-2-macroglobulin (α2M) in the circulation of patients with various types of cancer. Serum samples were collected from patients diagnosed with cancer and divided into eight groups according to the tumor type: liver, pancreas, colon, lung, prostate, breast, cervix and ovary. Results obtained for each cancer group were compared with results obtained for the age and gender-matched controls. Electrophoretic separation and densitometric evaluation of immunoreactive protein bands were performed. According to our results, IGFBP-1/α2M and IGFBP-2/α2M complexes did not exhibit the same presence in different tumors and were also not uniformly related to the amount of monomer forms. Variations in relative quantities of IGFBP-1 monomers and complexes in different tumor types were much more pronounced than those of IGFBP-2. The amount of IGFBP-2 monomer increased in sera from all studied patients compared to controls, whereas the amount of IGFBP-2/α2M complexes most often decreased, being significantly reduced in patients with pancreas, colon, breast or ovary tumor. Although there is still no confirmation of the physiological role of IGFBP-2/α2M complexes, their decreased concentration in the circulation provides greater amount of free IGFBP-2.