Anti-cancer potential of casein and its derivatives: novel strategies for cancer treatment

Cancer is one of the leading causes of death worldwide, with over 10 million fatalities annually. While tumors can be surgically removed and treated with chemotherapy, radiotherapy, immunotherapy, hormonal therapy, or combined therapies, current treatments often result in toxic side effects in normal tissue. Therefore, researchers are actively seeking ways to selectively eliminate cancerous cells, minimizing the toxic side effects in normal tissue. Caseins and its derivatives have shown promising anti-cancer potential, demonstrating antitumor and cytotoxic effects on cells from various tumor types without causing harm to normal cells. Collectively, these data reveals advancements in the study of caseins and their derivative peptides, particularly providing a comprehensive understanding of the molecular mechanism of action in cancer therapy. These mechanisms occur through various signaling pathways, including (i) the increase of interferon-associated STAT1 signaling, (ii) the suppression of stemness-related markers such as CD44, (iii) the attenuation of the STAT3/HIF1-α signaling, (iv) the down-expression of uPAR and PAI-1, (v) the loss of mitochondrial membrane potential and reduced intracellular ATP production, (vi) the increase of caspase-3 activity, and (vii) the suppression of TLR4/NF-кB signaling. Therefore, we conclude that casein could be an effective adjuvant for cancer treatment.

Structural Analysis of Breast-Milk αS1-Casein: An α-Helical Conformation Is Required for TLR4-Stimulation

Breast-milk αS1-casein is a Toll-like receptor 4 (TLR4) agonist, whereas phosphorylated αS1-casein does not bind TLR4. The objective of this study was to analyse the structural requirements for these effects. In silico analysis of αS1-casein indicated high α-helical content with coiled-coil characteristics. This was confirmed by CD-spectroscopy, showing the α-helical conformation to be stable between pH 2 and 7.4. After in vitro phosphorylation, the α-helical content was significantly reduced, similar to what it was after incubation at 80 °C. This conformation showed no in vitro induction of IL-8 secretion via TLR4. A synthetic peptide corresponding to V77-E92 of αS1-casein induced an IL-8 secretion of 0.95 ng/mL via TLR4. Our results indicate that αS1-casein appears in two distinct conformations, an α-helical TLR4-agonistic and a less α-helical TLR4 non-agonistic conformation induced by phosphorylation. This is to indicate that the immunomodulatory role of αS1-casein, as described before, could be regulated by conformational changes induced by phosphorylation.

In Silico and In Vitro Search for Dual Inhibitors of the Trypanosoma brucei and Leishmania major Pteridine Reductase 1 and Dihydrofolate Reductase

The parasites Trypanosoma brucei (Tb) and Leishmania major (Lm) cause the tropical diseases sleeping sickness, nagana, and cutaneous leishmaniasis. Every year, millions of humans, as well as animals, living in tropical to subtropical climates fall victim to these illnesses' health threats. The parasites' frequent drug resistance and widely spread natural reservoirs heavily impede disease prevention and treatment. Due to pteridine auxotrophy, trypanosomatid parasites have developed a peculiar enzyme system consisting of dihydrofolate reductase-thymidylate synthase (DHFR-TS) and pteridine reductase 1 (PTR1) to support cell survival. Extending our previous studies, we conducted a comparative study of the T. brucei (TbDHFR, TbPTR1) and L. major (LmDHFR, LmPTR1) enzymes to identify lead structures with a dual inhibitory effect. A pharmacophore-based in silico screening of three natural product databases (approximately 4880 compounds) was performed to preselect possible inhibitors. Building on the in silico results, the inhibitory potential of promising compounds was verified in vitro against the recombinant DHFR and PTR1 of both parasites using spectrophotometric enzyme assays. Twelve compounds were identified as dual inhibitors against the Tb enzymes (0.2 μM < IC50 < 85.1 μM) and ten against the respective Lm enzymes (0.6 μM < IC50 < 84.5 μM). These highly promising results may represent the starting point for the future development of new leads and drugs utilizing the trypanosomatid pteridine metabolism as a target.

Quantitative Label-Free Proteomic Analysis of Milk Fat Globule Membrane in Donkey and Human Milk

Previous studies have found donkey milk (DM) has the similar compositions with human milk (HM) and could be used as a potential hypoallergenic replacement diet for babies suffering from cow's milk allergy. Milk fat globule membrane (MFGM) proteins are involved in many biological functions, behaving as important indicators of the nutritional quality of milk. In this study, we used label-free proteomics to quantify the differentially expressed MFGM proteins (DEP) between DM (in 4-5 months of lactation) and HM (in 6-8 months of lactation). In total, 293 DEP were found in these two groups. Gene Ontology (GO) enrichment analysis revealed that the majority of DEP participated in regulation of immune system process, membrane invagination and lymphocyte activation. Several significant Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways were determined for the DEP, such as lysosome, galactose metabolism and peroxisome proliferator-activated receptor (PPAR) signaling pathway. Our study may provide valuable information in the composition of MFGM proteins in DM and HM, and expand our knowledge of different biological functions between DM and HM.

Validation of CSN1S1 transcriptional expression, promoter methylation, and prognostic power in breast cancer using independent datasets

Breast cancer ranked second among most frequent cancer in the world playing a significant role in mortality rate. Having prior knowledge on differentially expressed genes in breast cell carcinoma elucidated important indications to understand the molecular mechanism underneath breast carcinogenesis. In this study we have investigated the distinguished CSN1S1 expression in human breast cancer. We have analyzed CSN1S1 mRNA expression between cancer and normal tissues using TCGA datasets. Moreover, analysis including promoter methylation, mutations, prognosis, co-expression, gene ontology, and pathways of CSN1S1 were performed by the TCGA Wanderer, UCSC Xena, cBioPortal, PrognoScan, UALCAN, and Enricher server. We have observed low mRNA expression and high promoter methylation of CSN1S1 in cancer tissues compared to normal tissues. Furthermore, we have also identified low mRNA expression in clinicopathological patients, as well as 9 deleterious mutations with highly co-expressed protein MRC1, and significantly related signaling pathways. We have found a positive correlation between the lower expression of CSN1S1 and patients surviving with breast cancer. Here we have concluded that CSN1S1 acts as a biomarker for the surveillance and prognosis of breast cancer, and also works as a novel therapeutic target at the molecular and pathway levels.

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Low transcriptional expression and low survival rate of CSN1S1 in breast cancer.

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The investigation of clinical profiles and mutational positions of CSN1S1 in breast cancer.

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The investigation of gene ontology and signaling pathway of CSN1S1 and their co-expressed genes.

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We identified CSN1S1 and also their co-expressed proteins are the potential biomarkers in breast cancer.

Distinct abdominal and gluteal adipose tissue transcriptome signatures are altered by exercise training in African women with obesity

The differential associations of adipose depots with metabolic risk during obesity have been proposed to be controlled by environmental and genetic factors. We evaluated the regional differences in transcriptome signatures between abdominal (aSAT) and gluteal subcutaneous adipose tissue (gSAT) in obese black South African women and tested the hypothesis that 12-week exercise training alters gene expression patterns in a depot-specific manner. Twelve young women performed 12-weeks of supervised aerobic and resistance training. Pre- and post-intervention measurements included peak oxygen consumption (VO_2peak), whole-body composition and unbiased gene expression analysis of SAT depots. VO_2peak increased, body weight decreased, and body fat distribution improved with exercise training (p < 0.05). The expression of 15 genes, mainly associated with embryonic development, differed between SAT depots at baseline, whereas 318 genes were differentially expressed post-training (p < 0.05). Four developmental genes were differentially expressed between these depots at both time points (HOXA5, DMRT2, DMRT3 and CSN1S1). Exercise training induced changes in the expression of genes associated with immune and inflammatory responses, and lipid metabolism in gSAT, and muscle-associated processes in aSAT. This study showed differences in developmental processes regulating SAT distribution and expandability of distinct depots, and depot-specific adaptation to exercise training in black South African women with obesity.

Casein and Peptides Derived from Casein as Antileukaemic Agents

Milk is a heterogeneous lacteal secretion mixture of numerous components that exhibit a wide variety of chemical and functional activities. Casein, the main protein in milk, is composed of α-, β-, and κ-caseins, each of which is important for nutritional value and for promoting the release of cytokines, also are linked to the regulation of haematopoiesis and immune response and inhibit the proliferation and induce the differentiation of leukaemia cells. It has been shown that the digestive process of caseins leads to the release of bioactive peptides that are involved in the regulation of blood pressure and the inhibition or activation of the immune response by serving as agonists or antagonists of opioid receptors, thus controlling the expression of genes that exert epigenetic control. Later, they bind to opioid receptor, block nuclear factor κ-beta, increase the redox potential, and reduce oxidative stress and the pro-inflammatory agents that favour an antioxidant and anti-inflammatory environment. Therefore, the bioactive peptides of casein could be compounds with antileukaemia potential. This review provides a summary of current knowledge about caseins and casein peptides on the immune system as well as their roles in the natural defence against the development of leukaemia and as relevant epigenetic regulators that can help eradicate leukaemia.

El Sodium caseinate and alfa-casein inhibit proliferation of the mouse myeloid cell line 32D clone 3 (32Dcl3) via TNF-α

Introduction: Sodium caseinate (CS) and its components (alpha-casein, beta-casein, and kappa-casein) have been shown to inhibit the proliferation of the mouse hematopoietic 32D clone 3 (32Dcl3) cell line and induce its differentiation into macrophages. It is well-known that alpha-casein induces IL-1β production and that this cytokine inhibits the proliferation via the production of tumor necrosis factor alpha (TNF-alpha), but it is not known if CS and the caseins inhibit the proliferation via TNF-alpha production. Objective: To evaluate if CS and alpha-casein, beta-casein and kappa-casein inhibit the proliferation on 32Dcl3 cell line via TNF-alpha. Materials and methods: We used different concentrations of CS, alpha-casein, betacasein and kappa-casein in 32Dcl3 cells to evaluate cell proliferation. We assessed cell viability by MTT, induction to apoptosis by flow cytometry, and TNF-alpha synthesis by ELISA. Additionally, we performed anti-TNF-alpha neutralization assays on 32Dcl3 cells treated with CS and alpha-casein and we evaluated proliferation. Results: The results showed that CS, alpha-casein, beta-casein, and kappa-casein reduced proliferation of the 32Dcl3 cell line without affecting the viability and that only CS and alpha-casein induced apoptosis and the release of TNF-alpha. The 32Dcl3 cells treated with CS and alpha-casein reestablished their proliferation by using anti-TNF-alpha antibodies. Conclusion: TNF-alpha was the main responsible for the inhibition of proliferation in 32Dcl3 cells treated with CS or alpha-casein.

Integrative Analysis Revealing Human Adipose-Specific Genes and Consolidating Obesity Loci

Identification of adipose-specific genes has contributed to an understanding of mechanisms underlying adipocyte development and obesity. Herein, our analyses of the recent Genotype-Tissue Expression (GTEx) database revealed 38 adipose-specific/enhanced protein coding genes, among which 3 genes were novel adipose-specific, and 414 highly differentially expressed genes (DEGs) between subcutaneous and omental adipose depots. By integrative analyses of genome-wide association studies (GWASs), 14 adipose-specific/enhanced genes and 60 DEGs were found to be associated with obesity-related traits and diseases, consolidating evidence for contribution of these genes to the regional fat distribution and obesity phenotypes. In addition, expression of HOXC cluster was up-regulated in subcutaneous adipose tissue, and the majority of the HOXB cluster was expressed highly in omental adipose tissue, indicating differential expression patterns of HOX clusters in adipose depots. Our findings on the distinct gene expression profiles in adipose tissue and their relation to obesity provide an important foundation for future functional biological studies and therapeutic targets in obesity and associated diseases.

Human αS1-casein induces IL-8 secretion by binding to the ecto-domain of the TLR4/MD2 receptor complex

BACKGROUND

The milk protein α_S1-casein was recently reported to induce secretion of proinflammatory cytokines via Toll-like receptor 4 (TLR4). In this study, α_S1-casein was identified as binder of theTLR4 ecto domain.

METHODS

IL-8 secretion after stimulation of TLR4/MD2 (myeloid differentiation factor 2)/CD14 (cluster of differentiation 14)-transfected HEK293 cells (TLR4⁺) and Mono Mac 6 cells (MM6) with recombinant α_S1-casein, or LPS as control was monitored. Binding of α_S1-casein to TLR4 was quantified by microscale thermophoresis (MST).

RESULTS

α_S1-casein induced secretion of IL-8 in TLR4⁺ cells and in MM6 cells with a six-times higher final IL-8 concentration in supernatants. IL-8 secretion was inhibited by intracellular TLR4-domain antagonist TAK-242 with an IC₅₀-value of 259.6 nM, by ecto-domain TLR4 antagonistic mianserin with 10-51 μM and by anti-CD14-IgA. The binding constants (K_D) of α_S1-casein to the TLR4, MD2, and CD14 were 2.8 μM, 0.3 μM and 2.7 μM, respectively. Finally, α_S1-casein showed a higher affinity to TLR4/MD2 (K_D: 2.2 μM) compared to LPS (K_D: 8.2 μM).

CONCLUSION

Human α_S1-casein induced proinflammatory effects are dependent upon binding to the TLR4 ectodomain and the presence of CD14. α_S1-casein displayed stronger TLR4 agonistic activity than LPS via a different mode of action.

GENERAL SIGNIFICANCE

Breast milk protein α_S1-casein is a proinflammatory cytokine.

Ser71 of αS1-Casein is Phosphorylated in Breast Milk-Evidence from Targeted Mass Analysis

SCOPE

The casein phosphoproteins in mother's milk supply calcium and phosphate ions and make them biologically available to the newborn. Human αS1-casein is of particular interest being also an autoantigen and proinflammatory cytokine. Phosphorylation of αS1-casein by casein kinase 2 completely abolishes binding to toll-like receptor 4 and proinflammatory effects. It is, however, not known, which amino acids are affected. Therefore, breast milk samples were analyzed in an effort to detect the phosphorylation sites of αS1-casein.

METHODS AND RESULTS

Breast milk samples were tryptically digested. Target tandem MS analysis confirmed the known phosphorylation sites S33 and S41; evidence for pS89 was found in some samples. Experimental support for the presence of pS31 and pS34 was weak. Phosphorylation of a new site in αS1-casein, S71, was reproducibly measured in all samples, albeit at much lower intensity than pS33 and pS41.

CONCLUSION

Phospho-occupancy rates varied greatly and could not be confidently correlated to other parameters within the cohort of 20 donors. The new phosphosite S71 is located in the neighborhood of the serine-rich region and may contribute to the cluster of high charge density at normal milk pH, likely exerting an influence on protein tertiary structure and thus function.

Immune-modulating properties of horse milk administered to mice sensitized to cow milk

The aim of this study was to examine immune adaptive changes, the expression of innate biomarkers and variations in intestinal microbiota composition after horse-milk administration in BALB/c mice, which were sensitized intraperitoneally using cow β-lactoglobulin and α-casein with aluminum adjuvant. We measured serum antibody IgE levels and the expression of MCP-1, IL-4, and TNF-α in duodenal samples. Changes in immune cell populations in peripheral blood were quantified using flow cytometry, and intestinal microbiota composition was assessed using real-time PCR. We found that horse-milk administration decreased serum IgE levels in sensitized mice. The groups that received horse milk showed an increased population of regulatory T cells (CD4⁺Foxp3⁺). Horse-milk administration decreased the mRNA levels of IL-4 and resulted in higher transcripts of TLR-4 in all treatment groups; however, the levels of MCP-1, TNF-α, and TLR-2 were unaltered. After horse-milk treatment, we observed a positive effect, with increased numbers of intestinal Bifidobacterium spp. We observed immune-modulating properties of horse milk, but future studies should focus on testing horse-milk processing, such as fermentation and destroying most allergenic epitopes to continue research under clinical conditions.

Proteomic Investigation of Ram Spermatozoa and the Proteins Conferred by Seminal Plasma

Sperm proteomes have emerged for several species; however, the extent of species similarity is unknown. Sheep are an important agricultural species for which a comprehensive sperm proteome has not been produced. In addition, potential proteomic factors from seminal plasma that may contribute to improved fertility after cervical insemination are yet to be explored. Here we use liquid chromatography-tandem mass spectrometry to investigate the proteome of ejaculated ram spermatozoa, with quantitative comparison to epididymal spermatozoa. We also present a comparison to published proteomes of five other species. We identified 685 proteins in ejaculated ram spermatozoa, with the most abundant proteins involved in metabolic pathways. Only 5% of ram sperm proteins were not detected in other species, which suggest highly conserved structures and pathways. Of the proteins present in both epididymal and ejaculated ram spermatozoa, 7% were more abundant in ejaculated spermatozoa. Only two membrane-bound proteins were detected solely in ejaculated sperm lysates: liver enriched gene 1 (LEG1/C6orf58) and epidermal growth factor-like repeats and discoidin I-like domains 3 (EDIL3). This is the first evidence that despite its relatively complex proteomic composition, seminal plasma exposure leads to few novel proteins binding tightly to the ram sperm plasma membrane.

Site-Specific Labeling of Protein Kinase CK2: Combining Surface Display and Click Chemistry for Drug Discovery Applications

Human CK2 is a heterotetrameric constitutively active serine/threonine protein kinase and is an emerging target in current anti-cancer drug discovery. The kinase is composed of two catalytic CK2α subunits and two regulatory CK2β subunits. In order to establish an assay to identify protein-protein-interaction inhibitors (PPI) of the CK2α/CK2β interface, a bioorthogonal click reaction was used to modify the protein kinase α-subunit with a fluorophore. By expanding the genetic code, the unnatural amino acid para azidophenylalanine (pAzF) could be incorporated into CK2α. Performing the SPAAC click reaction (Strain-Promoted Azide-Alkyne Cycloaddition) by the use of a dibenzylcyclooctyne-fluorophore (DBCO-fluorophore) led to a specifically labeled human protein kinase CK2α. This site-specific labeling does not impair the phosphorylation activity of CK2, which was evaluated by capillary electrophoresis. Furthermore a dissociation constant (K_D) of 631 ± 86.2 nM was determined for the substrate α_S1-casein towards CK2α. This labeling strategy was also applied to CK2β subunit on Escherichia coli, indicating the site-specific modifications of proteins on the bacterial cell surface when displayed by Autodisplay.