The Multifaceted Roles of Bovine Lactoferrin: Molecular Structure, Isolation Methods, Analytical Characteristics, and Biological Properties

Bovine lactoferrin (bLF) is widely known as an iron-binding glycoprotein from the transferrin family. The bLF molecule exhibits a broad spectrum of biological activity, including iron delivery, antimicrobial, antiviral, immunomodulatory, antioxidant, antitumor, and prebiotic functions, thereby making it one of the most valuable representatives for biomedical applications. Remarkably, LF functionality might completely differ in dependence on the iron saturation state and glycosylation patterns. Recently, a violently growing demand for bLF production has been observed, mostly for infant formulas, dietary supplements, and functional food formulations. Unfortunately, one of the reasons that inhibit the development of the bLF market and widespread protein implementation is related to its negligible amount in both major sources─colostrum and mature milk. This study provides a comprehensive overview of the significance of bLF research by delineating the key structural characteristics of the protein and elucidating their impact on its physicochemical and biological properties. Progress in the development of optimal isolation techniques for bLF is critically assessed, alongside the challenges that arise during its production. Furthermore, this paper presents a curated list of the most relevant instrumental techniques for the characterization of bLF. Lastly, it discusses the prospective applications and future directions for bLF-based formulations, highlighting their potential in various fields.

Lactoferrin and Nanotechnology: The Potential for Cancer Treatment

Lactoferrin (Lf)-a glycoprotein of the transferrin family-has been investigated as a promising molecule with diverse applications, including infection inhibition, anti-inflammation, antioxidant properties and immune modulation. Along with that, Lf was found to inhibit the growth of cancerous tumors. Owing to unique properties such as iron-binding and positive charge, Lf could interrupt the cancer cell membrane or influence the apoptosis pathway. In addition, being a common mammalian excretion, Lf offers is promising in terms of targeting delivery or the diagnosis of cancer. Recently, nanotechnology significantly enhanced the therapeutic index of natural glycoproteins such as Lf. Therefore, in the context of this review, the understanding of Lf is summarized and followed by different strategies of nano-preparation, including inorganic nanoparticles, lipid-based nanoparticles and polymer-based nanoparticles in cancer management. At the end of the study, the potential future applications are discussed to pave the way for translating Lf into actual usage.

Bovine Lactoferrin Induces Cell Death in Human Prostate Cancer Cells

Bovine lactoferrin (bLf) is a multifunctional protein widely associated with anticancer activity. Prostate cancer is the second most frequent type of cancer worldwide. This study was aimed at evaluating the influence of bLf on cell viability, cell cycle progression, reactive oxygen species (ROS) production, and rate of apoptosis in the human prostate cancer cell line (DU-145). MTT assay and trypan blue exclusion were used to analyze cell viability. Morphological changes were analyzed through optical microscopy after 24 h and 48 h of bLf treatment. FITC-bLf internalization and cellular damage were observed within 24 h by confocal fluorescence microscopy. Cell cycle analyses were performed by flow cytometry and propidium iodide. For caspases 3/7 activation and reactive oxygen species production evaluation, cells were live-imaged using the high-throughput system Operetta. The cell viability assays demonstrated that bLf induces cell death and morphological changes after 24 h and 48 h of treatment compared to control on DU-145 cells. The bLf internalization was detected in DU-145 cells, G₁-phase arrest of the cell cycle, caspase 3/7 activation, and increased oxidative stress on bLf-treated cells. Our data support that bLf has an important anticancer activity, thus offering new perspectives in preventing and treating prostate cancer.

Enhanced antitumor activity of bovine lactoferrin through immobilization onto functionalized nano graphene oxide: an in vitro/in vivo study

This study aims to improve the anticancer activity of bovine lactoferrin through enhancing its stability by immobilization onto graphene oxide. Bovine lactoferrin was conjugated onto graphene oxide and the conjugation process was confirmed by FT-IR, SDS-PAGE, and UV spectrophotometry. Physical characterization was performed by DLS analysis and atomic force microscopy. The cytotoxicity and cellular uptake of the final construct (CGO-PEG-bLF) was inspected on lung cancer TC-1 cells by MTT assay and flow cytometry/confocal microscopy. The anticancer mechanism of the CGO-PEG-bLF was studied by cell cycle analysis, apoptosis assay, and western blot technique. Finally, the anticancer activity of CGO-PEG-bLF was assessed in an animal model of lung cancer. Size and zeta potential of CGO-PEG-bLF was obtained in the optimum range. Compared with free bLF, more cytotoxic activity, cellular uptake and more survival time was obtained for CGO-PEG-bLF. CGO-PEG-bLF significantly inhibited tumor growth in the animal model. Cell cycle arrest and apoptosis were more induced by CGO-PEG-bLF. Moreover, exposure to CGO-PEG-bLF decreased the phospho-AKT and pro-Caspase 3 levels and increased the amount of cleaved caspase 3 in the treated cells. This study revealed the potential of CGO-PEG as a promising nanocarrier for enhancing the therapeutic efficacy of anticancer agents.

Lactoferrin promotes murine C2C12 myoblast proliferation and differentiation and myotube hypertrophy

Lactoferrin (Lf) is a multifunctional glycoprotein, which promotes the proliferation of murine C2C12 myoblasts. In the present study, it was investigated how Lf promotes myoblast proliferation and whether Lf promotes myoblast differentiation or induces myotube hypertrophy. Lf promoted the proliferation of myoblasts in a dose-dependent manner. Myoblast proliferation increased on day 3 when myoblasts were cultured in the presence of Lf for three days and also when myoblasts were cultured in the presence of Lf for the first day and in the absence of Lf for the subsequent two days. In addition, Lf induced the phosphorylation of extracellular signal-regulated kinase (ERK)1/2 in myoblasts. The mitogen-activated protein kinase kinase 1/2 inhibitor U0126 inhibited Lf-induced ERK1/2 phosphorylation and repressed Lf-promoted myoblast proliferation. C2C12 myoblasts, myotubes and skeletal muscle expressed low-density lipoprotein receptor-related protein (LRP)1 mRNA and Lf-promoted myoblast proliferation was attenuated by an LRP1 antagonist or LRP1 gene silencing. The knockdown of LRP1 repressed Lf-induced phosphorylation of ERK1/2. Furthermore, when myoblasts were induced to differentiate, Lf increased the expression of the myotube-specific structural protein, myosin heavy chain (MyHC) and promoted myotube formation. Knockdown of LRP1 repressed Lf-induced MyHC expression. Lf also increased myotube size following differentiation. These results indicate that Lf promotes myoblast proliferation and differentiation, at least partially through LRP1 and also stimulates myotube hypertrophy.

Renoprotective Effect of Lactoferrin against Chromium-Induced Acute Kidney Injury in Rats: Involvement of IL-18 and IGF-1 Inhibition

Hexavalent chromium (CrVI) is a heavy metal widely used in more than 50 industries. Nephrotoxicity is a major adverse effect of chromium poisoning. The present study investigated the potential renoprotective effect of lactoferrin (Lf) against potassium dichromate (PDC)-induced acute kidney injury (AKI) in rats. Beside, because previous studies suggest that interlukin-18 (IL-18) and insulin-like growth factor-1 (IGF-1) play important roles in promoting kidney damage, the present work aimed to evaluate the involvement of these two cytokines in PDC model of AKI and in the potential renoprotective effect of lactoferrin. Adult male albino Wistar rats were pretreated with Lf (200mg/kg/day, p.o.) or (300mg/kg/day, p.o.); the doses that are usually used in the experiment studies, for 14 days followed by a single dose of PDC (15mg/kg, s.c.). PDC caused significant increase in serum urea, creatinine, and total protein levels. This was accompanied with decreased renal glutathione content, and increased renal malondialdehyde, IL-18, IL-4, nuclear factor kappa B (NFκB), IGF-1, and the phosphorylated form of forkhead box protein O1 (FoxO1) levels. Moreover, normal expression IFN-γ mRNA and enhanced expression of TNF-α mRNA was demonstrated in renal tissues. Histopathological investigations provoked deleterious changes in the renal tissues. Tubular epithelial hyperplasia and apoptosis were demonstrated immunohistochemically by positive proliferating cell nuclear antigen (PCNA), Bax, and Caspase-3 expression, respectively. Pretreatment of rats with Lf in both doses significantly corrected all previously mentioned PDC-induced changes with no significant difference between both doses. In conclusion, the findings of the present study demonstrated the involvement of oxidative stress, inflammatory reactions, tubular hyperplasia and apoptosis in PDC-induced AKI. It suggested a role of IL-18 through stimulation of IL-4-induced inflammatory pathway, and IGF-1 through triggering FoxO1-induced cell proliferation. Moreover, the study revealed that Lf protected the kidney against Cr-induced AKI in rats and significantly showed antioxidant, anti-inflammatory, and anti-proliferative properties with down-regulation of IL-18 and IGF-1.

A Tetrameric Peptide Derived from Bovine Lactoferricin Exhibits Specific Cytotoxic Effects against Oral Squamous-Cell Carcinoma Cell Lines

Several short linear peptides derived from cyclic bovine lactoferricin were synthesized and tested for their cytotoxic effect against the oral cavity squamous-cell carcinoma (OSCC) cell lines CAL27 and SCC15. As a control, an immortalized and nontumorigenic cell line, Het-1A, was used. Linear peptides based on the RRWQWR core sequence showed a moderate cytotoxic effect and specificity towards tumorigenic cells. A tetrameric peptide, LfcinB(20–25)₄, containing the RRWQWR motif, exhibited greater cytotoxic activity (>90%) in both OSCC cell lines compared to the linear lactoferricin peptide or the lactoferrin protein. Additionally, this tetrameric peptide showed the highest specificity towards tumorigenic cells among the tested peptides. Interestingly, this effect was very fast, with cell shrinkage, severe damage to cell membrane permeability, and lysis within one hour of treatment. Our results are consistent with a necrotic effect rather than an apoptotic one and suggest that this tetrameric peptide could be considered as a new candidate for the therapeutic treatment of OSCC.

Expression, purification, and breast cancer cell inhibiting effect of recombinant human lactoferrin C-lobe

Lactoferrin (LTF), a multifunctional glycoprotein of the transferrin family mainly found in exotic secretions in mammals, is an important defense molecule against not only microbial invasion but also tumors. It folds into two globular domains (N- and C-lobes) each containing an iron-binding site. The cationic antimicrobial peptide in N-lobe is known to exert anti-tumor effect via a non-receptor-mediated pathway. However, whether LTF C-lobe also contributes to its anti-tumor activity remains to be investigated. In this study, a human LTF fragment (amino acid residues 343-682) covering the C-lobe was expressed with a histidine tag in E. coli and the purified polypeptide refolded through a series of buffer changing procedure. The resultant recombinant protein caused significant growth arrest of breast carcinoma cells MDA-MB-231 in a dose- and time-dependent manner, evidently via induction of apoptosis of the cell. Our data suggest a positive role for the C-lobe of human LTF in controlling tumors in vitro.

Iron-free and iron-saturated bovine lactoferrin inhibit survivin expression and differentially modulate apoptosis in breast cancer

BACKGROUND

Iron binding, naturally occurring protein bovine lactoferrin (bLf) has attracted attention as a safe anti-cancer agent capable of inducing apoptosis. Naturally, bLf exists partially saturated (15-20%) with Fe(3+) however, it has been demonstrated that manipulating the saturation state can enhance bLf's anti-cancer activities.

METHODS

Apo-bLf (Fe(3+) free) and Fe-bLf (>90% Fe(3+) Saturated) were therefore, tested in MDA-MB-231 and MCF-7 human breast cancer cells in terms of cytotoxicity, proliferation, migration and invasion. Annexin-V Fluos staining was also employed in addition to apoptotic protein arrays and Western blotting to determine the specific mechanism of bLf-induced apoptosis with a key focus on p53 and inhibitor of apoptosis proteins (IAP), specifically survivin.

RESULTS

Apo-bLf induced significantly greater cytotoxicity and reduction in cell proliferation in both cancer cells showing a time and dose dependent effect. Importantly, no cytotoxicity was detected in normal MCF-10-2A cells. Both forms of bLf significantly reduced cell invasion in cancer cells. Key apoptotic molecules including p53, Bcl-2 family proteins, IAP members and their inhibitors were significantly modulated by both forms of bLf, though differentially in each cell line. Most interestingly, both Apo-bLf and Fe-bLf completely inhibited the expression of survivin protein (key IAP), after 48 h at 30 and 40 nM in cancer cells.

CONCLUSIONS

The capacity of these forms of bLf to target survivin expression and modulation of apoptosis demonstrates an exciting potential for bLf as an anti-cancer therapeutic in the existing void of survivin inhibitors, with a lack of successful inhibitors in the clinical management of cancer.

Anticancer effects of lactoferrin: underlying mechanisms and future trends in cancer therapy

Lactoferrin has been widely studied over the last 70 years, and its role in diverse biological functions is now well known and generally accepted by the scientific community. Usually, alterations of the lactoferrin gene in cells are associated with an increased incidence of cancer. Several studies suggest that exogenous treatment with lactoferrin and its derivatives can efficiently inhibit the growth of tumors and reduce susceptibility to cancer. None of these studies, however, reported a consistent outcome with regard to the mechanisms underlying the anticancer effects of lactoferrin. In this review, the association of lactoferrin with cancer is thoroughly discussed, from lactoferrin gene expression to the potential use of lactoferrin in cancer therapy. Lactoferrin cytotoxicity against several cancers is reported to occur in distinct ways under different conditions, namely by cell membrane disruption, apoptosis induction, cell cycle arrest, and cell immunoreaction. Based on these mechanisms, new strategies to improve the anticancer effects of the lactoferrin protein and/or its derivatives are proposed. The potential for lactoferrin in the field of cancer research (including as a chemotherapeutic agent in cancer therapy) is also discussed.

Bovine lactoferrin induces cell cycle arrest and inhibits mTOR signaling in breast cancer cells

Lactoferrin (LF) is predominantly found in mammalian secretions with recognized anticancer potential, although the mechanisms involved in such activity are still unclear. Here, the stability, internalization, and cytotoxicity of bovine LF (bLF) and its variants were tested against a panel of breast cancer cells. bLF was found to be very stable under incubation with cells and also able to internalize them, although most of the protein remained in the culture medium. Furthermore, bLF (up to 30 μM) inhibited the growth of breast cancer cells (T-47D, MDA-MB-231, Hs578T, and MCF-7) in a higher extent than in the normal counterpart cell line (MCF-10-2A), thus suggesting its selectivity. Regarding its variants, only the iron-saturated protein showed a higher activity compared with the commercial bLF. bLF growth inhibitory activity was associated with the induction of cell cycle arrest, but not with apoptosis. Moreover, exposure to bLF increased the cells phospho-AMPKα levels and decreased both phospho threonine mammalian target of rapamycin (mTOR) and total mTOR levels, indicating a novel mechanism of action through its ability to induce nutrient/energy-related stress. This study disclosed important findings to better understand the mechanisms underlying the bLF effects on breast cancer cell lines, which could be valuable for novel advances in the cancer research field.

Cell-penetrating properties of the transactivator of transcription and polyarginine (R9) peptides, their conjugative effect on nanoparticles and the prospect of conjugation with arsenic trioxide

Cell-penetrating peptides (CPPs) are short chains of amino acids with the distinct ability to cross cell plasma membranes. They are usually between seven and 30 residues in length. The mechanism of action is still a highly debated subject among researchers; it seems that a commonality between all CPPs is the presence of positively charged residues within the amino acid chain. Polyarginine and the transactivator of transcription peptide are two widely used CPPs. One distinct application of these CPPs is the ability to further enhance the therapeutic properties of a range of different agents. One group of agents of particular importance are nanoparticles (NPs). Most NPs have no mechanism for cellular uptake. Hence, by conjugating CPPs to NPs, the amount of NPs taken up by cells can be increased, and therefore, the therapeutic benefits can be maximized. Some examples of this will be explored further in this review. In addition to CPPs, the concept of conjugation with the anticancer drug arsenic trioxide is reviewed and the prospect of transactivator of transcription-conjugated arsenic trioxide albumin microspheres is also discussed. Recent locked nucleic acid technology to stabilize nucleotides (RNA or DNA) aptamer complexes able to target cancer cells more specifically and selectively to kill tumour cells and spare normal body cells. NPs tagged with modified locked nucleic acid-aptamers have the potential to kill cancer cells more specifically and effectively while sparing normal cells.

An investigation of growth factors and lactoferrin in naturally occurring ovine pulmonary adenomatosis

Ovine pulmonary adenomatosis (OPA), also known as jaagsiekte, is a transmissible beta retrovirus-induced lung tumour of sheep that has several features resembling human bronchoalveolar carcinoma (BAC). Angiogenesis has been suggested to be one of the most important factors underlying tumour growth and invasion. This process involves the action of growth factors including vascular endothelial growth factor (VEGF)-C, basic fibroblast growth factor (bFGF), platelet-derived growth factor (PDGF)-C and its receptor (PDGFR-α). Bovine lactoferrin (bLF), an iron and heparin-binding glycoprotein secreted into various biological fluids, has been implicated in innate immunity and has anti-inflammatory and anti-tumour functions. Tissues from 16 cases of OPA were compared with tissues from seven healthy control sheep by immunohistochemistry. Expression of the markers was assessed semi-quantitatively by ascribing an immunoreactivity score (IRS) with a maximum value of 300. VEGF-C, bFGF, PDGF-C, PDGFR-α and bLF signals were detected in 10/16, 15/16, 12/16, 15/16 and 10/16 of the OPA cases studied, respectively. bLF expression was weak in the neoplastic epithelial cells (IRS 21.4 ± 10.0) in contrast to high levels detected in infiltrating macrophages and plasma cells (IRS 141.3 ± 24.8 and 140.0 ± 25.1, respectively). The PDGFR-α IRS was elevated for neoplastic epithelial cells (108.9 ± 18.2) and was lowest for macrophages and plasma cells (20.4 ± 13.1 and 13.7 ± 12.4, respectively). These results suggest that bFGF, VEGF-C and PDGF-C have roles in the pathogenesis of OPA. bLF may activate macrophages and plasma cells in these lesions, but limited expression of bLF by neoplastic cells may be a consequence of defective or impaired function of this molecule.

Clinical effects of bovine lactoferrin on two canine cases with familial neutrophil dysfunction

This study reported detailed clinical effects of bovine lactoferrin on 2 canine littermates (1 female and 1 male) with familial neutrophil dysfunction and an investigation of their genetic background. Clinical signs caused by severe upper respiratory bacterial infections were observed in these dogs. Oral administration of bovine lactoferrin for a long duration improved their clinical signs (severe uveitis in the female dog and coughing from pneumonia in the male dog). Their backcross dogs that have the same father didn't show clinical signs of bacterial infection. Neutrophil function tests revealed that the backcross dogs didn't have any disorders. It is likely that abnormal clinical signs are associated with neutrophil dysfunction in the colony, and the mother dog of these cases might be the genetic carrier of this dysfunction.