Wheatgerm agglutinin-mediated toxicity in pancreatic cancer cells

Multifunctional Cell Regulation Activities of the Mussel Lectin SeviL: Induction of Macrophage Polarization toward the M1 Functional Phenotype

SeviL, a galactoside-binding lectin previously isolated from the mussel Mytilisepta virgata, was demonstrated to trigger apoptosis in HeLa ovarian cancer cells. Here, we show that this lectin can promote the polarization of macrophage cell lines toward an M1 functional phenotype at low concentrations. The administration of SeviL to monocyte and basophil cell lines reduced their growth in a dose-dependent manner. However, low lectin concentrations induced proliferation in the RAW264.7 macrophage cell line, which was supported by the significant up-regulation of TOM22, a component of the mitochondrial outer membrane. Furthermore, the morphology of lectin-treated macrophage cells markedly changed, shifting from a spherical to an elongated shape. The ability of SeviL to induce the polarization of RAW264.7 cells to M1 macrophages at low concentrations is supported by the secretion of proinflammatory cytokines and chemokines, as well as by the enhancement in the expression of IL-6- and TNF-α-encoding mRNAs, both of which encode inflammatory molecular markers. Moreover, we also observed a number of accessory molecular alterations, such as the activation of MAP kinases and the JAK/STAT pathway and the phosphorylation of platelet-derived growth factor receptor-α, which altogether support the functional reprogramming of RAW264.7 following SeviL treatment. These results indicate that this mussel β-trefoil lectin has a concentration-dependent multifunctional role in regulating cell proliferation, phenotype, and death in macrophages, suggesting its possible involvement in regulating hemocyte activity in vivo.

Micro-nanoemulsion and nanoparticle-assisted drug delivery against drug-resistant tuberculosis: recent developments

Tuberculosis (TB) is a major global health problem and the second most prevalent infectious killer after COVID-19. It is caused by Mycobacterium tuberculosis (Mtb) and has become increasingly challenging to treat due to drug resistance. The World Health Organization declared TB a global health emergency in 1993. Drug resistance in TB is driven by mutations in the bacterial genome that can be influenced by prolonged drug exposure and poor patient adherence. The development of drug-resistant forms of TB, such as multidrug resistant, extensively drug resistant, and totally drug resistant, poses significant therapeutic challenges. Researchers are exploring new drugs and novel drug delivery systems, such as nanotechnology-based therapies, to combat drug resistance. Nanodrug delivery offers targeted and precise drug delivery, improves treatment efficacy, and reduces adverse effects. Along with nanoscale drug delivery, a new generation of antibiotics with potent therapeutic efficacy, drug repurposing, and new treatment regimens (combinations) that can tackle the problem of drug resistance in a shorter duration could be promising therapies in clinical settings. However, the clinical translation of nanomedicines faces challenges such as safety, large-scale production, regulatory frameworks, and intellectual property issues. In this review, we present the current status, most recent findings, challenges, and limiting barriers to the use of emulsions and nanoparticles against drug-resistant TB.

Single-cell glycomics analysis by CyTOF-Lec reveals glycan features defining cells differentially susceptible to HIV

High-parameter single-cell phenotyping has enabled in-depth classification and interrogation of immune cells, but to date has not allowed for glycan characterization. Here, we develop CyTOF-Lec as an approach to simultaneously characterize many protein and glycan features of human immune cells at the single-cell level. We implemented CyTOF-Lec to compare glycan features between different immune subsets from blood and multiple tissue compartments, and to characterize HIV-infected cell cultures. Using bioinformatics approaches to distinguish preferential infection of cellular subsets from viral-induced remodeling, we demonstrate that HIV upregulates the levels of cell-surface fucose and sialic acid in a cell-intrinsic manner, and that memory CD4+ T cells co-expressing high levels of fucose and sialic acid are highly susceptible to HIV infection. Sialic acid levels were found to distinguish memory CD4+ T cell subsets expressing different amounts of viral entry receptors, pro-survival factors, homing receptors, and activation markers, and to play a direct role in memory CD4+ T cells' susceptibility to HIV infection. The ability of sialic acid to distinguish memory CD4+ T cells with different susceptibilities to HIV infection was experimentally validated through sorting experiments. Together, these results suggest that HIV remodels not only cellular proteins but also glycans, and that glycan expression can differentiate memory CD4+ T cells with vastly different susceptibility to HIV infection.

An update on dual targeting strategy for cancer treatment

The key issue in the treatment of solid tumors is the lack of efficient strategies for the targeted delivery and accumulation of therapeutic cargoes in the tumor microenvironment (TME). Targeting approaches are designed for more efficient delivery of therapeutic agents to cancer cells while minimizing drug toxicity to normal cells and off-targeting effects, while maximizing the eradication of cancer cells. The highly complicated interrelationship between the physicochemical properties of nanoparticles, and the physiological and pathological barriers that are required to cross, dictates the need for the success of targeting strategies. Dual targeting is an approach that uses both purely biological strategies and physicochemical responsive smart delivery strategies to increase the accumulation of nanoparticles within the TME and improve targeting efficiency towards cancer cells. In both approaches, either one single ligand is used for targeting a single receptor on different cells, or two different ligands for targeting two different receptors on the same or different cells. Smart delivery strategies are able to respond to triggers that are typical of specific disease sites, such as pH, certain specific enzymes, or redox conditions. These strategies are expected to lead to more precise targeting and better accumulation of nano-therapeutics. This review describes the classification and principles of dual targeting approaches and critically reviews the efficiency of dual targeting strategies, and the rationale behind the choice of ligands. We focus on new approaches for smart drug delivery in which synthetic and/or biological moieties are attached to nanoparticles by TME-specific responsive linkers and advanced camouflaged nanoparticles.

A Historical Review of Brain Drug Delivery

The history of brain drug delivery is reviewed beginning with the first demonstration, in 1914, that a drug for syphilis, salvarsan, did not enter the brain, due to the presence of a blood-brain barrier (BBB). Owing to restricted transport across the BBB, FDA-approved drugs for the CNS have been generally limited to lipid-soluble small molecules. Drugs that do not cross the BBB can be re-engineered for transport on endogenous BBB carrier-mediated transport and receptor-mediated transport systems, which were identified during the 1970s-1980s. By the 1990s, a multitude of brain drug delivery technologies emerged, including trans-cranial delivery, CSF delivery, BBB disruption, lipid carriers, prodrugs, stem cells, exosomes, nanoparticles, gene therapy, and biologics. The advantages and limitations of each of these brain drug delivery technologies are critically reviewed.

Hepatitis B virus envelope proteins can serve as therapeutic targets embedded in the host cell plasma membrane

Hepatitis B virus (HBV) infection is a major health threat causing 880,000 deaths each year. Available therapies control viral replication but do not cure HBV, leaving patients at risk to develop hepatocellular carcinoma. Here, we show that HBV envelope proteins (HBs)-besides their integration into endosomal membranes-become embedded in the plasma membrane where they can be targeted by redirected T-cells. HBs was detected on the surface of HBV-infected cells, in livers of mice replicating HBV and in HBV-induced hepatocellular carcinoma. Staining with HBs-specific recombinant antibody MoMab recognising a conformational epitope indicated that membrane-associated HBs remains correctly folded in HBV-replicating cells in cell culture and in livers of HBV-transgenic mice in vivo. MoMab coated onto superparamagnetic iron oxide nanoparticles allowed to detect membrane-associated HBs after HBV infection by electron microscopy in distinct stretches of the hepatocyte plasma membrane. Last but not least, we demonstrate that HBs located on the cell surface allow therapeutic targeting of HBV-positive cells by T-cells either engrafted with a chimeric antigen receptor or redirected by bispecific, T-cell engager antibodies. TAKE AWAYS: HBs become translocated to the plasma membrane. Novel, recombinant antibody confirmed proper conformation of HBs on the membrane. HBs provide an interesting target by T-cell-based, potentially curative therapies.

Lectin from Triticum vulgaris (WGA) Inhibits Infection with SARS-CoV-2 and Its Variants of Concern Alpha and Beta

Even in the face of global vaccination campaigns, there is still an urgent need for effective antivirals against SARS-CoV-2 and its rapidly spreading variants. Several natural compounds show potential as antiviral substances and have the advantages of broad availabilities and large therapeutic windows. Here, we report that lectin from Triticum vulgaris (Wheat Germ Agglutinin) displays antiviral activity against SARS-CoV-2 and its major Variants of Concern (VoC), Alpha and Beta. In Vero B4 cells, WGA potently inhibits SARS-CoV-2 infection with an IC₅₀ of <10 ng/mL. WGA is effective upon preincubation with the virus or when added during infection. Pull-down assays demonstrate direct binding of WGA to SARS-CoV-2, further strengthening the hypothesis that inhibition of viral entry by neutralizing free virions might be the mode of action behind its antiviral effect. Furthermore, WGA exhibits antiviral activity against human coronavirus OC43, but not against other non-coronaviruses causing respiratory tract infections. Finally, WGA inhibits infection of the lung cell line Calu-3 with wild type and VoC viruses with comparable IC₅₀ values. Altogether, our data indicate that topical administration of WGA might be effective for prophylaxis or treatment of SARS-CoV-2 infections.

Mass Spectrometry Imaging for Glycome in the Brain

Glycans are diverse structured biomolecules that play crucial roles in various biological processes. Glycosylation, an enzymatic system through which various glycans are bound to proteins and lipids, is the most common and functionally crucial post-translational modification process. It is known to be associated with brain development, signal transduction, molecular trafficking, neurodegenerative disorders, psychopathologies, and brain cancers. Glycans in glycoproteins and glycolipids expressed in brain cells are involved in neuronal development, biological processes, and central nervous system maintenance. The composition and expression of glycans are known to change during those physiological processes. Therefore, imaging of glycans and the glycoconjugates in the brain regions has become a “hot” topic nowadays. Imaging techniques using lectins, antibodies, and chemical reporters are traditionally used for glycan detection. However, those techniques offer limited glycome detection. Mass spectrometry imaging (MSI) is an evolving field that combines mass spectrometry with histology allowing spatial and label-free visualization of molecules in the brain. In the last decades, several studies have employed MSI for glycome imaging in brain tissues. The current state of MSI uses on-tissue enzymatic digestion or chemical reaction to facilitate successful glycome imaging. Here, we reviewed the available literature that applied MSI techniques for glycome visualization and characterization in the brain. We also described the general methodologies for glycome MSI and discussed its potential use in the three-dimensional MSI in the brain.

Wheat Germ Agglutinin—From Toxicity to Biomedical Applications

Wheat germ agglutinin is a hevein class N-Acetylglucosamine–binding protein with specific toxicity and biomedical potential. It is extractable from wheat germ—a low-value byproduct of the wheat industry—using well–established extraction methods based on salt precipitation and affinity chromatography. Due to its N-Acetylglucosamine affinity, wheat germ agglutinin exhibits antifungal properties as well as cytotoxic properties. Its anticancer properties have been demonstrated for various cancer cells, and toxicity mechanisms are well described. Wheat germ agglutinin has been demonstrated as a viable solution for various biomedical and therapeutic applications, such as chemotherapy, targeted drug delivery, antibiotic-resistant bacteria monitoring and elimination. This is performed mostly in conjunction with nanoparticles, liposomes, and other carrier mechanisms via surface functionalization. Combined with abundant wheat byproduct sources, wheat germ agglutinin has the potential to improve the biomedical field considerably.

Cytidine Monophosphate N-Acetylneuraminic Acid Synthetase and Solute Carrier Family 35 Member A1 Are Required for Reovirus Binding and Infection

Engagement of cell surface receptors by viruses is a critical determinant of viral tropism and disease. The reovirus attachment protein σ1 binds sialylated glycans and proteinaceous receptors to mediate infection, but the specific requirements for different cell types are not entirely known. To identify host factors required for reovirus-induced cell death, we conducted a CRISPR-knockout screen targeting over 20,000 genes in murine microglial BV2 cells. Candidate genes required for reovirus to cause cell death were highly enriched for sialic acid synthesis and transport. Two of the top candidates identified, CMP N-acetylneuraminic acid synthetase (Cmas) and solute carrier family 35 member A1 (Slc35a1), promote sialic acid expression on the cell surface. Two reovirus strains that differ in the capacity to bind sialic acid, T3SA⁺ and T3SA^-, were used to evaluate Cmas and Slc35a1 as potential host genes required for reovirus infection. Following CRISPR-Cas9 disruption of either gene, cell surface expression of sialic acid was diminished. These results correlated with decreased binding of strain T3SA⁺, which is capable of engaging sialic acid. Disruption of either gene did not alter the low-level binding of T3SA^-, which does not engage sialic acid. Furthermore, infectivity of T3SA⁺ was diminished to levels similar to those of T3SA^- in cells lacking Cmas and Slc35a1 by CRISPR ablation. However, exogenous expression of Cmas and Slc35a1 into the respective null cells restored sialic acid expression and T3SA⁺ binding and infectivity. These results demonstrate that Cmas and Slc35a1, which mediate cell surface expression of sialic acid, are required in murine microglial cells for efficient reovirus binding and infection.IMPORTANCE Attachment factors and receptors are important determinants of dissemination and tropism during reovirus-induced disease. In a CRISPR cell survival screen, we discovered two genes, Cmas and Slc35a1, which encode proteins required for sialic acid expression on the cell surface and mediate reovirus infection of microglial cells. This work elucidates host genes that render microglial cells susceptible to reovirus infection and expands current understanding of the receptors on microglial cells that are engaged by reovirus. Such knowledge may lead to new strategies to selectively target microglial cells for oncolytic applications.

Vaccine-Induced Adverse Effects in Cultured Neuroblastoma 2A (N2A) Cells Duplicate Toxicity of Serum from Patients with Gulf War Illness (GWI) and Are Prevented in the Presence of Specific Anti-Vaccine Antibodies

Gulf War illness (GWI) is a chronic disease of unknown etiology affecting over 200,000 veterans with symptoms including neurocognitive problems. We previously demonstrated GWI serum toxicity on neural cell cultures manifested by compromised neural network function, decreased cell spreading, and enhanced cell apoptosis. These patients lacked six human leukocyte antigen (HLA) class II alleles, resulting in an inability to form antibodies. Therefore, we hypothesized that GWI patients have vaccine-derived, persistent pathogens, which contribute to the development of the disease. Here, we examined whether individual vaccines were toxic in cultured N2A cells. Moreover, we used antibodies against each of the 20 vaccines administered to Gulf War (GW) veterans, to examine the effects of these antibodies on cell spreading and apoptosis in N2A cells. Antibodies against cholera toxin, hepatitis B, hemagglutinin H1N1, H3N2, and B from influenza A and B strains, measles, and Salmonella Typhi polysaccharide Vi had a remarkable protective effect on both cell spreading and apoptosis, whereas none of the other antibodies administered to GW veterans had an effect. The in vitro observed adverse effects of GWI serum may be due in part to vaccine-derived pathogens, antibodies against which had a protective effect in N2A cell cultures.

Dual function of lectins — new perspectives in targeted photodynamic therapy

Porphyrins and phthalocyanines are photosensitizers (PS) that are used in clinical imaging, detection of cancer cells and are particularly applied in photodynamic therapy (PDT). Many scientists have been focused on the design of different porphyrin compounds. However, similar to other anti-cancer agents, they cannot selectively recognize tumor tissues. Scientists are seeking new methods to overcome this problem and to find appropriate targeted delivery strategies. Plant lectins are especially suitable molecules for such targeting as they preferentially recognize specific antigens on the glycosylated cancer cells. This review will give more detailed information about the dual function of lectins and their interactions with PSs, which is a new perspective in targeted PDT. The implications and potential applications of such studies will also be discussed.

Plant lectins in cancer therapeutics: Targeting apoptosis and autophagy-dependent cell death

Plant lectins are non-immunoglobin in nature and bind to the carbohydrate moiety of the glycoconjugates without altering any of the recognized glycosyl ligands. Plant lectins have found applications as cancer biomarkers for recognizing the malignant tumor cells for the diagnosis and prognosis of cancer. Interestingly, plant lectins contribute to inducing cell death through autophagy and apoptosis, indicating their potential implication in cancer inhibitory mechanism. In the present review, anticancer activities of major plant lectins have been documented, with a detailed focus on the signaling circuit for the possible molecular targeted cancer therapy. In this context, several lectins have exhibited preclinical and clinical significance, driving toward therapeutic potential in cancer treatment. Moreover, several plant lectins induce immunomodulatory activities, and therefore, novel strategies have been established from preclinical and clinical investigations for the development of combinatorial treatment consisting of immunotherapy along with other anticancer therapies. Although the application of plant lectins in cancer is still in very preliminary stage, advanced high-throughput technology could pave the way for the development of lectin-based complimentary medicine for cancer treatment.

Wheat Germ Agglutinin as a Potential Therapeutic Agent for Leukemia

Dietary lectins are carbohydrate-binding proteins found in food sources. We used a panel of seven dietary lectins to analyze cytotoxicity against hematological cancers. Wheat germ agglutinin (WGA), even at low doses, demonstrated maximum toxicity toward acute myeloid leukemia (AML) cells. Using AML cell lines, we show time- and dose-dependent killing by WGA. We also show that low doses of WGA kills primary patient AML cells, irrespective of subtype, with no significant toxicity to normal cells. WGA caused AML cell agglutination, but failed to agglutinate RBC's at this dose. WGA, primarily, binds to N-acetyl-D-glucosamine (GlcNAc) and is also reported to interact with sialic-acid-containing glycoconjugates and oligosaccharides. After neuraminidase pre-treatment, which catalyzes the hydrolysis of terminal sialic acid residues, AML cells were less sensitive to WGA-induced cell death. AML cells were also not sensitive to succinyl-WGA, which does not react with sialic acid. Incubation with LEL lectin, which recognizes GlcNAc or SNA, which binds preferentially to sialic acid attached to terminal galactose in α-2,6 and to a lesser degree α-2,3 linkage, did not alter AML cell viability. These data indicate that WGA-induced AML cell death is dependent on both GlcNAc binding and interaction with sialic acids. We did not observe any in vitro or in vivo toxicity of WGA toward normal cells at the concentrations tested. Finally, low doses of WGA injection demonstrated significant in vivo toxicity toward AML cells, using xenograft mouse model. Thus, WGA is a potential candidate for leukemia therapy.

Differential Apoptotic and Mitogenic Effects of Lectins in Zebrafish

Plant lectins represent a major group of anti-nutritional factors that can be toxic to human and animals. However, the mechanisms by which lectins regulate cell fates are not well-understood. In the present study, the cellular and molecular impacts of three common lectins, agglutinins from wheat germ [wheat germ agglutinin (WGA)], soybean [soybean agglutinin (SBA)], and peanut [peanut agglutinin (PNA)] were examined in zebrafish embryo and liver cells. WGA and SBA were found to induce cell apoptosis both in vitro and in vivo, while PNA stimulated cell proliferation. WGA and SBA reduced levels of B cell lymphoma-2 (Bcl-2), phosphorylation of Bcl-2-associated death promoter (Bad), cyclin-dependent kinase 4 (Cdk4), and phosphorylation of the retinoblastoma (Rb). WGA and SBA also inhibited the activities of cell survival pathways including protein kinase B (Akt), extracellular signal-regulated protein kinases 1 and 2 (Erk1/2), and target of rapamycin (Tor). Furthermore, WGA and SBA shifted the cellular metabolism characterized by reduced expression of glucose-6-phosphate dehydrogenase (g6pd) and increased expression of glutamine synthetase (glul) and glutamate dehydrogenase (glud). However, PNA showed the opposite effects toward these molecular markers compared to those of WGA and SBA. Therefore, our results revealed some plant lectins (WGA and SBA) were toxic while the other (PNA) was mitogenic. Further characterization of the distinct functions of individual lectins should be valuable for both nutrition and other potential applications.

A New Galactose-Specific Lectin from Clerodendrum infortunatum

Background

The ethno-medical significance of Clerodendrum genus raises the interest towards the characterization of its seed lectin by inexpensive and most effective technique.

Objective

The focus of this study is the purification, characterization, and evaluation of the antioxidant and antiproliferative potential of a galactose-specific lectin from Clerodendrum infortunatum L. seeds.

Materials and Methods

The crude extract, homogenized in 6 volumes of the saline containing 10 mM β-mercaptoethanol was subjected to pigment removal by Toyopeal HW-55 column prior to ammonium sulfate fractionation (40-80 %). The crude protein extract was then loaded to the gel filtration column Sephadex G-200 followed by affinity chromatography using activated galactose coupled Sepharose-4B.

Results

The SDS-PAGE analysis showed a single band of about 30 kDa which further determined by MALDI-TOF analysis. The MALDI-TOF spectra revealed that Clerodendrum infortunatum lectin (CIL) is a homo-tetramer of 120 kDa consisting of four identical subunits of 30 kDa. The haemagglutination inhibition assay was done with purified lectin by many sugars, among which N-acetyl-D-galactosmine (NAG), D-galactose and lactose exhibited high inhibition. NAG showed the highest inhibition amongst the tested sugars, having the minimum inhibitory concentration of about 0.97 mM. The lectin exhibited a moderate antioxidant activity with an IC₅₀ value of 6.1 ± 0.1 mg.mL^-1 and induced cell death with IC₅₀ of 82.8 μg.mL^-1 against human gastric cancer cell line, AGS, indicated the potential of CIL for clinical and therapeutic applications.

Conclusion

The present study demonstrated the moderate ability of the CIL to inhibit the growth of human gastric cancer cells, AGS either by causing cytotoxic or anti-proliferative effects. Thus, CIL due to its remarkable properties may be considered as a potential bio-molecule in tumor research and glycobiology.

Characterization of chickpea (Cicer arietinum L.) lectin for biological activity

Lectins are proteins that are subject of intense investigations. Information on lectin from chickpea (Cicer arietinum L.) with respect to its biological activities are very limited. In this study, we purified lectin from the seeds of chickpea employing DEAE-cellulose and SP-Sephadex ion exchange chromatography and identified its molecular subunit mass as 35 kDa. The free radical scavenging activity of lectin measured by the DPPH assay has IC₅₀ of 0.88 µg/mL. Lectin exerted antifungal activity against Candida krusei, Fusarium oxysporium oxysporium, Saccharomyces cerevisiae and Candida albicans, while antibacterial activity against E. coli, B. subtilis, S. marcescens and P. aeruginosa. The minimum inhibitory concentrations were 200, 240, 160 and 140 µg for C. krusei, F. oxysporium, S. cerevisiae and C. albicans respectively. Lectin was further examined for its antiproliferative potential against cancerous cell line. The cell viability assay indicated a high inhibition activity on Ishikawa, HepG2, MCF-7 and MDA-MB-231 with IC₅₀ value of 46.67, 44.20, 53.58 and 37.46 µg/mL respectively. These results can provide a background for future research into the benefits of chickpea lectin to pharmacological perspective.

Plant Lectins as Medical Tools against Digestive System Cancers

Digestive system cancers-those of the esophagus, stomach, small intestine, colon-rectum, liver, and pancreas-are highly related to genetics and lifestyle. Most are considered highly mortal due to the frequency of late diagnosis, usually in advanced stages, caused by the absence of symptoms or masked by other pathologies. Different tools are being investigated in the search of a more precise diagnosis and treatment. Plant lectins have been studied because of their ability to recognize and bind to carbohydrates, exerting a variety of biological activities on animal cells, including anticancer activities. The present report integrates existing information on the activity of plant lectins on various types of digestive system cancers, and surveys the current state of research into their properties for diagnosis and selective treatment.

Quantitating morphological changes in biological samples during scanning electron microscopy sample preparation with correlative super-resolution microscopy

Sample preparation is critical to biological electron microscopy (EM), and there have been continuous efforts on optimizing the procedures to best preserve structures of interest in the sample. However, a quantitative characterization of the morphological changes associated with each step in EM sample preparation is currently lacking. Using correlative EM and superresolution microscopy (SRM), we have examined the effects of different drying methods as well as osmium tetroxide (OsO4) post-fixation on cell morphology during scanning electron microscopy (SEM) sample preparation. Here, SRM images of the sample acquired under hydrated conditions were used as a baseline for evaluating morphological changes as the sample went through SEM sample processing. We found that both chemical drying and critical point drying lead to a mild cellular boundary retraction of ~60 nm. Post-fixation by OsO4 causes at least 40 nm additional boundary retraction. We also found that coating coverslips with adhesion molecules such as fibronectin prior to cell plating helps reduce cell distortion from OsO4 post-fixation. These quantitative measurements offer useful information for identifying causes of cell distortions in SEM sample preparation and improving current procedures.

Cancer cell death induced by nanomagnetolectin

Magnetic nanoparticles represent a new paradigm for molecular targeting therapy in cancer. However, the transformative targeting potential of magnetic nanoparticles has been stymied by a key obstacle-safe delivery to specified target cells in vivo. As cancer cells grow under nutrient deprivation and hypoxic conditions and decorate cell surface with excessive sialoglycans, sialic acid binding lectins might be suitable for targeting cancer cells in vivo. Here we explore the potential of magnetic nanoparticles functionalized with wheat germ lectin (WGA) conjugate, so-called nanomagnetolectin, as apoptotic targetable agents for prostate cancer. In the presence of magnetic field (magnetofection) for 15min, 2.46nM nanomagnetolectin significantly promoted apoptosis (∼12-fold, p value <0.01) of prostate cancer cells (LNCaP, PC-3, DU-145) compared to normal prostate epithelial cells (PrEC, PNT2, PZ-HPV-7), when supplemented with 10mM sialic acid under nutrient deprived condition. Nanomagnetolectin targets cell-surface glycosylation, particularly sialic acid as nanomagnetolectin induced apoptosis of cancer cells largely diminished (only 2 to 2.5-fold) compared to normal cells. The efficacy of magnetofected nanomagnetolectin was demonstrated in orthotopically xenografted (DU-145) mice, where tumor was not only completely arrested, but also reduced significantly (p value <0.001). This was further corroborated in subcutaneous xenograft model, where nanomagnetolectin in the presence of magnetic field and photothermal heating at ∼42°C induced apoptosis of tumor by ∼4-fold compared to tumor section heated at ∼42°C, but without magnetic field. Taken all together, the study demonstrates, for the first time, the utility of nanomagnetolectin as a potential cancer therapeutic.

The number of α-synuclein proteins per vesicle gives insights into its physiological function

Although it is well established that the protein α-synuclein (αS) plays an important role in Parkinson’s disease, its physiological function remains largely unknown. It has been reported to bind membranes and to play a role in membrane remodeling processes. The mechanism by which αS remodels membranes is still debated; it may either affect its physical properties or act as a chaperone for other membrane associated proteins. To obtain insight into the role of αS in membrane remodeling we investigated the number of αS proteins associated with single small vesicles in a neuronal cell model. Using single-molecule microscopy and photo-bleaching approaches, we most frequently found 70 αS-GFPs per vesicle. Although this number is high enough to modulate physical membrane properties, it is also strikingly similar to the number of synaptobrevins, a putative interaction partner of αS, per vesicle. We therefore hypothesize a dual, synergistic role for αS in membrane remodeling.

Use of proteins as biomarkers and their role in carcinogenesis

Summary: Improved diagnostic methods and medical therapies are necessary for early detection and treatment and an improved prognosis. It is thus vital to both examine and evaluate the role of the various existing proteins as biomarkers in carcinogenesis and to assess the contribution of these proteins in anti-cancer activity, for consideration in therapeutic strategies. It is essential to both examine and evaluate the role of the various existing proteins as biomarkers in carcinogenesis and to assess the contribution of these proteins in anti-cancer activity, for consideration in therapeutic strategies. The purpose of this review is twofold. Firstly, it is to evaluate recent data about which proteins can be utilized as biomarkers in carcinogenesis. The proteins reviewed include: CPTP, IL-6, CCN, and S100. Secondly, it is to evaluate the contribution of dietary proteins in cancer activity. Specifically, how whey protein, soy proteins and lectin, a phytochemical could be useful in cancer prevention and treatment.

Recent Findings: Whey protein, present in dairy products, is an excellent source of the sulphur amino acid cysteine, the rate limiting substrate in glutathione synthesis. Notably, this protein survives digestion and has been shown to have anti-carcinogenic properties in animal studies. Lectins are phytochemicals present in plant foods, and have active components which alters cancer initiation, promotion and progression. Lectins have been characterized as a useful tool in biochemistry, cell biology, immunology and in diagnostic and therapeutic purposes in cancer research. Soy proteins contain various compounds, including isoflavones, protease inhibitors and protein kinase inhibitors, which have been proven effective in tumor growth inhibition. They have therefore, been greatly emphasized in cancer prevention and treatment. It has been proved that soy food consumption was associated with decreased risk of death and recurrence of breast cancer. CPTP is a recently discovered protein whose main role is to transport C1P, a pro-inflammatory molecule. The discovery of CPTP may shine a light on the mechanism of inflammatory diseases, and hopefully offer a potential target for therapeutic purposes in cancer research. Interleukin-6 is a multifunctional cytokine that affects the activity of cancer cells. It is involved in tumor growth, and elevated levels is associated with an increased risk of cancer. S100B is a well-established biomarker for malignant melanoma, and useful in assessing tumor load, stage and prognosis for patients with this disease. Other members of this family of proteins include S100A4, which has been associated with several malignancies and S100A2, which has been found to be decreased in some cancers. CCN are a group of regulatory proteins, located in the extracellular matrix (maricellular). They are involved in cellular adhesion, mitogenesis, chemotaxis, cell survival, and wound healing. CCN proteins are also able to modulate the signals of several proteins, which may also influence skeletal development and angiogenesis. Many of the functions of these proteins are thus also related to tumor growth. Furthermore, CCN interacts with estrogen in the development of cancer, and is implicated in some breast and ovarian cancers.

Mucin multilayers assembled through sugar-lectin interactions

Multilayer films of biopolymers are attractive tools to exploit the extraordinary properties of certain biomacromolecules and introduce new functionalities to surfaces. Mucins, the gel-forming constituents of mucus, are versatile glycoproteins that have potential as new building blocks for biomaterial surface coatings. Multilayer films have mostly been assembled through the electrostatic pairing of polyelectrolytes, which results in limited pH and salt stability and screens charges otherwise available for useful payload binding. Here, we aim at assembling mucin multilayer films that differ from conventional paired polyelectrolyte assemblies to obtain highly stable and functional surface modifications. Using the lectin wheat germ agglutinin (WGA) to cross-link mucin-bound sugar residues, we show that (Mucin/WGA) films can grow into hydrated films and sustain exceptional resistance to extreme salt conditions and a large range of pH. Furthermore, we show that the addition of soluble N-acetyl-d-glucosamine can induce the controlled release of WGA from (Mucin/WGA) films. Last, we show that (Mucin/WGA) films can repeatedly incorporate and release a positively charged model cargo. The lubricating, hydration, barrier, and antimicrobial properties of mucins open multiple applicative perspectives for these highly stable mucin-based multilayer films.

A lactose-binding lectin from the marine sponge Cinachyrella apion (Cal) induces cell death in human cervical adenocarcinoma cells

Cancer represents a set of more than 100 diseases, including malignant tumors from different locations. Strategies inducing differentiation have had limited success in the treatment of established cancers. Marine sponges are a biological reservoir of bioactive molecules, especially lectins. Several animal and plant lectins were purified with antitumor activity, mitogenic, anti-inflammatory and antiviral, but there are few reports in the literature describing the mechanism of action of lectins purified from marine sponges to induce apoptosis in human tumor cells. In this work, a lectin purified from the marine sponge Cinachyrella apion (CaL) was evaluated with respect to its hemolytic, cytotoxic and antiproliferative properties, besides the ability to induce cell death in tumor cells. The antiproliferative activity of CaL was tested against HeLa, PC3 and 3T3 cell lines, with highest growth inhibition for HeLa, reducing cell growth at a dose dependent manner (0.5–10 µg/mL). Hemolytic activity and toxicity against peripheral blood cells were tested using the concentration of IC₅₀ (10 µg/mL) for both trials and twice the IC₅₀ for analysis in flow cytometry, indicating that CaL is not toxic to these cells. To assess the mechanism of cell death caused by CaL in HeLa cells, we performed flow cytometry and western blotting. Results showed that lectin probably induces cell death by apoptosis activation by pro-apoptotic protein Bax, promoting mitochondrial membrane permeabilization, cell cycle arrest in S phase and acting as both dependent and/or independent of caspases pathway. These results indicate the potential of CaL in studies of medicine for treating cancer.

Detection of cytotoxic activity of lectin on human colon adenocarcinoma (Sw480) and epithelial cervical carcinoma (C33-A)

Lectins comprise a heterogeneous class of proteins that recognize the carbohydrate moieties of glycoconjugates with high specificity. Numerous studies have shown that lectins are capable of recognizing specific carbohydrate moieties displayed by malignant cells or tissues. The present work was performed to investigate the effects of tepary bean (Phaseolus acutifolius) lectins on proliferation, colony formation, and alteration of DNA synthesis of human malignant cells. Tepary bean lectin showed dose dependent  effects on the inhibition of viability as well as on colony formation in two human malignant cells lines (C33-A, Sw480); By contrast, tepary bean lectin only showed significant effects on DNA synthesis on Sw480 cells. Our results provide evidence of the anti- proliferative and cytotoxic effects of the tepary bean lectins on C33-A and Sw480 cells lines.

Exposure of insect midgut cells to Sambucus nigra L. agglutinins I and II causes cell death via caspase-dependent apoptosis

Sambucus nigra agglutinins I and II, further referred to as SNA-I and SNA-II, are two ricin-related lectins from elderberry. SNA-I is a chimeric lectin composed of an A-chain with enzymatic activity and a B-chain with carbohydrate-binding activity, and therefore belongs to the group of type 2 ribosome-inactivating proteins. In contrast, SNA-II consists only of carbohydrate-binding B-chains. The physiological effect of SNA-I was tested on different insect cell lines (midgut, ovary, fat body, embryo). In sensitive midgut CF-203 cells, SNA-I induced cell death with typical characteristics such as cell shrinkage, plasma membrane blebbing, nuclear condensation and DNA fragmentation. The effect was dose-dependent with 50% death of 4-day-exposed cells at 3nM. SNA-I exposure induced caspase-3 like activities, suggesting that SNA-I can induce the apoptotic pathway. Interestingly, the hololectin SNA-II also induced apoptosis in CF-203 cells at similar doses with the same physiological events. SNA-I and SNA-II both induced caspase-dependent apoptosis at low concentrations (nM order), leading to typical symptoms of cell death in sensitive cells. This effect seems independent from the catalytic activity of the A-chain, but depends on the carbohydrate-binding B-chain.

Plant lectins: potential antineoplastic drugs from bench to clinic

Plant lectins, carbohydrate-binding proteins distributed widely in a variety of plant species, have drawn a rising attention for cancer biologists due to their remarkable anti-tumour properties. In this review, we present a brief outline of the up-to-date advances of plant lectins in elucidating their complex anti-cancer mechanisms implicated in apoptosis and autophagy. In addition, we further discuss the pre-clinical and clinical studies of plant lectins for their potential therapeutic applications. In conclusion, these inspiring findings would open a new perspective for plant lectins as potential antineoplastic drugs from bench to clinic.

Imaging the glycome

Molecular imaging enables visualization of specific molecules in vivo and without substantial perturbation to the target molecule's environment. Glycans are appealing targets for molecular imaging but are inaccessible with conventional approaches. Classic methods for monitoring glycans rely on molecular recognition with probe-bearing lectins or antibodies, but these techniques are not well suited to in vivo imaging. In an emerging strategy, glycans are imaged by metabolic labeling with chemical reporters and subsequent ligation to fluorescent probes. This technique has enabled visualization of glycans in living cells and in live organisms such as zebrafish. Molecular imaging with chemical reporters offers a new avenue for probing changes in the glycome that accompany development and disease.

Exosomes as a tumor immune escape mechanism: possible therapeutic implications

Advances in cancer therapy have been substantial in terms of molecular understanding of disease mechanisms, however these advances have not translated into increased survival in the majority of cancer types. One unsolved problem in current cancer therapeutics is the substantial immune suppression seen in patients. Conventionally, investigations in this area have focused on antigen-nonspecific immune suppressive molecules such as cytokines and T cell apoptosis inducing molecules such as Fas ligand. More recently, studies have demonstrated nanovesicle particles termed exosomes are involved not only in stimulation but also inhibition of immunity in physiological conditions. Interestingly, exosomes secreted by cancer cells have been demonstrated to express tumor antigens, as well as immune suppressive molecules such as PD-1L and FasL. Concentrations of exosomes from plasma of cancer patients have been associated with spontaneous T cell apoptosis, which is associated in some situations with shortened survival. In this paper we place the "exosome-immune suppression" concept in perspective of other tumor immune evasion mechanisms. We conclude by discussing a novel therapeutic approach to cancer immune suppression by extracorporeal removal of exosomes using hollow fiber filtration technology

Pouterin, a novel potential cytotoxic lectin-like protein with apoptosis-inducing activity in tumorigenic mammalian cells

In this study, the cytotoxicity of pouterin in tumorigenic and non-tumorigenic mammalian cell lines was investigated. We found that HeLa, Hep-2 and HT-29 tumor cells were highly sensitive to pouterin cytotoxicity in a dose-dependent manner, whereas non-tumorigenic Vero cells and human lymphocytes were relatively resistant to the protein. Among the tumor cell lines, HeLa cells showed the highest susceptibility to pouterin cytotoxicity, exhibiting a time-dependent increase in LDH leakage and an IC(50) value of 5mug/mL. Morphological alterations such as rounding, cell shrinkage and chromatin condensation, consistent with apoptotic cell death were observed. Apoptosis induction was demonstrated by DNA fragmentation as detected by terminal dUTP nick-end labeling (TUNEL). Furthermore, HeLa cells incubated with pouterin showed disruption of the actin cytoskeleton. Western blot analysis revealed that pouterin caused increased expression of p21, thus indicating cell cycle arrest. Subsequent studies provided evidence that apoptosis may be partially explained in the activation of the tumor necrosis factor receptor 1 (TNFR1) signaling. Interestingly, a time-dependent decrease of the expression of p65 nuclear factor kappa B (NFkappaB) subunit, concomitant with a downregulation of the inhibitor of apoptosis protein 1 (IAP1) was observed, suggesting that TNFR-mediated apoptosis is the predominant pathway induced by pouterin in HeLa cells.

Inhibition of spontaneous breast cancer metastasis by anti-Thomsen-Friedenreich antigen monoclonal antibody JAA-F11

Thomsen-Friedenreich antigen (TF-Ag) is expressed in many carcinomas, including those of the breast, colon, bladder, and prostate. TF-Ag is important in adhesion and metastasis and as a potential immunotherapy target. We hypothesized that passive transfer of JAA-F11, an anti-TF-Ag monoclonal antibody, may create a survival advantage for patients with TF-Ag-expressing tumors by cytotoxicity, blocking of tumor cell adhesion, and inhibition of metastasis. This was tested using in vitro models of tumor cell growth; cytotoxicity assays; in vitro, ex vivo, and in vivo models of cancer metastasis; and, finally, in vivo effects in mice with metastatic breast cancer. Unlike some anti-TF-Ag antibodies, JAA-F11 did not enhance breast carcinoma cell growth. JAA-F11 did not induce the killing of 4T1 tumor cells through complement-dependent cytotoxicity or apoptotic mechanisms. However, JAA-F11 blocked the stages of metastasis that involve the adhesion of human breast carcinoma cells to human endothelial cells (human umbilical vein endothelial cells and human bone marrow endothelial cells 60) in in vitro static adhesion models, in a perfused ex vivo model, and in murine lung vasculature in an in vivo metastatic deposit formation assay. JAA-F11 significantly extended the median survival time of animals bearing metastatic 4T1 breast tumors and caused a > 50% inhibition of lung metastasis.

Analysis of unconventional approaches for the rapid detection of surface lectin binding ligands on human cell lines

For over a decade our laboratory has developed and used a novel histochemical assay using derivatized agarose beads to examine the surface properties of various cell types. Most recently, we have used this assay to examine lectin binding ligands on two human cell types, CCL-220, a colon cancer cell line, and CRL-1459, a non-cancer colon cell line. We found that CCL-220 cells bound specific lectins better than CRL-1459, and this information was used to test for possible differential toxicity of these lectins in culture, as a possible approach in the design of more specific anti-cancer drugs. Although we have examined the validity of the bead-binding assay in sea urchin cell systems, we have not previously validated this technique for mammalian cells. Here the binding results of the bead assay are compared with conventional fluorescence assays, using lectins from three species (Triticum vulgaris, Phaseolus vulgaris, and Lens culinaris) on the two colon cell lines. These lectins were chosen because they seemed to interact with the two cell lines differently. Binding results obtained using both assays were compared for frozen, thawed and fixed; cultured and fixed; and live cells. Both qualitative and quantitative fluorescence results generally correlated with those using the bead assay. Similar results were also obtained with all of the three different cell preparation protocols. The fluorescence assay was able to detect lower lectin binding ligand levels than the bead assay, while the bead assay, because it can so rapidly detect cells with large numbers of lectin binding ligands, is ideal for initial screening studies that seek to identify cells that are rich in surface binders for specific molecules. The direct use of frozen, thawed and fixed cells allows rapid mass screening for surface molecules, without the requirement for costly and time consuming cell culture.

Direct targeting of cancer cells: a multiparameter approach

Lectins have been widely used in cell surface studies and in the development of potential anticancer drugs. Many past studies that have examined lectin toxicity have only evaluated the effects on cancer cells, not their non-cancer counterparts. In addition, few past studies have evaluated the relationship between lectin-cell binding and lectin toxicity on both cell types. Here we examine these parameters in one study: lectin-cell binding and lectin toxicity with both cancer cells and their normal counterparts. We found that the human colon cancer cell line CCL-220/Colo320DM bound to agarose beads derivatized with Phaseolus vulgaris agglutinin (PHA-L) and wheat germ agglutinin (WGA), while the non-cancer human colon cell line CRL-1459/CCD-18Co did not. When these lectins were tested for their effects on cell viability in culture, both cell lines were affected by the lectins but at 6, 48 and 72 h incubation times, PHA-L was most toxic to the cancer cell line in a concentration dependent manner. At 48 h incubation, WGA was more toxic to the cancer cell line. The results suggest that it may be possible to develop lectin protocols that selectively target cancer cells for death. In any case, examination of both malignant cells and their non-malignant counterparts, analysis of their binding characteristics to immobilized lectins, and examination of the toxicity of free lectins in culture, provides a multiparameter model for obtaining more comprehensive information than from more limited approaches.

Lectins as Bioactive Plant Proteins: A Potential in Cancer Treatment

Plant lectins, a unique group of proteins and glycoproteins with potent biological activity, occur in foods like wheat, corn, tomato, peanut, kidney bean, banana, pea, lentil, soybean, mushroom, rice, and potato. Thus, dietary intakes by humans can be significant. Many lectins resist digestion, survive gut passage, and bind to gastrointestinal cells and/or enter the circulation intact, maintaining full biological activity. Several lectins have been found to possess anticancer properties in vitro, in vivo, and in human case studies; they are used as therapeutic agents, preferentially binding to cancer cell membranes or their receptors, causing cytotoxicity, apoptosis, and inhibition of tumor growth. These compounds can become internalized into cells, causing cancer cell agglutination and/or aggregation. Ingestion of lectins also sequesters the available body pool of polyamines, thereby thwarting cancer cell growth. They also affect the immune system by altering the production of various interleukins, or by activating certain protein kinases. Lectins can bind to ribosomes and inhibit protein synthesis. They also modify the cell cycle by inducing non-apoptotic G1-phase accumulation mechanisms, G2/M phase cell cycle arrest and apoptosis, and can activate the caspase cascade. Lectins can also downregulate telomerase activity and inhibit angiogenesis. Although lectins seem to have great potential as anticancer agents, further research is still needed and should include a genomic and proteomic approach.

Reduction of spontaneous metastases through induction of carbohydrate cross-reactive apoptotic antibodies

The selective targeting of tumor-associated carbohydrate Ags by the induction of serum Abs that trigger apoptosis of tumor cells as a means to reduce circulating tumor cells and micrometastases would be an advantage in cancer vaccine development. Some plant lectins like Griffonia simplicifolia lectin I and wheat germ agglutinin mediate the apoptosis of tumor cells. We investigated the possibility of using these lectins as templates to select peptide mimotopes of tumor-associated carbohydrate Ags as immunogens to generate cross-reactive Abs capable of mediating apoptosis of tumor cells. In this study, we show that immunization with a mimotope selected based on its reactivity with Griffonia simplicifolia lectin I and wheat germ agglutinin induced serum IgM Abs in mice that mediated the apoptosis of murine 4T1 and human MCF7 cell lines in vitro, paralleling the apoptotic activity of the lectins. Vaccine-induced anti-carbohydrate Abs reduced the outgrowth of micrometastases in the 4T1 spontaneous tumor model, significantly increasing survival time of tumor-bearing animals. This finding parallels suggestions that carbohydrate-reactive IgM with apoptotic activity may have merit in the adjuvant setting if the right carbohydrate-associated targets are identified.

Influence of mistletoe lectins and cytokines induced by them on cell proliferation of human melanoma cells in vitro

Although aqueous mistletoe extracts are widely used in complementary cancer therapy, the precise mode of action of their main therapeutic agents, the three mistletoe lectins (MLs), is poorly understood as they act both as cytotoxic agents and as immunomodulators due to their cytokine release by mononuclear cells. Thus, this study aims to investigate both the direct and the indirect effects of MLs on the growth of human melanoma cells in vitro. Proliferation of six human melanoma cell lines under ML treatment and additionally under the influence of cytokines induced by them (TNF-alpha, IL-1, IL-6) was assessed by means of the tetrazolium derived reduction (XTT) assay. Furthermore, ML binding patterns were analysed and correlated with the biological effects. All three MLs inhibited melanoma cell proliferation in a dose-dependent manner starting at very low ML concentrations (0.001-100 ng/ml) with ML-I being the most cytotoxic lectin (significant inhibition of ultra-sensitive cell line MV3 at 1 x 10(-13) ng ML-I/ml). Even if applied in a broad concentration range (0.0001-100 ng/ml) cytokines had no influence on cell proliferation at all. For ML-I, no association between binding intensity and cytotoxicity was observed, while for ML-II and -III an association between binding and toxicity was established. In conclusion, this study emphasises the direct anti-proliferative effect of the mistletoe lectins on melanoma cells with ML-I being superior to MLs-II and -III. The observation of an ultra-sensitivity of one cell line towards ML-I toxicity may serve as an explanation for the therapeutic success in anecdotal case reports and needs further investigations.

Studies on the joint cytotoxicity of Wheat Germ Agglutinin and monensin

Wheat Germ Agglutinin (WGA) cytotoxicity has been studied using two human leukemia cell lines, Molt3 and K562, and human peripheral blood mononuclear cells (PBMC). In spite of similar binding at the cell surface, WGA was found to promote cell death to a different extent in Molt3, K562 and PBMC and to induce different death events leading to apoptosis in Molt3 and either apoptosis and necrosis in K562 cells and PBMC. In Molt3 but not in K562 cells, WGA cytotoxicity could be potentiated 66-200 fold by 50 nM monensin, a carboxylic ionophore that perturbs the intracellular trafficking of endocytosed molecules. Synergism between the cytotoxic activities of WGA and monensin was demonstrated in Molt3 cells by comparing non toxic, or slightly toxic, doses of WGA and monensin alone or in combination. These results show that the cytotoxic effect of WGA is dependent on internalisation events which may differ among the cell lines used. WGA and monensin can enter the human diet being a component of wheat germ and an antibiotic used for zootechnic reasons in the bioindustry, respectively. These data reveal the synergistic effect between two dietary molecules, otherwise per se toxic at much higher concentrations, with possible implications for human and animal health.

A novel apoptotic pathway as defined by lectin cellular initiation

In this study of lectin-induced apoptosis we found that wheat germ agglutinin (WGA) initiated an accelerated type of programmed cell death developing after only 30 min of incubation with tumor cells. To analyze possible mechanisms, studies were focused using the WGA lectin whose carbohydrate specificity is well defined. We found that WGA could induce apoptosis by binding to either N-acetylneuraminic acid or N-acetylglucosamine (GlcNAc) on the cell surface of normal and malignant cells. We also showed that it is unlikely that WGA triggers apoptosis by binding to the carbohydrate portion of Fas. CrmA gene transfection did not inhibit WGA-mediated apoptosis of Jurkat cells. In addition, Jurkat-R cells selected for resistance to Fas signaled apoptosis manifested high sensitivity to WGA as did Fas-negative BL6 melanoma cells. WGA-induced apoptosis is also caspase-3-independent and was found to be triggered via a mitochondrial pathway. WGA induced a loss of transmembrane potential, disruption of the inner mitochondria membrane, and release of cytochrome c and caspase-9 activation after 30 min of cell interaction. Interestingly, Bcl-2 gene transfection did not affect sensitivity of Jurkat cells to WGA. The Jurkat-R subline that has been shown to be Bax and Bak deficient and resistant to various apoptotic signals was highly sensitive to WGA-induced apoptosis. In summary, WGA triggers a unique pattern of apoptosis that is extremely fast, Fas- and caspase-3-independent, and is mediated via a mitochondrial pathway. However, its mitochondrial component is unrestrained by the loss of Bax and Bak or the upregulation of Bcl-2 expression.

Lectin-based three-color flow cytometric approach for studying cell surface glycosylation changes that occur during apoptosis

BACKGROUND

Changes in cell surface glycosylation that accompany apoptosis are thought to be involved in the recognition and removal of apoptotic cells by phagocytes, but in most instances these changes are ill defined. To improve our understanding of this phenomenon, we designed a trivariate flow cytometry procedure that allows direct comparison of cell surface glycosylation in apoptotic and viable cells.

METHODS

The annexin V/propidium iodide assay has been adapted for cell surface glycosylation analysis by combining the use of these two reagents with biotinylated lectins, and this has been used to investigate camptothecin-induced apoptosis in U-937 cells.

RESULTS

Although numerous lectins are potent inducers of apoptosis, we found that it is possible to determine lectin concentrations that produce interpretable data without inducing significant cytotoxicity even when using apoptogenic lectins. That apoptosis is associated with a marked decrease in cell surface sialylation was confirmed by using the sialic acid-specific lectins Maackia amurensis agglutinin and Sambucus nigra agglutinin. These observations were corroborated by lectin blotting analysis with the same lectins.

CONCLUSIONS

Species- and cell-dependent altered glycosylation patterns are likely to be associated with different modes of apoptosis. The easy and versatile method described in this report should be useful for exploring this field.

Pancreatic cancer in vitro toxicity mediated by Chinese herbs SPES and PC-SPES: implications for monotherapy and combination treatment

One of the greatest challenges in the treatment of pancreatic cancer remains its inherent lack of beneficial response to cytotoxic chemotherapy. Chinese herbal extracts have been widely used for the treatment of various cancers, but objective information on their efficacy in pancreatic cancer is lacking. Eight human pancreatic cancer cell lines (MIA, Panc-1, BxPC, ASPC, HS-766T, CaPan-2, CFPAC, and HTB-147) were studied for in vitro susceptibility to ethanol extracts of SPES and PC-SPES, two quality-controlled, dried, encapsulated supplements of 15 and eight Chinese herbs, respectively. Resulting toxicities, alone and in combination with doxorubicin or gemcitabine, were analyzed by [(3)H]thymidine incorporation or sulforhodamine B staining, colony formation, and TUNEL flow cytometry assays. Combination toxicity mechanisms were calculated by the combination index method of Chou and Talalay. In all cell lines, there was dose-dependent inhibition of proliferation. By [(3)H]thymidine incorporation assay, 50% growth inhibition after 48 h continuous exposure (IC(50)) occurred at concentrations of 0.2-0.8 microl/ml SPES and 0.4-1.3 microl/ml PC-SPES. Growth inhibition was accompanied by a significant enhancement of the TUNEL-positive apoptotic fraction of all cell lines after treatment with either extract. After treatment with PC-SPES, the cell lines consistently displayed a G2 cell cycle block; SPES induced an increase in S phase, with a smaller impact on G2. When added at a concentration of 0.2 microl/ml (approximately IC(20)), both extracts enhanced Panc-1 cell killing mediated by doxorubicin, with an average decrease in the corresponding IC(50) of 33% (range 11-62%). Combination effects with either extract appeared to be antagonistic in the case of gemcitabine and additive to mildly synergistic in the case of doxorubicin. Both SPES and PC-SPES exhibited significant toxicity in pancreatic cancer cells, mediated via induction of apoptosis. Both mixtures should be evaluated for their in vivo and clinical therapeutic utility as monotherapy agents against pancreatic cancer. SPES could possibly be combined with cell cycle-independent cytotoxic drugs. Due to a consistent G2 blocking pattern, PC-SPES may prove useful as a radiation sensitizer.

Purification and acute toxicity of a lectin extracted from tepary bean (Phaseolus acutifolius)

Lectins are proteins or glycoproteins known for their ability to agglutinate cells, especially erythrocytes. Several lectins are toxic to mammalian cells both in vitro and in vivo, inhibit growth when incorporated into the diet and are toxic when injected into animals. On the other hand, the use of lectins has been suggested as an alternative in cancer treatment. The objective of the present study was to evaluate the acute toxicity of a lectin extracted and purified from tepary bean (Phaseolus acutifolius, G-400-34) on CD-1 mice. Fetuin affinity chromatography, electrophoretic pattern and Western-immunoblot techniques were used to purify and partially characterize the lectin. This tepary bean line presented high levels of lectin activity. Western blot revealed that the sera reacted with the known PHA subunits in the 34-40 kD range. Four major lectin and lectin-related glycopolypeptides were identified. The purified lectin from tepary bean was a tetrameric one that ran at about 115-120 kD. The LD(50) (ip) was 1100 mg/kg body weight for males and 1120 mg/kg body weight for females. The body weight of experimental animals decreased in a dose-dependent manner. The main target organs affected were small intestine, spleen and thymus. The lectin isolated from tepary bean showed affinity towards fetuin, with high agglutination values and low acute toxicity.

Apoptosis induction by lectin isolated from the mushroom Boletopsis leucomelas in U937 cells

A 15-kDa lectin was isolated from the edible mushroom Kurokawa by affinity chromatography using N,N'-diacetylchitobiose-Sepharose 4B. The results of microsequencing analysis indicated that the lectin has a partial amino acid sequence similar to the mushroom lectin, Agaricus bisporus agglutinin (ABA). We found that the Kurokawa lectin inhibited proliferation of human monoblastic leukemia U937 cells dose-dependently. Several lines of evidence indicated that this inhibition was due to its apoptosis induction. We observed that the lectin induced apoptotic bodies formation, chromatin condensation, and DNA ladder formation, features of apoptosis. The DNA ladder formation was inhibited by a general inhibitor of caspases, which are known to play essential roles in apoptosis. In contrast, ABA did not have cell growth-inhibiting or apoptosis-inducing activities. Thus, the Kurokawa lectin is the first mushroom lectin with apoptosis-inducing activity.