Bauhinia forficata lectin (BfL) induces cell death and inhibits integrin-mediated adhesion on MCF7 human breast cancer cells

Novel Lectins from Bauhinia with Differential N-Glycan Binding Profiles

The specific interaction of lectins with carbohydrates and glycoconjugates grants these proteins a distinct ability to decode the glycocode. Essential for various biological processes in all organisms, this carbohydrate-binding activity also establishes lectins as valuable tools in fields such as glycomics, medicine, and biotechnology. Considering that the discovery of novel lectins with unique binding profiles is particularly relevant, this study investigated the binding specificity of two lectins extracted from Bauhinia seeds toward simple sugars, N-glycans and O-glycans. The combination of agglutination-inhibition assays and glycan arrays revealed subtle differences in the binding of the lectins to galactosides and glycans containing specific motifs, such as LewisX, LacdiNAc, and fucosylated LacdiNAc. Despite slight differences in carbohydrate-binding patterns, both lectins showed similar results in toxicity assays using Artemia salina nauplii and cytotoxicity assays on cancer cell lines, with neither lectin exhibiting significant toxicity. Additionally, both lectins demonstrated low cytotoxicity toward HeLa (cervical adenocarcinoma), HT1080 (fibrosarcoma), and NHDF (normal fibroblasts), even at concentrations up to 125 μg/mL. Analysis of the partial amino acid sequences of these lectins revealed conserved residues compared to other lectins of the genus, as well as secondary structure conformations similar to those of other legume lectins. This research represents a significant advancement in the understanding of lectins from the genus Bauhinia, and future structural studies could further elucidate the interactions of these proteins with their ligands, providing fundamental insights into their biological functions and paving the way toward potential applications.

Lectin-glycan interactions: a comprehensive cataloguing of cancer-associated glycans for biorecognition and bio-alteration: a review

This comprehensive review meticulously compiles data on an array of lectins and their interactions with different cancer types through specific glycans. Crucially, it establishes the link between aberrant glycosylation and cancer types. This repository of lectin-defined glycan signatures, assumes paramount importance in the realm of cancer and its dynamic nature. Cancer, known for its remarkable heterogeneity and individualized behaviour, can be better understood through these glycan signatures. The current review discusses the important lectins and their carbohydrate specificities, especially recognizing glycans of cancer origin. The review also addresses the key aspects of differentially expressed glycans on normal and cancerous cell surfaces. Specific cancer types highlighted in this review include breast cancer, colon cancer, glioblastoma, cervical cancer, lung cancer, liver cancer, and leukaemia. The glycan profiles unveiled through this review hold the key to tailor-made treatment and precise diagnostics. It opens up avenues to explore the potential of targeting glycosyltransferases and glycosidases linked with cancer advancement and metastasis. Armed with knowledge about specific glycan expressions, researchers can design targeted therapies to modulate glycan profiles, potentially hampering the advance of this relentless disease.

Phytochemistry and pharmacological activities of five species of Bauhinia genus: A review

Genus Bauhinia has been widely used in the treatment of diabetes, malaria, cough, headache, fever, piles, dysentery, flatulence, diarrhoea, ulcer and cardiovascular problems. Among 600 species of this genus, Bauhinia variegata, B. purpurea, B. championii, B. racemosa, and B. forficata are commonly used in the traditional medicine and found to be throughly investigated for their medicinal properties. They possess diverse pharmacological activities such as anti-diabetic, anti-microbial, antioxidant, anti-arthritic, cardioprotective, hepatoprotective, nephroprotective, fibrinolytic, and wound healing properties and most of the biological activities are corelating with traditional knowledge. Phytochemical analysis indicated that steroids, terpenoids, and flavonoids are prominent in the selected species, whereas bauhiniastatins, bauhinoxepins, racemosols, roseosides, and bauhichamines are found unique to the genus. This review aims to decipher active molecules from the aforementioned species of Bauhinia covering comprehensive analysis of phytochemistry, pharmacological activities and traditional uses. The data has been carefully analyzed to find compounds or fractions with a translational value. In most of the cases, the pharmacological activities have been established, however, further studies are needed such as safety evaluations, target identification, bioavailability, metabolite identification, and pharmacokinetic properties. In conclusion, the pharmacological potential of Bauhinia plants show promise with various leads such as insulin-like protein, roseoside, bauhiniastatin, and melibiose binding lectin. However, further investigations are required to address existing gaps and advance them towards product development. This review will lay the groundwork for future research initiatives aimed at fully realizing the therapeutic potential of Bauhinia plants.

Genome-wide identification, classification, and characterization of lectin gene superfamily in sweet orange (Citrus sinensis L.)

Lectins are sugar-binding proteins found abundantly in plants. Lectin superfamily members have diverse roles, including plant growth, development, cellular processes, stress responses, and defense against microbes. However, the genome-wide identification and functional analysis of lectin genes in sweet orange (Citrus sinensis L.) remain unexplored. Therefore, we used integrated bioinformatics approaches (IBA) for in-depth genome-wide identification, characterization, and regulatory factor analysis of sweet orange lectin genes. Through genome-wide comparative analysis, we identified a total of 141 lectin genes distributed across 10 distinct gene families such as 68 CsB-Lectin, 13 CsLysin Motif (LysM), 4 CsChitin-Bind1, 1 CsLec-C, 3 CsGal-B, 1 CsCalreticulin, 3 CsJacalin, 13 CsPhloem, 11 CsGal-Lec, and 24 CsLectinlegB.This classification relied on characteristic domain and phylogenetic analysis, showing significant homology with Arabidopsis thaliana's lectin gene families. A thorough analysis unveiled common similarities within specific groups and notable variations across different protein groups. Gene Ontology (GO) enrichment analysis highlighted the predicted genes' roles in diverse cellular components, metabolic processes, and stress-related regulation. Additionally, network analysis of lectin genes with transcription factors (TFs) identified pivotal regulators like ERF, MYB, NAC, WRKY, bHLH, bZIP, and TCP. The cis-acting regulatory elements (CAREs) found in sweet orange lectin genes showed their roles in crucial pathways, including light-responsive (LR), stress-responsive (SR), hormone-responsive (HR), and more. These findings will aid in the in-depth molecular examination of these potential genes and their regulatory elements, contributing to targeted enhancements of sweet orange species in breeding programs.

Purification, Characterization, and Assessment of Antimicrobial Activity and Toxicity of Portulaca elatior Leaf Lectin (PeLL)

Lectins are carbohydrate-binding proteins with several bioactivities, including antimicrobial properties. Portulaca elatior is a species found at Brazilian Caatinga and data on the biochemical composition of this plant are scarce. The present work describes the purification of P. elatior leaf lectin (PeLL) as well as the assessment of its antimicrobial activity and toxicity. PeLL, isolated by chromatography on a chitin column, had native liquid charge and subunit composition evaluated by electrophoresis. Hemagglutinating activity (HA) of PeLL was determined in the presence of carbohydrates or divalent cations, as well as after heating and incubation at different pH values. Changes in the lectin conformation were monitored by evaluating intrinsic tryptophan fluorescence and using the extrinsic probe bis-ANS. Antimicrobial activity was evaluated against Pectobacterium strains and Candida species. The minimal inhibitory (MIC), bactericidal (MBC), and fungicidal (MFC) concentrations were determined. Finally, PeLL was evaluated for in vitro hemolytic activity in human erythrocytes and in vivo acute toxicity in mice (5 and 10 mg/kg b.w. per os). PeLL (pI 5.4; 20 kDa) had its HA was inhibited by mannose, galactose, Ca²⁺, Mg²⁺, and Mn²⁺. PeLL HA was resistant to heating at 100 °C, although conformational changes were detected. PeLL was more active in the acidic pH range, in which no conformational changes were observed. The lectin presented MIC and MBC of 0.185 and 0.74 μg/mL for all Pectobacterium strains, respectively; MIC of 1.48 μg/mL for C. albicans, C. tropicalis, and C. krusei; MIC and MFC of 0.74 and 2.96 μg/mL for C. parapsilosis. No hemolytic activity or signs of acute toxicity were observed in the mice. In conclusion, a new, low-toxic, and thermostable lectin was isolated from P. elatior leaves, being the first plant compound to show antibacterial activity against Pectobacterium.

Recent advances in the use of legume lectins for the diagnosis and treatment of breast cancer

Poor lifestyle choices and genetic predisposition are factors that increase the number of cancer cases, one example being breast cancer, the third most diagnosed type of malignancy. Currently, there is a demand for the development of new strategies to ensure early detection and treatment options that could contribute to the complete remission of breast tumors, which could lead to increased overall survival rates. In this context, the glycans observed at the surface of cancer cells are presented as efficient tumor cell markers. These carbohydrate structures can be recognized by lectins which can act as decoders of the glycocode. The application of plant lectins as tools for diagnosis/treatment of breast cancer encompasses the detection and sorting of glycans found in healthy and malignant cells. Here, we present an overview of the most recent studies in this field, demonstrating the potential of lectins as: mapping agents to detect differentially expressed glycans in breast cancer, as histochemistry/cytochemistry analysis agents, in lectin arrays, immobilized in chromatographic matrices, in drug delivery, and as biosensing agents. In addition, we describe lectins that present antiproliferative effects by themselves and/or in conjunction with other drugs in a synergistic effect.

"Cow's Hoof" (Bauhinia L., Leguminosae): A Review on Pharmacological Properties of Austral South American Species

The genus Bauhinia s.l. (Leguminosae), known as cow's hoof, unha de boi or pata de vaca, has been used in traditional medicine worldwide. The aim of the present review is to summarize the studies published on the biological activity of the main native medicinal species reported in austral South America. Of the 14 species present in the region, 10 are consumed as leaf infusions to regulate glucose and lipid metabolism, as well as used for their anti-inflammatory and analgesic effects and to treat various diseases. Pharmacological properties have been recorded in seven species. Antioxidant, anticoagulant, antihypertensive, diuretic, antimicrobial and antitumor properties have been reported in B. forficata. Together with B. holophylla, they are important for their antidiabetic properties, since several studies indicate their effectiveness as a hypoglycemic agent. B. bauhinioides is distinguished for its anti-inflammatory and antithrombotic activities and S. microstachya for its analgesic properties. Anti-ulcer and wound healing activities recorded in B. holophylla and B. ungulata, respectively, are of particular interest. Most of the species possess antitumor activity. The antioxidant capacity of flavonoids and other bioactive compounds make these plants good candidates to assist or treat various alterations related with oxidative stress, such as diabetic complications. Thus, these species constitute promising targets for new bioactive substance research and phytotherapy.

The Deposition of a Lectin from Oreochromis niloticus on the Surface of Titanium Dioxide Nanotubes Improved the Cell Adhesion, Proliferation, and Osteogenic Activity of Osteoblast-like Cells

Titanium and its alloys are used as biomaterials for medical and dental applications, due to their mechanical and physical properties. Surface modifications of titanium with bioactive molecules can increase the osseointegration by improving the interface between the bone and implant. In this work, titanium dioxide nanotubes (TiO2NTs) were functionalized with a lectin from the plasma of the fish Oreochromis niloticus aiming to favor the adhesion and proliferation of osteoblast-like cells, improving its biocompatibility. The TiO2NTs were obtained by anodization of titanium and annealed at 400 °C for 3 h. The resulting TiO2NTs were characterized by high-resolution scanning electron microscopy. The successful incorporation of OniL on the surface of TiO2NTs, by spin coating, was demonstrated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIE), and attenuated total reflection-Fourier transform infrared spectrum (ATR-FTIR). Our results showed that TiO2NTs were successfully synthesized in a regular and well-distributed way. The modification of TiO2NTs with OniL favored adhesion, proliferation, and the osteogenic activity of osteoblast-like cells, suggesting its use to improve the quality and biocompatibility of titanium-based biomaterials.

Research advances and prospects of legume lectins

Lectins are widely distributed proteins having ability of binding selectively and reversibly with carbohydrates moieties and glycoconjugates. Although lectins have been reported from different biological sources, the legume lectins are the best-characterized family of plant lectins. Legume lectins are a large family of homologous proteins with considerable similarity in amino acid sequence and their tertiary structures. Despite having strong sequence conservation, these lectins show remarkable variability in carbohydrate specificity and quaternary structures. The ability of legume lectins in recognizing glycans and glycoconjugates on cells and other intracellular structures make them a valuable research tool in glycomic research. Due to variability in binding with glycans, glycoconjugates and multiple biological functions, legume lectins are the subject of intense research for their diverse application in different fields such as glycobiology, biomedical research and crop improvement. The present review specially focuses on structural and functional characteristics of legume lectins along with their potential areas of application.

A new lectin from the floral capitula of Egletes viscosa (EgviL): Biochemical and biophysical characterization and cytotoxicity to human cancer cells

Egletes viscosa is a plant with therapeutic value due to its antibacterial, antinociceptive and gastroprotective properties. This study aimed to purify, characterize, and evaluate the cytotoxicity of a lectin (EgviL) from the floral capitula of E. viscosa. The lectin was isolated from saline extract through precipitation with ammonium sulfate followed by Sephadex G-75 chromatography. The molecular mass and isoelectric point (pI) of EgviL were determined as well as its temperature and pH stability. Physical-chemical parameters of interaction between EgviL and carbohydrates were investigated by fluorescence quenching and ¹H nuclear magnetic resonance (NMR). Cytotoxicity was investigated against human peripheral blood mononuclear cells (PBMCs) and neoplastic cells. EgviL (28.8 kDa, pI 5.4) showed hemagglutinating activity stable towards heating until 60 °C and at the pH range 5.0-7.0. This lectin is able to interact through hydrophobic and electrostatic bonds with galactose and glucose, respectively. EgviL reduced the viability of PBMCs only at the highest concentration tested (100 μg/mL) while was toxic to Jurkat E6-1 cells with IC₅₀ of 24.1 μg/mL,inducing apoptosis. In summary, EgviL is a galactose/glucose-binding protein with acidic character, stable to heating and with cytotoxic effect on leukemic cells.

Antitumoral Potential of Lansbermin-I, a Novel Disintegrin from Porthidium lansbergii lansbergii Venom on Breast Cancer Cells

Background:

Disintegrins from snake venoms bind with high specificity cell surface integrins, which are important pharmacological targets associated with cancer development and progression.

Objective:

In this study, we isolated a disintegrin from the Porthidium lansbergii lansbergii venom and evaluated its antitumoral effects on breast cancer cells.

Methods:

The isolation of the disintegrin was performed on RP-HPLC and the inhibition of platelet aggregation was evaluated on human platelet-rich plasma. The inhibition of cell adhesion was also evaluated in vitro on cultures of cell lines by the MTT method as well as the inhibition of breast cancer cell migration by the wound healing assay. The binding of the disintegrin to integrin subunits was verified by flow cytometry and confocal microscopy. Finally, inhibition of angiogenesis was assessed in vitro on HUVEC cells and the concentration of VEGF was measured in the cellular supernatants.

Results:

The disintegrin, named Lansbermin-I, is a low molecular weight protein (< 10 kDa) that includes an RGD on its sequence identified previously. Lansbermin-I showed potent inhibition of ADP and collagen-induced platelet aggregation on human plasma and also displayed inhibitory effects on the adhesion and migration of breast cancer MCF7 and MDA-MB 231cell lines, without affecting nontumorigenic breast MCF-10A and lung BEAS cells. Additionally, Lansbermin-I prevented MCF7 cells to adhere to fibronectin and collagen, and also inhibited in vitro angiogenesis on human endothelial HUVEC cells.

Conclusion:

Our results display the first report on the antitumor and anti-metastatic effects of an RGDdisintegrin isolated from a Porthidium snake venom by possibly interfering with α2 and/or β1-containing integrins. Thus, Lansbermin-I could be an attractive model to elucidate the role of disintegrins against breast cancer development.

New Lectins from Mediterranean Flora. Activity against HT29 Colon Cancer Cells

Experiments conducted in vitro and in vivo, as well as some preclinical trials for cancer therapeutics, support the antineoplastic properties of lectins. A screening of antitumoral activity on HT29 colon cancer cells, based on polypeptide characterization and specific lectin binding to HT29 cells membrane receptors, was performed in order to assess the bioactivities present in four Mediterranean plant species: Juniperus oxycedrus subsp. oxycedrus, Juniperus oxycedrus subsp. badia, Arbutus unedo and Corema album. Total leaf proteins from each species were evaluated with respect to cell viability and inhibitory activities on HT29 cells (cell migration, matrix metalloproteinase –MMP proteolytic activities). A discussion is presented on a possible mechanism justifying the specific binding of lectins to HT29 cell receptors. All species revealed the presence of proteins with affinity to HT29 cell glycosylated receptors, possibly explaining the differential antitumor activity exhibited by the two most promising species, Juniperus oxycedrus subsp. badia and Arbutus unedo.

Development of Caco-2 cells-based gene reporter assays and evaluation of herb-drug interactions involving CYP3A4 and CYP2D6 gene expression

The indiscriminate use of medicinal plants and herbal medicinal products concomitantly with conventional drugs may result in herb-drug interactions that may lead to fluctuations in drug bioavailability, therapeutic failure, and/or toxic effects. CYP450 enzymes play an important role in drug biotransformation and herb-drug interactions. Thus, the aim of this study was to develop and apply Caco-2 cells-based gene reporter assays to study in vitro the potential occurrence of CYP3A4 and CYP2D6 gene expression modulation by standardized extracts of selected medicinal plants. Reporter cell lines developed showed a significant increase in CYP3A4 and CYP2D6 reporter fluorescent emission, 4 and 16-fold respectively, when compared to the controls. The standardized extracts of Cecropia glaziovii, Bauhinia forficata and Echinacea sp. significantly increased CYP3A4 reporter fluorescence, and those of Ilex paraguariensis, Bauhinia forficata and Echinacea sp. significantly decreased CYP2D6 reporter fluorescence in Caco-2 cells-based gene reporter assays. The data obtained suggest that CYP3A4 and CYP2D6 gene expression seem to be modulated by the extracts tested. In addition, the reporter cell lines developed are functional assays that could be used to study drug-drug and herb-drug interactions during the research and development of new drugs.

Morniga-G, a T/Tn-Specific Lectin, Induces Leukemic Cell Death via Caspase and DR5 Receptor-Dependent Pathways

Morniga-G, the Gal-specific black mulberry (Morus nigra) lectin, displays high affinity for T (CD176) and Tn (CD175) antigens, frequently expressed at the cancer cell surface. The effects of Morniga-G were investigated on a Tn-positive leukemic Jurkat cell line. The lectin, used in a concentration range between 5⁻20 μg/mL, induced cell death in leukemic Jurkat cells. Microscopic and cytofluorometric analyses indicated that Jurkat cell death was essentially apoptotic, associated with an increase in the ceramide content and a depolarization of the mitochondrial transmembrane potential. This lectin-mediated cell death was inhibited by the pan caspase-inhibitor zVAD. In addition, cleavage of caspases 8, 9, and 3 was observed in Morniga-G-treated Jurkat cells whereas Jurkat cell lines that are deficient in caspase 8⁻10, caspase 9, or FADD, survived to the lectin-mediated toxicity. Furthermore, in the presence of TRAIL- or DR5-blocking mononoclonal antibodies, Jurkat cells became resistant to Morniga-G, suggesting that the lectin triggers cell death via the TRAIL/DR5 pathway. In silico computer simulations suggest that Morniga-G might facilitate both the DR5 dimerization and the building of TRAIL/DR5 complexes. Finally, upon treatment of Jurkat cells with benzyl-GalNAc, an O-glycosylation inhibitor, a decrease in Tn antigen expression associating with a reduced Morniga-G toxicity, was observed. Taken together, these results suggest that Morniga-G induces the cell death of Tn-positive leukemic cells via concomitant O-glycosylation-, caspase-, and TRAIL/DR5-dependent pathways.

Pinellia pedatisecta lectin exerts a proinflammatory activity correlated with ROS-MAPKs/NF-κB pathways and the NLRP3 inflammasome in RAW264.7 cells accompanied by cell pyroptosis

Pinellia pedatisecta, a widely used herb in Chinese medicine, has proinflammatory toxicity related to its Pinellia pedatisecta lectin (PPL), but the mechanism is still unknown. However, for safer use, it is necessary to clarify its proinflammatory mechanism. Herein, we studied the mechanism in RAW264.7 cells. PPL decreased the mitochondrial membrane potential (MMP) and increased the outflow of calcium, accompanied by the overproduction of reactive oxygen species (ROS), which resulted in the activation of the MAPK and NF-κB pathways and the release of IL-1β. The maturation of IL-1β relied on caspase-1 p20, the active caspase-1, as demonstrated by adding caspase-1 inhibitor. While caspase-1 was associated with the activation of the NLRP3 inflammasome, we further found that the stimulation of PPL also contributed to the activation. In addition, TXNIP was downregulated, whereas NLRP3/caspase-1 p20/ASC was upregulated, and there was binding of TXNIP with NLRP3. There was also binding of NLRP3 with ASC and caspase-1. Further, we found that N-acetylcysteine (NAC), an ROS scavenger, could inhibit the PPL-stimulated activation of these pathways and the release of IL-1β. Moreover, PPL led to cell pyroptosis with pyknotic nuclei and plasma membrane rupture, which could be inhibited by NAC. All of these findings demonstrated an important role of ROS in the inflammation caused by PPL. Taken together, our data provide new mechanistic insights into the possible endogenous signaling pathways involved in the inflammation of RAW264.7 cells, stimulated by PPL.

Ethnopharmacological, Phytochemical, Pharmacological and Toxicological Aspects of Bauhinia forficata: A Mini-Review Covering the Last Five Years

This mini review focuses on the ethnopharmacology, phytochemical, and biological/pharmacological activity and toxicology of the medicinal plant, Bauhinia forficata reported during 2012–2016. The results confirmed the continuous use of this plant, especially the leaves, for medicinal purposes, particularly as remedies for the treatment of diabetes and other ailments. Other new biological potential was evidenced, including anti-ulcerogenic, hypocholesterolemic, hepatoprotective and diuretic effects. Clinical and toxicological studies have advanced gradually, requiring more detailed experiments, to ensure the safe use of this plant for medication. Some new flavonoids were detected in this species, but significant differences were observed when comparing the chemical composition of its sub-species.

Could a plant derived protein potentiate the anticancer effects of a stem cell in brain cancer?

Glioblastoma is the most aggressive brain tumor with poor overall survival bellow 2 years. The natural compounds with anti-cancer properties, are thus gaining attention for possible adjuvant GBM treatment. In various cancer models Enterolobium contortisiliquum Trypsin Inhibitor (EcTI) proved to have anti-cancer effects. Here, we investigated the EcTI effects on GBM U87 cells and on mesenchymal stem cells (MSC) compared to their direct coculture (MSC/U87). MSC are present in tumor stroma, modulating GBM cells phenotype, and also represent potential drug delivery vehicle due to their tumor tropism. We showed that in p53-wild type U87 cells, metabolic activity was less affected by EcTI as in MSC monocuture, but the metabolic rate of mixed coculture was significantly reduced at lower EcTI concentration. Under coculture condition, EcTI potentiated MSC induced cell cycle arrest, possible due to highly increased p53, p21 and lower D1 expression, but there was no effect on apoptosis. Accordingly, in the coculture EcTI also enhanced Ca²⁺ signalling mediated via bradykinin receptor 2, being associated with nitric oxide release that highly impaired proliferation and invasion. The mechanism did not seem to involve changes in cell adhesion but rather it down-regulated the β₁ integrin signaling with associated p-FAK in U87 cells, both supporting inhibition of invasion. Finally, some cytokines were down-regulated, indicating that EcTI inhibition of signalling might be mediated by cytokines. In conclusion, these results indicate that in cocultured MSC/U87 cells EcTI impairs the metabolic activity, proliferation, and reduced invasion, possibly associated with observed cytokines secretion. In this context, we confirmed that the plant derived protein potentiated the anticancer effects, induced by MSC, as represented by GBM U87 cell line.

Lectins: an effective tool for screening of potential cancer biomarkers

In recent years, the use of lectins for screening of potential biomarkers has gained increased importance in cancer research, given the development in glycobiology that highlights altered structural changes of glycans in cancer associated processes. Lectins, having the properties of recognizing specific carbohydrate moieties of glycoconjugates, have become an effective tool for detection of new cancer biomarkers in complex bodily fluids and tissues. The specificity of lectins provides an added advantage of selecting peptides that are differently glycosylated and aberrantly expressed in cancer patients, many of which are not possibly detected using conventional methods because of their low abundance in bodily fluids. When coupled with mass spectrometry, research utilizing lectins, which are mainly from plants and fungi, has led to identification of numerous potential cancer biomarkers that may be used in the future. This article reviews lectin-based methods that are commonly adopted in cancer biomarker discovery research.

The potent anti-cancer activity of Dioclea lasiocarpa lectin

The lectin DLasiL was isolated from seeds of the Dioclea lasiocarpa collected from the northeast coast of Brazil and characterized for the first time by mass spectrometry, DNA sequencing, inductively coupled plasma-mass spectrometry, electron paramagnetic resonance, and fluorescence spectroscopy. The structure of DLasiL lectin obtained by homology modelling suggested strong conservation of the dinuclear Ca/Mn and sugar-binding sites, and dependence of the solvent accessibility of tryptophan-88 on the oligomerisation state of the protein. DLasiL showed highly potent (low nanomolar) antiproliferative activity against several human carcinoma cell lines including A2780 (ovarian), A549 (lung), MCF-7 (breast) and PC3 (prostate), and was as, or more, potent than the lectins ConBr (Canavalia brasiliensis), ConM (Canavalia maritima) and DSclerL (Dioclea sclerocarpa) against A2780 and PC3 cells. Interestingly, DLasiL lectin caused a G2/M arrest in A2780 cells after 24h exposure, activating caspase 9 and delaying the on-set of apoptosis. Confocal microscopy showed that fluorescently-labelled DLasiL localized around the nuclei of A2780 cells at lectin doses of 0.5-2× IC₅₀ and gave rise to enlarged nuclei and spreading of the cells at high doses. These data reveal the interesting antiproliferative activity of DLasiL lectin, and suggest that further investigations to explore the potential of DLasiL as a new anticancer agent are warranted.

Plant Lectins Targeting O-Glycans at the Cell Surface as Tools for Cancer Diagnosis, Prognosis and Therapy

Aberrant O-glycans expressed at the surface of cancer cells consist of membrane-tethered glycoproteins (T and Tn antigens) and glycolipids (Lewis a, Lewis x and Forssman antigens). All of these O-glycans have been identified as glyco-markers of interest for the diagnosis and the prognosis of cancer diseases. These epitopes are specifically detected using T/Tn-specific lectins isolated from various plants such as jacalin from Artocarpus integrifola, and fungi such as the Agaricus bisporus lectin. These lectins accommodate T/Tn antigens at the monosaccharide-binding site; residues located in the surrounding extended binding-site of the lectins often participate in the binding of more extended epitopes. Depending on the shape and size of the extended carbohydrate-binding site, their fine sugar-binding specificity towards complex O-glycans readily differs from one lectin to another, resulting in a great diversity in their sugar-recognition capacity. T/Tn-specific lectins have been extensively used for the histochemical detection of cancer cells in biopsies and for the follow up of the cancer progression and evolution. T/Tn-specific lectins also induce a caspase-dependent apoptosis in cancer cells, often associated with a more or less severe inhibition of proliferation. Moreover, they provide another potential source of molecules adapted to the building of photosensitizer-conjugates allowing a specific targeting to cancer cells, for the photodynamic treatment of tumors.

Lectins, Interconnecting Proteins with Biotechnological/Pharmacological and Therapeutic Applications

Lectins are proteins extensively used in biomedical applications with property to recognize carbohydrates through carbohydrate-binding sites, which identify glycans attached to cell surfaces, glycoconjugates, or free sugars, detecting abnormal cells and biomarkers related to diseases. These lectin abilities promoted interesting results in experimental treatments of immunological diseases, wounds, and cancer. Lectins obtained from virus, microorganisms, algae, animals, and plants were reported as modulators and tool markers in vivo and in vitro; these molecules also play a role in the induction of mitosis and immune responses, contributing for resolution of infections and inflammations. Lectins revealed healing effect through induction of reepithelialization and cicatrization of wounds. Some lectins have been efficient agents against virus, fungi, bacteria, and helminths at low concentrations. Lectin-mediated bioadhesion has been an interesting characteristic for development of drug delivery systems. Lectin histochemistry and lectin-based biosensors are useful to detect transformed tissues and biomarkers related to disease occurrence; antitumor lectins reported are promising for cancer therapy. Here, we address lectins from distinct sources with some biological effect and biotechnological potential in the diagnosis and therapeutic of diseases, highlighting many advances in this growing field.

Structural analysis and unique molecular recognition properties of a Bauhinia forficata lectin that inhibits cancer cell growth

Lectins have been used at length for basic research and clinical applications. New insights into the molecular recognition properties enhance our basic understanding of carbohydrate-protein interactions and aid in the design/development of new lectins. In this study, we used a combination of cell-based assays, glycan microarrays, and X-ray crystallography to evaluate the structure and function of the recombinant Bauhinia forficata lectin (BfL). The lectin was shown to be cytostatic for several cancer cell lines included in the NCI-60 panel; in particular, it inhibited growth of melanoma cancer cells (LOX IMVI) by over 95%. BfL is dimeric in solution and highly specific for binding of oligosaccharides and glycopeptides with terminal N-acetylgalactosamine (GalNAc). BfL was found to have especially strong binding (apparent Kd  = 0.5-1.0 nm) to the tumor-associated Tn antigen. High-resolution crystal structures were determined for the ligand-free lectin, as well as for its complexes with three Tn glycopeptides, globotetraose, and the blood group A antigen. Extensive analysis of the eight crystal structures and comparison to structures of related lectins revealed several unique features of GalNAc recognition. Of special note, the carboxylate group of Glu126, lining the glycan-binding pocket, forms H-bonds with both the N-acetyl of GalNAc and the peptide amido group of Tn antigens. Stabilization provided by Glu126 is described here for the first time for any GalNAc-specific lectin. Taken together, the results provide new insights into the molecular recognition of carbohydrates and provide a structural understanding that will enable rational engineering of BfL for a variety of applications.

DATABASE

Structural data are available in the PDB under the accession numbers 5T50, 5T52, 5T55, 5T54, 5T5L, 5T5J, 5T5P, and 5T5O.

A Multivalent Marine Lectin from Crenomytilus grayanus Possesses Anti-cancer Activity through Recognizing Globotriose Gb3

In this study, we report the structure and function of a lectin from the sea mollusk Crenomytilus grayanus collected from the sublittoral zone of Peter the Great Bay of the Sea of Japan. The crystal structure of C. grayanus lectin (CGL) was solved to a resolution of 1.08 Å, revealing a β-trefoil fold that dimerizes into a dumbbell-shaped quaternary structure. Analysis of the crystal CGL structures bound to galactose, galactosamine, and globotriose Gb3 indicated that each CGL can bind three ligands through a carbohydrate-binding motif involving an extensive histidine- and water-mediated hydrogen bond network. CGL binding to Gb3 is further enhanced by additional side-chain-mediated hydrogen bonds in each of the three ligand-binding sites. NMR titrations revealed that the three binding sites have distinct microscopic affinities toward galactose and galactosamine. Cell viability assays showed that CGL recognizes Gb3 on the surface of breast cancer cells, leading to cell death. Our findings suggest the use of this lectin in cancer diagnosis and treatment.

Polyethylene sebacate doxorubicin nanoparticles: role of carbohydrate anchoring on in vitro and in vivo anticancer efficacy

We report carbohydrate-anchored polyethylene sebacate (PES)-Gantrez® AN 119 Doxorubicin hydrochloride (Dox) nanoparticles (NPs) for enhanced anticancer efficacy. The carbohydrates Arabinogalactan (AGn), an adjuvant in anticancer chemotherapy and pullulan (Pul) reported to promote collagen synthesis, were selected as ligands. PES Dox NPs of an average size around 200 nm, greater than 20% w/w Dox loading and negative zeta potential were anchored with Pul, AGn, and Pul-AGn combination by simple incubation. Increase in particle size and zeta potential confirmed carbohydrate anchoring. FTIR confirmed ionic complexation of Dox and Gantrez® AN 119. DSC and XRD demonstrated amorphization of Dox. Higher Dox release in pH 5.5 as compared with pH 7.4 is beneficial for reduced systemic toxicity and enhanced drug release in tumors. Good in vitro serum stability and low hemolysis revealed suitability for intravenous administration. All NPs revealed circulation longevity in normal rats. Pul NPs revealed superior anticancer efficacy in vitro and an 11-fold enhancement in uptake in MCF-7 breast cancer cells. The greater efficacy in vivo is attributed to possible pullulan-mediated integrin receptor uptake and interaction with tumor collagen. Histopathology confirmed safety and suggested promise of Pul NPs in improved anticancer efficacy.

Epididymal protein ASF is a D-galactose-specific lectin with apoptotic effect on human breast cancer cell line MCF7

Isolated caprine epididymal plasma glycoprotein "anti sticking factor" (ASF) interacts with caudal sperm surface in a D-galactose dependent manner. ASF acts as a Ca(2+) dependent soluble lectin principally activated in acidic pH. As a D-galactose specific lectin, it has a specific affinity for fibronectin as well as fibronectin receptor, i.e. integrins α5β3 and α5β1. By virtue of this particular property, it hampers the in vitro adhesion of the adherent breast cancer cell MCF7 with fibronectin. The effective anti-adhesive concentration of ASF promotes p53 dependent apoptosis in MCF7, which was established by Hoechst 33342 staining, DNA fragmentation assay, FITC tagged Annexin-V flowcytometry and western blot analysis. We suggest that ASF inhibits fibronectin-integrin interactions by binding with them and induces adhesion dependent apoptosis on adherent MCF7.

Role of the flavonoid-rich fraction in the antioxidant and cytotoxic activities of Bauhinia forficata Link. (Fabaceae) leaves extract

Bauhinia forficata Link. is utilised as an antidiabetic in Brazilian folk-medicine; furthermore, its antioxidant properties suggest a potential usefulness in the prevention of diabetes complications associated with oxidative stress. The contribution of a flavonoid-rich fraction (FRF), HPLC-PDA-ESI-MS characterised, to the antioxidant and cytotoxic properties of B. forficata hydro-alcoholic leaves extract was evaluated for the first time. Both extract and FRF showed radical-scavenging activity and reducing power with a strong relationship with the flavonoid content found; hence, flavonoids are mainly responsible for the primary antioxidant activity of B. forficata extract. The extract significantly decreased FO-1 cell viability at the higher concentrations. FRF did not exert any effect; thus, flavonoids do not appear to be responsible for the cytotoxicity of the extract. The extract resulted virtually non-toxic against both Artemia salina and normal human lymphocytes, demonstrating potential selectivity in inhibiting cancer cell growth. Finally, no antimicrobial activity was observed against the bacteria and yeasts tested.

Exogenous natural glycoprotein multiple mechanisms of anti-tumor activity

Natural glycoproteins can induce apoptosis of tumor cells and exert anti-tumor activity by immunomodulatory functions, cytotoxic and anti-inflammation effects, and inhibition of endothelial growth factor. Given their prospects as novel agents, sources of natural antitumor glycoproteins have attracted attention and new research directions in glycoprotein biology are gradually shifting to the direction of cancer treatment and prevention of neoplastic disease. In this review, we summarize the latest findings with regard to the tumor suppressor signature of glycoproteins and underlying regulatory mechanisms.