A novel sialic acid-specific lectin from Phaseolus coccineus seeds with potent antineoplastic and antifungal activities

Antiproliferative effects of heated Japanese runner bean (Phaseolus coccineus) lectins

In this study, we examined the biological properties of lectins isolated from raw and heated Japanese white runner beans (WRB; Phaseolus coccineus). Notably, we studied the agglutination activity of lectins that persisted after both dry and wet heating processes. Raw and heated WRB lectins were fractionated using thyroglobulin-sepharose chromatography. Raw WRB lectins displayed strong specificity for thyroglobulin but weak specificity for fetuin, demonstrated resistance to proteases, and tolerated temperatures of 60°C for 30 min. The antiproliferative effects of WRB lectins on cancer cells were assessed and compared between raw and heated beans. Both raw and heated WRB lectins exhibited significant antiproliferative activity against five cancer cell lines: LM8, B16, HeLa, HepG2, and Colo679. Interestingly, in terms of antiproliferative activity, raw and heated lectins showed no significant differences. Fractionated lectins from raw and heated beans showed strong inhibitory effects against B16 and HeLa cells. Furthermore, crude extracts from raw beans demonstrated anti-inflammatory activity. In summary, our findings highlight that lectin from heated WRB beans retained bioactivity, including anti-inflammatory and anticancer properties, after heating. These results suggest that WRB lectins could be developed as bioactive compounds for medical applications as functional food components. PRACTICAL APPLICATION: Japanese white runner beans (WRB), cultivated in northeastern Japan and traditionally used in confectionery, retain hemagglutination activity under dry and wet heating conditions. Heat-treated WRB lectins demonstrated anticancer activity comparable to that of raw bean lectins, supporting their potential use as bioactive proteins in medical research. WRB lectins may serve as promising candidates for development as anticancer agents or other therapeutic applications.

Partial Characterization of Lectins Purified from the Surco and Vara (Furrow and Rod) Varieties of Black Phaseolus vulgaris

As they manifest specifically and reversibly, lectins are proteins or glycoproteins with the characteristic of agglutinating erythrocytes. Given that grain legume lectins can represent 10% of protein content and can have various biological functions, they are extensively studied. The objective of this work was to purify and partially characterize the lectins of Phaseolus vulgaris black, var surco and vara (LBBS and LBBV). Both lectin types were purified by affinity chromatography on stroma matrix, which agglutinated human erythrocytes type A, B, and O, as well as rabbit, hamster, pig, and chicken erythrocytes. Native-PAGE was employed for molecular mass determination, yielding 109.36 and 112.68 kDa for BBS and BBV, respectively. Further analyses revealed that these lectins are tetrameric glycoproteins that require Ca⁺², Mn⁺² and Mg⁺² ions for exhibiting their hemagglutinating function, which can be inhibited by fetuin. Moreover, optimal pH was established for both lectins (10.5 for LBBS and 7-9 for LBBV), while their activity was temperature-dependent and ceased above 70 °C. Finally, the observed differences in the biochemical characteristics and bioactive functions were ascribed to the different physiological characteristics of each seed, as well as the protein itself.

Plant lectins: A new antimicrobial frontier

Pathogenic bacteria, viruses, fungi, parasites, and other microbes constantly change to ensure survival. Several pathogens have adopted strict and intricate strategies to fight medical treatments. Many drugs, frequently prescribed to treat these pathogens, are becoming obsolete and ineffective. Because pathogens have gained the capacity to tolerate or resist medications targeted at them, hence the term antimicrobial resistance (AMR), in that regard, many natural compounds have been routinely used as new antimicrobial agents to treat infections. Thus, plant lectins, the carbohydrate-binding proteins, have been targeted as promising drug candidates. This article reviewed more than 150 published papers on plant lectins with promising antibacterial and antifungal properties. We have also demonstrated how some plant lectins could express a synergistic action as adjuvants to boost the efficacy of obsolete or abandoned antimicrobial drugs. Emphasis has also been given to their plausible mechanism of action. The study further reports on the immunomodulatory effect of plant lectins and how they boost the immune system to curb or prevent infection.

A review on the antimicrobial properties of lectins

Lectins are biologically versatile biomolecules with remarkable antimicrobial effects, notably against bacteria, fungi and protozoa, in addition to modulating host immunity. For this, the lectins bind to carbohydrates on the surface of the pathogen, which can cause damage to the cell wall and prevent the attachment of microorganisms to host cells. Thus, this study intends to review the biological activities of lectins, with an emphasis on antimicrobial activity. Lectins of plant stood out for its antimicrobial effects, demonstrating that they act against a variety of strains, where in vitro were able to inhibit their development and affect their morphology. In vivo, they modulated host immunity, signaling and activating defense cells. Some of these lectins were capable to modulate the action of antibiotics, indicating their potential to minimize the antibiotic resistance. The results suggest that lectins have antimicrobial activity with potential to be used in drug development.

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.

Tailor-made recombinant prokaryotic lectins for characterisation of glycoproteins

Development of biosimilars is costly, where glycan analysis is a significant constraint on time and money. This paper provides an in-depth characterisation of several novel recombinant prokaryotic lectins (RPLs), developed through directed evolution, displaying specific binding activities to α-mannose, β-galactose, fucose and sialic acid residues, tested against major biosimilar targets. The binding characterisation of all lectins was performed employing the principles of bio-layer interferometry (BLI), with help of the streptavidin-coated sensor with the biotinylated lectins. The binding activity of the RPLs and the specificity to a broad range of glycoproteins and glycoconjugates were evaluated and compared to those of equivalent plant-derived lectins. While exhibiting better or similar specificity, RPLs displayed significantly better binding in all cases. The binding mechanisms are explained with particular focus on the role hydrogen bonding plays in the change of specificity for a galactose specific lectin. Furthermore, different sets of RPLs and their plant equivalents were assayed against the different glycoprotein targets to evaluate the analytical parameters of the lectin-glycoprotein interaction. The obtained LoDs reached by the RPLs were lower than those of their plant counterparts apart from one, exhibiting RPL:PL LoD ratios of 0.8, 2.5, 14.2 and 380 for the sets of lectins specific to fucose, α-mannose, β-galactose and sialic acid, respectively. Such enhancement in analytical parameters of RPLs shows their applicability in protein purification and as bioanalytical tools for glycan analysis and biosensor development.

Role of Protein Glycosylation in Host-Pathogen Interaction

Host-pathogen interactions are fundamental to our understanding of infectious diseases. Protein glycosylation is one kind of common post-translational modification, forming glycoproteins and modulating numerous important biological processes. It also occurs in host-pathogen interaction, affecting host resistance or pathogen virulence often because glycans regulate protein conformation, activity, and stability, etc. This review summarizes various roles of different glycoproteins during the interaction, which include: host glycoproteins prevent pathogens as barriers; pathogen glycoproteins promote pathogens to attack host proteins as weapons; pathogens glycosylate proteins of the host to enhance virulence; and hosts sense pathogen glycoproteins to induce resistance. In addition, this review also intends to summarize the roles of lectin (a class of protein entangled with glycoprotein) in host-pathogen interactions, including bacterial adhesins, viral lectins or host lectins. Although these studies show the importance of protein glycosylation in host-pathogen interaction, much remains to be discovered about the interaction mechanism.

Tepary Bean (Phaseolus acutifolius) Lectins Induce Apoptosis and Cell Arrest in G0/G1 by P53(Ser46) Phosphorylation in Colon Cancer Cells

A Tepary bean lectin fraction (TBLF) has been studied because it exhibits differential cytotoxic and anticancer effects on colon cancer. The present work focuses on the evaluation of the apoptotic mechanism of action on colon cancer cells. Initially, lethal concentrations (LC₅₀) were obtained for the three studied cell lines (HT-29, RKO and SW-480). HT-29 showed the highest LC₅₀, 10 and 100 times higher than that of RKO and SW-480 cells, respectively. Apoptosis was evaluated by flow cytometry, where HT-29 cells showed the highest levels of early and total apoptosis, caspases activity was confirmed and necrosis was discarded. The effect on cell cycle arrest was shown in the G0/G1 phase. Specific apoptosis-related gene expression was determined, where an increase in p53 and a decrease in Bcl-2 were observed. Expression of p53 gene showed the maximum level at 8 h with an important decrease at 12 and 24 h, also the phosphorylated p53(ser46) increased at 8 h. Our results show that TBLF induces apoptosis in colon cancer cells by p-p53(ser46) involvement. Further studies will focus on studying the specific signal transduction pathway.

Legume lectins: Potential use as a diagnostics and therapeutics against the cancer

Legume lectins are carbohydrate-binding protein and widely distributed in a variety of species of leguminous plants and have drawn increased attention toward cancer. Nowadays, the lectins have been studied for the screening of potential biomarkers which increased its importance in cancer research. Few plant lectins have been shown to destroy cancer cells, suggesting that lectins may have biological potential in cancer treatments. In this review, we present a focused outline of legume lectins in descriptive their complex anti-cancer mechanisms on the bases of their properties of recognition and interacting specifically with carbohydrates binding sites. Existing reports suggested the binding of lectins to cancerous cells with their cell surface markers speculated by histochemistry in vitro and in vivo. In this review, we illuminate the use of legume lectins as a natural source for diagnostics and therapeutics purpose against cancer.

Structure-function and application of plant lectins in disease biology and immunity

Lectins are proteins with a high degree of stereospecificity to recognize various sugar structures and form reversible linkages upon interaction with glyco-conjugate complexes. These are abundantly found in plants, animals and many other species and are known to agglutinate various blood groups of erythrocytes. Further, due to the unique carbohydrate recognition property, lectins have been extensively used in many biological functions that make use of protein-carbohydrate recognition like detection, isolation and characterization of glycoconjugates, histochemistry of cells and tissues, tumor cell recognition and many more. In this review, we have summarized the immunomodulatory effects of plant lectins and their effects against diseases, including antimicrobial action. We found that many plant lectins mediate its microbicidal activity by triggering host immune responses that result in the release of several cytokines followed by activation of effector mechanism. Moreover, certain lectins also enhance the phagocytic activity of macrophages during microbial infections. Lectins along with heat killed microbes can act as vaccine to provide long term protection from deadly microbes. Hence, lectin based therapy can be used as a better substitute to fight microbial diseases efficiently in future.

Two-Step Isolation, Purification, and Characterization of Lectin from Zihua Snap Bean (Phaseolus vulgaris) Seeds

A two-step method based on an aqueous two-phase system and Sephadex G-75 was used to separate and purify lectin from the seeds of the Zihua snap bean. The preliminary properties and bioactivity of the Zihua snap bean lectin were characterized by different instrumental methods, such as sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS–PAGE), liquid chromatography-nano electrospray ionization mass spectrometry (Nano LC-ESI-MS/MS), and Fourier transform infrared spectroscopy (FTIR). The hemagglutinating activity of the Zihua snap bean lectin could not be inhibited by glucose, N-acetyl-d-glucosamine, d-galactose, N-acetyl-d-galactosamine, fructose, sucrose, d-maltose, d-trehalose, and lactose. It was found that the hemagglutinating activity of the lectin showed strong dependence on Mn²⁺ and Ca²⁺. The thermal and pH stability of the Zihua snap bean lectin was studied by FTIR and fluorescence spectroscopy. Relatively good stability was observed when the temperature was not higher than 70 °C, as well as in the pH range of 2.0 to 10.0. Digestive stability in vitro was investigated. The untreated lectin was relatively stable to pepsin and trypsin activity, but heat treatment could significantly reduce the digestive stability in vitro. Moreover, the lectin showed an inhibitory effect on the tested bacteria (Staphylococcus aureus (S. aureus), Escherichia coli (E. coli), Bacillus subtilis (B. subtilis)), and it also showed a certain inhibitory effect on the growth of Phytophthora infestans (P. infestans) at higher concentrations.

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.

WITHDRAWN: Purification and characterizations of a new mannose specific lectin from Bangladeshi cultivated sword bean with antiproliferative activities against Ehrlich ascites carcinoma cells in vivo in mice

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Isolation and characterization of lectin with antibacterial, antibiofilm and antiproliferative activities from Acinetobacter baumannii of environmental origin

AIMS

Lectin is a nonimmunogenic glycoprotein that has been extracted mostly from the primary plant source leguminoase. Its ability to precisely recognize and bind to the complex cell bound structure enables it to play diverse roles. In this study, we obligate to define new sources of lectins since the production of lectins is very expensive. Therefore, we performed a study with the goal to isolate and characterize lectin from bacteria of plant origin and screen its ability as an antibacterial, antibiofilm and antiproliferative agent.

METHODS AND RESULTS

We investigated isolates of environmental origin for their ability to produce lectin using phenotypic and molecular detection. The lectin was purified from an isolate AB119 which has abundant lectin activity and its molecular weight was determined by SDS-PAGE and HPLC. This lectin has a molecular weight of 30 kD and used to evaluate its antimicrobial, antibiofilm and antiproliferative activities using earlier published protocols. All bacterial isolates tested in this study showed the ability to produce biofilm which was inhibited in the presence of lectin significantly. In microtitre plate assay, the scale of biofilm inhibition by the purified lectin was significantly reduced for all bacterial species. Lectin inhibited the growth of all three tested bacterial species after treatment for 24 h and this antimicrobial effect was uniform to all species irrespective of Gram positive or Gram negative. The antiproliferative effects of lectin against HeLa cells were determined using MTT assay showed significant inhibitory effects on the proliferation at an IC50 of 10 μM for 24 h.

CONCLUSION

This study concludes that lectin has a promising application as an antimicrobial and, antibiofilm agent to control multidrug-resistant pathogen-associated infections. At the same time, it has also promising ability to control the proliferation of tumour cell as evident by our study results.

SIGNIFICANCE AND IMPACT OF STUDY

AB119 lectin from A.baumannii species was verified for its capability to control microbial growth and its biofilm formation. Results showed lectin was able to reduce growth as well biofilm formation of both Gram-positive and Gram-negative bacterial species. Lectin has a promising application as an antibiofilm agent to combat the growing number of multidrug-resistant pathogen-associated infections.

Phaseolus acutifolius Lectin Fractions Exhibit Apoptotic Effects on Colon Cancer: Preclinical Studies Using Dimethilhydrazine or Azoxi-Methane as Cancer Induction Agents

Phaseolus acutifolius (Tepary bean) lectins have been studied as cytotoxic molecules on colon cancer cells. The toxicological profile of a Tepary bean lectin fraction (TBLF) has shown low toxicity in experimental animals; exhibiting anti-nutritional effects such as a reduction in body weight gain and a decrease in food intake when using a dose of 50 mg/kg on alternate days for six weeks. Taking this information into account, the focus of this work was to evaluate the effect of the TBLF on colon cancer using 1,2-dimethylhydrazine (DMH) or azoxy-methane/dextran sodium sulfate (AOM/DSS) as colon cancer inductors. Rats were treated with DMH or AOM/DSS and then administered with TBFL (50 mg/kg) for six weeks. TBLF significantly decreased early tumorigenesis triggered by DMH by 70%, but without any evidence of an apoptotic effect. In an independent experiment, AOM/DSS was used to generate aberrant cryptic foci, which decreased by 50% after TBLF treatment. TBLF exhibited antiproliferative and proapoptotic effects related to a decrease of the signal transduction pathway protein Akt in its activated form and an increase of caspase 3 activity, but not to p53 activation. Further studies will deepen our knowledge of specific apoptosis pathways and cellular stress processes such as oxidative damage.

Legume Lectins: Proteins with Diverse Applications

Lectins are a diverse class of proteins distributed extensively in nature. Among these proteins; legume lectins display a variety of interesting features including antimicrobial; insecticidal and antitumor activities. Because lectins recognize and bind to specific glycoconjugates present on the surface of cells and intracellular structures; they can serve as potential target molecules for developing practical applications in the fields of food; agriculture; health and pharmaceutical research. This review presents the current knowledge of the main structural characteristics of legume lectins and the relationship of structure to the exhibited specificities; provides an overview of their particular antimicrobial; insecticidal and antitumor biological activities and describes possible applications based on the pattern of recognized glyco-targets.

A new TRAF-like protein from B. oleracea ssp. botrytis with lectin activity and its effect on macrophages

Lectins are involved in a wide range of biological mechanisms, like immunomodulatory agent able to activate the innate immunity. In this study, we purified and characterized a new lectin from cauliflower (Brassica oleracea ssp. botrytis - BOL) by three sequential chromatographic steps and confirmed the purity by SDS-PAGE. Additionally, we evaluated the role of the lectin in innate immunity by a phagocytosis assay, production of H₂O₂ and NO. BOL was characterized like a non-glycosylated protein that showed a molecular mass of ∼34kDa in SDS-PAGE. Its N-terminal sequence (ETRAFREERPSSKIVTIAG) did not reveal any similarity to the other lectins; nevertheless, it showed 100% homology to a putative TRAF-like protein from Brassica rapa and Brassica napus. This is a first report of the TRAF-protein with lectinic activity. The BOL retained its complete hemagglutination activity from 4°C up to 60°C, with stability being more apparent between pH 7.0 and 8.0. Moreover, the lectin was able to stimulate phagocytosis and induce the production of H₂O₂ and NO. Therefore, BOL can be explored as an immunomodulatory agent by being able to activate the innate immunity and favor antigen removal.

A dimeric Phaseolus coccineus lectin with anti-oxidative, anti-proliferative and cytokine-inducing activities

In the present study, a dimeric glucosamine binding lectin, designated as CHL, was purified from Phaseolus coccineus L. var. albonanus Bailey through three chromatographic steps. The molecular weight of CHL was approximately 66kDa. Its hemagglutinating activity toward rabbit erythrocytes was dependent on carbohydrates, especially glucosamine, and was stable at temperatures between 20 and 70°C, and at pH between 1 and 13. Intriguingly, further characterization showed that CHL served as a potent antioxidant to prevent erythrocytes from haemolysis induced by 2'-azobis (2-amidinopropane) dihydrochloride (AAPH) in a dose-dependent manner. Moreover, it exerted antitumor activity against human nasopharyngeal carcinoma CNE1 cells, hepatoma HepG2 cells, and breast cancer MCF7 cells but was devoid of antifungal activity. In addition, the CHL could bring about a significant dose-dependent increase in the production of mRNAs of pro-inflammatory cytokines including interferon-gamma and interleukin-2. These results suggest the potential therapeutic utility of CHL.

Plant lectins, from ancient sugar-binding proteins to emerging anti-cancer drugs in apoptosis and autophagy

Ubiquitously distributed in different plant species, plant lectins are highly diverse carbohydrate-binding proteins of non-immune origin. They have interesting pharmacological activities and currently are of great interest to thousands of people working on biomedical research in cancer-related problems. It has been widely accepted that plant lectins affect both apoptosis and autophagy by modulating representative signalling pathways involved in Bcl-2 family, caspase family, p53, PI3K/Akt, ERK, BNIP3, Ras-Raf and ATG families, in cancer. Plant lectins may have a role as potential new anti-tumour agents in cancer drug discovery. Thus, here we summarize these findings on pathway- involved plant lectins, to provide a comprehensive perspective for further elucidating their potential role as novel anti-cancer drugs, with respect to both apoptosis and autophagy in cancer pathogenesis, and future therapy.

A lectin from Dioclea violacea Interacts with midgut surface of Lutzomyia migonei, unlike its homologues, Cratylia floribunda lectin and Canavalia gladiata lectin

Leishmaniasis is a vector-borne disease transmitted by phlebotomine sand fly. Susceptibility and refractoriness to Leishmania depend on the outcome of multiple interactions that take place within the sand fly gut. Promastigote attachment to sand fly midgut epithelium is essential to avoid being excreted together with the digested blood meal. Promastigote and gut sand fly surface glycans are important ligands in this attachment. The purpose of the present study was to evaluate the interaction of three lectins isolated from leguminous seeds (Diocleinae subtribe), D-glucose and D-mannose-binding, with glycans on Lutzomyia migonei midgut. To study this interaction the lectins were labeled with FITC and a fluorescence assay was performed. The results showed that only Dioclea violacea lectin (DVL) was able to interact with midgut glycans, unlike Cratylia floribunda lectin (CFL) and Canavalia gladiata lectin (CGL). Furthermore, when DVL was blocked with D-mannose the interaction was inhibited. Differences of spatial arrangement of residues and volume of carbohydrate recognition domain (CRD) may be the cause of the fine specificity of DVL for glycans in the surface on Lu. migonei midgut. The findings in this study showed the presence of glycans in the midgut with glucose/mannose residues in its composition and these residues may be important in interaction between Lu. migonei midgut and Leishmania.

The lectin BJcuL induces apoptosis through TRAIL expression, caspase cascade activation and mitochondrial membrane permeability in a human colon adenocarcinoma cell line

It has been demonstrated that the cytotoxic effect of BJcuL, the lectin isolated from Bothrops jararacussu venom, on human gastric carcinoma is accompanied by the inhibition of extracellular matrix adhesion, cytoskeleton disassembly and apoptosis induction. The present study aimed to evaluate the apoptosis mechanisms triggered by the BJcuL interaction with specific glycans on the surface of HT29 human colon adenocarcinoma cells. The results demonstrated that BJcuL interacts with glycoligands targets on the cell, which were inhibited in the presence of d-galactose. It shows a dose-dependently cytotoxic effect that is inhibited in the presence of d-galactose. A dose-dependent cell aggregation decrease was also observed for the HT29 cells. Analysis of cell proliferation inhibition was assessed by anti-PCNA and demonstrated that lectin diminishes PCNA expression when compared with untreated cells. Differences in apoptotic marker expression estimated by immunohistochemistry revealed that the lectin promotes an increase in TRAIL expression, leading to an increase in the expression of FADD, caspase-8 and Bax. Besides the increased expression of apoptosis-related proteins, our results revealed that the lectin promotes a mitochondrial respiration decrease and a 75% increase in the amount of cytochrome c released. Together these results suggest that the cytotoxicity of BJcuL can sensitize pro-apoptotic proteins in the cytoplasm and mitochondria, leading to the apoptotic cascade.

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

BACKGROUND

Plant lectins have attracted great interest in cancer studies due to their antitumor activities. These proteins or glycoproteins specifically and reversibly bind to different types of carbohydrates or glycoproteins. Breast cancer, which presents altered glycosylation of cell surface glycoproteins, is one of the most frequent malignant diseases in women. In this work, we describe the effect of the lectin Bauhinia forficata lectin (BfL), which was purified from B. forficata Link subsp. forficata seeds, on the MCF7 human breast cancer cellular line, investigating the mechanisms involved in its antiproliferative activity.

METHODS

MCF7 cells were treated with BfL. Viability and adhesion alterations were evaluated using flow cytometry and western blotting.

RESULTS

BfL inhibited the viability of the MCF7 cell line but was ineffective on MDA-MB-231 and MCF 10A cells. It inhibits MCF7 adhesion on laminin, collagen I and fibronectin, decreases α1, α6 and β1 integrin subunit expression, and increases α5 subunit expression. BfL triggers necrosis and secondary necrosis, with caspase-9 inhibition. It also causes deoxyribonucleic acid (DNA) fragmentation, which leads to cell cycle arrest in the G2/M phase and a decrease in the expression of the regulatory proteins pRb and p21.

CONCLUSION

BfL shows selective cytotoxic effect and adhesion inhibition on MCF7 breast cancer cells.

GENERAL SIGNIFICANCE

Cell death induction and inhibition of cell adhesion may contribute to understanding the action of lectins in breast cancer.

Antitumor effects of concanavalin A and Sophora flavescens lectin in vitro and in vivo

AIM

Proteins with legume lectin domains are known to possess a wide range of biological functions. Here, the antitumor effects of two representative legume lectins, concanavalin A (ConA) and Sophora flavescens lectin (SFL), on human breast carcinoma cells were investigated in vitro and in vivo.

METHODS

Human breast carcinoma MCF-7 cells and human normal mammary epithelial MCF-10A cells were examined. Cell viability was detected using WST-1 and CCK-8 assays. Cell apoptosis was analyzed with Hoechst 33258 staining. Cell cycle was investigated using flow cytometry. The expression of relevant proteins was measured using Western blotting. Breast carcinoma MCF-7 bearing nude mice were used to study the antitumor effects in vivo. The mice were injected with ConA (40 mg/kg, ip) and SFL (55 mg/kg, ip) daily for 14 d.

RESULTS

ConA and SFL inhibited the growth of MCF-7 cells in dose- and time-dependent manners (IC50 values were 15 and 20 μg/mL, respectively). Both ConA and SFL induced apoptotic morphology in MCF-7 cells without affecting MCF-10A cells. ConA and SFL dose-dependently increased the sub-G1 proportion in MCF-7 cells, while SFL also triggered the G2/M phase cell cycle arrest. Both ConA and SFL dose-dependently increased the activities of caspase-3 and caspase-9 and release of cytochrome C from mitochondria into cytoplasm, up-regulated Bax and Bid, and down-regulated Bcl-2 and Bcl-XL in MCF-7 cells. ConA reduced NF-κB, ERK, and JNK levels, and increased p53 and p21 levels, while SFL caused similar changes in NF-κB, ERK, p53, and p21 levels, but did not affect JNK expression. Administration of ConA and SFL significantly decreased the subcutaneous tumor mass volume and weight in MCF-7 bearing nude mice.

CONCLUSION

ConA and SFL exert anti-tumor actions against human breast carcinoma MCF-7 cells both in vitro and in vivo.

Purification and characterization of an α-galactosidase from Phaseolus coccineus seeds showing degrading capability on raffinose family oligosaccharides

An acidic α-galactosidase (EC 3.2.1.22) designated as Phaseolus coccineus seeds galactosidase (PCG) was purified from P. coccineus seeds using ion-exchange chromatography on DEAE- and CM-cellulose, Q- and SP-Sepharose and gel filtration on Superdex 75. The molecular weight of PCG was 43 kDa as judged by SDS-PAGE and gel filtration. Two inner peptides of PCG were sequenced by MALDI-TOF-MS. The optimum pH and temperature was 3.0 and 70 °C, respectively but was stable up to 60 °C for 30 min. The enzyme activity was inhibited by NBS signifying the pivotal role played by tryptophan in the catalytic activity of the enzyme. The Km for hydrolysis of pNPGal was 0.0025 mM. Besides hydrolyzing pNPGal, α-galactosidases also hydrolyzed natural substrates such as melibiose, raffinose and stachyose. Hence it can be exploited commercially for improving the nutritional value of soymilk. Thus the PCG has great potential in the feed industries for removal of non-digestible oligosaccharide from legumes.

In silico analysis of molecular mechanisms of legume lectin-induced apoptosis in cancer cells

OBJECTIVES

The legume lectin family, one of the most extensively studied plant lectin families, has received increasing attention for the remarkable anti-tumor activities of its members for binding specific cancer cell surface glycoconjugates. MicroRNAs, a class of small, non-coding RNAs, control translation and stability of mRNAs at post-transcriptional and translational levels. To date, accumulating evidence has revealed that microRNAs are involved in progression of a number of human diseases, especially cancers. However, the molecular manners of microRNA-modulated apoptosis in legume lectin-treated cancer cells are still under investigation.

MATERIALS AND METHODS

We performed in silico analyses to study the interactions between three typical legume lectins (ConA, SFL and SAL) and some specific sugar-containing receptors (for example, EGFR, TNFR1, HSP70 and HSP90). Additionally, we predicted some relevant microRNAs which could significantly regulate these aforementioned targetreceptors and thus inhibiting down-stream cancer-related signaling pathways.

RESULTS

The results showed that these three legume lectins could competitively bind sugar-containing receptors such as EGFR, TNFR1, HSP70 and HSP90 in two ways, via anti-apoptotic or survival pathways. On the one hand, the legume lectins could induce cancer cell death through triggering receptor-mediated signaling pathways, which resulted from indirect binding between legume lectins and mannoses resided in receptors. On the other hand, direct binding between legume lectins and receptors could lead to steric hindrance, which would disturb efficient interactions between them, and thus, the legume lectins would induce cancer cell death by triggering receptor-mediated signaling pathways. In addition, we identified several relevant microRNAs that regulated these targeted receptors, thereby ultimately causing cancer cell apoptosis.

CONCLUSIONS

These findings provide new perspectives for exploring microRNA-modulated cell death in legume lectin-treated cancer cells, which could be utilized in combination therapy for future cancer drug development.

Isolation and characterization of a novel lectin with antifungal and antiproliferative activities from Sophora alopecuroides seeds

Sophora alopecuroides lectin (SAL), a novel lectin from the seeds of Sophora alopecuroides, was purified by ion-exchange chromatography on diethylaminoethyl (DEAE)- and carboxymethyl (CM)-Sepharose columns, followed by gel filtration on a Sephadex 75 10/300 GL column. SAL was found to be a monomer of 39916.3 Da, as determined by tricine-sodium dodecyl sulphate-polyacrylamide gel electrophoresis and high-performance liquid chromatography (HPLC). The N-terminal 10-amino acid sequence of SAL, KPWALSFSFG, resembles those of other legume lectins. SAL exhibits hemagglutinating activity against rabbit erythrocytes at 11.9 μg/ml. Its hemagglutinating activity is stable in the pH range 7-11 and in the temperature range 30-90°C, and is stimulated by Mn(2+). The hemagglutinating activity of SAL is most potently inhibited by 50-mM d-galactose. SAL suppresses mycelial growth in Penicillium digitatum and Alternaria alternata; the IC(50) of the antifungal activity toward P. digitatum and A. alternata were found to be 3.125 and 3.338 μM, respectively. SAL suppresses the proliferation of human cervical cancer cells (HeLa) at an IC(50) of 6.25 μM (P< 0.05). But it has no inhibiting effect on bacteria. This is the first report of a lectin from seeds of S. alopecuroides.

CNL, a ricin B-like lectin from mushroom Clitocybe nebularis, induces maturation and activation of dendritic cells via the toll-like receptor 4 pathway

A novel lectin, isolated from the basidiomycete mushroom Clitocybe nebularis and termed C. nebularis lectin (CNL), exhibits an immunostimulatory effect on the most potent antigen-presenting cells, the dendritic cells (DCs). Treatment of human monocyte-derived DCs with CNL in doses from 1 to 10 μg/ml resulted in a dose-dependent induction of overall DC maturation characteristics. Exposure of DCs to CNL for 48 hr resulted in extensive up-regulation of co-stimulatory molecules CD80 and CD86, as well as of the maturation marker CD83 and HLA-DR molecules. Such CNL-matured DCs (CNL-DCs) were capable of inducing a T helper type 1-polarized response in naive CD4+  CD45RA+ T cells in 5-day allogeneic co-cultures. The allostimulatory potential of CNL-DCs was significantly increased relative to untreated controls, as was their capacity to produce several pro-inflammatory cytokines such as interleukin-6, interleukin-8 and tumour necrosis factor-α. By using a specific Toll-like receptor 4 (TLR4) signalling inhibitor, CLI-095, as well as Myd88 inhibitory peptide, we have shown that DC activation by CNL is completely dependent on the TLR4 activation pathway. Furthermore, activation of TLR4 by CNL was confirmed via TLR4 reporter assay. Measurement of p65 nuclear factor-κB and p38 mitogen-activated protein kinase (MAPK) phosphorylation levels following CNL stimulation of DCs revealed primarily an increase in nuclear factor-κB activity, with less effect on the induction of p38 MAPK signalling than of lipopolysaccharide-matured DCs. The CNL had the ability to activate human DCs in such a way as to subsequently direct T helper type 1 T-cell responses. Our results encourage the use of mushroom-derived lectins for use in therapeutic strategies with aims such as to strengthen anti-tumour immune responses.

Plant lectins: targeting programmed cell death pathways as antitumor agents

Lectins, a group of highly diverse, carbohydrate-binding proteins of non-immune origin that are ubiquitously distributed in plants, animals and fungi, are well-characterized to have numerous links a wide range of pathological processes, most notably cancer. In this review, we present a brief outline of the representative plant lectins including Ricin-B family, proteins with legume lectin domains and GNA family that can induce cancer cell death via targeting programmed cell death pathways. Amongst these above-mentioned lectins, we demonstrate that mistletoe lectins (MLs), Ricin, Concanavalin A (ConA) and Polygonatum cyrtonema lectin (PCL) can lead to cancer cell programmed death via targeting apoptotic pathways. In addition, we show that ConA and PCL can also result in cancer cell programmed death by targeting autophagic pathways. Moreover, we summarize the possible anti-cancer therapeutic implications of plant lectins such as ConA, Phaseolus vulgaris lectin (PHA) and MLs that have been utilized at different stages of preclinical and clinical trials. Together, these findings can provide a comprehensive perspective for further elucidating the roles of plant lectins that may target programmed cell death pathways in cancer pathogenesis and therapeutics. And, this research may, in turn, ultimately help cancer biologists and clinicians to exploit lectins as potential novel antitumor drugs in the future.

Characterization, molecular cloning, and in silico analysis of a novel mannose-binding lectin from Polygonatum odoratum (Mill.) with anti-HSV-II and apoptosis-inducing activities

Polygonatum odoratum lectin (POL), a novel mannose-binding lectin with anti-viral and apoptosis-inducing activities, was isolated from rhizomes of Polygonatum odoratum (Mill.) Druce. POL was a homo-tetramer with molecular weight of 11953.623Da per subunits as determined by gel filtration, SDS-PAGE and mass spectrometry. Based on its N-terminal 29-amino acid sequence the full-length cDNA sequence of POL was cloned. Subsequent phylogenetic analysis and molecular modeling revealed that POL belonged to the Galanthus nivalis agglutinin (GNA)-related lectin family, which acquired unique mannose-binding specificity. The hemagglutinating activities of POL were metal ion-independent, and were stable within certain range of pH and temperature alterations. Moreover, POL showed remarkable anti-HSV-II activity towards Vero cells, cytotoxicity towards human melanoma A375 cells and induced apoptosis in a caspase-dependent manner.

The role of nutraceutical proteins and peptides in apoptosis, angiogenesis, and metastasis of cancer cells

The process of carcinogenesis is complex and not easy to eliminate. It includes the initial occurrence of genetic alterations which can lead to the inactivation of tumor-suppressor genes and further accumulation of genetic alterations during tumor progression. Looking for food and food components with biological properties, collectively called nutraceuticals, that can hinder such alterations and prevent the inactivation of tumor-suppressor genes is a very promising area for cancer prevention. Proteins and peptides are one group of nutraceuticals that show potential results in preventing the different stages of cancer including initiation, promotion, and progression. In this review, we summarized current knowledge on the use of nutraceutical proteins and peptides in cancer prevention and treatment. We focused on the role of plant protease inhibitors, lactoferrin and lactoferricin, shark cartilage, plant lectins, and lunasin in the apoptosis, angiogenesis, and metastasis of cancer cells. Also included are studies on bioavailability and clinical trials conducted on these promising proteins and peptides.

Polygonatum cyrtonema lectin induces murine fibrosarcoma L929 cell apoptosis via a caspase-dependent pathway as compared to Ophiopogon japonicus lectin

Galanthus nivalis agglutinin (GNA)-related lectin family, a superfamily of strictly mannose-binding specific lectins, has been well-known to possess several biological functions including apoptosis-inducing activities. However, the precise mechanisms of GNA-related lectins to induce apoptosis remains to be clarified. In this study, we showed that Polygonatum cyrtonema lectin (PCL) and Ophiopogon japonicus lectin (OJL), the two mannose-binding GNA-related lectins, could induce murine fibrosarcoma L929 cell apoptosis. In addition, we found that there was a close link between their sugar-binding and apoptosis-inducing activities. Interestingly, we further confirmed that the mechanism of lectin-induced apoptosis was a caspase-dependent pathway. Moreover, we found that the two lectins could amplify tumor necrosis factor α (TNFα)-induced apoptosis. Taken together, these findings would open a new perspective for GNA-related lectins as potential anti-tumor agents.

Lectins: production and practical applications

Lectins are proteins found in a diversity of organisms. They possess the ability to agglutinate erythrocytes with known carbohydrate specificity since they have at least one non-catalytic domain that binds reversibly to specific monosaccharides or oligosaccharides. This articles aims to review the production and practical applications of lectins. Lectins are isolated from their natural sources by chromatographic procedures or produced by recombinant DNA technology. The yields of animal lectins are usually low compared with the yields of plant lectins such as legume lectins. Lectins manifest a diversity of activities including antitumor, immunomodulatory, antifungal, HIV-1 reverse transcriptase inhibitory, and anti-insect activities, which may find practical applications. A small number of lectins demonstrate antibacterial and anti-nematode activities.

Evolutionary history and stress regulation of the lectin superfamily in higher plants

BACKGROUND

Lectins are a class of carbohydrate-binding proteins. They play roles in various biological processes. However, little is known about their evolutionary history and their functions in plant stress regulation. The availability of full genome sequences from various plant species makes it possible to perform a whole-genome exploration for further understanding their biological functions.

RESULTS

Higher plant genomes encode large numbers of lectin proteins. Based on their domain structures and phylogenetic analyses, a new classification system has been proposed. In this system, 12 different families have been classified and four of them consist of recently identified plant lectin members. Further analyses show that some of lectin families exhibit species-specific expansion and rapid birth-and-death evolution. Tandem and segmental duplications have been regarded as the major mechanisms to drive lectin expansion although retrogenes also significantly contributed to the birth of new lectin genes in soybean and rice. Evidence shows that lectin genes have been involved in biotic/abiotic stress regulations and tandem/segmental duplications may be regarded as drivers for plants to adapt various environmental stresses through duplication followed by expression divergence. Each member of this gene superfamily may play specialized roles in a specific stress condition and function as a regulator of various environmental factors such as cold, drought and high salinity as well as biotic stresses.

CONCLUSIONS

Our studies provide a new outline of the plant lectin gene superfamily and advance the understanding of plant lectin genes in lineage-specific expansion and their functions in biotic/abiotic stress-related developmental processes.

A lectin with anti-HIV-1 reverse transcriptase, antitumor, and nitric oxide inducing activities from seeds of Phaseolus vulgaris cv. extralong autumn purple bean

Lectins/hemagglutinins are a class of sugar-binding proteins which agglutinate cells and/or precipitate glycoconjugates. They occur widely in plants but manifest significant differences in activities, which means only a few of them own exploitable potentials. The objective of this study was to find and characterize a multifunctional plant lectin with high potential values in food chemistry and medicine. A 60-kDa lectin from Phaseolus vulgaris L. cv. Extralong Autumn Purple Bean (EAPL) was purified by liquid chromatography, and the sequence of its first 20 N-terminal amino acids was ANEIYFSFQRFNETNLILQR. It was galactose-specific and manifested hemagglutinating activity toward erythrocytes of rabbit, rat, mouse, and human ABO blood types. EAPL manifested anti-HIV-1-RT activity, and it could inhibit the proliferation of human tumor cells by inducing the production of apoptotic bodies. The nitric oxide-inducing activity of EAPL may find application in tumor therapy.

Antiproliferation and apoptosis of human tumor cell lines by a lectin (AMML) of Astragalus mongholicus

A lectin (AMML) from the roots of Astragalus mongholicus was extracted and purified by affinity chromatographic technique. Human cervical carcinoma cell line (HeLa), human osteoblast-like cell line (MG63) and human leukemia cell line (K562) were used to check the effects of AMML on cell proliferation, apoptosis and cell cycle. Maximum growth inhibition (92%) was observed with HeLa cells, followed by K562 cells (84%) and MG63 (48%) cells. Morphological observation showed that AMML-treated HeLa cells displayed outstanding apoptosis characteristics, such as nuclear fragmentation and appearance of membrane-enclosed apoptotic bodies. The apoptosis of HeLa cells was confirmed by flow cytometry using Annexin V/FITC and propidium iodide (PI) staining technique. For the first time we also report a significant cell cycle arrest at S phase of HeLa cells by AMML. Therefore, the present investigation may lead to the possible therapeutic use of Astragalus mongholicus lectin.

Bioinformatics analyses of the mannose-binding lectins from Polygonatum cyrtonema, Ophiopogon japonicus and Liparis noversa with antiproliferative and apoptosis-inducing activities

In the present study, three typical monocot mannose-binding lectins (e.g., Polygonatum cyrtonema lectin [PCL], Ophiopogon japonicus lectin [OJL] and Liparis noversa lectin [LNL]), were reported to possess a similar tertiary structure with three mannose-binding sites and a close phylogenetic relationship. Subsequently, these lectins were found to bear remarkable inhibitory effects on the growth of MCF-7 cells. Further experiments confirmed that there is a link among the hemagglutinating activity, antiproliferative activity and mannose-binding activity. In addition, these lectins were shown to induce MCF-7 cell apoptosis and caspase was found to be involved in this apoptotic pathway. In conclusion, these findings demonstrate that the different antiproliferative effects may be due to the conserved motifs of mannose-binding sites. Furthermore, our results demonstrate that these lectins induce apoptosis in MCF-7 cells via a caspase-dependent pathway.

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.