In vitro influence of Phaseolus vulgaris, Griffonia simplicifolia, concanavalin A, wheat germ, and peanut agglutinins on HCT-15, LoVo, and SW837 human colorectal cancer cell growth

Plant-Derived Food Grade Substances (PDFGS) Active Against Respiratory Viruses: A Systematic Review of Non-clinical Studies

Human diet comprises several classes of phytochemicals some of which are potentially active against human pathogenic viruses. This study examined available evidence that identifies existing food plants or constituents of edible foods that have been reported to inhibit viral pathogenesis of the human respiratory tract. SCOPUS and PUBMED databases were searched with keywords designed to retrieve articles that investigated the effect of plant-derived food grade substances (PDFGS) on the activities of human pathogenic viruses. Eligible studies for this review were those done on viruses that infect the human respiratory tract. Forty six (46) studies met the specified inclusion criteria from the initial 5,734 hits. The selected studies investigated the effects of different PDFGS on the infectivity, proliferation and cytotoxicity of different respiratory viruses including influenza A virus (IAV), influenza B virus (IBV), Respiratory syncytial virus (RSV), human parainfluenza virus (hPIV), Human coronavirus NL63 (HCoV-NL63), and rhinovirus (RV) in cell lines and mouse models. This review reveals that PDFGS inhibits different stages of the pathological pathways of respiratory viruses including cell entry, replication, viral release and viral-induced dysregulation of cellular homeostasis and functions. These alterations eventually lead to the reduction of virus titer, viral-induced cellular damages and improved survival of host cells. Major food constituents active against respiratory viruses include flavonoids, phenolic acids, tannins, lectins, vitamin D, curcumin, and plant glycosides such as glycyrrhizin, acteoside, geniposide, and iridoid glycosides. Herbal teas such as guava tea, green and black tea, adlay tea, cistanche tea, kuding tea, licorice extracts, and edible bird nest extracts were also effective against respiratory viruses in vitro. The authors of this review recommend an increased consumption of foods rich in these PDFGS including legumes, fruits (e.g berries, citrus), tea, fatty fish and curcumin amongst human populations with high prevalence of respiratory viral infections in order to prevent, manage and/or reduce the severity of respiratory virus infections.

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.

Lectin Isolated from Japanese Red Sword Beans (Canavalia gladiata) as a Potential Cancer Chemopreventive Agent

In this study, we investigated the chemical and biological profile of lectin isolated from Japanese red sword beans (Canavalia gladiata; RSBs). RSB lectin was purified using maltamyl-Sepharose 4B and subjected to amino acid composition and partial amino acid sequencing analyses, and evaluated for blood and carbohydrate specificity, mitogenic activity, splenic natural killer (NK) cell activity, and its effect on B16 melanoma cell proliferation, compared with Concanavalin A (Con A). The amino acid composition and sequences of RSB lectin were similar to those of Con A. RSB lectin showed specificity to mannose, glucose, maltose, methyl-D-mannoside, and thyroglobulin, but not rhamnose, using mouse, sheep, and rabbit erythrocytes. Compared with Con A, RSB lectin showed low resistance to proteases and to temperatures greater than 70 °C, but high mitogenic activity for mouse splenic cells. Notably, while treatment with RSB lectin and Con A (0.01 and 0.1 μg/mL) promoted similar levels of splenic NK cell activity, which were higher than that observed in the control (0 μg/mL) and interleukin 2 (IL-2) (25 U)-treated populations, RBS lectin exerted a significantly stronger anti-proliferative effect than Con A at a concentration of 125.0 μg per well. Overall, our results show that RSB lectin might exert immunological effects on mouse splenic cells and could thus be used as a potential cancer chemopreventive agent.

PRACTICAL APPLICATION

Japanese red sword bean (RSB) is a tropical perennial legume consumed in many Asian countries. RSB lectin shows specificity to mannose, glucose, maltose, methyl-d-mannoside, and thyroglobulin, but not to rhamnose, using mouse, sheep, and rabbit erythrocytes. RSB lectin exhibits similarities to Concanavalin A in amino acid composition and sequence, shows mitogenic activity for mouse splenic cells and strong anti-proliferative activity for B16 melanoma cells, and also enhances the activity of splenic natural killer (NK) cells against YAC-1 cells. Thus, RSB lectin has the potential to be used as a bioactive protein in medical research.

Dairy propionibacteria prevent the proliferative effect of plant lectins on SW480 cells and protect the metabolic activity of the intestinal microbiota in vitro

Plant lectins are specific carbohydrate-binding proteins that are widespread in legumes such as beans and pulses, seeds, cereals, and many plants used as farm feeds. They are highly resistant to cooking and digestion, reaching the intestinal lumen and/or blood circulation with biological activity. Since many legume lectins trigger harmful local and systemic reactions after their binding to the mucosal surface, these molecules are generally considered anti-nutritive and/or toxic substances. In the gut, specific cell receptors and bacteria may interact with these dietary components, leading to changes in intestinal physiology. It has been proposed that probiotic microorganisms with suitable surface glycosidic moieties could bind to dietary lectins, favoring their elimination from the intestinal lumen or inhibiting their interaction with epithelial cells. In this work, we assessed in vitro the effects of two representative plant lectins, concanavalin A (Con A) and jacalin (AIL) on the proliferation of SW480 colonic adenocarcinoma cells and metabolic activity of colonic microbiota in the absence or presence of Propionibacterium acidipropionici CRL 1198. Both lectins induced proliferation of colonic cells in a dose-dependent manner, whereas ConA inhibited fermentative activities of colonic microbiota. Pre-incubation of propionibacteria with lectins prevented these effects, which could be ascribed to the binding of lectins by bacterial cells since P. acidipropionici CRL 1198 was unable to metabolize these proteins, and its adhesion to colonic cells was reduced after reaction with Con A or AIL. The results suggest that consumption of propionibacteria at the same time as lectins could reduce the incidence of lectin-induced alterations in the gut and may be a tool to protect intestinal physiology.

A hemagglutinin isolated from Northeast China black beans induced mitochondrial dysfunction and apoptosis in colorectal cancer cells

Incidence of colorectal cancer is closely related with the lifestyle, especially the dietary habits of patients. Epidemiological researches have demonstrated a negative correlation between legume consumption and colorectal cancer incidence. Lectins/hemagglutinins are a type of carbohydrate binding proteins which are abundantly stored in legumes. Their eminent pH-stability allows them to survive digestion and remain active in the intestine where they may have direct contact with colorectal tumors. It is therefore interesting to explore the direct interaction between lectins/hemagglutinins and colorectal cancer. In the present research, we reported a detailed research on the interaction between a hemagglutinin isolated from an edible legume with two colorectal cancer cell lines. This hemagglutinin (NCBBH) was found to first bind to tumor cell membrane as early as 30min post treatment and was gradually transported inside the cytoplasm within 3h, with some of it localized in the Golgi apparatus and some in the lysosomes. After its entrance, the hemagglutinin induced aggregation of the Golgi apparatus, which in turn adversely affected the transportation of protein from endoplasmic reticulum (ER) to the Golgi apparatus, resulting in protein accumulation in ER and ER stress. The hemagglutinin-treated cells also manifested severe mitochondrial malformation and membrane depolarization, accompanied by obvious apoptosis characteristics, like chromatin condensation, phosphatidylserine exposure and caspase activation. Collectively, our results indicate that the hemaggltuinin could successfully enter the cytoplasm of colorectal cancer cells and adversely affect their growth, providing a mechanism in support of the application of edible legumes to the prevention and treatment of colorectal cancer.

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.

A hemagglutinin from northeast red beans with immunomodulatory activity and anti-proliferative and apoptosis-inducing activities toward tumor cells

A 64-kDa hemagglutinin from a Phaseolus vulgaris cultivar, the northeast red bean, was purified by a protocol composed of three chromatographic steps involving affinity chromatography on Affi-gel blue gel, cation exchange chromatography on SP-Sepharose and FPLC-gel filtration on Superdex 75. The purified hemagglutinin appeared as a single 32-kDa band in SDS-PAGE indicating its dimeric nature. The N-terminal amino acid sequence of the hemagglutinin resembled the sequences of lectins and hemagglutinins from a number of Phaseolus species. The hemagglutinin manifested moderate thermostability and pH stability. It retained full activity up to 65 °C and in the pH range 2-12. It did not interact with simple sugars such as glucose, mannose and galactose. The hemagglutinin exerted immunostimulatory effects by upregulating the expression of cytokines like interferon-γ and tumor necrosis factor-α. It also exhibited antiproliferative activity on a number of tumor cells including MCF7 (breast cancer), HepG2 (liver cancer), CNE1 and CNE2 (nasopharyngeal cancer) cells, with stronger activity toward MCF7 and CNE1 cells. The hemagglutinin induced phophatidylserine externalization, mitochondrial depolarization and DNA condensation in MCF7 cells, indicating initiation of apoptosis. However, at high hemagglutinin concentrations, severe damage to the MCF7 cells was detected.

A characterization of four B16 murine melanoma cell sublines molecular fingerprint and proliferation behavior

Background

One of the most popular and versatile model of murine melanoma is by inoculating B16 cells in the syngeneic C57BL6J mouse strain. A characterization of different B16 modified cell sub-lines will be of real practical interest. For this aim, modern analytical tools like surface enhanced Raman spectroscopy/scattering (SERS) and MTT were employed to characterize both chemical composition and proliferation behavior of the selected cells.

Methods

High quality SERS signal was recorded from each of the four types of B16 cell sub-lines: B164A5, B16GMCSF, B16FLT3, B16F10, in order to observe the differences between a parent cell line (B164A5) and other derived B16 cell sub-lines. Cells were incubated with silver nanoparticles of 50–100 nm diameter and the nanoparticles uptake inside the cells cytoplasm was proved by transmission electron microscopy (TEM) investigations. In order to characterize proliferation, growth curves of the four B16 cell lines, using different cell numbers and FCS concentration were obtained employing the MTT proliferation assay. For correlations doubling time were calculated.

Results

SERS bands allowed the identification inside the cells of the main bio-molecular components such as: proteins, nucleic acids, and lipids. An "on and off" SERS effect was constantly present, which may be explained in terms of the employed laser power, as well as the possible different orientations of the adsorbed species in the cells in respect to the Ag nanoparticles. MTT results showed that among the four tested cell sub-lines B16 F10 is the most proliferative and B164A5 has the lower growth capacity. Regarding B16FLT3 cells and B16GMCSF cells, they present proliferation ability in between with slight slower potency for B16GMCSF cells.

Conclusion

Molecular fingerprint and proliferation behavior of four B16 melanoma cell sub-lines were elucidated by associating SERS investigations with MTT proliferation assay.

Phytochemical composition, anti-inflammatory, and antiproliferative activity of whole wheat flour

Whole wheat flour from five wheat cultivars was evaluated for phenolic, carotenoid, and tocopherol compositions as well as anti-inflammatory and antiproliferative activities against HT-29 cells. The total ferulic acid content ranged from 452 to 731 μg/g among the five cultivars and was primarily present in the insoluble-bound form. Lutein was the only carotenoid detected and ranged from 1.5 to 4.0 μg/g, and α-tocopherol levels ranged from 12 to 61 μg/g. Extracts of four cultivars demonstrated significant anti-inflammatory activity, measured as inhibition of interleukin-1β (IL-1β) mRNA expression; however, none of the extracts inhibited tumor necrosis factor-α (TNF-α) mRNA expression, a second indicator of anti-inflammatory activity. Proliferation of HT-29 adenocarcinoma cells was inhibited by extracts from all cultivars at the dose of 100 mg botanical equivalent/mL. The cultivar WestBred 936 had the greatest antiproliferative activity at lower concentrations (20 and 50 mg botanical equivalent/mL), had the greatest anti-inflammatory effect against IL-1β, and also had the highest levels of ferulic acid and α-tocopherol. This research shows that whole wheat flours of these five cultivars varied significantly in their contents of phenolics, carotenoids, and α-tocopherol as well as in their anti-inflammatory and antiproliferative potentials, suggesting the possibility that wheat varieties can be selected based on potential health benefits.

Effects of Tepary bean (Phaseolus acutifolius) protease inhibitor and semipure lectin fractions on cancer cells

Some natural and synthetic protease inhibitors (PI), such as the Bowman-Birk PI from soybean, have anticancer effects. We previously purified and characterized a Bowman-Birk-type PI from Tepary bean (Phaseolus acutifolius) seeds (TBPI). A semipure protein fraction containing this inhibitor, when tested its in vitro effect on transformed cells, showed a differential cytotoxic effect, as well as an increase in cell attachment to culture dishes. In this article we report that lectins were responsible for the cytotoxic effect previously observed, exhibiting a differential, antiproliferative effect on nontransformed cells and on different lineages of cancer cells. Although the purified TBPI lacked cytotoxicity, it was found to be responsible for the increase in cell adhesion, decreasing culture dishes' extracellular matrix degradation, leading to a decrease of the in vitro cell invasion capacity. This effect coincided with the suppression of Matrix Metalloproteinase-9 activity. These results indicate that Tepary bean seeds contain at least 2 different groups of bioactive proteins with distinct effects on cancer cells.

Astragalus membranaceus lectin (AML) induces caspase-dependent apoptosis in human leukemia cells

OBJECTIVES

Recently, plant lectins have attracted great interest due to their various biological activities such as anti-cancer, anti-fungal and anti-viral activities. We have reported earlier concerning anti-proliferation of human cancer cell lines by a galactose-binding lectin (AML), from a Chinese herb, ASTRAGALUS MEMBRANACEUS: In the present study, detailed investigations into the mechanism of such anti-proliferation properties have been carried out.

MATERIALS AND METHODS

Mechanism of apoptosis initiation in K562 cells by AML was investigated by morphology, flow cytometry and western blot analysis.

RESULTS

AML induced apoptosis in a caspase-dependent manner in the chronic myeloid leukemia cell line, K562. Furthermore, we observed that cytotoxicity and apoptosis of K562 cells induced by AML were completely abolished in presence of lactose or galactose.

CONCLUSIONS

Our results suggest that AML could act as a potential anti-cancer drug.

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.

Induction of the mitochondria apoptosis pathway by phytohemagglutinin erythroagglutinating in human lung cancer cells

BACKGROUND

Deregulation of apoptosis will influence the balance of cell proliferation and cell death, resulting in various fatal diseases that can include cancer. In prior research reports related to cancer therapy, phytohemagglutinin, a lectin extracted from red kidney beans, demonstrated the ability to inhibit the growth of human cancer cells. However, one of its isoforms, erythroagglutinating, has yet to be evaluated on its anticancer effects.

METHODS

PHA-E was used to induce apoptosis of A-549 lung cancer cells and the possible signal transduction pathway was elucidated, as measured by the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay, G6PD release assay, flow cytometry, and Western blot analysis.

RESULTS

PHA-E treatment caused a dose-dependent increase of cell growth inhibition and cytotoxicity on A-549 cells. In annexin V/propidium iodide [i.e., PI] and TUNEL (terminal deoxynucleotidyl transferase dUTP nick-end labeling)/PI assay, we found that the rate of apoptotic cells was raised as the concentration of PHA-E increased. Treatment of A-549 cells with PHA-E resulted in enhancing the release of cytochrome c, which thus activated an increase in caspase 9 and caspase 3, the upregulation of Bax and Bad, the downregulation of Bcl-2 and phosphorylated Bad, and finally the inhibition of the epidermal growth factor receptor and its downstream signal pathway PI3K/Akt and MEK/ERK.

CONCLUSIONS

PHA-E can induce growth inhibition and cytotoxicity of lung cancer cells, which is mediated through an activation of the mitochondria apoptosis pathway. These results suggest that PHA-E can be developed into a new therapeutic treatment that can be applied as an effective anti-lung cancer drug in the near future.

Purification of lectin from larvae of the fly, Musca domestica, and in vitro anti-tumor activity in MCF-7 cells

A new lectin was purified from larvae of the fly, Musca domestica L. (Diptera: Muscidae) (MLL-2, 38 kDa) using affinity chromatography and HPLC. Anti-tumor activity of MLL-2 was demonstrated by its inhibition of proliferation of human breast cancer (MCF-7) cells in a time-and dose-dependent manner. The results of acridine orange staining indicated that MLL-2 caused apoptosis in MCF-7 cells. DNA fragmentation in MCF-7 cells has been detected by TUNEL. Flow cytometric analysis also demonstrated that MLL-2 caused dose-dependent apoptosis of MCF-7 cells through cell arrest at G2/M phase. The MLL-2 induced a sustained increase in concentration of intracellular free calcium. Western blot revealed that MLL-2 induced apoptosis in MCF-7 cells was associated with typical apoptosis proteins in the mitochondrial pathway. In addition, the caspase-3 activity in MCF-7 cells treated with MLL-2 for 48 hours was significantly increased compared to controls (407.4 ± 3.0 vs. 1749.2 ± 6.0, P <0.01). Since MLL-2 induced apoptosis in MCF-7cells the mitochondrial pathway may be the main pathway of antitumor activity.

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.

Lectin-mediated cytotoxicity and specificity of 5-fluorouracil conjugated with peanut agglutinin (5-Fu-PNA)in vitro

In order to take advantage of the biorecognition between lectin and carbohydrate for targeted drug delivery, the lectin of peanut (Arachis hypogaea) agglutinin (PNA) was coupled by fixing its amino groups to the carbodiimide-activated carboxylic groups of 5-fluorouracil (5-Fu) derivative (N1-substituted 5-Fu acetate) to form 5-Fu-PNA conjugate. When the coupling reaction was carried out in the presence of d-galactose (d-gal, specific sugar for PNA), the affinity of PNA was maintained after its coupling to N1-substituted 5-Fu acetate, which was confirmed by the result of the haemagglutination test. Otherwise, PNA would lose its affinity after the cross-linking reaction. The cytotoxicity, specificity and selectivity of 5-Fu-PNA were examined on the human colorectal cancer cell line LoVo and the human normal liver cell line Chang using MTT assay. Compared with free drug, the active conjugate, which maintained the affinity of lectin, had similar cytotoxic effect on LoVo cells with much lower cytotoxicity on Chang cells On the other hand, lower cytotoxic effects on LoVo cells were observed for the non-active conjugate even at higher drug concentrations. The cytotoxic effect of conjugate was specific because only the active conjugate could inhibit the growth of LoVo cells in a dose- and time-dependent manner as that of the free drug. The achieved results indicate the significance to maintain the affinity of lectin for lectin-mediated cytotoxicity. Still, the potential of 5-Fu-PNA conjugate as a targeting agent for colorectal cancer needs to be further investigated in vivo.

Lectin binding and effects in culture on human cancer and non-cancer cell lines: examination of issues of interest in drug design strategies

By using a non-cancer and a cancer cell line originally from the same tissue (colon), coupled with testing lectins for cell binding and for their effects on these cell lines in culture, this study describes a simple multi-parameter approach that has revealed some interesting results that could be useful in drug development strategies. Two human cell lines, CCL-220/Colo320DM (human colon cancer cells, tumorigenic in nude mice) and CRL-1459/CCD-18Co (non-malignant human colon cells) were tested for their ability to bind to agarose microbeads derivatized with two lectins, peanut agglutinin (Arachis hypogaea agglutinin, PNA) and Dolichos biflorus agglutinin (DBA), and the effects of these lectins were assessed in culture using the MTT assay. Both cell lines bound to DBA-derivatized microbeads, and binding was inhibited by N-acetyl-D-galactosamine, but not by L-fucose. Neither cell line bound to PNA-derivatized microbeads. Despite the lack of lectin binding using the rapid microbead method, PNA was mitogenic in culture at some time points and its mitogenic effect displayed a reverse-dose response. This was also seen with effects of DBA on cells in culture. While this is a simple study, the results were statistically highly significant and suggest that: (1) agents may not need to bind strongly to cells to exert biological effects, (2) cell line pairs derived from diseased and non-diseased tissue can provide useful comparative data on potential drug effects and (3) very low concentrations of potential drugs might be initially tested experimentally because reverse-dose responses should be considered.

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.

Upregulation of galectins-1 and -3 in human colon cancer and their role in regulating cell migration

To probe the potential contribution of beta-galactoside-contributing epitopes and receptor proteins (gal-1 and gal-3) to colon malignancy, we first examined the expression of galectins and binding sites in clinical specimens by lectin and immunohistochemistry. Sixty-seven colonic surgical resections were studied, including 10 normal, 10 mild dysplasias, 10 severe dysplasias and 37 cancers. gal-1 and gal-3 were expressed in variable amounts in the epithelial cells and the connective tissue of normal colon. Their expression significantly increased with the degree of dysplasia, suggesting that gal-1 and gal-3 and their binding sites are related to malignant progression, while gal-8 has been associated with suppressor activity. To study the functional aspects, the influence of these galectins on the migration of 4 human colorectal cancer cell lines (HCT-15, LoVo, DLD-1, CoLo201) was studied. In agreement with histopathologic monitoring, these tumor cells were found to produce gal-3, while only CoLo201 was positive for gal-1. Except for DLD-1 and gal-1, the lines exhibited gal-1 binding sites on the surface, prompting study by computer-assisted videomicroscopy of the effect on cell migration of the presence of galectin on the culture substrate. The level of cell migration for HCT-15, LoVo and CoLo201 cells was significantly reduced by 0.15 microg/cm(2) gal-1, and the presence of a blocking antibody at least reduced this effect. gal-3 significantly reduced cell migration in all 4 of the in vitro cell lines.

Influencing receptor-ligand binding mechanisms with multivalent ligand architecture

Multivalent ligands can function as inhibitors or effectors of biological processes. Potent inhibitory activity can arise from the high functional affinities of multivalent ligand-receptor interactions. Effector functions, however, are influenced not only by apparent affinities but also by alternate factors, including the ability of a ligand to cluster receptors. Little is known about the molecular features of a multivalent ligand that determine whether it will function as an inhibitor or effector. We envisioned that, by altering multivalent ligand architecture, ligands with preferences for different binding mechanisms would be generated. To this end, a series of 28 ligands possessing structural diversity was synthesized. This series provides the means to explore the effects of ligand architecture on the inhibition and clustering of a model protein, the lectin concanavalin A (Con A). The structural parameters that were varied include scaffold shape, size, valency, and density of binding elements. We found that ligands with certain architectures are effective inhibitors, but others mediate receptor clustering. Specifically, high molecular weight, polydisperse polyvalent ligands are effective inhibitors of Con A binding, whereas linear oligomeric ligands generated by the ring-opening metathesis polymerization have structural properties that favor clustering. The shape of a multivalent ligand also influences specific aspects of receptor clustering. These include the rate at which the receptor is clustered, the number of receptors in the clusters, and the average interreceptor distance. Our results indicate that the architecture of a multivalent ligand is a key parameter in determining its activity as an inhibitor or effector. Diversity-oriented syntheses of multivalent ligands coupled with effective assays that can be used to compare the contributions of different binding parameters may afford ligands that function by specific mechanisms.

Galectin-8 expression decreases in cancer compared with normal and dysplastic human colon tissue and acts significantly on human colon cancer cell migration as a suppressor

BACKGROUND AND AIMS

Galectins are beta-galactoside binding proteins. This ability may have a bearing on cell adhesion and migration/proliferation in human colon cancer cells. In addition to galectins-1 and -3 studied to date, other members of this family not investigated in detail may contribute to modulation of tumour cell features. This evident gap has prompted us to extend galectin analysis beyond the two prototypes. The present study deals with the quantitative determination of immunohistochemical expression of galectin-8 in normal, benign, and malignant human colon tissue samples and in four human colon cancer models (HCT-15, LoVo, CoLo201, and DLD-1) maintained both in vitro as permanent cell lines and in vivo as nude mice xenografts. The role of galectin-8 (and its neutralising antibody) in cell migration was investigated in HCT-15, LoVo, CoLo201, and DLD-1 cell lines.

METHODS

Immunohistochemical expression of galectin-8 and its overall ability to bind to sugar ligands (revealed glycohistochemically by means of biotinylated histochemically inert carrier bovine serum albumin with alpha- and beta-D-galactose, alpha-D-glucose, and lactose derivatives as ligands) were quantitatively determined using computer assisted microscopy. The presence of galectin-8 mRNA in the four human colon cancer cell lines was examined by reverse transcriptase-polymerase chain reaction. In vitro, cellular localisation of exogenously added galectin-8 in the culture media of these colon cancer cells was visualised by fluorescence microscopy. In vitro galectin-8 mediated effects (and the influence of its neutralising antibody) on migration levels of living HCT-15, LoVo, CoLo201, and DLD-1 cells were quantitatively determined by computer assisted phase contrast microscopy.

RESULTS

A marked decrease in immunohistochemical expression of galectin-8 occurred with malignancy development in human colon tissue. Malignant colon tissue exhibited a significantly lower galectin-8 level than normal or benign tissue colon cancers; those with extensive invasion capacities (T3-4/N+/M+) harboured significantly less galectin-8 than colon cancers with localised invasion capacities (T1-2/N0/M0). The four experimental models (HCT-15, LoVo, CoLo201, and DLD-1) had more intense galectin-8 dependent staining in vitro than in vivo. Grafting the four experimental human colon cancer models onto nude mice enabled us to show that the immunohistochemical expression of galectin-8 was inversely related to tumour growth rate. In vitro, galectin-8 reduced the migration rate of only those human experimental models (HCT-15 and CoLo201) that exhibited the lowest growth rate in vivo.

CONCLUSIONS

Expression of galectin-8 correlated with malignancy development, with suppressor activity, as shown by analysis of clinical samples and xenografts. In vitro, only the two models with low growth rates were sensitive to the inhibitory potential of this galectin. Future investigations in this field should involve fingerprinting of these newly detected galectins, transcending the common focus on galectins-1 and -3.

The cytotoxic effect of mistletoe lectins I, II and III on sensitive and multidrug resistant human colon cancer cell lines in vitro

Multidrug resistance glycoprotein1 (MDR-1) eliminates amphiphilic chemotherapeutic agents out of tumour cells leading to therapeutic failures. The aim of this study was to investigate the cytotoxic effect of mistletoe lectins (MLs) I, II and III on the sensitive human colon cancer cell line HT 29(mdr-), its multidrug resistant variant HT 29(mdr+), the variant HT 29(SF1m) transfected with the MDR-1 gene and its sensitive control cell line HT 29(deltaSF). Both cell proliferation and ML binding pattern were analysed. Marked quantitative differences concerning the cytotoxic effect of the three MLs on the different cell lines were observed. All MLs showed the greatest cytotoxicity towards the HT 29(mdr+) cells, in which multidrug resistance (MDR) was induced by increasing concentrations of a MDR inducing agent. In contrast, MDR-1 and mock-transfected cells showed almost the same sensitivity towards the three MLs as the control cells (HT 29(mdr-)). FACS analysis showed that the HT 29(mdr+) cells were the cells with the highest density of ML binding sites. Thus, higher sensitivity of HT 29(mdr+) cells are not caused by the overexpression of MDR-1, but are caused by the general changes of the cellular glycosylation during the acquisition of the MDR phenotype.

Effect of BJcuL (a lectin from the venom of the snake Bothrops jararacussu) on adhesion and growth of tumor and endothelial cells

Lectins are polyvalent carbohydrate-binding proteins of non-immune origin. Recently, we have isolated and characterized a lectin from the venom of the snake Bothrops jararacussu. This lectin (BJcuL) has been shown to bind to lactose moieties and induce agglutination of erythrocytes. In the present work, we observed that cells from human metastatic breast cancer (MDA-MB-435) and human ovarian carcinoma (OVCAR-5) cell lines adhere, although weakly, to BJcuL. However, BJcuL did not inhibit adhesion of these cells to the extracellular matrix proteins fibronectin, laminin and type I collagen. Importantly, viability of these tumor cells and cells from other human tumor cell lines and a bovine brain endothelial cell line was suppressed by BJcuL. These findings suggest that the lectin BJcuL may serve as an interesting tool for combating tumor progression by inhibiting tumor cell and endothelial cell growth.

Lectin histochemistry as a predictor of dysplasia grade in colorectal adenomas

Lectins are sugar-binding proteins that bind to specific cellular carbohydrates, commonly affecting cellular physiology. Phaseolus vulgaris leucoagglutinin (PHA), ulex europaeus isoagglutinin-I (UEA-I), wheat germ agglutinin (WGA) and peanut agglutinin (PNA) are among the most well studied lectins in various tissues. The purpose of this study was to detect the above lectins binding sites and so examine alterations in glycoconjugate expression in neoplastic cells of 52 colorectal adenomas with various clinicopathologic characteristics and proliferation rates. Lectin histochemistry was performed in paraffin sections with and without neuraminidase treatment. Proliferative fraction was determined by immunolabelling for Proliferating Cell Nuclear Antigen. PHA was the more frequently positive lectin in the examined specimens; however, it was simultaneously detected in normal colonic mucosa and so was WGA. The frequency of high grade dysplasia was significantly greater in older patients and in samples with UEA-I positivity without neuraminidase pretreatment. UEA-I-reactive adenomas were generally characterized by high cell proliferation rates. A statistical model based on patients age and UEA-I binding without neuraminidase treatment can generally predict grade of dysplasia in 83% of adenomas and particularly high grade dysplasia in up to 93% of adenomas; so, such a model may be potentially useful for the early detection of neoplasia, for instance in exfoliative cells from the large intestine.

Vicia faba agglutinin, the lectin present in broad beans, stimulates differentiation of undifferentiated colon cancer cells

BACKGROUND

Dietary lectins can alter the proliferation of colonic cells. Differentiation is regulated by adhesion molecules which, being glycosylated, are targets for lectin binding.

AIMS

To examine the effects of dietary lectins on differentiation, adhesion, and proliferation of colorectal cancer cells.

METHODS

Differentiation was assessed in three dimensional gels, adhesion by aggregation assay, and proliferation by 3H thymidine incorporation. The role of the epithelial cell adhesion molecule (epCAM) was studied using a specific monoclonal antibody in blocking studies and Western blots. The human colon cancer cell lines LS174T, SW1222, and HT29 were studied.

RESULTS

The cell line LS174T differentiated in the presence of Vicia faba agglutinin (VFA) into gland like structures. This was inhibited by anti-epCAM monoclonal antibody. Expression of epCAM itself was unaffected. VFA as well as wheat germ agglutinin (WGA) and the edible mushroom lectin (Agaricus bisporus lectin, ABL) significantly aggregated LS174T cells but peanut agglutinin (PNA) and soybean agglutinin (SBA) did not. All lectins aggregated SW1222 and HT29 cells. Aggregation was blocked by the corresponding sugars. Aggregation of cells by VFA was also inhibited by anti-epCAM. VFA, ABL, and WGL inhibited proliferation of all the cell lines; PNA stimulated proliferation of HT29 and SW1222 cells. In competition studies all sugars blocked aggregation and proliferation of all cell lines, except that the addition of mannose alone inhibited proliferation.

CONCLUSION

VFA stimulated an undifferentiated colon cancer cell line to differentiate into gland like structures. The adhesion molecule epCAM is involved in this. Dietary or therapeutic VFA may slow progression of colon cancer.

Gastrointestinal responses to a panel of lectins in rats maintained on total parenteral nutrition

Total parenteral nutrition (TPN) causes atrophy of gastrointestinal epithelia, so we asked whether lectins that stimulate epithelial proliferation can reverse this effect of TPN. Two lectins stimulate pancreatic proliferation by releasing CCK, so we asked whether lectins that stimulate gastrointestinal proliferation also release hormones that might mediate their effects. Six rats per group received continuous infusion of TPN and a once daily bolus dose of purified lectin (25 mg. rat-1. day-1) or vehicle alone (control group) for 4 days via an intragastric cannula. Proliferation rates were estimated by metaphase arrest, and hormones were measured by RIAs. Phytohemagglutinin (PHA) increased proliferation by 90% in the gastric fundus (P < 0.05), doubled proliferation in the small intestine (P < 0.001), and had a small effect in the midcolon (P < 0.05). Peanut agglutinin (PNA) had a minor trophic effect in the proximal small intestine (P < 0.05) and increased proliferation by 166% in the proximal colon (P < 0.001) and by 40% in the midcolon (P < 0.001). PNA elevated circulating gastrin and CCK by 97 (P < 0.05) and 81% (P < 0.01), respectively, and PHA elevated plasma enteroglucagon by 69% and CCK by 60% (both P < 0.05). Only wheat germ agglutinin increased the release of glucagon-like peptide-1 by 100% (P < 0.05). PHA and PNA consistently reverse the fall in gastrointestinal and pancreatic growth associated with TPN in rats. Both lectins stimulated the release of specific hormones that may have been responsible for the trophic effects. It is suggested that lectins could be used to prevent gastrointestinal atrophy during TPN. Their hormone-releasing effects might be involved.

Differences in sialyl-Tn antigen expression between keratoacanthomas and cutaneous squamous cell carcinomas

Keratoacanthoma and squamous cell carcinoma are common skin tumors, especially in immunosuppressed transplant recipients, but the distinction between these two types of epidermal neoplasia may be difficult. Sialyl-Tn (Sia-GalNAc-O-Ser/Thr) is a cell surface carbohydrate associated with hyperplasia in squamous epithelium, and correlated with poor prognosis in several human adenocarcinomas. Twenty-seven keratoacanthomas and 29 cutaneous squamous cell carcinomas were examined for the expression of sialyl-Tn and of the Ki67 epitope, the latter a marker for cell proliferation. By immunohistochemistry, basaloid tumor cells at the periphery of tumor nests showed some degree of sialyl-Tn expression in 16 keratoacanthomas (59%), while only three squamous cell carcinomas (10%) showed sialyl-Tn-positive basaloid tumor cells (p<0.001). Keratinized, differentiated tumor cells were more often sialyl-Tn-positive in keratoacanthomas (89%) than in squamous cell carcinomas (31%) (p<0.001). A striking sialyl-Tn-positivity in the basal cell layer was found in a border zone directly adjacent to most tumors of both types (88 and 88%). By immunohistochemical examination of parallel sections and by double immunofluorescence, sialyl-Tn antigen expression was primarily seen in cells that did not express Ki67, although some overlap was present. Keratoacanthomas from transplant recipients did not differ in sialyl-Tn expression compared to those from non-immunosuppressed patients. The results indicate that sialyl-Tn expression is not directly related to cell proliferation, but rather to cellular features of post-mitotic cells, and that sialyl-Tn is not associated with a malignant phenotype. Sialyl-Tn may be linked to tumor regression, as seen in keratoacanthomas.