Tumor cell surfaces: general alterations detected by agglutinins

An update on dual targeting strategy for cancer treatment

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

Inhibition of Substrate-Tumor Cell Adhesion Under the Effect of Gnidilatimonoein Purified fromDaphne mucronata

Alteration of the cell surface glycoproteins of cancerous cells correlate with malignancy potential. To evaluate the mediation of membrane glycoproteins in wehi-164 cancerous cells, under the effect of D. mucronata crude extract and one of its purified active components, gnidilatimonoein, their attachment to fibronectin-coated wells were investigated. The plant extract, 27 μl/ml (equivalent to 0.54 mg/of plant leaves powder per ml of culture medium), as well as gnidilatimonoein (0.94 μM), were capable of quenching by 58% and 64%, respectively, the attachment of wehi-164 cells to fibronectin-coated wells (4 μg/ml). In addition to alteration of cell adhesive properties, the morphology of the treated cells were significantly changed upon treatment with the non-toxic dose of the plant extract or gnidilatimonoein. While the untreated cells have polygonal shapes, the treated cells had spherical shapes.

Paclitaxel-loaded PLGA nanoparticles: Potentiation of anticancer activity by surface conjugation with wheat germ agglutinin

PURPOSE

To potentiate the anticancer activity of paclitaxel-loaded PLGA nanoparticles through surface conjugation with wheat germ agglutinin (WGA).

METHODS

PLGA nanoparticles loaded with paclitaxel and isopropyl myristate (IPM) as release modifier were prepared by a solvent evaporation method. WGA was conjugated to the nanoparticle surface to give novel WIT-NP of 330+/-3 nm. In vitro cytotoxicity of WIT-NP against malignant (A549 and H1299) and normal (CCL-186) pulmonary cell lines was evaluated alongside control formulations. IC50 doses were determined by the MTT assay, while cellular apoptosis was detected by cell nuclei staining and DeadEndtrade mark Fluorometric TUNEL assay. Cell cycle arrest was confirmed by flow cytometry. Cellular uptake of 3[H]-paclitaxel from the test and control formulations was also quantified. In vivo anticancer efficacy was evaluated in the SCID mice model engrafted with the A549 tumor nodule.

RESULTS

WIT-NP had superior anti-proliferation activity against the A549 and H1299 cell lines compared with conventional paclitaxel formulations as measured by IC50 doses. This was attributed to a more efficient intracellular accumulation of paclitaxel via WGA-receptor-mediated endocytosis and IPM-facilitated intracellular paclitaxel release. WIT-NP activity was associated with paclitaxel-induced apoptosis and cell arrest in the G2/M phase. A single intratumoral injection of WIT-NP at paclitaxel dose of 10 mg/kg inhibited the growth of A549 tumor nodules without inducing significant weight loss in the SCID mice over a period of 25 days. Tumor doubling time was greater than 25 days, compared with 11 days for nodules treated with conventional paclitaxel formulation.

CONCLUSION

The formulation of WIT-NP, in which WGA is conjugated to the surface of paclitaxel and IPM-loaded PLGA nanoparticles, significantly potentiates the anticancer activity of paclitaxel.

Energetics of carbohydrate binding to Momordica charantia (bitter gourd) lectin: an isothermal titration calorimetric study

Physico-chemical and carbohydrate binding studies have been carried out on the Momordica charantia (bitter gourd) seed lectin (MCL). The lectin activity is maximal in the pH range 7.4-11.0, but decreases steeply below pH 7.0. The lectin activity is mostly unaffected in the temperature range 4-50 degrees C, but a sharp decrease is seen between 50 and 60 degrees C, which could be correlated to changes in the structure of the protein as seen by circular dichroism and fluorescence spectroscopy. Isothermal titration calorimetric studies show that the tetrameric MCL binds two sugar molecules and the binding constants (Kb), determined at 288.15 K, for various saccharides were found to vary between 7.3 x 10(3) and 1.52 x 10(4)M(-1). The binding reactions for all the saccharides investigated were essentially enthalpy driven, with the binding enthalpies (DeltaHb) at 288.15 K being in the range of -50.99 and -43.39 kJ mol(-1), whereas the contribution to the binding reaction from the entropy of binding was negative, with values of binding entropy (DeltaSb) ranging between -99.2 and -72.0 J mol(-1)K(-1) at 288.15 K. Changes in heat capacity (DeltaCp) for the binding of disaccharides, lactose and lactulose, were significantly larger in magnitude than those obtained for the monosaccharides, methyl-beta-D-galactopyranoside, and methyl-alpha-D-galactopyranoside, and could be correlated reasonably well with the surface areas of these ligands. Enthalpy-entropy compensation was observed for all the sugars studied, suggesting that water structure plays an important role in the overall binding reaction. CD spectroscopy indicates that carbohydrate binding does not lead to significant changes in the secondary and tertiary structures of MCL, suggesting that the carbohydrate binding sites on this lectin are mostly preformed.

Overexpression of human UDP-glucose pyrophosphorylase rescues galactose-1-phosphate uridyltransferase-deficient yeast

To better understand the pathophysiology of galactose-1-phosphate uridyltransferase (GALT) deficiency in humans, we studied the mechanisms by which a GALT-deficient yeast survived on galactose medium. Under normal conditions, GALT-deficient yeast cannot grow in medium that contains 0.2% galactose as the sole carbohydrate, a phenotype of Gal(-). We isolated revertants from a GALT-deficient yeast by direct selection for growth in galactose, a phenotype of Gal(+). Comparison of gene expression profiles among wild-type and revertant strains on galactose medium revealed that the revertant down-regulated genes encoding enzymes including galactokinase, galactose permease, and UDP-galactose-4-epimerase (the GAL regulon). By contrast, the revertant strain up-regulated the gene for UDP-glucose pyrophosphorylase, UGP1. There was reduced accumulation of galactose-1-phosphate in the galactose-grown revertant cells when compared to the GALT-deficient parent cells. In vitro biochemical analysis showed that UDP-glucose pyrophosphorylase had bifunctional properties and could catalyze the conversion of galactose-1-phosphate to UDP-galactose in the presence of UTP. To test if augmented expression of this gene could produce a Gal(+) phenotype in the GALT-deficient parent cells, we overexpressed the yeast UGP1 and the human homolog, hUGP2 in the mutant strain. The Gal(-) yeast transformed with either UGP1 or hUGP2 regained their ability to grow on galactose. We conclude that revertant can grow on galactose medium by reducing the accumulation of toxic precursors through down-regulation of the GAL regulon and up-regulation of the UGP1 gene. We speculate that increased expression of hUGP2 in humans could alleviate poor outcomes in humans with classic galactosemia.

The hyperinsulinemia produced by concanavalin A in rats is opioid-dependent and hormonally regulated

The present study examines the effect of concanavalin A (Con A) on the blood insulin and glucose levels of rats. Male and female rats treated with Con A (62.5-500 micrograms/kg) for three days showed a dose- and time-dependent hyperinsulinemia that lasted more than 48 h. Male rats were more sensitive to Con A. Thus, 6 h after treatment with Con A the circulating insulin levels in male rats had increased by 85% (control: 10.2 +/- 0.9 mU/l and Con A-treated: 18.8 +/- 1 mU/l) compared to only 38% (control: 7.5 +/- 0.2 mU/l; Con A-treated: 10.3 +/- mU/l) in females. An identical response was seen after 12 h. Con A (250 micrograms/kg) produced time-dependent hypoglycemia in both sexes but more pronounced in males. There was no correlation between the hypoglycemia and hyperinsulinemia described above. The Con A-induced hyperinsulinemia in rats of both sexes was abolished in gonadectomized animals (intact males: +101 +/- 17% vs orchiectomized males: -5 +/- 3%; intact females: +86 +/- 23% vs ovariectomized females: -18 +/- 7.2%). Pretreating intact male and female rats with human chorionic gonadotropin also significantly inhibited the Con A-induced hyperinsulinemia. Estradiol (10 micrograms/kg,i.m.) significantly blocked the Con A-induced increase in circulating insulin in male rats (101 +/- 17% for controls vs 32 +/- 5.3% for estradiol-treated animals, P < 0.05) while testosterone (10 mg/kg, i.m.) had no similar effect on intact female rats. Pretreating Con A-injected rats with opioid antagonists such as naloxone (1 mg/kg, s.c.) and naltrexone (5 mg/kg, s.c.) blocked the hyperinsulinemia produced by the lectin in males (control: +101 +/- 17% vs naloxone-treated: +5 +/- 14%, or naltrexone-treated: -23 +/- 4.5%) and females (control: +86 +/- 23% vs naloxone-treated: +21 +/- 20%, or naltrexone-treated: -18 +/- 11%). These results demonstrate that Con A increases the levels of circulating insulin in rats and that this response is opioid-dependent and hormonally regulated.

Lectin histochemistry of rat placental tissues

Lectin binding of rat trophoblast subpopulations was examined at days 10, 12 and 15 of gestation. Biotinylated lectins, specific for a range of carbohydrates, were applied to paraffin wax embedded tissues. At day 10 of pregnancy, a wide and similar range of lectins reacted with ectoplacental cone and giant cells: chorionic lamina was relatively unreactive except with wheat germ agglutinin. At days 12 and 15, the range of lectins reacting with the placental labyrinth was relatively restricted. Spongiotrophoblast at day 12 showed lectin reactivity similar to that of ectoplacental cone cells but at day 15 the reaction pattern indicated loss of N-acetylgalactosamine residues in the large, glycogen-rich cells. Trophoblastic giant cells also showed wide lectin reactivity: some reacted only with cytoplasmic components whilst others showed pericellular reactivity. Varying lectin reactivity of giant cells in different regions of the placenta suggests functional differences. There was reduced lectin reactivity of endovascular trophoblast at day 15, compared with day 12 of pregnancy, which may reflect altered invasive potential associated with loss of sialic acid and N-acetylgalactosamine residues. The pattern of lectin reactivity suggests that ectoplacental cells, as well as giving rise to giant cells, may also contribute to spongiotrophoblast and to endovascular trophoblast.

Failure of glucose-binding lectins Con A and Lentil Lectin to identify glycation of haemoglobin

We have studied the interaction of Concanavalin A and Lentil Lectin with glycohaemoglobin by a nephelometric lectin-glycogen/dextran precipitation system and monitored the inhibitory effect of glycohaemoglobin on the precipitation. Although inhibitory effects were clearly demonstrated using simple sugars and transferrin, no effect was observed by glycohaemoglobin in relevant concentrations. This is compared to affinity chromatography, binding studies using gel filtration and electrophoresis, and affinity studies using Concanavalin A immobilised on magnetisable polymer particles. Lack of interaction between glycohaemoglobin and lectins is discussed in view of steric constraints and reduced availability of the glycated residues and the stereochemical form of the glycated 1-amino-1-deoxy-fructosyl residues in glycohaemoglobin.

Sialic acid-binding lectins: submolecular specificity and interaction with sialoglycoproteins and tumour cells

We examined the specificity of limulin, Limax flavus agglutinin (LFA) and Sambucus nigra agglutinin I (SNA I) at the submolecular level of sialic acid, and characterized their interactions with a panel of structurally distinct sialoglycoproteins. In haemagglutination inhibition assays NeuAc-alpha-glycosides were stronger inhibitors for limulin and LFA than native N-acetylneuraminic acid (NeuAc). The N-acetyl of NeuAc was crucial for binding to both lectins. N-thioacetylated NeuAc lost affinity for LFA, but still bound to limulin. Thus, distinct intermolecular interactions are involved in binding of sialic acid to the lectins. The glyceryl side chain was required for interaction with LFA, but not with limulin. SNA I specifically bound NeuAc alpha 2 --> 6Gal beta 1 --> 4Glc, but not monomeric sialic acids. Limulin and LFA strongly interacted with O-chain glycoproteins, whereas SNA I preferred N-chain proteins that carry NeuAc alpha 2 --> 6 residues. The lectins were compared with those from Cepaea hortensis and Tachypleus tridentatus (TTA) and to wheat-germ agglutinin, and were then used to probe tumour cell lines for cell surface sialylation. With the exception of TTA, all lectins interacted with the tumour cells. Limulin distinguished between the low (Eb) and highly (ESb) metastatic mouse lymphoma lines by selectively agglutinating sialidase-treated ESb cells.

Lectin histochemical study of cholangiocarcinoma arising from stone-bearing intrahepatic bile duct

With the purpose of studying changes in the expression of glycoconjugate structures in cholangiocarcinoma and the nonneoplastic epithelium of stone-bearing intrahepatic bile ducts, a panel of 12 biotinylated lectins were used on formalin-fixed, paraffin-embedded tissue sections from 13 patients who had undergone surgical resection of cholangiocarcinoma and on nonneoplastic stone-bearing intrahepatic bile ducts from 10 patients. Of the 13 patients with cholangiocarcinoma 10 had hepatolithiasis and 3 did not. Among the 12 lectins, only wheat germ agglutinin (WGA) stained the cholangiocarcinoma and nonneoplastic epithelium of the stone-bearing intrahepatic bile duct. All nonneoplastic epithelia of stone-bearing intrahepatic bile ducts were stained heavily and homogeneously by WGA, the GlcNAC-specific lectin. The high columnar epithelium of both intramural and extramural glands was stained in the supranuclear region, while the low columnar epithelium of serous acini was stained in the whole cytoplasm. cytoplasm. In the well-differentiated cholangiocarcinoma, the WGA weakly stained the neoplastic cells in the supranuclear region, while it stained the luminal cytoplasmic membrane heavily. In the poorly-differentiated cholangiocarcinoma, about 50% of cancer cells were stained with WGA. The carcinoma was moderately stained in the cytoplasm. Less reactivity and a lower percentage of cells stained with lectin were found in cholangiocarcinomas when compared to nonneoplastic epithelia. This led us to conclude that there is a dramatic decrease in lectin-binding carbohydrate structures associated with cholangiocarcinoma progression.

Relationship between the concanavalin A-agglutinability and deformability of human erythrocytes

Cellular deformability has been proposed in the past as a major determinant of lectin-mediated agglutination of cells. In this paper we have evaluated the correlation between deformability and Con A-agglutinability of human erythrocytes by subjecting them to agents that alter either one of the properties and evaluating the effect on the other property. The following results have been obtained: (i) Treatment with pronase or trypsin, which makes the Con A-nonagglutinable normal red cells highly agglutinable, has practically no effect on deformability; while neuraminidase treatment, with a similar effect on agglutinability, produces a small but statistically significant reduction in deformability. (ii) Diamide treatment, on the other hand, produces a drastic reduction in the deformability of pronase-treated erythrocytes but has no effect on the Con A-agglutinability of the cells. Dinitrophenol also reduces deformability but without altering the agglutinability, (iii) Chlorpromazine, at 2 x 10(-5) M, does not have any effect on the deformability of trypsinized cells, but increases the agglutinability substantially. When the Con A-agglutinability of the cells and their deformability after these treatments are compared, a correlation coefficient r = -0.353 (P greater than 0.1) is obtained. This indicates the lack of any direct correlation between the two parameters, and rules out any significant role of deformability in the determination of Con A-agglutinability of erythrocytes. The agglutination with the lectin is completely reversed by methyl alpha-D-mannoside, the specific inhibitory sugar for Con A, also ruling out any secondary role for deformability in the non-lectin-mediated stabilization of clumps. Upon incubation of normal erythrocytes with Con A. a dose-dependent decrease in deformability is observed, with the deformability index falling to almost 25% of the normal value with 500 microgram/ml Con A. This indicates that Con A binding to its receptor produces changes in the membrane probably by altering properties of the membrane skeleton.

Role of the Golgi apparatus in cellular pathology

The Golgi apparatus response to pathological disorders is predominantly as an intermediary component of membrane biogenesis where it is involved in processing, sorting and secretion of materials via secretory granules, and in the formation of lysosomes. A common initial response of the Golgi apparatus to any stress is an alteration or cessation of secretory activity. In the transformed cell, the Golgi apparatus is altered both morphologically and biochemically, suggesting a shift from a secretory to a membrane-generating mode of functioning. However, since fewer or less well-developed Golgi apparatus are frequently found in transformed cells, analytical methods of membrane isolation developed for normal tissues may not always yield equivalent results when applied to tumors. Cell surface alterations characteristic of malignant cells may result from modifications occurring at the level of the Golgi apparatus. Some lysosomal dysfunctions may result from underglycosylation of acid hydrolases by the Golgi apparatus. The use of cell-free systems between endoplasmic reticulum and Golgi apparatus or within Golgi apparatus cisterane is providing a new approach to the elucidation of the role of the Golgi apparatus in normal as well as pathological states.

Gangliosides depleted in plasma membrane are directed to internal membranes of rat hepatomas: evidence for a glycolipid sorting defect in hepatocarcinogenesis

Ganglioside compositions of plasma membrane fractions highly purified from rat liver and hepatomas by phase partitioning were compared with those of fractions composed of internal membranes, free of plasma membrane. With liver, 70-80% of the the lipid bound sialic acid were accounted for by a plasma membrane location. In hepatomas this percentage was reduced to 50-65%. More pronounced was the distribution of the simple monosialoganglioside GM3. In the hepatomas, 60-80% of the GM3 was found associated with internal membranes as compared to liver where only 35% of the GM3 was present in internal membranes. The findings suggest a glycolipid sorting defect in hepatocarcinogenesis where gangliosides, and especially monosialogangliosides, are diverted to internal membranes rather than being correctly transported to the cell surface. Since GM3 is synthesized exclusively in the Golgi apparatus of both liver and hepatomas, the basis for the sorting defect may reside in a functionally altered Golgi apparatus.

Lectin binding in tissues from hydatidiform mole, invasive mole and choriocarcinoma to concanavalin-A, wheat germ agglutinin and peanut agglutinin

A light microscopic analysis of lectin receptors in normal placenta and trophoblastic disease was performed utilizing biotinylated Concanavalin-A (Con-A), wheat germ agglutinin (WGA), and peanut agglutinin (PNA), in conjunction with an avidin-biotin peroxidase complex. Hydatidiform mole, invasive mole and choriocarcinoma exhibited increased receptors to Con-A and WGA compared to normal placenta. Increased reactivity to Con-A and WGA was associated merely with increased growth and proliferation of trophoblasts rather than a malignant transformation. Normal placenta, partial and complete mole generally showed moderate to strong binding with PNA after neuraminidase treatment, while invasive mole and choriocarcinoma (11 of 15 cases) generally showed minimal to absent reaction with PNA. Heterogeneity of PNA binding in choriocarcinoma was manifested by the presence of PNA reactivity in the trophoblast membrane in 2 cases wherein no prior neuraminidase treatment was given. This suggests that in some malignant trophoblasts, there is absence of sialic acid in the terminal cell surface carbohydrate groups resulting in the exposure of N-acetylgalactoseamine.

Studies on the tryptophan residues of soybean agglutinin. Involvement in saccharide binding

Modification of tryptophan side chains of soybean agglutinin (SBA) with N-bromosuccinimide results in a loss of the hemagglutinating and carbohydrate binding activities of the protein. One residue/subunit is probably essential for the binding activity. Modification leads to a large decrease in the fluorescence of the protein accompanied by a blue shift. Iodide ion quenching of the protein fluorescence shows that saccharide binding results in a decreased accessibility of some of the tryptophan side chains. These results strongly point towards the involvement of tryptophan residues in the active site of SBA.

Cellular carbohydrate components in human, rabbit and rat lacrimal gland. Studies using fluorescein and peroxidase labelled lectins

Orbital lacrimal glands from adult male and female rabbits, rats and humans were examined for the presence of intracellular receptors of four lectins: concanavalin-A agglutinin, lutus tetragonolobus agglutinin, ricinus comunis-60 agglutinin and wheat-germ agglutinin using fluorescein-conjugated lectin and peroxidase labelling methods for fluorescence and electron microscopy, respectively. Lectins were used as specific probes to detect carbohydrate moiety of the lacrimal gland. The pattern of labelling with the lectins suggests that N-acetyl-glucosamine, N-acetyl-D-galactosamine, D-galactose, D-mannose, sialic acid and L-fucose are contained in the lacrimal gland of the three species. The significance of these findings is discussed.

Differences between preneoplastic cells, neoplastic cells and their normal counterparts

A number of changes occur in preneoplastic and neoplastic cells as they progress towards a greater degree of malignancy. These alterations include genetic changes, epigenetic changes, surface alterations and alterations in intercellular interactions. In some instances, these changes are contributing factors to the degree of pathology noted, whilst other are resultant. In many situations, the relationship between these changes and the progression towards neoplasia is not understood. Nevertheless, it seems probable that these changes are ultimately involved in driving cells further along the path to neoplastic transformation. It is the purpose of this review to consider the changes which occur as cells progress from normality to being neoplastic, with particular reference to the cells of the oral mucosa, and the use to which detectable changes can be used as prognostic indicators.

Lectin binding sites in the vitelline envelope of Bufo arenarum oocytes: role in fertilization

Incubation of dejellied spawned oocytes from Bufo arenarum with different lectins results in a decrease of oocyte fertility. Concanavalin A was the most effective lectin; phytohemagglutinin P and wheat germ lectin were less effective. Agglutinin from soybean was scarcely active. These lectin effects could be ascribed to a hindering of specific sites for some proteases, since the same treatment renders the oocyte vitelline envelope insensitive to spermatolysin (an essential requisite for fertilization) and to trypsin. Also in this case concanavalin A was the most effective lectin. Univalent concanavalin A was also effective in blocking the fertility of dejellied oocytes. These results indicate that the residues of alpha-D-glucose and alpha-D-mannose present in the vitelline envelope are involved in gamete interactions in Bufo arenarum. This idea is also supported by the finding that dejellied oocytes (fertilizables) have a number of binding sites for concanavalin A that is three or four orders of magnitude higher than coelomic or fertilized oocytes (both not penetrable by spermatozoa).

Purification and characterization of a major glycoprotein in rat hepatoma plasma membranes. One of the membrane proteins released by phosphatidylinositol-specific phospholipase C

A major glycoprotein of rat hepatoma plasma membranes was selectively released as a soluble form by incubating the membrane with phosphatidylinositol-specific phospholipase C. The soluble form corresponding to the glycoprotein was also prepared by butan-1-ol extraction of microsomal membranes at pH 5.5, whereas extraction at pH 8.5 yielded an electrophoretically different form with a hydrophobic nature. The soluble glycoprotein extracted at pH 5.5 was purified by sequential chromatography on concanavalin A-Sepharose, Sephacryl S-300 and anti-(alkaline phosphatase) IgG-Sepharose, the last step being used to remove a contaminating alkaline phosphatase. The glycoprotein thus purified was a single protein with Mr 130,000 in SDS/polyacrylamide-gel electrophoresis, although it behaved as a dimer in gel filtration on Sephacryl S-300. The glycoprotein was analysed for amino acid and carbohydrate composition. The composition of the carbohydrate moiety, which amounted to 64% by weight, suggested that the glycoprotein contained much larger numbers of N-linked oligosaccharide chains than those with O-linkage. It was confirmed that the purified glycoprotein was immunologically identical not only with that released by the phospholipase C but also with the hydrophobic form extracted with butan-1-ol at pH 8.5. The results indicate that the glycoprotein of rat hepatoma plasma membranes, which has an unusually high content of carbohydrate, is another membrane protein released by phosphatidylinositol-specific phospholipase C, as documented for alkaline phosphatase, acetylcholinesterase and Thy-1 antigen.

Analyses of avidin-biotin complexes with lectins of membrane glycoproteins in the urinary bladder of rats treated with N-butyl-N-(4-hydroxybutyl)nitrosamine

The bladder epithelium was examined by staining with avidin-biotin complexes with lectins to determine the early membrane changes during bladder carcinogenesis in rats treated with N-butyl-N-(4-hydroxybutyl)-nitrosamine (BHBN). Concanavalia ensiformis (Con A), Triticum vulgaris (WGA), Ricinus communis (RCA) and Arachis hypogaea (PNA) were used as probes. The cellular distributions of lectin particles were distinguished into membranous and cytoplasmic patterns. Normal bladder cells stained very slightly and showed a spotty membranous pattern. After treatment of rats with BHBN for two or three weeks, staining became stronger and its pattern changed from a membranous to a cytoplasmic type. The staining of bladder cancer cells induced by BHBN varied from area to area and with different lectins. These data indicated that changes in carbohydrates occur in the bladder cell membrane during the early phase of carcinogenesis.

Peroxidase-labelled lectin binding of human extravillous trophoblast

The binding of four peroxidase-conjugated lectins, concanavalin A (Con-A), wheat germ agglutinin (WGA), peanut agglutinin (PNA) and soybean agglutinin (SBA), in both fixed and frozen tissue sections of human extravillous trophoblast (EVT) was determined. On the basis of its lectin binding properties the EVT cell population was found to be heterogeneous. PNA and SBA did not bind to any of the EVT cells. Con-A and WGA bound to most EVT cells, with the exception of the trophoblast of the chorion laeve. The trophoblast giant cells bound only Con-A and not WGA. The villous cytotrophoblast, from which the EVT cells are said to derive, does not express the sugar groups detected by the above lectin probes. The expression of mannosylated and di-N-acetylchitobiosyl residues by a fetally derived cell invites speculation that such expression enables it both to invade host maternal tissues and to avoid any adverse host immunological response.

Transient increase in intracellular concentration of adenosine 3':5'-cyclic monophosphate results in morphological and biochemical differentiation of C6 glioma cells in culture

Incubation of C6-BU1 glioma cells in the presence of isoproterenol and Ro20-1724--a potent cAMP phosphodiesterase inhibitor--results in a transient increase in intracellular cAMP levels, followed by a rapid efflux of cyclic AMP from the cells into the media. Two distinct types of morphological changes could be seen: rounded cell bodies with multipolar processes and beadings after 30 minutes of incubation--this period coincides with a 70-80-fold increase in intracellular cAMP levels, and elongated cell bodies with extended bipolar processes after 24-48 hours. By this time the intracellular cAMP concentration dropped to a low level, which was only three- to four fold higher than that in control. The transient increase in intracellular cAMP concentration results in retardation of cell growth, diminished uptake of 3H-2-deoxyglucose, and abolition of enhanced synthesis of cyclic AMP by concanavalin A.

Product identification of ameloblastomas: an immunohistochemical study

Twenty-nine solid, plexiform and follicular ameloblastomas and control human developing teeth at different stages of maturation were formalin-fixed, paraffin-embedded and sectioned for the study of laminin, fibronectin, and mannosyl, glucosyl, and galactosyl residues using the peroxidase antiperoxidase (PAP) and avidin-biotin peroxidase complex (ABC) staining methods, respectively. Monospecific antibodies to laminin and fibronectin and the affinity of the lectins for mannosyl, glucosyl, and galactosyl residues with RCA-I. Laminin is present during the stage of morphodifferentiation of normal tooth development within the basement membrane. Following cytodifferentiation and calcified matrix deposition, laminin is not detectable. Laminin is also found in the basement membrane of both follicular and plexiform ameloblastomas. In contrast, fibronectin is reactive only up to the stage of morphodifferentiation among the mesenchymal cells and at the epithelial-mesenchymal interface, and it becomes unreactive upon differentiation of odontoblasts and mesenchymal pulp tissue as well. Unlike laminin, fibronectin is unreactive in the basement membrane of plexiform follicular and ameloblastomas.

Thermodynamic and kinetic studies on saccharide binding to soya-bean agglutinin

The fluorescence of N-dansylgalactosamine [N-(5-dimethylaminonaphthalene-1-sulphonyl)galactosamine] was enhanced 11-fold with a 25 nm blue-shift in the emission maximum upon binding to soya-bean agglutinin (SBA). This change was used to determine the association constants and thermodynamic parameters for this interaction. The association constant of 1.51 X 10(6) M-1 at 20 degrees C indicated a very strong binding, which is mainly due to a relatively small entropy value, as revealed by the thermodynamic parameters: delta G = -34.7 kJ X mol-1, delta H = -37.9 kJ X mol-1 and delta S = -10.9 J X mol-1 X K-1. The specific binding of this sugar to SBA shows that the lectin can accommodate a large hydrophobic substituent on the C-2 of galactose. Binding of non-fluorescent ligands, studied by monitoring the fluorescence changes when they are added to a mixture of SBA and N-dansylgalactosamine, indicates that a hydrophobic substituent at the anomeric position increases the affinity of the interaction. The C-6 hydroxy group also stabilizes the binding considerably. Kinetics of binding of N-dansylgalactosamine to SBA studied by stopped-flow spectrofluorimetry are consistent with a single-step mechanism and yielded k+1 = 2.4 X 10(5) M-1 X s-1 and k-1 = 0.2 s-1 at 20 degrees C. The activation parameters indicate an enthalpicly controlled association process.

Oligosaccharide modification by swainsonine treatment inhibits pulmonary colonization by B16-F10 murine melanoma cells

Oligosaccharide moieties of cell-surface glycoconjugates are thought to be involved in recognition events associated with tumor metastasis and invasion. Using swainsonine (SW), an inhibitor of Golgi alpha-mannosidase II that results in the formation of hybrid-type oligosaccharides on N-linked glycoproteins, we have tested the hypothesis that specific glycan structures are required for pulmonary colonization by tumor cells. B16-F10 murine melanoma cells were treated with SW in growth medium and then injected intravenously into syngeneic C57BL/6 mice. This treatment resulted in dramatic inhibition of colonization, but it had no effect on B16-F10 viability or on cellular tumorigenicity after subcutaneous implantation. SW-treated radiolabeled B16-F10 cells were cleared from the lungs at a greater rate than control cells, suggesting that one effect of treatment is to alter tumor cell retention in the target organ. Our results implicate specific glycan structures in pulmonary colonization and offer a potential approach for identification of specific macromolecules involved in tumor cell-organ recognition during metastasis.

Lectin binding sites in cultured human breast cancer cells

Two estrogen-sensitive (ZR 75.1 and 734 B) and two estrogen-independent (BT 20 and Hs 578 T) human breast cancer cell lines, and one larynx carcinoma cell line (Hep. 2), were investigated immunocytochemically for the occurrence of lectin binding sites. Peroxidase-labeled peanut agglutinin (PNA) was used. PNA binding sites could be observed in estrogen-sensitive cell lines only. In ZR 75.1, the most estrogen-sensitive cell line, PNA binding sites were also observed without neuraminidase pretreatment. In our study, PNA binding is associated with the biological estrogen dependence of the tumor cells.

Cancer metastasis: experimental approaches, theoretical concepts, and impacts for treatment strategies

It has been the purpose of this article to describe recent advances in cancer metastasis research. Clinical realities and experimental approaches to the study of underlying basic mechanisms of metastasis formation were discussed. Wherever possible, results were reported which led to the development of theoretical concepts. Such results and concepts were finally evaluated in light of their possible impact for the design of new treatment strategies. Experimental findings from many diverse research fields were summarized with the help of tables, figures, and references. It was concluded that the process of metastasis is a dynamic event that can be described as a sequence of interrelated steps. Experimental results indicated that malignant cells that migrate and disseminate from the primary organ to distant sites and there eventually develop into metastases have to survive a series of potentially lethal interactions. Intimate tumor-host interactions were reported to take place all along the metastatic process. They were elucidated at the steps of angiogenesis, invasion, organ interaction, dormancy, tumor rejection, and tumor immune escape. The outcome of such tumor-host interactions seemed to depend on intrinsic properties of the tumor cells themselves as well as on the responsiveness of the host. Metastasis does not appear as a merely random process. Both clinical and experimental studies revealed that the whole process can be described more appropriately in terms of stochastic, sequential, and selective events, each of which is controlled and influenced by a number of mechanisms. With regard to therapeutic intervention, a selective event offers more possibilities than a random one because it is governed by rules that can be exploited experimentally. Various impacts from experimental studies for the design of antimetastatic cancer treatment strategies were discussed. Sequential steps of the metastatic cascade could become new therapy targets. Conventional empirically derived treatment modalities should become flanked by methods aimed more specifically at critical steps of cancer spread in order to prevent progression of the disease. This is where basic research on mechanisms could make significant contributions to therapy planning in the future. Furthermore, possible negative effects of surgery, radiotherapy, and adjuvant chemotherapy or immunotherapy that could result in enhancement of metastatic progression need to be critically evaluated to limit them as much as possible.(ABSTRACT TRUNCATED AT 400 WORDS)

The binding of peroxidase-labelled lectins to human breast epithelium. II—the reactivity of breast carcinomas to wheat germ agglutinin

The binding of peroxidase-labelled wheat germ agglutinin (WGA) to a series of 125 human breast carcinomas has been studied. Routine fixation and processing has been shown to have no deleterious effect on reactivity. In contrast to the homogeneous binding of WGA to normal and hyperplastic human breast previously reported, the binding of WGA to breast carcinomas exhibits heterogeneity. This is of two forms: (1) in relation to cell reactivity, which is significantly correlated to tumour differentiation, with fewer cells reacting in those carcinomas showing loss of histological differentiation; (2) with regard to the interaction between WGA and specific saccharides of cellular glycan-components, binding to sialic acid appearing to be of significance to varying degrees in some carcinomas but not in others nor, as previously reported, in normal breast. The alteration in WGA-saccharide interaction is an indicator of the heterogeneity of the carbohydrate chains of glycoproteins within neoplastic cells of the same tumour and between carcinomas. The other finding of note has been that of the significant association between heterogeneity of cellular reactivity to WGA and the presence of axillary lymph node metastasis, but a lack of correlation between virtual absence of reactivity and nodal metastasis.

Fixed-tissue binding of fluorescein-conjugated concanavalin A to malignant melanomas versus nevi

Concanavalin A (con A) is a plant-derived lectin that has the capability of agglutinating malignant cells in vitro. We studied the binding of fluorescein isothiocyanate-conjugated con A to formalin-fixed, paraffin-embedded malignant melanomas and nevocellular nevi. Both malignant melanoma cells and nevus cells emitted partial or circumferential, cytoplasmic rim, apple green fluorescence. There was no demonstrable difference between fluorescence distribution or intensity between the two groups. Control, unstained tissue specimens yielded a brilliant nuclear and nucleolar yellow-green autofluorescence, which is peculiar to melanoma cells and rare to absent in nevus cells. Fluorescein isothiocyanate-conjugated con A provided no clear differentiation between malignant melanomas and nevocellular nevi in fixed tissue. However, characteristic melanoma cell autofluorescence may prove to be of benefit for differentiating malignant melanocytic from benign nevocytic lesions.

Reduced insulin endocytosis in serum-transformed fibroblasts demonstrated by flow cytometry

Neoplastic transformation often results in the loss of growth control and concomitant changes in cell surface properties. The changes in endocytosis of a variety of probes after serum or anchorage transformation were measured for mouse fibroblasts by flow cytofluorometry. No major differences in dextran (fluid phase) or histone (nonspecific-adsorptive) endocytosis were observed among four cell lines with different growth properties. However, decreased receptor-mediated internalization of alpha 2-macroglobulin was observed for cell lines transformed to either serum or anchorage independence. Furthermore, increased wheat germ agglutinin and decreased insulin endocytosis were observed, but only in serum transformants. The changes specific to serum transformants were not accounted for by changes in binding of wheat germ agglutinin or insulin. The possible implications of these observations regarding serum transformation and the insulin requirement for growth in serum-free medium are discussed.

The binding of peroxidase-labelled lectins to human breast epithelium. I--Normal, hyperplastic and lactating breast

Six peroxidase-labelled lectins have been applied to tissue sections of normal, hyperplastic and lactating human breast. The effect of fixation on binding has been assessed by the comparison of specimens treated with a variety of fixatives with frozen material; the effect of trypsin has also been considered. The other objective has been to establish the consistency of lectin reactivity with this non-malignant breast tissue. Fixation has little effect on the binding of wheat germ agglutinin and peanut lectin, although reactivity with the latter was sometimes increased above that seen in frozen material by the use of Bouin's fluid. Trypsinization of formalin-fixed tissue appears to be a prerequisite for staining with soy bean agglutinin and Ulex europeus. The binding of Lotus tetragonolobus and Dolichos biflorus to fixed tissue has been found to be unreliable in comparison to frozen samples. Soy bean agglutinin and Dolichos biflorus, both specific for N-acetyl-D-galactosamine, have binding patterns which vary between specimens and often between themselves. Of the two fucose-binding lectins Ulex europeus has shown a variability of reaction between specimens, whilst Lotus tetragonolobus consistently reacts with ductal and acinar epithelium but with varying intensities. Consistent binding patterns have been found for wheat germ agglutinin and peanut lectin, the latter after the use of neuraminidase. They therefore form a useful basis for comparison with the reactivity of malignant breast tissue.

Molecular analysis of the lymphocyte membrane

Methods for the molecular analysis of lymphocyte membranes are reviewed briefly, and wherever possible presented in a manner relevant to comparative studies. The specific areas reviewed include the bulk isolation of lymphocyte membranes, the use of radioisotopes to covalently label lymphocyte membrane molecules, the use of lectins to characterize membrane glycoconjugates, and our current understanding of lymphocyte membrane immunoglobulins.

Lectin binding patterns in diffuse large cell lymphoma

The staining reaction of a panel of lectins in paraffin embedded lymph node specimens of diffuse large cell lymphoma was studied in relation to survival. In 47 of 49 patients, varying degrees of lectin binding were observed with Ricinus communis agglutinin (RCA), crude extract of Arachis hypogaea (c-PNA), Concanavalin ensiformis A (Con A), Triticum vulgaris A (WGA) and Phaseolus vulgaris A (PHA). Binding was either absent or only minimal with Pisum sativum A (PSA) and Lens culinaris A (LCA). Two categories of binding were observed: cell surface and cytoplasmic. Cell surface binding was seen in tumor cells, while cytoplasmic binding was observed in macrophage-histiocytes. Varying numbers of tumor cells were stained with RCA, WGA, c-PNA or PHA; but with Con A virtually no tumor cells were stained. Stromal macrophage-histiocytes were stained with RCA, WGA, or Con A in all but one case, frequently with all three lectins; c-PNA binding macrophage-histiocytes were absent in one third of the cases. With PHA the staining of stromal macrophage-histiocytes was extremely rare. Tumor cells that stained with RCA but not with c-PNA were observed in 9 of 15 patients who survived more than 2 years after diagnosis. In all 15 long-term survivors, stromal macrophage-histiocytes were positive for c-PNA. Tumor cells that reacted with c-PNA but not with RCA were seen in five patients who survived less than two years. All 16 patients whose tumors lacked c-PNA binding stromal macrophage-histiocytes in the presence of RCA binding macrophage-histiocytes were short-term survivors. These observations suggest the heterogeneity of stromal macrophage-histiocytes as well as that of tumor cells. Furthermore, the variation of lectin binding might be useful in assessing prognosis.

Selective lectin binding of the developing mouse retina

A battery of eight lectins with different carbohydrate specificities was used to study changes in glycoconjugate expression during cell differentiation in the mouse retina. The lectins tested included concanavalin A (Con A), wheat germ agglutinin (WGA), soybean agglutinin (SBA), peanut agglutinin (PNA), Ulex europaeus agglutinin (UEA), Ricinus communis agglutinin I (RCA), Dolichos biflorus agglutinin (DBA), and Limulus polyphemus agglutinin (LPA). Unfixed frozen sections of adult and early postnatal mouse retina were treated with fluorescein isothiocyanate-conjugated lectins and examined by fluorescence microscopy. The results showed selective lectin binding in both cellular and synaptic retinal layers of the adult mouse and throughout postnatal development. In general, an increase in intensity of fluorescent lectin staining during retinal development was observed for Con A, WGA, DBA, LPA, RCA, and PNA. This suggests an increase in the expression or accessibility of carbohydrate moieties during development. SBA and UEA showed little to no binding to adult or neonatal retina. Retinal vasculature was intensely stained by RCA, both during development and in the adult. All lectins binding to adult or neonatal retinal layers showed some degree of reactivity with the inner segment region of photoreceptor cells. However, only Con A, PNA and WGA bound to photoreceptor outer segments, suggesting significant differences in the glycosylated components of inner and outer segment membranes. PNA bound specifically to a subpopulation of photoreceptor cells and to discrete regions within the outer synaptic layer. The pattern of PNA binding suggests that this lectin binds preferentially to cone photoreceptor inner and outer segments and cone synaptic pedicles rather than to rod photoreceptor cells. This marked specificity of PNA binding suggests that it may provide a basis for the physical separation of cone and rod photoreceptor cells.