Binding of <Superscript>3</Superscript>H-Concanavalin A by Normal and Transformed Cells

CERTAIN plant lectins selectively agglutinate tissue culture cells transformed by oncogenic viruses and chemical carcinogens^1–7. Agglutination of transformed cells is inhibited by certain small carbohydrates which are thought to be sterically similar to the lectin-binding sites on the cell surface. Agglutination induced by a protein from wheatgerm is inhibited by N-acetyl-glucosamine^2,3 and that induced by concanavalin A (Con A) is inhibited by α-methyl-D-glucopyranoside (α-MG⁴). Normal cells are thought also to have lectin-binding sites but in a “cryptic” form, for mild protease treatment renders them agglutinable by wheatgerm agglutinin and Con A^4,6. Transformed cells are thought to bind more lectin than untransformed cells⁵. This study was designed to test this hypothesis for jackbean lectin, Con A.     

Trypanosoma rhodesiense Bloodstream Trypomastigote and Culture Procyclic Cell Surface Carbohydrates1, 2, 3

Bloodstream trypomastigote and culture procyclic (insect midgut) forms of a cloned T. rhodesiense variant (WRATat 1) were tested for agglutination with the lectins concanavalin A (Con A), phytohemagglutinin P (PP), soybean agglutinin (SBA), fucose binding protein (FBP), wheat germ agglutinin (WGA), and castor bean lectin (RCA). Fluorescence-microscopic localization of lectin binding to both formalin-fixed trypomastigotes and red cells was determined with fluorescein isothiocyanate (FITC)-conjugated Con A, SBA, FBP, WGA, RCA, PNA (peanut agglutinin), DBA (Dolichos bifloris), and UEA (Ulex europaeus) lectins. Electron microscopic localization of lectin binding sites on bloodstream trypomastigotes was accomplished by the Con A-horseradish peroxidase-diaminobenzidine (HRP-DAB) technique, and by a Con A-biotin/avidin-ferritin method. Trypomastigotes, isolated by centrifugation or filtration through DEAE-cellulose or thawed after cryopreservation, were agglutinated by the lectins Con A and PP with agglutination strength scored as Con A < PP. No agglutination was observed in control preparations or with the lectins WGA, FBA or SBA. Red cells were agglutinated by all the lectins tested. Formalin-fixed bloodstream trypomastigotes bound FITC-Con A and FITC-RCA but not FITC-WGA, -SBA, -PNA, -UEA or -DBA lectins. All FITC-labeled lectins bound to red cells. Con A receptors, visualized by Con A-HRP-DAB and Con A-biotin/avidin-ferritin techniques, were distributed uniformly on T. rhodesiense bloodstream forms. No lectin receptors were visualized on control preparations. Culture procyclics lacked a cell surface coat and were agglutinated by Con A and WGA but not RCA, SBA, PP and FBP. Procyclics were not agglutinated by lectins in the presence of competing sugar at 0.25 M. The expression of lectin binding cell surface saccharides of T. rhodesiense WRATat 1 is related to the parasite stage. Sugars resembling α-D-mannose are on the surface of bloodstream trypomastigotes and culture procyclics; n-acetyl-D-galactosamine and D-galactose residues are on bloodstream forms; and n-acetyl-D-glucosamine-like sugars are on procyclic stages.     

EVIDENCE FOR PLEIOTROPIC CHANGES IN LINES OF CHINESE HAMSTER OVARY CELLS RESISTANT TO CONCANAVALIN A AND PHYTOHEMAGGLUTININ-P

Lines of Chinese hamster ovary cells resistant to the lectins concanavalin A (Con A) and phytohemagglutinin-P (PHA-P) have been isolated and characterized. Lines were isolated by a stepwise, a single-step, or a cycling single-step procedure, from both mutagen-treated and untreated cultures. The resistant lines showed a higher efficiency of colony formation in the presence of the appropriate lectin than did the wild-type parental line. The cell lines resistant to Con A did not exhibit any detectable cross resistance to PHA-P, nor did the PHA-resistant cells exhibit cross resistance to Con A. The toxicity of Con A from the wild-type and Con A-resistant lines was reduced in the presence of methyl α-D-glucopyranoside; this effect was not seen with the PHA-resistant line. Using ¹²⁵I-labeled Con A, it was found that Con A was bound preferentially to the surface of intact cells, and that the amount of labeled Con A bound to intact cells was similar for the wild-type and lectin-resistant lines. The Con A-resistant lines were found to be more susceptible to the toxic effects of a number of different compounds, including cyclic AMP and its dibutyryl derivative, sodium butyrate, high concentrations of glucose, phenethyl alcohol, phenol, ouabain, and testosterone. It appears that, in these lines, acquisition of resistance to Con A gave rise to pleiotropic effects which were detected by changes in the sensitivity of the cells to a variety of agents.     

Epidermal growth factor receptors on PC12 cells: Alteration of binding properties by lectins

The PC12 cell line displays cell surface receptors for both nerve growth factor (NGF) and epidermal growth factor (EGF). It has been previously shown that the lectin wheat germ agglutinin (WGA) alters the properties of NGF receptors on these cells. We now report that preincubations with either WGA or concanavalin A (Con A) decrease the binding of ¹²⁵I-EGF to PC12 cells by greater than 50%. The inhibition of binding occurred at 37°C and 4°C and could be blocked or reversed by the addition of sugars which bind specifically to WGA or Con A. Scatchard analysis revealed that these lectins decreased binding primarily by lowering the affinity of the receptor and to a lesser extent by decreasing receptor number. Succinylalion of Con A (sCon A) produced a derivative that was less effective than the native lectin in decreasing EGF binding; however, addition of an antibody against Con A restored the ability of sCon A to decrease binding. Similar to results obtained with ¹²⁵I-NGF binding, WGA but not Con A was found to increase, by scveralfold; the proportion of ¹²⁵I-EGF binding that is resistant to solubilization by Triton X-100 detergent. A potential association of the EGF receptor with cytoskeletal elements is discussed which could account for such results.     

Heterogeneity of the population of lymphoma NK/Ly and leukemia L-1210 cells according to the carbohydrate structure of cell surfaces: Immunocytochemical analysis of lectin binding

This paper investigates the heterogeneity of surface carbohydrate determinants in a population of ascites cells of lymphoma NK/Ly and leukemia L-1210 according to the binding of lectins in lentil, wheat germs, peanut, and concavalin A. Bound lectins were detected by an indirect immunochemical method using obtained by the authors colloidal gold-labeled polyclonal antilectin antibodies with further development with silver acetate. Significant differences were detected in the binding of concavalin A between NK/Ly (67% Con A⁺) and L-1210 (7.2% Con A⁺) cells, while the difference in the binding of other lectins with both types of tumor cells were not significant. A relatively high percentage of PNA⁺ cells was recorded; it can indicate on a high degree of desialization of membrane glycoproteins.     

Nature of lectin-induced alteration of potassium transfer in Ehrlich ascites tumor cells

The way in which the lectins concanavalin A (Con A) and Ricinus communis agglutinin (Ricin) alter the K⁺ content of Ehrlich ascites tumor cells was investigated. Unidirectional and net fluxes were determined in unwashed cells during a time course following lectin addition. Total influx, ouabain sensitive influx, Mg⁺⁺- and Na⁺-K⁺-ATPase activity were all unaffected. Cell ATP content was normal for at least 19 minutes after exposure to Con A. Early after contact with Ricin or Con A efflux was stimulated 2-3-fold, resulting in net K⁺ loss, but after 20 minutes efflux had returned to normal. Ricin and Con A acted similarly although Ricin was present at only 1/50 the concentration of Con A. When the findings are evaluated together with previous work it is suggested that a particular membrane glycoprotein may be concerned in the efflux alteration observed.     

Cell-to-substratum adhesion of dissociated embryonic cells of the sea urchin,Pseudocentrotus depressus

Summary Some plant lectins, Concanavalin agglutinin (Con A), succinyl Con A and wheat germ agglutinin (WGA) increased the adhesion of dissociated embryonic cells of the sea urchin,Pseudocentrotus depressus, to the substratum (plastic and glass surface) in vitro. Other plant lectins,Ulex europeus agglutinin (UEA) andDolichos biflorus agglutinin (DBA) had no effect on the cell-to-substratum interaction. A specific monocarbohydrate inhibitor of lectins, -methyl-d-mannoside, inhibited the Con A-induced cell-to-substratum adhesion of dissociated embryonic cells. This observation suggests that the Con A-induced cell-to-substratum adhesion may be attributed to the Con A-carbohydrate interaction. In Millipore-filtered sea water (MPFSW) containing Con A (0.1 mg/ml), dissociated embryonic cells adhered to the substratum for more than 6 h at 18°C, while in MPFSW as control, almost all the dissociated cells were released from the substratum after 1 h. A scanning electron microscopic study showed that dissociated embryonic cells adhered to the substratum were surrounded by an extracellular fibrous material, when the cells were cultured in MPFSW containing Con A. The induction of the extracellular fibrous material by Con A was inhibited by -methyl-d-mannoside. The appearance of this material may be related to the cell-to-substratum adhesion of dissociated cells. Sequential extractions of Con A-treated dissociated cells with Triton X 100 and urea solubilized most of the cellular components, leaving the fibrous material on the surface. Biochemical conponents of the isolated fibrous material included sea urchin fibronectin, Con A and minor components (88 and 140 kilodalton proteins). Fibronectin preformed in the cells was excreted after the dissociation, while the 88 and 140 kilodalton proteins were synthesized and released to the extracellular space.     

Selection and characterization of chinese hamster ovary cells resistant to the cytotoxicity of lectins

Summary Chinese hamster ovary (CHO) cells selected in a single step for resistance to the cytotoxicity of the lectin from red kidney beans (PHA) behave as authentic somatic cell mutants. The PHA-resistant (Pha^R) phenotype is stable in the absence of selection; its frequency in a sensitive population is increased several-fold by mutagenesis; and it behaves recessively in somatic cell hybrids. The activity of a specific glycosyl transferase which transfers N-acetylglucosamine (GlcNAc) to terminalα-mannose residues is dramatically reduced (⩽5% of the activity detected in wild-type CHO cells) in several independent Pha^R clones. These clones also exhibit (a) a decreased ability to bind [¹²⁵I]-PHA; (b) a marked resistance to the cytotoxicity of wheat germ agglutinin (WGA), Ricin (RIC) andLens culinaris agglutinin (LCA); (c) a 4- to 5-fold increased sensitivity to the cytotoxicity of concanavalin A (Con A); (d) an increased ability to bind¹²⁵I-Con A; and (e) decreased surface galactose residues—all properties consistent with the specific loss of the GlcNAc transferase activity. The lectins WGA, RIC, LCA and Con A have also been used to select, in a single step, resistant clones from each of two complementary CHO auxotrophic lines. These lectin-resistant clones have been characterized by their ability to survive cytotoxic doses of PHA, Con A, WGA, RIC or LCA, and 4–5 “lectin-resistance” phenotypes have been demonstrated. Complementation data is being sought by somatic cell hybridization. Preliminary results show that two phenotypically-distinct Con A^R mutants are complementary in that hybrid cells formed between them exhibit wild-type sensitivity to Con A. Presented in the formal symposium on Information Transfer in Eukaryotic Cells, at the 26th Annual Meeting of the Tissue Culture Association, Montreal, Quebec, June 2–5, 1975.     

Modulation of T-cell functions: I. Effect of 2-mercaptoethanol and macrophages on T-cell proliferation

The in vitro effects of 2-mercaptoethanol (2-ME), macrophages (MØ), and concanavalin A (Con A) on the proliferation of normal spleen cells (NSC), MØ-depleted spleen cells (DSC), T cells, T-cell subpopulations, and B cells were assessed by [³H]thymidine incorporation. 2-ME alone was consistently shown not to be mitogenic for purified T cells; however, 2-ME enhanced the early (Days 1 and 2) Con A (2 μg/ml)-induced response of NSC, DSC, and T-cell preparations, but depressed the late response (Days 4 and 5). 2-ME alone was mitogenic for purified B-cells, as reported previously; and the 2-ME-induced B-cell response was inhibited by Con A. Preincubation of T cells with 2-ME was sufficient for enhanced Con A responsiveness; however, if 2-ME was added 24 hr after the initiation of culture, no alteration of the Con A-induced response was observed. Ly-2,3⁺ T cells were unresponsive to Con A (0.3–20 μg/ml), but the addition of 2-ME or peritoneal cells enhanced the Con A responsiveness of Ly-2,3⁺ T cells over 200-fold. Ly-1⁺ T cells responded with a similar doseresponse and kinetic profile as unselected T cells. Although Ly-1⁺ T cells responded to Con A, unlike Ly-2, 3⁺ T cells, extensive removal of MØ significantly reduced the Con A-induced responsiveness of the Ly-1⁺ T cells. The reactivities of Ly-1⁺ and Ly-2,3⁺ DSC could be reconstituted by the addition of MØ or 2-ME; however, the kinetic response of Ly-1⁺ T cells peaked on Day 2–3, and Ly-2,3⁺ T cells had a delayed response which peaked on Day 4–5. The results indicated that (i) 2-ME and/or MØ accelerate the response kinetics of T-cells to Con A; (ii) T-cell subpopulations have differential requirements for MØ and/or 2-ME in the response to Con A; (iii) T-cell subpopulations exhibit differential dose responsiveness to Con A; and (iiii) 2-ME alters Con A responsiveness by a direct effect on T cells.     

Trypanosoma rhodesiense bloodstream trypomastigote and culture procyclic cell surface carbohydrates

Bloodstream trypomastigote and culture procyclic (insect midgut) forms of a cloned T. rhodesiense variant (WRAT at 1) were tested for agglutination with the lectins concanavalin A (Con A), phytohemagglutinin P (PP), soybean agglutinin (SBA), fucose binding protein (FBP), wheat germ agglutinin (WGA), and castor bean lectin (RCA). Fluorescence-microscopic localization of lectin binding to both formalin-fixed trypomastigotes and red cells was determined with fluorescein isothiocyanate (FITC)-conjugated Con A, SBA, FBP, WGA, RCA, PNA (peanut agglutinin), DBA (Dolichos bifloris), and UEA (Ulex europaeus) lectins. Electron microscopic localization of lectin binding sites on bloodstream trypomastigotes was accomplished by the Con A-horseradish peroxidase-diamino-benzidine (HRP-DAB) technique, and by a Con A-biotin/avidin-ferritin method. Trypomastigotes, isolated by centrifugation or filtration through DEAE-cellulose or thawed after cryopreservation, were agglutinated by the lectins Con A and PP with agglutination strength scored as Con A greater than PP. No agglutination was observed in control preparations or with the lectins WGA, FBA or SBA. Red cells were agglutinated by all the lectins tested. Formalin-fixed bloodstream trypomastigotes bound FITC-Con A and FITC-RCA but not FITC-WAG, -SBA, -PNA, -UEA or -DBA lectins. All FITC-labeled lectins bound to red cells. Con A receptors, visualized by Con A-HRP-DAB and Con A-biotin/avidin-ferritin techniques, were distributed uniformly on T. rhodesiense bloodstream forms. No lectin receptors were visualized on control preparations. Culture procyclics lacked a cell surface coat and were agglutinated by Con A and WGA but not RCA, SBA, PP and FBP. Procyclics were not agglutinated by lectins in the presence of competing sugar at 0.25 M.(ABSTRACT TRUNCATED AT 250 WORDS)     

Lectin histochemistry of rainbow trout (Oncorhynchus mykiss) gill and skin

In order to characterize the glycoconjugate residues in skin and gills of the adult rainbow trout, the binding pattern of five biotinylated lectins with different carbohydrate specificities was examined. In the skin, mucous cells revealed binding sites for PNA and SBA; filament-containing cells were additionally labelled with Con A. However, the basal cell layer showed no reaction. In the gill, subpopulations of mucous cells reacted with Con A, PNA, SBA and UEA-I. This broader spectrum of glycoconjugates in gill mucous cells compared with the epidermal mucous cells could point to the additional function of gill mucus in ion and osmoregulation. Lectin binding sites were less common in the respiratory epithelial cells of the secondary lamellae than in those of the primary lamellae. Chloride cells revealed mannose, galactose and fucose residues. Immature chloride cells, as indicated by a comparison with Na⁺/K⁺ ATPase immunolabelling, reacted with Con A; subpopulations of them reacted with PNA, SBA and UEA-I. The results form the basis for further investigations in which these cell populations can be analysed under different environmental conditions     

Lymphocyte receptors for polyclonal T mitogens: II. High-molecular-weight glycoproteins are the best candidate sites for mitogenic action by concanavalin A and galactose oxidase

Murine lymphocytes oxidized by galactose oxidase were radiolabeled by reduction with NaB³H₄. The labeled cells were incubated with Con A and the Con A-Con A receptor complexes formed in situ on the viable cells were isolated by immuno-precipitation with anti-Con A serum and fixed Staphylococcus aureus. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis fluorography analysis of the precipitates demonstrated four high-molecular-weight glycoproteins which were oxidized by GO and which bound Con A. These same four glycoproteins were also oxidized and labeled by $\text{IO}{}_4\text{NaB}{}^3\text{H}{}_4$. [³H]Tyrosine biosynthetic labeling identified these four plus several other Con A receptors. Because Con A sterically inhibits GO mitogenic stimulation, these four glycoproteins are likely to represent the necessary sites of oxidative mitogenic action and are good candidates for the targets of Con A mitogenesis.     

Production of monoclonal antibodies against a cell surface concanavalin a binding glycoprotein

Concanavalin A-binding (Con A)-binding cell surface glycoproteins were isolated, via Con A-affinity chromatography, from Triton X-100-solubilized Chinese hamster ovary (CHO) cell plasma membranes. The Con A binding glycoproteins isolated in this manner displayed a significantly different profile on sodium dodecyl sulfate-polyacrylamide gels than did the Tritonsoluble surface components, which were not retarded by the Con A-Sepharose column. [¹²⁵I]-Con A overlays of the pooled column fractions displayed on sodium dodecyl sulfate-polyacrylamide gel electro-phoresis (SDS-PAGE) demonstrated that there were virtually no Con A receptors associated with the unretarded peak released by the Con A-Sepharose column, whereas the material which was bound and specifically eluted from the Con A-Sepharose column with the sugar hapten α-methyl-D-mannopyranoside contained at least 15 prominent bands which bound [¹²⁵I]-Con A. In order to produce monoclonal antibodies against various cell surface Con A receptors, Balb/c mice were immunized with the pooled Con A receptor fraction. Following immunization spleens were excised from the animals and single spleen cell suspensions were fused with mouse myeloma P3/X63-Ag8 cells. Numerous hybridoma clones were subsequently picked on the basis of their ability to secrete antibody which could bind to both live and glutaraldehyde-fixed CHO cells as well as to the Triton-soluble fraction isolated from the CHO plasma membrane fraction. Antibody from two of these clones was able to precipitate a single [¹²⁵I]-labeled CHO surface component of ～265,000 daltons.     

Effects of con A and other lectins on pure 5'nucleotidase isolated from lymphocyte plasma membranes.

Inhibition of purified or membrane-bound 5′nucleotidase by various lectins was studied in lymphocytes from pig mesenteric lymph nodes. Con A or $\text{Lens culinaris}$ lectin LcH inhibited (75 %) purified 5′nucleotidase by a non-competitive process without cooperativity. Inhibition by these lectins of 5′ nucleotidase activity in whole lymphocytes, plasma membranes (untreated or solubilized) and LcH-receptor fraction displayed high positive cooperativity, reached higher level (90 %) and was of mixed type. An interaction between lectin receptors and 5′nucleotidase accounted for these differences. Wheat germ agglutinin (WGA) and divalent Con A which are not mitogenic for T lymphocytes had no effect on 5′nucleotidase; pokeweed mitogen (PWM), mitogen of T and B cells, was not inhibitor. When membrane proteins were cross-linked by glutaraldehyde, Con A inhibition of whole lymphocyte 5′nucleotidase presented the same properties as the purified enzyme. Possible correlation between 5′nucleotidase inhibition and lymphocyte stimulation is discussed.     

The effects of lectins on the interaction between macrophages and bone in vitro

Summary Recent studies have demonstrated that the attachment of elicited rat macrophages to bone is mediated by specific saccharides located on the cell and/or bone surfaces. We have used a macrophage-bone culture system to study the effects of two lectins, concanavalin A (con A) and soybean agglutinin (SBA), on the morphology of macrophage attachment to a devitalized bone surface and subsequent functional activity. Macrophages were obtained from 3- to 4-week-old rats by peritoneal lavage and the adherent pool was used to prepare cell suspensions. Con A-treated, SBA-treated or control cell suspensions were aliquoted onto the endocranial surface of devitalized rat calvariae. The cells were allowed to attach for 1 h at 37° C, after which, the bone samples were removed from culture and prepared for scanning electron microscopy (SEM). The morphology of con A-treated macrophages attached to bone was markedly different from that of control or SBA-treated cells. Con A altered the attachment and subsequent spreading of macrophages on bone as visualized by SEM. Furthermore, the number of con A-treated cells that attached to bone and the average surface area of cell membrane apposed to the matrix was significantly different from that of control or SBA-treated cells. A ⁴⁵Ca bone-release assay was performed to evaluate the functional significance of the morphological findings. Lectin-treated or control cell suspensions were allowed to attach to the endocranial surface of ⁴⁵Ca pre-labeled calvariae for 1 h. Following attachment, the samples were cultured for 72 h. The con A-treated cultures demonstrated a significant decrease in the release of ⁴⁵Ca after 48 and 72 h in comparison to control cultures, while the ⁴⁵Ca released from SBA-treated cultures did not differ significantly from controls. These results suggest that certain sugar residues common to membrane-associated glycoconjugates and the organic component of the bone matrix regulate the attachment of macrophages to bone and their subsequent bone-resorbing activity.     

A history of theories of acquired immunity

Alloimmune mouse spleen cells are capable of carrying out nonspecific cell-mediated cytolysis of syngeneic target cells when incubated in the presence of lectins such as Con A or PHA (lectin-dependent cell-mediated cytotoxicity). In the present study plant lectins from a variety of sources were examined for their ability to participate in alloimmune-LDCC. Reactivity was then compared to mitogenic activity and the ability to activate cytotoxic effector cells in vitro. Of the lectins tested only those reported to be T-cell mitogens were capable of participating in alloimmune-LDCC. Agglutinating but nonmitogenic lectins (e.g., WGA) or mitogens such as LPS or PWM failed to yield positive LDCC. Of the T-cell mitogens demonstrating positive reactivity in the alloimmune-LDCC assay, only a portion were able to generate cytolytic activity when incubated with normal spleen cells in vitro (Con A, GPA, lentil). Crude PHA, purified erythroagglutinin, or leukagglutinin failed to generate cytotoxic effector cells in this system even though these were mitogenic and demonstrated positive alloimmune-LDCC. The results suggest that T-cell mitogens interact with cytotoxic effector cells in a manner which specifically triggers cytolysis. The relationship of this interaction to other lymphocyte-lectin interactions is discussed.     

Lectin histochemistry of rainbow trout (Oncorhynchus mykiss) gill and skin

In order to characterize the glycoconjugate residues in skin and gills of the adult rainbow trout, the binding pattern of five biotinylated lectins with different carbohydrate specificities was examined. In the skin, mucous cells revealed binding sites for PNA and SBA; filament-containing cells were additionally labelled with Con A. However, the basal cell layer showed no reaction. In the gill, subpopulations of mucous cells reacted with Con A, PNA, SBA and UEA-I. This broader spectrum of glycoconjugates in gill mucous cells compared with the epidermal mucous cells could point to the additional function of gill mucus in ion and osmoregulation. Lectin binding sites were less common in the respiratory epithelial cells of the secondary lamellae than in those of the primary lamellae. Chloride cells revealed mannose, galactose and fucose residues. Immature chloride cells, as indicated by a comparison with Na⁺/K⁺ ATPase immunolabelling, reacted with Con A; subpopulations of them reacted with PNA, SBA and UEA-I. The results form the basis for further investigations in which these cell populations can be analysed under different environmental conditions This revised version was published online in November 2006 with corrections to the Cover Date.     

Lectin of Concanavalin A as an anti-hepatoma therapeutic agent

Liver cancer is the predominant cause of cancer mortality in males of Southern China and Taiwan. The current therapy is not satisfactory, and more effective treatments are needed. In the search for new therapies for liver tumor, we found that Concanavalin A (Con A), a lectin from Jack bean seeds, can have a potent anti-hepatoma effect. Con A after binding to the mannose moiety on the cell membrane glycoprotein is internalized preferentially to the mitochondria. An autophagy is triggered which leads to cell death. Con A as a T cell mitogen subsequently activates the immune response in the liver and results in the eradication of the tumor in a murine in situ hepatoma model. The liver tumor nodule formation is inhibited by the CD8⁺ T cells, and a tumor antigen-specific immune memory is established during the hepatic inflammation. The dual properties (autophagic cytotoxicity and immunomodulation) via the specific carbohydrate binding let Con A exert a potent anti-hepatoma therapeutic effect. The novel mechanism of the Con A anti-hepatoma effect is discussed. The prototype of Con with an anti-hepatoma activity gives support to the search for other natural lectins as anti-cancer compounds.     

Surface Alterations of Cells Carrying RNA Tumour Virus Genetic Information

CELLS transformed by the DNA tumour viruses, polyoma virus and SV40, are agglutinated by lectins such as wheat germ agglutinin¹, concanavalin A (Con A)² and soybean agglutinin³. Agglutination in these cases presumably reflects changes in the cell surface related to the transformed properties of the cell; studies with a temperature-dependent mutant of polyoma virus has shown that cell surface changes are controlled by viral genes⁴. Here we describe experiments in which we investigated the agglutinability of cells transformed by RNA tumour viruses. One recent report had suggested that cells transformed by RNA tumour viruses were not specifically agglutinated⁵, whereas a second more recent report claimed the specific agglutination of cells transformed by RSV⁶. We find that transformed rat, mouse and cat cells that replicate the sarcoma-leukaemia virus complex of murine (MSV) and feline (FeSV) origin are strongly agglutinated by Con A, but mouse and human cells that replicate the murine and feline leukaemia virus components alone are not agglutinated. The ability to agglutinate is rapidly acquired by normal mouse cells on infection with the murine sarcoma virus at a rate that parallels virus replication. In contrast to the results obtained with cells producing virus, non-virus-producing transformed hamster and mouse cells that synthesize virus-specific RNA are either not agglutinated or are agglutinated to a lesser degree. These results suggest that the cell surface alterations responsible for agglutination are not necessarily associated with the transformed state of the cell, but rather with the possession of sarcoma virus-specific information.     

Induction of Autophagy by Concanavalin A and its Application in Anti-Tumor Therapy

Concanavalin A (Con A), a lectin from Jack bean seeds that, once bound to the mannose moiety on the cell membrane glycoprotein, is internalized preferentially to the mitochondria. A BNIP3-mediated mitochondria autophagy is then induced, and causes the tumor cells to undergo autophagic cell death. Con A is also a T cell mitogen that can induce autoimmune hepatitis in mice. Because of the dual properties (autophagic cytotoxicity and immunomodulation) via the specific mannose binding, Con A can exert a potent anti-hepatoma therapeutic effect by inhibiting tumor nodule formation in the liver and prolonging the survival of the tumor-bearing mice. The anti-tumor effect is primarily mediated by activated CD8⁺ T cells, and will also establish a tumor antigen-specific immune memory during the hepatic inflammation. This finding provides a novel mechanism in which Con A can be used as an anti-hepatoma agent, and also gives support for the search for natural lectins as anti-cancer compounds.

Addendum to:

Concanavalin A Induces Autophagy in Hepatoma Cells and has a Therapeutic Effect in a Murine In Situ Hepatoma Model

C.P. Chang, M.C. Yang, H.S. Liu, Y.S. Lin, H.Y. Lei HY.Hepatology 2007; 45:286-296.