Mark Jordinson

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 fabaagglutinin (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.

Proglucagon-Derived Peptides in Intestinal Epithelial Proliferation

Proglucagon-derived peptides have been implicated in the control of intestinal mucosal cell division. To investigate the actions of these peptides on intestinal cell proliferation, different doses of enteroglucagon, oxyntomodulin, glucagon-like peptide-1 (GLP-1) and glucagon-like peptide-2 (GLP-2) were tested in male Wistar rats maintained on total parenteral nutrition. Crypt cell proliferation was assessed by the analysis of arrested metaphases in microdissected crypts. Enteroglucagon and oxyntomodulin had no effect on intestinal weight or cell proliferation. GLP-1 had a slight effect on stomach and small intestinal weights and on epithelial cell proliferation in the small and large intestines. GLP-2 infusion dose-dependently increased the weights of the stomach, small intestine, colon, and cecum and increased crypt cell proliferation in the small and large intestines of parenterally fed rats. In orally fed animals, GLP-2 increased intestinal weight but had little effect on proliferation. Therefore, of the proglucagon-derived peptides, GLP-2 appears to be a major mediator of intestinal epithelial proliferation.

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.

Comparison of the effects of concanavalin-A and epidermal growth factor on epithelial cell proliferation in the rat intestine.

Concanavalin‐A, the lectin present in Jack beans, binds to mannose‐ and glucose‐containing residues and can interact with the epidermal growth factor receptor and moderate cell proliferation in vitro.

Characterization of the E-cadherin-catenin complexes in pancreatic carcinoma cell lines.

E‐cadherin and its associated cytoplasmic proteins α‐, β‐, and γ‐catenins play important roles in cell adhesion and signal transduction, as well as in maintenance of the structural and functional organization of polarized epithelial cells. In this study, the expression, distribution, and complex assembly of catenins with E‐cadherin was analysed at the steady state in a panel of human pancreatic adenocarcinoma cell lines (BxPc3, HPAF, T3M4, and PaTuII cell lines). The expression and subcellular distribution were determined by western blotting and immunocytochemistry. Co‐immunoprecipitation and cross‐linking studies were performed to examine the complex assembly in both Triton X‐100 (TX‐100)‐soluble and ‐insoluble fractions. In BxPc3 and T3M4 cells, E‐cadherin exists in two complexes, one with α‐ and γ‐catenin, and the other with β‐catenin alone. In HPAF cells there are two complexes, one consisting of E‐cadherin with α‐ and β‐catenin, and another of E‐cadherin with γ‐catenin. In PaTuII cells, there is only a single complex of E‐cadherin with α‐catenin and γ‐catenin. Modification of E‐cadherin–catenin complexes in HPAF and PaTuII cells was associated with loss of membranous E‐cadherin immunolocalization. The common denominator is impaired β‐catenin association with either E‐cadherin (PaTuII) or α‐catenin (BxPc3 and T3M4). This may suggest the presence of distinct mechanisms that modulate the assembly of each complex, which could disturb the tumour suppressor function of E‐cadherin and the catenins. Copyright

Soybean agglutinin stimulated cholecystokinin release from cultured rabbit jejunal cells requires calcium influx via L-type calcium channels.

We have studied the mechanism of soybean agglutinin (SBA) mediated cholecystokinin (CCK) release in enriched cultured cholecystokinin-secreting cells. 12-O-Tetradecanoylphorbol-13-acetate 1 mM significantly stimulated release of CCK-like-immunoreactivity (CCK-LI) by 55%+/-17% (p < 0.05), which was blocked by the protein kinase C inhibitor staurosporine 100 nM. Forskolin 10 mM stimulated CCK-LI by 82%+/-12% (p < 0.05) and this was inhibited by somatostatin 1 nM. 1-Phenylalanine 20 mM and Bay K 8644 1 mM stimulated CCK-LI by 69%+/-22% and 60%+/-19% respectively (p < 0.05), these responses were completely abolished by the L-type calcium channel antagonist verapamil 10 mM. SBA 10 and 100 microg/ml stimulated CCK-LI by 65%+/-22% and 74%+/-24% respectively (p < 0.05). The effect of SBA was inhibited by verapamil and N-acetylgalactosamine. We conclude that SBA stimulates CCK-LI through calcium flux via L-type calcium channels.

Lectins: from basic science to clinical application in cancer prevention

Many physiological functions are attributable to lectin-carbohydrate interactions. Lectins are currently being studied for their ability to destroy tumour growth by binding to specific carbohydrate motifs on cancer cells. Cell-surface molecules, including growth factor receptors are often glycosylated, and lectins may act by binding to these. Certain lectins effect the proliferation of intestinal epithelial cells. This effect is cell-type and lectin specific and occurs in the intestine of intact animals, in human colonic explants and colorectal cancer cell lines. Lectins present in mammalian tissue are involved in cell-matrix adhesion, differentiation, lymphocyte circulation and immunomodulation. Mammalian lectins contribute to detection, diagnosis and prognosis of tumour cells, and can be targeted for therapy. New lectins of plant and mammalian origin that have one or more of these functions are currently being developed as tools that could be used to target tumour cells.