Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0699790 (colon cancer)
 28,837 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Specific inhibitors of the glycosylation of O-glycosidically linked glycoproteins have not previously been described. When tested for their effects on mucin glycosylation in a mucin-producing colon cancer cell line, LS174T, benzyl-, phenyl-, and p-nitrophenyl-N-acetyl-alpha-galactosaminide inhibited the formation of fully glycosylated mucin in a dose-dependent manner. Free aryl-oligosaccharides were found in the medium of treated cells labeled with [3H]glucosamine, [3H]galactose, [3H]fucose, [3H]mannosamine, or phenyl-alpha-[6-3H] N-acetylgalactosamine. UDP-Gal:GalNAc-beta 1,3-galactosyltransferase was inhibited by aryl-N-acetyl-alpha-galactosaminides but not by a number of other aryl-glycosides. Treatment with these inhibitors also causes reversible morphologic changes including formation of intercellular cysts. Aryl-N-acetyl-alpha-galactosaminides can be useful for the structural and functional studies of mucin macromolecules and other O-linked glycoproteins.
 ...
PMID:Inhibition of mucin glycosylation by aryl-N-acetyl-alpha-galactosaminides in human colon cancer cells. 250 74

Colon cancer cells in culture synthesize and secrete mucin glycoproteins, which carry a number of cancer-associated antigens. However, the structures and mechanisms of biosynthetic processing are not well understood. Mucins synthesized and secreted by LS174T human colon cancer cells were compared to those in LS174T xenografts in athymic mice. Mucins radiolabeled with glucosamine or sulfate were purified by gel filtration and cesium chloride density gradient centrifugation. The mucins were of high molecular weight and were resistant to chondroitinase ABC, hyaluronidase and HNO2 treatment. They were, however, susceptible to pronase digestion and mild alkaline treatment. Using radiochemical precursors, the cellular mucin was shown to contain fucose, galactose, N-acetylgalactosamine, N-acetylglucosamine, N-acetylneuraminic acid, and sulfate. Oligosaccharides released by beta-elimination had N-acetylgalactosaminitol as the reduced amino sugar and also unreduced galactosamine, indicating that there is N-acetyl-galactosamine O-glycosidically attached to protein core and also peripheral N-acetyl-galactosamine not directly linked to protein. DEAE-cellulose chromatography of mucins showed two major peaks with both intracellular and secreted mucins, but xenograft mucins also had more acidic components. Sulfate-labeled mucins were shifted to less acidic peaks by neuraminidase digestion, which indicates that the same mucin molecules are both sialylated and sulfated. We conclude that the intracellular mucins of cultured colon cancer cells, those secreted into the medium, and those in nude mouse xenografts are chemically similar, but differ in sialic acid and sulfate content. This experimental model system, LS174T cells maintained in culture and as nude mouse xenografts, may be useful for further biosynthetic and structural studies of colon cancer mucin.
 ...
PMID:Comparison of metabolically labeled mucins of LS174T human colon cancer cells in tissue culture and xenograft. 273 49

Mucin from xenografts of LS174T human colon cancer cells was treated with anhydrous HF for 1 h at 0 degree C to give a product (HFA) with over 80% of the glucosamine and hexose removed, but retaining some galactosamine, and for 3 h at room temperature to give a product (HFB) devoid of carbohydrate. Rabbit antibodies against HFA bound to HFA much more than to HFB, and bound to native mucin to an intermediate extent. Antibodies to HFB bound to HFB more than to HFA, and did not bind to native mucin. Both HFA and native mucin bound a number of lectins, but HFB did not. By SDS/polyacrylamide-gel electrophoresis and size-exclusion h.p.l.c., native mucin and HFA are of apparent molecular mass greater than 400 kDa, whereas HFB is heterogeneous and of low molecular mass. On Western blots, antibody to HFA detected both high-molecular-mass mucin and a 90 kDa protein in homogenates of LS174T cells. Antibody to HFB detected a major 70 kDa band as well as higher-molecular-mass species. In tissue sections of normal colon and colon cancers, antibody to HFA showed both cytoplasmic and extracellular staining, whereas antibody to HFB generally stained only cytoplasmic antigens. These results indicate that anti-HFB antibody is specific for apo-mucin, whereas anti-HFA antibody is specific for GalNAc-apo-mucin.
 ...
PMID:Deglycosylation of mucin from LS174T colon cancer cells by hydrogen fluoride treatment. 277 37

Mucin glycoproteins are major secretory products of the colon and contain O-linked oligosaccharides synthesized on a polypeptide backbone. The initial step in the synthesis of O-linked oligosaccharides is the addition of N-acetylgalactosamine to serine or threonine residues forming the Tn antigen. This substance can then receive additional carbohydrate residues such as sialic acid to form sialosyl-Tn antigen, or galactose to form T antigen. In the colon, the T antigen is an oncodevelopmental cancer-associated antigen but little is known about Tn and sialosyl-Tn expression. The present comparative immunohistochemical study was performed to analyze the expression of these antigens in fetal, normal adult, and malignant colorectal tissues with an aim toward elucidating whether Tn and sialosyl-Tn are also oncodevelopmental colon cancer-associated antigens and to gain insight into the earliest steps of mucin glycosylation in colonocytes. We used three reagents to detect Tn antigen (two monoclonal antibodies ETn1.01 and CU-1, and one lectin Vicia villosa), two reagents to detect sialosyl-Tn (monoclonal antibodies TKH2 and B72.3) and one to detect T antigen (monoclonal antibody AH9-16). Except for occasional reactivity with VVA and CU-1, cells of normal colonic mucosa did not express Tn, sialosyl-Tn, or T antigens. However, in the transitional mucosa immediately adjacent to cancer, all three antigens were expressed (ranging from 35 to 67% of cases depending upon the reagent). In colon cancers, the percentage of cases expressing each antigen were as follows: Tn 72-81%, sialosyl-Tn 93-96%, and T 71%. Unlike T antigen, which was preferentially expressed by moderately well- and well-differentiated adenocarcinomas, both Tn and sialosyl-Tn antigens were expressed by most histological subsets of colon cancers, including poorly differentiated adenocarcinomas and mucinous (colloid and signet ring cell type) carcinomas. The majority of cancers expressed both Tn and sialosyl-Tn, usually in association with T antigen. Only one cancer lacked all three antigens. Fetal colonic mucosal cells expressed all three antigens, particularly in goblet cell mucin. These results indicate that like T antigen, Tn and sialosyl-Tn are oncodevelopmental cancer-associated antigens in the colon. Moreover, Tn and sialosyl-Tn antigens appear to be useful markers of poorly differentiated adenocarcinomas and mucinous carcinomas: two histological subsets that often fail to express other cancer-associated antigens and that are often associated with a poor clinical outcome.(ABSTRACT TRUNCATED AT 400 WORDS)
 ...
PMID:Expression of Tn, sialosyl-Tn, and T antigens in human colon cancer. 290 46

Altered expression of ABH blood group substances is a common feature of human colorectal carcinoma, yet it remains unclear how these structural changes influence the biological properties of tumor cells. Azoxymethane-induced rat colon tumors display many features of the human disease, thereby providing a potentially useful model to study the role of blood group substances in colon cancer progression. We have prepared monoclonal antibodies to a microsomal fraction isolated from an azoxymethane-induced rat colon tumor and selected an antibody that detects cancer-associated changes. Monoclonal antibody (mAb) 3A7 recognizes a determinant on type 2 chain blood group A (GalNAc alpha 1-3[Fuc alpha 1-2]Gal beta 1-4GlcNAc-R) and B (Gal alpha 1-3[Fuc alpha 1-2]Gal beta 1-4GlcNAc-R) oligosaccharides. Expression of the epitope detected by this antibody was developmentally regulated in rat colon, with maximal expression from day 4-21 after birth. Immunohistochemical staining and Western blotting analyses of azoxymethane-induced colon tumors revealed increased expression of the epitope in all of the 21 colonic tumors examined, including preneoplastic glands within transitional mucosa. Conventional and signet-ring adenocarcinomas that had invaded through the muscularis propria (Duke's B2) consistently showed the most intense staining with mAb 3A7, including regions depicting angioinvasion. Some of the lymph node metastases (Duke's C2) stained poorly with the antibody. The epitope was also expressed in blood group A positive human colon carcinoma cell lines, including HT29 and SW480 but not by SW620, a cell line derived from a lymph node metastasis isolated in vivo from the SW480 primary tumor, or in the blood group B cell line SW1417. The glycoproteins detected by mAb 3A7 in rat colon tumors and HT29 cells ranged in size between 50 and 200 kd, including a major species of 140 kd. Affinity chromatography of detergent lysates of normal rat colon on the blood group A specific lectin Dolichos biflorus (DBA)-agarose resulted in nearly quantitative binding of glycoprotein species detected by the antibody. By contrast, immunoreactive glycoproteins from rat colon tumors or HT29 cells bound poorly to DBA-agarose but were retained by another blood group A-binding lectin, Helix-pomatia (HPA)-agarose. These results indicate that colon carcinogenesis results in quantitative as well as qualitative changes in oligosaccharides detected by mAb 3A7 and suggest that the combined use of mAb 3A7 and blood group A-specific lectins may provide a useful tool for early detection of colon cancer.
 ...
PMID:Monoclonal antibody recognizing a determinant on type 2 chain blood group A and B oligosaccharides detects oncodevelopmental changes in azoxymethane-induced rat colon tumors and human colon cancer cell lines. 753 50

Previous studies from our laboratory have shown that benzyl-alpha-GalNAc inhibits the glycosylation of mucin in colon cancer cells. In this study, we determined whether benzyl-alpha-GalNAc inhibits mucin glycosylation in KATO III gastric cancer cells. We also examined its effects on expression of mucin antigens, and compared the mucins made by KATO III with those of a colonic cancer cell line, Caco-2. Results of these experiments suggest that benzyl-alpha-GalNAc (2 mM) inhibited [3H]glucosamine labelling of mucins by 82% in KATO III and by 70% in Caco-2. For both cell lines, the mucin secreted in the presence of benzyl-alpha-GalNAc was less acidic. Both cell lines secreted benzyl-oligosaccharides, but those from KATO III (8-9 sugars) were larger than those from Caco-2 (6-7 sugars). In mucins purified from the medium of treated cells, peripheral carbohydrate antigens (sialyl Lex in KATO III and terminal fucose in Caco-2) were decreased (compared with control), while core carbohydrate antigens (T antigen in both cell lines and sialyl Tn in Caco-2) were increased. Western blots of cell homogenates showed differences between KATO III and Caco-2 in MUC 1 apomucin protein antigens, in sialyl Lex and in sialyl Tn antigens. We conclude that benzyl-alpha-GalNAc does inhibit the glycosylation of mucin in KATO III gastric cancer cells as in human colon cancer cells, but that alterations in mucin antigens occur in a cell line-specific manner.
 ...
PMID:Inhibition of mucin synthesis by benzyl-alpha-GalNAc in KATO III gastric cancer and Caco-2 colon cancer cells. 757 79

UDP-GlcNAc: GalNAc-R beta 3-GlcNAc-transferase (core 3 beta 3-GlcNAc-T, where GlcNAc is N-acetyl-D-glucosamine, GalNAc is N-acetyl-D-galactosamine and T is transferase) is expressed in a tissue-specific fashion and is high in normal colonic tissue, but downregulated in colon cancer. To further study the control of this enzyme, we examined the activity in pig, rat and human colonic tissues, and several human cancer cell lines. The enzyme was difficult to solubilize by detergents and was extremely unstable in the solubilized form. Using synthetic derivatives of the GalNAc-R substrate, we showed that the specificity of the enzyme in normal rat and human colonic mucosa requires all the substituents of the GalNAc-sugar ring of substrates for maximal activity. Core 3 beta 3-GlcNAc-T was significantly influenced by the structure of the aglycon group. None of the inactive substrate derivatives could inhibit the activity. N-Iodoacetamido-galactosamine alpha-benzyl was a weak substrate and significantly inhibited the incorporation of GLcNAc into GalNAc alpha-benzyl by human colonic homogenates. Surprisingly, none of the colonic cancer cell lines or any other cancer and leukaemia cells examined exhibited detectable activity of the enzyme, although a number of other glycosyltransferase activities involved in O-glycan biosynthesis were active. Mixing experiments did not reveal an endogenous inhibitor in HL60 cells or an activator of core 3 beta 3-GlcNAc-T in human colonic mucosa. Thus, the lack of core 3 beta 3-GlcNAc-T in human colonic mucosa. Thus, the lack of core 3 beta 3-GlcNAc-T activity in cancer cell lines may be due to cell transformation or cell culturing.
 ...
PMID:Synthesis of O-glycan core 3: characterization of UDP-GlcNAc: GalNAc-R beta 3-N-acetyl-glucosaminyltransferase activity from colonic mucosal tissues and lack of the activity in human cancer cell lines. 765 72

Inositol hexaphosphate (InsP6 or phytic acid) has been shown to have antineoplastic action in in vivo models of colon carcinogenesis. We therefore investigated its effect on proliferation and differentiation of the human colon cancer cell line HT-29 in vitro. Proliferation was evaluated by neutral red incorporation assay, and differentiation was assessed by expression of the markers, cytokeratin, carcinoembryonic antigen (CEA) and beta-D-galactose-[1-->3]-N-acetyl-galactosamine (Gal-GalNAc). InsP6 in the culture media (0.66-10 mM) inhibited cell proliferation in a dose-dependent manner (P < 0.001), while inositol or inositol hexasulfate used as controls or media without InsP6 did not show any suppressive effect. The expression of the tumor marker, Gal-GalNac, was augmented (100.7% increase) by low dose (0.66 mM) of InsP6 but was subsequently suppressed with higher concentrations of InsP6. The expression of cytokeratin and CEA were both augmented by either InsP6 or inositol at all concentrations tested, although the degree of augmentation was milder with inositol than with InsP6. The combination of InsP6 and inositol (both 0.66 mm) resulted in augmentation (P < 0.001) of cytokeratin expression, while that of CEA remained unchanged. The inhibitory effect of InsP6 on cell proliferation was not altered by combination with additional inositol at any concentrations tested. Our results show that InsP6 inhibits cell proliferation and concomitantly increases differentiation and is therefore a candidate chemopreventive and chemotherapeutic agent for human large intestinal cancer.
 ...
PMID:Growth inhibition and differentiation of HT-29 cells in vitro by inositol hexaphosphate (phytic acid). 769 27

Neoplastic transformation is commonly associated with altered glycosylation of proteins and lipids. To understand the basis for altered mucin glycosylation, we have examined the distribution of RER markers, a cis-Golgi resident protein, and the GalNAc alpha-O-Ser/Thr epitope (Tn) in human colon cancer cells and in normal colon. In cultured mucin-producing colon cancer cells, Gal-NAc alpha-O-Ser/Thr was found in mucin droplets and in RER cisternae. In addition, the Golgi apparatus was disorganized in a proportion of cells and a 130 kDa cis-Golgi resident protein was also abnormally redistributed to the RER. The distribution of the MUC2 intestinal apomucin, protein disulphide isomerase, Gal-NAc alpha-O-Ser/Thr, and the 130 kDa cis-Golgi resident protein was analysed in normal colon and in colon cancer tissues. In normal colon, MUC2 apomucin and protein disulphide isomerase were located in the RER, whereas the cis-Golgi resident protein and GalNAc alpha-O-Ser/Thr were detected only in the cis-Golgi compartment. In contrast, the two Golgi markers colocalized with the MUC2 apomucin and protein disulphide isomerase in the RER of colon cancer cells. On the basis of these results, we propose that in colon cancer cells a redistribution of molecules normally present in the Golgi apparatus takes place; this alteration may contribute to the abnormal glycosylation of proteins and lipids associated with neoplastic transformation.
 ...
PMID:cis-Golgi resident proteins and O-glycans are abnormally compartmentalized in the RER of colon cancer cells. 769 49

It has previously been reported that about 90% of human colon carcinomas express increased levels of the sialyltransferase which adds sialic acid in alpha 2,6 linkage to galactose residues on N-linked chains of glycoproteins. To ascertain whether colon cancer tissues actually express increased amounts of alpha 2,6-sialylated sugar chains on their glycoconjugates, we screened tissue sections of normal colon, benign and malignant colon tumors with digoxigenin-conjugated Sambucus nigra agglutinin (SNA), a NeuAc alpha 2,6Gal/GalNAc-specific lectin. At the concentration of lectin used, epithelial cells of all the 13 normal colon specimens examined were unreactive; 3 out of 8 benign lesions showed a weak reactivity being the remainder unreactive, while 23 out of 26 carcinomas were positive at a variable degree. Qualitative differences were evident among different carcinoma specimens. In some cases a large number of intensely stained intracytoplasmatic particles was present, thus suggesting that reactivity may be associated with secretions, very likely of mucus droplets. In other specimens there was a more uniform distribution of the staining which suggest that reactivity is associated with cell membrane glycoconjugates. These data indicate that the expression of a2,6-sialylated sugar chains is remarkably increased in the majority of colon cancer specimens examined.
 ...
PMID:Expression of alpha 2,6-sialylated sugar chains in normal and neoplastic colon tissues. Detection by digoxigenin-conjugated Sambucus nigra agglutinin. 769 64


<< Previous 1 2 3 4 5 6 Next >>