Enzymatic basis for changes in fucoganglioside during chemical carcinogenesis. Induction of a specific alpha-fucosyltransferase and status of an alpha-galactosyltransferase in precancerous rat liver and hepatoma

Cancer-Associated Glycosphingolipids as Tumor Markers and Targets for Cancer Immunotherapy

Aberrant expression of glycosphingolipids is a hallmark of cancer cells and is associated with their malignant properties. Disialylated gangliosides GD2 and GD3 are considered as markers of neuroectoderm origin in tumors, whereas fucosyl-GM1 is expressed in very few normal tissues but overexpressed in a variety of cancers, especially in small cell lung carcinoma. These gangliosides are absent in most normal adult tissues, making them targets of interest in immuno-oncology. Passive and active immunotherapy strategies have been developed, and have shown promising results in clinical trials. In this review, we summarized the current knowledge on GD2, GD3, and fucosyl-GM1 expression in health and cancer, their biosynthesis pathways in the Golgi apparatus, and their biological roles. We described how their overexpression can affect intracellular signaling pathways, increasing the malignant phenotypes of cancer cells, including their metastatic potential and invasiveness. Finally, the different strategies used to target these tumor-associated gangliosides for immunotherapy were discussed, including the use and development of monoclonal antibodies, vaccines, immune system modulators, and immune effector-cell therapy, with a special focus on adoptive cellular therapy with T cells engineered to express chimeric antigen receptors.

Rat encodes the paralogous gene equivalent of the human histo-blood group ABO gene. Association with antigen expression by overexpression of human ABO transferase

We cloned a rat ABO homologue and established human A- and B-transferase transgenic rats. A DNA fragment corresponding to exon 7 of the human ABO gene was amplified from Wistar rat genomic DNA and sequenced. Using the amplified fragments as a probe for Southern blotting, multiple hybridized bands appeared on both EcoRI- and BamHI-digested genomes of seven rat strains, which showed variations in the band numbers among the strains. Four cDNAs were cloned from a Wistar rat, three of which showed A-transferase activity and one of which showed B-transferase activity. These activities were dependent on the equivalent residues at 266 and 268 of human ABO transferase. Wild Wistar rats expressed A-antigen in salivary gland, intestine, and urinary bladder tissue, but B-antigen was not stained in any organs studied, whereas a transcript from the ABO homologue with B-transferase activity was ubiquitous. Human A-transferase and B-transferase were transferred into Wistar rats. A-transgenic rats expressed A-antigen in ectopic tissue of the brain plexus, type II lung epithelium, pancreas, and epidermis. B-antigen in the B-transgenic rat was expressed in the same organs as A-transgenic rats. These results may shed light on the function and evolution of the ABO gene in primates.

Cloning and expression of the catalytic domain from rat hepatoma H35 cell GDP-fucose:GM1 alpha 1-->2fucosyltransferase, an enzyme which is activated during early stages of chemical carcinogenesis in rat liver

A ganglioside GM1-specific alpha 1-->2fucosyltransferase is induced during the early stages of chemical carcinogenesis with N-2-acetylaminofluorene (AAF) in rat liver hepatocytes. The induction of this enzyme gives rise to the expression of a fucose-containing ganglioside with the same determinant structure as blood group B on a GM1 ganglioside core. Fucoganglioside synthesis is not found in normal rat liver but is elevated in premalignant liver and is often highly expressed in derived rat hepatoma cell lines. Based upon the consensus sequence from portions of previously cloned human, rabbit, and rat alpha 1-->2fucosyltransferase enzymes, primers were designed which were used in RT-PCR experiments with rat hepatoma H35 cell total RNA to generate cDNAs encoding the extracellular, catalytic domain of the H35 cell alpha 1-->2fucosyltransferase. Sequencing of these PCR fragments showed them to encode a novel enzyme with high homology to other cloned enzymes, particularly secretor alpha 1-->2fucosyltransferases. The derived sequence indicated that the 3' portion of the gene was virtually identical to the alpha 1-->2fucosyltransferase B (FTB) fragment reported earlier in rat PROb colon-adenocarcinoma cells (J-P. Piau et al. Biochem. J. 300, 623-626, 1994). A PCR product corresponding to the H35 cell alpha 1-->2fucosyltransferase was obtained from total RNA isolated from F344 rat liver after 0.03% N-2-acetylaminofluorene administration. No PCR product was obtained from total RNA isolated from normal F344 liver using PCR primers for the H35 cell alpha 1-->2fucosyltransferase. The H35 cell alpha 1-->2fucosyltransferase was expressed in the pPROTA vector and the derived fusion protein demonstrated the ability to transfer fucose to ganglioside GM1 but not to the neolacto-series acceptor nLcOse4Cer.

Biosynthesis of a blood group H1 antigen by alpha 1, 2-fucosyltransferase in PC12 cells

We have examined the expression of GDP-fucose: glycosphingolipid fucosyltransferase activity in PC12 cells and PC12 sublines in relation to the neuronal differentiation induced by nerve growth factor (NGF) or dexamethasone. Transfer of fucose to paragloboside (nLc4Cer) yielded a product which was determined to be a blood group H1 antigen (Fuc alpha 1-2Gal beta 1-4GlcNAc beta 1-3Gal beta 1-4Glc-Cer) by gas chromatography/mass spectrometry analysis and enzymatic hydrolysis, suggesting that PC12 cells have an alpha 1,2-fucosyltransferase. Lactosylceramide was also fucosylated at a reduced rate. When the differentiation of PC12 cells and PC12 subline cells, PC12D and MR31, was induced by exposure to either NGF or dexamethasone, the fucosyltransferase activity for nLc4Cer was found to decrease in both cell lines, suggesting the association with cell differentiation. This is the first report of the presence of an alpha 1,2-fucosyltransferase in cultured neuronal cell lines which catalyses the in vitro biosynthesis from nLc4Cer of a type-2 chain glycosphingolipid having the blood group H1 determinant. The disaccharides, beta-lactose and N-acetyllactosamine, were also fucosylated by PC12 cell enzyme, although the specificity for the carbohydrate structure was different from that for glycosphingolipids.

Characterization of gangliosides from Ehrlich ascites tumour cells and their variants

Differences in the nature of the gangliosides present in two types of Ehrlich ascites tumour (EAT) cells, the adherent and non-adherent EAT cells, were studied. Gangliosides were isolated by DEAE Sephadex column chromatography and analysed by high-performance thin-layer chromatography (HPTLC). The non-adherent EAT (na-EAT) cells which grow in the peritoneal cavity of mice were selected for growth on basement membrane and tissue culture plastic to give the adherent EAT (a-EAT) cells. na-EAT cells contained 1.57 nmol lipid-bound sialic acid per mg protein and at least 12 different gangliosides, including major gangliosides such as GM3, GM2, GM1, GD3, GD1a and GT1b. On the other hand, the ganglioside pattern of a-EAT cells differed significantly from that of na-EAT cells, both quantitatively and qualitatively. The content of lipid-bound sialic acid in a-EAT cells was only 0.24 nmol per mg of protein. The gangliosides in a-EAT cells were characterized as GD1a and trisialogangliosides and, significantly, a-EAT cells did not contain monosialogangliosides. Neutral glycolipids were isolated from both cell lines and their patterns were compared. In contrast to the gangliosides pattern, their neutral glycolipid patterns were similar. Glucosylceramide and lactosylceramide were the major components in both types of cells. In addition to na- and a-EAT cells, a-EAT cells were passaged in mice by intraperitoneal injection, giving rise to a third variant (c/m EAT cells). We analysed the gangliosides in c/m EAT cells to determine whether there was a change in the ganglioside pattern found in na-EAT cells. After repeated passage of c/m EAT cells in mice, the pattern of gangliosides shifted to that of na-EAT cells. Alterations of ganglioside composition may be associated with the growth environment of the murine peritoneal cavity; alternatively, a selection process may have occurred.

Determinants of differential liver-colonizing potential of variants of the MCA-38 murine colon cancer cell line

We investigated factors that might contribute to the differing liver tumor colonizing potentials of MCA-38 colonic cancer cell line variants injected into the ileocolic veins of C57Bl/6J mice. Non-colonizing (MCA-38 CD) cells were sensitive to lysis by hepatic natural killer (NK) cells in vitro (51Cr-release assay) and cells with high liver-colonizing potential (MCA-38 LD) were resistant. Following abrogation of NK activity by treatment with anti-asialoGM1, liver-colonizing ability to LD cells but not CD cells was enhanced. MCA-38 CD cells were, however, capable of initial liver colonization after ileocolic vein injection. Differing patterns of membrane sialylation may have contributed to the contrasting hepatic tumorigenicities of LD and CD cells; beta-galactoside alpha 2,6-sialyltransferase mRNA levels and activity were approximately four-fold higher in LD than CD cells and qualitative and quantitative differences existed between their ganglioside profiles. In the MCA-38 model outlined, tumor cell susceptibility or resistance to NK lysis was a relatively unimportant determinant of liver-colonizing potential.

Gangliosides associated with primary brain tumors and their expression in cell lines established from these tumors

Human primary brain tumors differ in their ganglioside composition when compared to adjacent tissues. One ganglioside found in all malignant glioma specimens, but not detected in normal adult brain, is 3'-isoLM1, a ganglioside of the lacto series. This ganglioside was also identified in medulloblastomas with astrocytic differentiation and in brain tissues containing benign proliferating astrocytes. The appearance of 3'-isoLM1 was seen over large regions of brain from glioma but was found mainly in areas either adjacent to the macroscopic tumor or areas corresponding to the tumor in the opposite hemisphere. A high concentration of 3'-isoLM1 was also seen in the corpus callosum, the anatomical structure along which glioma cells may migrate to the opposite brain hemisphere. Ganglioside expressed by cell lines established from primary malignant brain tumors varied widely among cell lines and within a given cell line propagated under different conditions. In in vitro-cultured glioma and medulloblastoma cell lines, gangliosides of the ganglio series dominated and the expression of the lacto series gangliosides, including 3'-isoLM1 was low if at all detectable. However, in vivo growth of solid subcutaneous tumors in nude mice or rats led to a significantly increased expression of the often dominant gangliosides of the lacto series and revealed a decreased expression of ganglio series gangliosides. In conclusion, these findings indicate that environmental factors could strongly influence the expression of gangliosides that may lead to a switch from the ganglio to the lacto series. These results also suggest that ganglioside 3'-isoLM1 is associated with proliferating astrocytes, of both neoplastic and non-neoplastic origin and that this ganglioside may be involved in cell-cell recognition and attachment during development and tumor cell migration.

Glycolipid changes in murine myelogenous leukemias: neutral glycolipids as markers for specific populations of leukemias

We have studied the glycolipid composition of six different murine myelogenous leukemias as well as that of T-cell leukemias and normal spleen cells. Neutral and acidic lipid fractions were isolated by column chromatography on DEAE-Sephadex and analyzed by high-performance thin-layer chromatography (HPTLC) and an HPTLC overlay method. Murine myelogenous leukemias were found to contain globo- and ganglio-series neutral glycolipids, e.g., glucosylceramide (Glc-cer), lactosylceramide (Lac-cer), globotriaosylceramide (Gb3), globoside (Gb4), Forssman glycolipid (Gb5), and asialo-GM1 (GA1). Monoblastic leukemia cells contained increased proportions of Gb3, Gb4, Gb5, and GA1. Monocytic and myelomonocytic leukemia cells contained increased proportions of Glc-cer and Lac-cer. Especially, Glc-cer accounted for approximately 60% of the total neutral glycolipids in monocytic leukemia cells. Gb3 was the major neutral glycolipid in reticulum cell neoplasm type A, and it accounted for approximately 75% of the neutral glycolipids. GA1 was the major neutral glycolipid in myeloblastic and granulocytic leukemia cells as well as T-cell leukemias. Especially, granulocytic leukemia cells contained predominantly GA1, and it accounted for approximately 80% of the total neutral glycolipids. The pattern of gangliosides in myelogenous leukemias was more complex when compared with that of the neutral glycolipids; murine myelogenous leukemias contained at least 13 gangliosides, including such major gangliosides as GM1, GM1b containing N-acetyl neuraminic acid and N-glycolyl neuraminic acid, and Ga1NAc-GM1b. Alterations of glycolipid composition in murine myeloid leukemias may be associated with cellular differentiation and maturation, and therefore these characteristic glycolipid species may be regarded as markers for specific populations of leukemia cells.

Fucosyltransferases: differential plasma and tissue alterations in hepatocellular carcinoma and cirrhosis

To determine whether abnormal metabolism of L-fucose in hepatocellular carcinoma is accompanied by alterations in the activities of fucosyltransferases, the latter were determined in plasma and liver tissue of patients with this disease and in cirrhotic and normal subjects. Activities of alpha-2/alpha-3 and alpha-6-L-fucosyltransferases were all significantly greater in plasma from patients with hepatocellular carcinoma than in plasma from cirrhotic patients or normal subjects (p less than 0.025). The activity of each enzyme was dependent, to a similar extent, on Mn2+, Mg2+ and triton X-10, irrespective of the source, and all displayed pH optimums in the range of 7.5 to 8.0. In contrast, activities of alpha-2/alpha-3 fucosyltransferases were significantly lower (p less than 0.025) in homogenates prepared from tumorous liver tissue than in that prepared from nontumorous tissue from hepatocellular carcinoma and cirrhotic patients, whereas for the alpha-6 enzyme the situation was reversed (typically, tumor tissue levels were 5 pmol/hr/mg; in nontumor tissue they were 2 pmol/hr/mg). Activities of galactosyl and mannosyltransferase in tumor tissue were greater in all cases than in nontumor cirrhotic tissue. Plasma fucosyltransferases are specifically elevated in hepatocellular carcinoma but different mechanisms appear to underlie the changes seen for alpha-2/alpha-3 and alpha-6-L-fucosyltransferases.

Changes in the ganglioside composition of human neuroblastoma cells under different growth conditions

The ganglioside composition of human neuroblastoma cells (LA-N-1 and LA-N-5) was studied in samples obtained from (1) original cells in tissue cultures, (2) tumors grown in nude mice inoculated with original cells and (3) cells in tissue cultures re-established from the mouse tumors. The amounts of "a" pathway gangliosides (GM2, GM1 and GD1a) and those of the "b" pathway (GD3, GD2, GD1b and GT1b) differed according to the culture conditions. The "b" pathway gangliosides were markedly increased in the tumors grown in nude mice. In contrast, the "a" pathway gangliosides were abundant in cultures of both original and re-established cells. We also measured the enzymatic activities of UDP-N-acetylgalactosamine: GM3, N-acetylgalactosaminyl transferase (EC 2.4.1.92) and of CMP-N-acetylneuraminic acid: GM3 sialyl transferase (EC 2.4.99.8) in neuroblastoma cells cultured under these conditions. These enzymes are thought to be the key enzymes involved in the synthesis of the "a" and "b" pathway gangliosides. Though there was no significant difference in the activity of N-acetylgalactosaminyl transferase between original cells and tumors in nude mice, re-established cells showed a definitely higher activity (3.5 times higher than in the original cells). On the other hand, tumors grown in nude mice had a markedly higher activity of sialyl transferase than that of original cells or re-established cells. These findings suggest that the culture conditions and/or the type of cell growth play some role in the synthesis and expression of gangliosides in neuroblastoma cells.

The sialosyl Lewis a ganglioside is present in tumorigenic human urothelial cell lines

The sialosyl Lewis a antigen was identified in a ganglioside extract from a malignant human urothelial cell line (Hu 1703He) by fast atom bombardment mass spectrometry. The presence of this antigen in urothelial cell lines with varying tumorigenic properties was further studied using the 19-9 monoclonal antibody (MAb). The sialosyl Lewis a ganglioside was expressed only in the tumorigenic cell lines. Thus, the expression of this antigen is a marker of malignancy for human urothelial cell lines. Mass spectrometry also suggests that the fucosyl GM1 ganglioside was expressed in the Hu 1703He cell line. This was confirmed using the F12 MAb, specific for fucosyl GM1. However, the expression of this antigen was not confined to cell lines with tumorigenic properties.

An enzyme-linked immunosorbent assay for the measurement of Lewis blood-group alpha-(1----4)-fucosyltransferase activity

An enzyme-linked immunosorbent assay (ELISA) has been developed for the Lewis blood-group associated alpha-(1----4)-fucosyltransferase activity. Microtiter plates coated with the bovine serum albumin conjugate of a synthetic beta-D-Galp-(1----3)-beta-D-GlcpNAc disaccharide are incubated with a fucosyltransferase preparation in the presence of guanosine 5'-diphosphofucose. The resulting immobilized Lewis-a active trisaccharide beta-D-Galp-(1----3)-[alpha-L-Fucp-(1----4)]-beta-D-GlcpNAc is then detected and quantitated using a monoclonal anti-Lewis-a antibody. Product formation detected in this manner is linear with time, proportional to enzyme activity, and reproducibly quantitated in the 50-400 fmol range.

Malignant cell glycoproteins and glycolipids

The cell surface is involved in cell growth and division, cell-cell interaction, communication, differentiation and migration, and other processes likely to be involved in malignant transformation and/or the metastatic spread of cancer. Although there are many alterations of glycoproteins and glycolipids on the malignant cell surface, it is unclear whether these alterations are epiphenomena or an integral part of the malignancy process. This article reviews the recent literature and some earlier studies relevant for understanding emerging concepts and trends with respect to malignant cell glycoconjugates. Emphasis is on structural alterations of the carbohydrate portions of malignant cell glycoproteins and glycolipids and on the enzymes (glycosyltransferases and glycosidases) involved in their metabolism. Practical applications derived from malignant cell glycoconjugate studies are discussed briefly with respect to the diagnosis, staging, monitoring, and treatment of malignant disease. The review concludes by indicating which research areas on malignant cell glycoconjugates are likely to be fruitful in increasing our basic understanding of, and ability to deal effectively with, malignant disease.

A monoclonal antibody, WCC4, recognizes a developmentally regulated ganglioside containing alpha-galactose and alpha-fucose present in the rat nervous system

A monoclonal antibody, WCC4, raised against PC12 cells, recognizes a ganglioside which is present in low concentrations in the postnatal rat nervous system. The antigen is also present in the adrenal and kidney, as determined immunohistochemically, but is not detectable in liver or spleen. A neutral glycosphingolipid is also immunoreactive. In the present report, the chemical characterization of this ganglioside, isolated from PC12 cells, and the anatomical distribution of the antigens recognized by the WCC4 antibody are described. By enzymatic cleavage of terminal saccharide moieties, the ganglioside is identified as alpha-galactosyl, (alpha-fucosyl) GM1. The ganglioside increases in concentration postnatally to day 35 (P35) and is present in a slightly diminished concentration in the adult. Immunohistochemical studies revealed that this glycolipid is also present on neuronal cell soma throughout the cerebrum, cerebellum and spinal cord. It is expressed in highest concentration in the molecular layer of the dentate gyrus and is also present in the olfactory bulb, the molecular layer of the hippocampus, the piriform cortex, the olfactory tubercle and the entorhinal cortex. The dentate molecular layer receives most of its innervation from neurons in the entorhinal cortex, and gangliosides are known to have an effect on plasticity following entorhinal cortical lesions. Therefore, the WCC4 antibody should prove to be a useful tool for the study of the role of endogenous gangliosides in this region of the nervous system.

Synthesis of 2-acetamido-2-deoxy-4-O-(2-O-methyl-beta-D-galactopyranosyl)- D-glucopyranose (N-acetyl-2'-O-methyllactosamine)

1,3,4,6-Tetra-O-acetyl-2-O-methyl-D-galactopyranose, prepared from known methyl 6-O-acetyl-3,4-O-isopropylidene-beta-D-galactopyranoside, was treated with hydrogen bromide in dichloromethane to afford 3,4,6-tri-O-acetl-2-O-methyl-alpha-D-galactopyranosyl bromide. Condensation with benzyl 2-acetamido-3,6-di-O-benzyl-2-deoxy-alpha-D-glucopyranoside in acetonitrile in the presence of mercuric cyanide gave an approximately 1:1 mixture of benzyl 2-acetamido-3, 6-di-O-benzyl-2-deoxy-4-O-(3,4,6-tri-O-acetyl-2-O-methyl-beta- (8) and -alpha-D-galactopyranosyl)-alpha-D-glucopyranoside. O-Deacetylation and catalytic hydrogenolysis of the benzyl group furnished 2-acetamido-2-deoxy-4-O-(2-O-methyl-beta- and alpha-D-galactopyranosyl)-D-glucopyranose. Alternatively, benzyl 2-acetamido-3,6-di-O-benzyl-2-deoxy-4-O-beta-D- galactopyranosyl-alpha-D-glucopyranoside was treated with tert-butyldiphenyl-chlorosilane in N,N-dimethylformamide, in the presence of imidazole, to give a 6'-O-tert-butyldiphenylsilyl intermediate that was in turn converted into its 3',4'-O-isopropylidene acetal. Methylation with methyl iodide-silver oxide in N,N-dimethylformamide, followed by removal of the silyl and isopropylidene groups gave benzyl 2-acetamido-3,6-di-O-benzyl-2-deoxy-4-O-(2-O-methyl-beta-D- galactopyranosyl)-alpha-D-glucopyranoside, which was further characterized as its triacetate 8.

Tumor-associated glycolipid antigens, their metabolism and organization

A number of experimental animal tumors as well as human cancers have been characterized by dramatic changes of glycolipid composition and metabolism. This review focuses on the chemical and enzymatic basis of the appearance of tumor-associated glycolipid antigens belonging to four major structural classes, i.e., globo, ganglio, lacto type 1, and lacto type 2 series. Some antigens represent the accumulation of precursors with deletion of more complex glycolipids, and others are the result of enhanced synthesis of new structures, most of which are aberrant fucosylation or sialylation or their combination; thus, novel structures such as di- or trimeric Le chi, trifucosyl Le gamma, sialyl Le chi, sialyl dimeric Le chi and disialyl Le alpha A have been isolated and characterized. Many monoclonal antibodies are capable of recognizing antigens in high density but are not capable of reacting with the same antigen in low density. Therefore, the expression of novel structures in high densities at the cell surface is important for recognition of tumor-association antigens. Molecular models of a typical tumor-associated antigen and its organization in membranes are also presented.

Glycolipid modulation of membrane adhesion

A novel test of carbohydrate-mediated adhesion has been developed. At the tips of two syringes, large spherical model membranes have been made from phosphatidylcholine and varying amounts of mixed brain gangliosides dissolved in n-decane. The apposition of two such membranes resulted in adhesion, not fusion, as judged by the absence of fluorescence mixing in the junction with NBD-phosphatidylethanolamine in one membrane and perylene in the other. Adhesion was observed without gangliosides. The rate of formation of the adhesion area ("rate" of adhesion) was unchanged from 0 to 0.8 mol% gangliosides. A slightly lower but constant rate was observed within the physiological range from 2 to 10 mol%. Adhesion was frequently blocked at 11 to 15 mol% gangliosides. The rate of adhesion with pure gangliosides increased with the number of sialic acid residues: GT greater than GD1a greater than GM1. These results are interpreted in terms of a sialic acid-dependent segregation of gangliosides into the adhesion zone.

Synthesis of 2-acetamido-2-deoxy-4-O-beta-D-galactopyranosyl-3-O-methyl -D-glucopyranose (N-acetyl-3-O-methyllactosamine) and its benzyl alpha-glycoside

Benzyl 2-acetamido-2-deoxy-3-O-methyl-alpha-D-glucopyranoside (3) was obtained by deacetalation of its 4,6-O-benzylidene derivative (2). Compound 2 was prepared by methylation of benzyl 2-acetamido-4,6-O-benzylidene-2-deoxy-alpha-D-glucopyranoside with methyl iodide-silver oxide in N,N-dimethylformamide. Diol 3 was selectively benzoylated and p-toluenesulfonylated, to give the 6-benzoic and 6-p-toluenesulfonic esters (4 and 5, respectively). Displacement of the sulfonyl group of 5 with sodium benzoxide in benzyl alcohol afforded the 6-O-benzyl derivative (6). Glycosylation of 4 with 2,3,4,6-tetra-O-acetyl-alpha-D-galactopyranosyl bromide (7) in dichloromethane, in the presence of 1,1,3,3-tetramethylurea, furnished the disaccharide derivative 8. Similar glycosylation of compound 6 with bromide 7 gave the disaccharide derivative 10. O-Deacetylation of 8 and 10 afforded disaccharides 9 and 11. The structure of compound 9 was established by 13C-n.m.r. spectroscopy. Hydrogenolysis of the benzyl groups of 11 furnished the disaccharide 2-acetamido-2-deoxy-4-O-beta-D-galactopyranosyl-3-O-methyl-D-glucopyr ano se (N-acetyl-3-O-methyllactosamine).