Various tumors express oligosaccharide sequences which are different from the non-malignant glycosylation of the same cell or tissue type. Examples of the known or speculated cancer associated oligosaccharide structures include: glycolipid structures such as globo-H (Fucα2Galβ3GalNAcβ3Galα4LacβCer), gangliosides: GM1 Galβ3GalNAcβ4(NeuNAcα3)LacβCer or GD2 GalNAcβ4(NeuNAcα8NeuNAcα3)LacβCer; Lewis-type fucosylated structures such as Lewis a and x: Galβ3/4(Fucα4/3)GlcNAc, Lewis y: Fucα2Galβ4(Fucα3)GlcNAc, sialyl-Lewis x: NeuNAcα3Galβ4(Fucα3)GlcNAc, and some combinations of these on polylactosamine chains; O-glycan core structures, such as T-antigen Galβ3GalNAcαSer/Thr-Protein, Tn-antigen GalNAcαSer/Thr-Protein or sialyl Tn-antigen NeuNAcα6GalNAcαSer/Thr-Protein. Presence of non-human structures such as N-glycolyl-neuraminic acid in cancers has also been indicated. Association and specificity of oligosaccharide structures with regard to cancers have been well established only in few cases, some of the structures are present in normal cells and tissues and are possibly only more concentrated in cancers.
One report has indicated that structures with terminal GlcNAcβ3Galβ4GlcNAc sequence are present in human leukaemia cells (Hu et al., 1994). The structures may also be equally present on normal leukocytes. Thus, the relation of the finding to glycosylation patterns generally present in solid tumors was not indicated. This type of saccharide structures may be a part of rare normal glycosylations of human tissues: GlcNAcβ3Galβ4GlcNAcβ6 sequence linked on O-glycans is probably present on human gastric mucin. A study shows that a monoclonal antibody recognizing GlcNAcβ3Galβ4GlcNAcβ6 sequence may possibly recognize similar structures on malignant tissues, such as mucinous ovarian neoplasms, pseudopyloric metaplasia of gallbladder and pancreatic epithelia, gastric differentiated carcinoma of stomach, gallbladder and pancreas, and on non-malignant tissues, such as human amniotic fluid, but, however, the structures from malignant tissues were not characterized (Hanisch et al., 1993). The antibody did not recognize neoglycolipid structure GlcNAcβ3Galβ4GlcNAcβ3Galβ4 nor carcinomas of lung, colorectum, endometrium or other organs. Another monoclonal antibody raised against testicular cells probably recognizes branched N-acetyllactosamines such as GlcNAcβ3(GlcNAcβ6)Galβ4GlcNAc- (Symington et al., 1984). Terminal GlcNAc has also been reported from mucins of human foetal mucin (Hounsell et al., 1989). In normal tissues terminal GlcNAc may be present in minor amounts as biosynthetic intermediates in the biosynthesis of poly-N-acetyllactosamines.
Several monoclonal antibodies has been raised against a semisynthetic glycolipid GlcNAcβ3Galβ4GlcNAcβ3LacβCer, these antibodies were shown to recognize glycolipids from cultured colon cancer cell lines and tumors (Holmes et al., 1991). However, the antibodies recognized several structures and the binding data was contradictory. Moreover the glycolipids were not recognized by all of the antibodies and the glycolipid structures from cancer cells or tumors were not characterized. Therefore the presence of terminal GlcNAc structures on tumors were not established. Another study showed production of a monoclonal antibody against GlcNAcβ3LacβCer (Nakamura et al., 1993). This antibody also weakly recognized the pentasaccharide structure described above. Moreover, the antibody recognized a protease sensitive epitope on COS-1 cells, which cell line is not of human origin. The immunization protocols of these studies did not describe induced antibody responses against polyvalent conjugates of the saccharides, but immunization by glycolipids.
Normally there are large amounts of antibodies recognizing terminal GlcNAc structures in human serum. There are also a class of natural antibodies recognizing terminal Galα3Galβ4GlcNAc- structures. The Galα antigen is not naturally present in man and recently it was also shown that the natural antibodies bind structures such as GalNAcα3Galβ4GlcNAc, GalNAcβ3Galβ4GlcNAc, and GlcNAcβ3Galβ4GlcNAc (Teneberg et al., 1996). The X2-structure, GalNAcβ3Galβ4GlcNAc, is a normal antigen on human tissues and structures GalNAcα3Galβ4GlcNAc and Galα3Galβ4GlcNAc have not been described from normal or cancer tissues. Thus, the present finding that the terminal GlcNAc structure is a tumor antigen indicates that the actual function of the natural antibodies might be the prevention of cancers having terminal GlcNAc structures.
The following patents describe cancer antigens and their use for making antibodies for therapeutic and diagnostic uses and for cancer vaccines. The antigen structures are not related to saccharides of the present invention:    Cancer vaccines: U.S. Pat. Nos. 5,102,663; 5,660,834; 5,747,048; 5,229,289 and 6,083,929.    Therapeutic antibodies: U.S. Pat. Nos. 4,851,511; 4,904,596; 5,874,060; 6,025,481 and 5,795,961.    Diagnostics: U.S. Pat. Nos. 4,725,557; 5,059,520; 5,171,667; 5,173,292; 6,090,789; 5,708,163; 5,679,769; 5,543,505; 5,902,725 and 6,203,999.
In the prior art tumor diagnostic and therapeutic antibodies recognizing chitobiose-mannose trisaccharides has been described in DE 38 07 594 A1. The application also describes other N-glycans with numerous varying terminal structures some of which may also comprise non-reducing terminal N-acetyl glucosamine. Several of the desired structures have been later characterized as normal glycans and not cancer specific structures. The application claims to describe structures useful for cancer applications. However, it is not quite clear from the application what the structures of desired glycan are. It is indicated that the GlcNAc residues can be α2, α4, or α6-linked. The present invention is not directed to such unusual structures.
Another patent application WO 00/21552 claims several unusual O-glycan structures isolated from bovine submaxillary mucin. Some of the structures such as GlcNAcβ6GalNAcα6GalNAc and GalNAcβ3(GlcNAcβ6)GalNAc comprise terminal GlcNAc-residues. Present invention is not directed to these structures comprising two GalNAc-residues. The application contains speculation about potential therapeutic use of the structures as antigens related to cancer. It has not been shown that the structures are related to bovine cancer but the structures are present in bovine normal submaxillary secretion. Moreover, it is even less probable that the structures would be present in human tissues, as the glycosylations are species specific and vary between human and bovine, so that glycosyltransferase and glycosylation profiles are different in bovine and human. The human genome is also known and glycosyltransferases which could be related to synthesis of the claimed bovine structures has not been produced and characterized. So far none of the six novel glycosyltransferases claimed has been described from human, or human cancer (nor from bovine cancer). Moreover, any bovine glycosylations has not been found from human salivary mucins which have been carefully characterized.