Abstract
Two glycolipid fractions that inhibit Blood Group A hemagglutination were isolated from hepatocarcinoma tissue of a Blood Group O individual.
One fraction corresponding to a ceramide penta- to hexasac-charide weakly inhibited hemagglutination caused by blood group anti-A sera and gave a precipitin reaction with Rana catesbiana lectin. The fraction had no Forssman activity, showed a single spot on thin-layer chromatography, and was degraded by hog liver α-N-acetylgalactosaminidase to a glycolipid with a higher thin-layer chromatography mobility than that of the original glycolipid. The enzyme-treated product had no A-like activity. The direct probe mass spectrometry of the fraction after permethylation indicated the presence of the immunodominant sugar sequence GalNAc→Hex→HexN, but the absence of a tetrasaccharide A determinant, HexN→[Fuc→]Hex→HexN,and a fucosyl residue.
The other fraction corresponding to a ceramide di- to trisaccharide showed only a very low A-like inhibition but showed a strong Forssman activity (inhibition of sheep erythrocyte hemolysis by anti-Forssman antibodies and complement). The activity was completely abolished by hog liver α-N-acetylgalactosaminidase with a simultaneous elimination of thin-layer chromatography spots, one corresponding to ceramide trisaccharide and the other with slightly higher mobility. The presence of the Forssman determinant, HexN→HexN, in this fraction was clearly indicated by direct-probe mass spectrometry with a selected ion recording during continuous-temperature-gradient evaporation.
Although the supply of the tumor tissue in this case was extremely limited, the above information clearly indicates the presence of an aberrant A determinant and an unusual short-chain Forssman determinant in the hepatocarcinoma of the Blood Group O individual. The tissue did not contain normal Forssman glycolipid with a ceramide pentasaccharide structure.
This investigation has been supported by NIH Research Grants CA19224 and CA20026. A part of this work was presented at the Japanese Society of Medical Mass Spectrometry, October 17, 1980 (9).