GLYCOLIPID CHANGES DURING CHEMICAL HEPATOCARCINOGENESIS

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Glycosphingolipids (glycolipids) are membrane bound cell surface antigens occurring in nearly all vertebrate tissues. Structural modifications of the carbohydrate moiety were originally observed in association with end- stage tumorigenesis. Subsequently, these changes were shown to appear during a premalignant stage of chemical carcinogenesis. Thus, glycolipid alterations may be of functional significance during chemical carcinogenesis. Proposed herein are studies to enhance understanding of the nature of glycolipid alterations during chemical hepatocarcinogenesis. A departure from traditional carcinogenesis studies entails utilization of rainbow trout. Studies with trout will permit exploitation of novel aspects of this model system. First generations experiments include whole animal tumor induction studies with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) to elucidate specific glycolipid changes throughout carcinogenesis. These experiments will utilize high doses of carcinogen to insure adequate tumor tissue for characterizing glycolipid alterations. Second generation experiments will follow traditional complete carcinogenesis as well as initiation/promotion regiments with MNNG. Sensitive probes developed from the first generation experiments will be used to elucidate the ontogeny of these alterations. Coincident with these experiments will be detailed study of the histology of developing lesions (preneoplastic foci through end-stage tumors). Thus, it will be possible ascertain the specificity of particular lesion types with altered glycolipid profiles. Glycolipids will be isolated and examined from normal and premalignant tissues, tumors, and cell lines as well as fetal, developing, and regenerating liver. From such comparisons the nature and extent of glycolipid alterations will be determined. The enzymatic lesion(s) associated with these alterations will then be investigated to ascertain the manner in which such modifications in carbohydrate structure are mediated. Finally, information collected concerning glycolipid changes during chemical carcinogenesis in the rainbow trout will be carefully compared and contrasted with published mammalian studies to provide a broader base for further understanding of the significant role of glycolipids during carcinogenesis in all vertebrate species.