cdw17-antigen and Carcinoma

Multidrug-resistant tumor cells display enhanced levels of glucosylceramide. In this study, we investigated how this relates to the overall sphingolipid composition of multidrug-resistant ovarian carcinoma cells and which mechanisms are responsible for adapted sphingolipid metabolism. We found in multidrug-resistant cells substantially lower levels of lactosylceramide and gangliosides in sharp contrast to glucosylceramide, galactosylceramide, and sphingomyelin levels. This indicates a block in the glycolipid biosynthetic pathway at the level of lactosylceramide formation, with concomitant accumulation of glucosylceramide. A series of observations exclude regulation at the enzyme level as the underlying mechanism. First, reduced lactosylceramide formation occurred only in intact resistant cells whereas cell-free activity of lactosylceramide synthase was higher compared with the parental cells. Second, the level of lactosylceramide synthase gene expression was equal in both phenotypes. Third, glucosylceramide synthase (mRNA and protein) expression and activity were equal or lower in resistant cells. Based on the kinetics of sphingolipid metabolism, the observation that brefeldin A does not restore lactosylceramide synthesis, and altered localization of lactosylceramide synthase fused to green fluorescent protein, we conclude that lactosylceramide biosynthesis is highly uncoupled from glucosylceramide biosynthesis in the Golgi apparatus of resistant cells.

Topics: Animals; Antigens, CD; ATP Binding Cassette Transporter, Subfamily B; Biological Transport; Carcinoma; Drug Resistance, Multiple; Drug Resistance, Neoplasm; Female; Galactosylceramides; Galactosyltransferases; Glucosylceramides; Glycolipids; Golgi Apparatus; Kinetics; Lactosylceramides; Models, Biological; Ovarian Neoplasms; Sphingolipids; Tumor Cells, Cultured

Monoclonal antibody KH2 (IgM) reactive with lactosyl ceramide and neolactotetraosyl ceramide was applied for the first time to the staining of human cancerous and noncancerous tissues which were fixed with formalin and embedded in paraffin. Digestive-tract cancers originating from stomach, colon, pancreas, gallbladder and bile duct were clearly stained. The staining intensity was especially strong in the apical portion and the intraluminal content of adenocarcinomas. In noncancerous tissues, it was of interest that gastric intestinal metaplasia and certain fetal tissues were stained. A part of the tubules of the kidney, pancreatic ductal cells, lung alveolar epithelial cells and polymorphonuclear leukocytes were stained in normal adult tissues in our study. Enhancement of the intensity of immunostaining by neuraminidase treatment indicated that most of the antigenic determinants should be sialylated and the antigenicity exposed after neuraminidase treatment in several kinds of cancerous and noncancerous tissues. These data suggest that the monoclonal antibody KH2 may be useful in the immunohistologic diagnosis of formalin-fixed human cancerous tissues.

Topics: Antibodies, Monoclonal; Antigens, CD; Antigens, Tumor-Associated, Carbohydrate; Carcinoma; Carcinoma, Hepatocellular; Colonic Neoplasms; Glycosphingolipids; Humans; Immunoenzyme Techniques; Lactosylceramides; Liver Neoplasms; Neoplasms; Neuraminidase; Stomach Neoplasms

Topics: Antigens; Antigens, CD; Carcinoma; Haptens; Humans; Lactosylceramides; Neoplasms