Cell Density Regulates Antibody Accessibility and Metabolic Turnover of Gangliosides in Human Glioma Cells

The effects of cell density on the gangliosides of 4 human glioma cell lines were studied. The cell lines used were KG-1C (GM3-dominant) , A172 and H4 (GM2-dominant), and Hs683 (GM3, GM2-co-dominant) cells. All these cell lines showed higher immunofluorescence with anti-ganglioside antibodies in FACS analysis at sparse density than at confluent density. Steric hindrance from cell surface proteins had been removed by the pretreatment of the cells with trypsin. The chemical content of gangliosides was consistent throughout the time of cell growth. The mechanisms of crypticity of gangliosides at confluent culture were under investigation. We first evaluated the metabolic turnover rate of gang-liosides at different cell densities. The results clearly showed a more rapid turn-over of gangliosides at sparse density from approximately 2 to 4 fold in terms of radioactivities of incorporated tritium into gangliosides. The profiles of labeled gangliosides were also different between the sparse and confluent cultures. We speculate that better accessibilities of antibodies toward gangliosides should be facilitated by the same mechanism which should, in turn, provide easier access of carbohydrate-hydrolysis enzymes to gangliosides at sparse cell density in order to keep an enhanced turnover rate

Reduction of glycolipids with D-PDMP, a glucosylceramide synthetase inhibitor, caused cell growth inhibition, enhanced cell adhesion, and facilitated cell motility in human glioma cells

Glycolipid synthesis inhibitor, D-PDMP, not only inhibited the production of glycolipid but also inhibited cell growth in human glioma cell line KG-1C in a cell cycle non-dependent manner. The reduction of glycolipid from the cell membrane allowed us to study the biological functions of glycolipids. The ability of cells to adhere to collagen was enhanced by the reduction of glycoli-pids, and random cell migration was also activated by the effect of D-PDMP. The results supported our speculation that glycolipids might function in cell growth, adherence and locomotion

Study of Glycolipid Profiles of Low Grade Astrocytomas

We analyzed the glycolipid composition of eight cases with low grade astrocytomas. In all of the cases the composition of neutral glycolipids was notably different from the normal brain. The composition of acidic glycolipids was almost the same as normal. An increase of minor gangliosides as well as some that are usually undetectable in the normal brain was recognized in acidic glycolipids. We classified those glycolipid alterations into three types : a) an increase in short chain gangliosides ; b) novel expression of lacto series gang-liosides ; and c) both a) and b). Glycolipids did not correlate with microscopic findings, proliferation (Ki-index), or prognosis