Gangliosides associated with primary brain tumors and their expression in cell lines established from these tumors

Human primary brain tumors differ in their ganglioside composition when compared to adjacent tissues. One ganglioside found in all malignant glioma specimens, but not detected in normal adult brain, is 3'-isoLM1, a ganglioside of the lacto series. This ganglioside was also identified in medulloblastomas with astrocytic differentiation and in brain tissues containing benign proliferating astrocytes. The appearance of 3'-isoLM1 was seen over large regions of brain from glioma but was found mainly in areas either adjacent to the macroscopic tumor or areas corresponding to the tumor in the opposite hemisphere. A high concentration of 3'-isoLM1 was also seen in the corpus callosum, the anatomical structure along which glioma cells may migrate to the opposite brain hemisphere. Ganglioside expressed by cell lines established from primary malignant brain tumors varied widely among cell lines and within a given cell line propagated under different conditions. In in vitro-cultured glioma and medulloblastoma cell lines, gangliosides of the ganglio series dominated and the expression of the lacto series gangliosides, including 3'-isoLM1 was low if at all detectable. However, in vivo growth of solid subcutaneous tumors in nude mice or rats led to a significantly increased expression of the often dominant gangliosides of the lacto series and revealed a decreased expression of ganglio series gangliosides. In conclusion, these findings indicate that environmental factors could strongly influence the expression of gangliosides that may lead to a switch from the ganglio to the lacto series. These results also suggest that ganglioside 3'-isoLM1 is associated with proliferating astrocytes, of both neoplastic and non-neoplastic origin and that this ganglioside may be involved in cell-cell recognition and attachment during development and tumor cell migration.