Glioma
This group comprises anaplastic astrocytomas and glioblastoma multiforme. Whereas the median overall survival of anaplastic (WHO grade III) gliomas is approximately 3 years, glioblastoma multiforme has a poor median overall survival of c. 15 months.
Glioblastoma
The "IDH1" gene encodes for the enzyme isocitrate dehydrogenase 1 and is frequently mutated in glioblastoma (primary GBM: 5%, secondary GBM >80%). By producing very high concentrations of the "oncometabolite" D-2-hydroxyglutarate and dysregulating the function of the wild-type IDH1-enzyme it induces profound changes to the metabolism of "IDH1"-mutated glioblastoma, compared with "IDH1" wild-type glioblastoma or healthy astrocytes. Among others, it increases the glioblastoma cells' dependence on glutamine or glutamate as an energy source. It has been hypothesized that "IDH1"-mutated glioblastoma are in a very high demand for glutamate and use this amino acid and neurotransmitter as a chemotactic signal. Since healthy astrocytes excrete glutamate, "IDH1"-mutated glioblastoma cells do not favor dense tumor structures but instead migrate, invade and disperse into healthy parts of the brain where glutamate concentrations are higher. This may explain the invasive behaviour of these "IDH1"-mutated glioblastoma.