Mechanisms of tumor cell invasion and angiogenesis in the central nervous system.

Despite extensive progress in characterizing the genetic events involved in the development of gliomas, the cellular origin and the defined molecular mechanisms that lead to their occurrence are still unclear. It is known that tumours are of monoclonal origin. This is contrasted by the fact that gliomas frequently express features of different glial cell lineages. With the identification of pluripotent neural stem cells and the growth factors that control neural cell development, we are now making early inroads towards understanding glial cell migration as well as the neural cell plasticity within the adult central nervous system (CNS). Gliomas share several fetal antigens with immature brain cells. It is therefore tempting to speculate that the migration of neural precursor cells actually represents the normal counterpart of glioma cell migration. The migratory behavior of gliomas may be due to a predetermined interplay between normal brain tissue and the migrating cells, where the brain represents a permissive tissue for guiding cells with certain phenotypic traits to migrate along specific anatomical structures. Malignant progression is also accompanied by extensive angiogenesis which is especially prominent in glioblastoma multiforme (GBM). For cell proliferation to take place, several cell signaling cues mediated by specific growth factors are shared between the glioma cells and the endothelial cells while others are unique for endothelial cells. Therefore the endothelial cell compartment represents a promising target for novel therapeutic strategies including gene therapy and cell-based therapies.