ABSTRACT
During the development of the central nervous system (CNS), a careful equilibrium is maintained between the processes of cell proliferation, differentiation, and apoptosis. In contrast, tumorigenesis is a complex, multistep sequence of cellular transformations resulting from the accumulation of mutations in the very genes that govern these three balanced processes. According to the currently
accepted paradigm for tumorigenesis, these mutations can manifest by either of two mechanisms: activation of a dominantly acting oncogene or inactivation of a recessive tumor suppressor gene. Particularly exciting in recent years has been the elucidation of not only the diversity of mutations in these genes, but also the interplay that occurs between them in the genesis/progression of specific CNS tumor types. As a consequence of this improved molecular genetic understanding, it is now possible to make sense of the extraordinary karyotypic changes observed in tumor cells and thereby gain insight into the pathogenesis, progression, and prognosis of primary CNS tumors. The following chapter reviews the emerging knowledge of the molecular mechanisms involved in the initiation and progression of primary CNS tumors, with particular emphasis on the malignant lesions whose prognosis still remains grim.
