Cancer stem cells in pediatric brain tumors

Central nervous system (CNS) tumors remain the leading cause of death among pediatric neoplasms. Although standard therapies cure many pediatric CNS tumors, the long-term cognitive and physical consequences of these therapies are devastating. Furthermore, recurrent disease carries a dismal prognosis. Although recent studies have focused on molecular mechanisms that underlie the initiation and progression of adult glioblastoma multiforme (GBM), these tumors differ phenotypically and at a molecular level from pediatric brain tumors. Recent investigations have identified a stem cell population, termed "brain tumor stem cells" (BTSC) within the heterogeneous cell populations that comprise malignant brain tumors which may be partly responsible for the resistance to current therapies. These have been identified in several pediatric tumors including medulloblastoma, ependymomas, and malignant gliomas. By exploiting molecular differences present within these heterogeneous populations of brain tumor cells, we may be able to achieve specific eradication of BTSC and long-lasting remissions, while causing less toxicity to normal tissues. In this review, we describe the issues surrounding the identification and characterization of BTSC, the molecular biology of BTSC for different pediatric brain tumors, and suggest future avenues for the development of treatments for this devastating disease.