npy and y1 receptor, in addition to pharmacological derivatives, in providing for manageable forms of neurodegenerative disorders of the striatal area. as a potential source of brain tumors in an attempt to characterize the role of the subventricular zone in potential tumorigenesis, quinones-hinojosa et al. found that brain tumor stem cells (btscs) are stem cells that can be isolated from brain tumors by similar assays used for neuronal stem cells. in forming clonal spheres similar to neurospheres of neuronal stem cells, these btscs were able to differentiate into neurons, astrocytes and oligodendrocytes in vitro, yet more importantly capable of initiating tumors at low cell concentrations, providing a self-renewal capacity. it was therefore proposed that a small population of btscs with such self-renewal capabilities were maintaining tumors in diseases such as leukemia and breast cancer. several characterizing factors lead to the proposed idea of neuronal stem cells (nscs) being the origin for btscs, as they share several features. these features are shown in the figure. this group provides evidence of the svz's apparent role in tumorigenesis as demonstrated by the possession of mitogenic receptors and their response to mitogenic stimulation, specifically type c cells that express the epidermal growth factor receptor (egfr), making them highly proliferative and invasive. additionally, the existence of microglia and endothelial cells within the svz was found to enhance neurogenesis, as well as providing for some directional migration of neuroblasts from the svz. recently, the human svz has been characterized in brain tumor patients at phenotypic and genetic level. these data reveal that in half of the patients the svz is an exact site of tumorigenesis whereas in the remaining patients it represents an infiltrated region. thus, it is distinctly possible that in humans a relationship exists between the nsc generation of the region and the consistently self-renewing cells of primary tumors that give way to secondary tumors once removed or irradiated. while it remains to be definitely proven whether the svz stem cells are the cell of origin for brain tumors such as gliomas, there is strong evidence that suggests increased tumor aggressiveness and mortality in those patients whose high-grade gliomas infiltrate or contact the svz. in prostate cancer, tumor-induced neurogenesis is characterized by the recruitment of neural progenitor cells (npc) from svz. npcs infiltrate the tumor where they differentiate into autonomic neurons (adrenergic neurons mainly) that stimulate tumor growth.