On the origin and growth of gliomas

This review begins with the description of the nervous cytogenesis, proliferation of primitive cells, migration and differentiation with antigen expression and regulation through factors. Emphasis is given to neural stem cells, progenitors and to radial glia as belonging to early stages of gliogenesis. Experimental production of brain tumors in the rat by transplacental administration of ethylnitrosourea and systemic administration of methylnitrosourea effective through neural stem cells and progenitors is briefly described as a preamble to the recent conception of gliomas as originating from stem cells or brain tumor stem cells (BTSCs). The nature and origin of BTSCs, their molecular regulation and their recognition in vivo are discussed. In the growth of tumors, the role of nestin, migration of neural stem cells toward the tumor from the subventricular zone or from the tumor to the brain and the migration from bone marrow of mesenchymal stem cells for angiogenesis of the tumors are considered. Special mention is made of the relationship between glio-vascular niches in the subventricular zone and the neo-niches around the tumors with their importance in the tumor growth as points of joint between cytogenesis and angiogenesis. Finally, besides the importance of hypoxia, cell traffic in the brain adjacent to tumor is emphasized in relation to the growth of gliomas.