GFAP and central nervous system cancer: The recent demonstration that tumor cells isolated from some human gliomas can differentiate into neural and mesenchymal derivatives, and our earlier observations of neural and mesenchymal differentiation of GFAP+NNP cells, with multilineage (discordant) phenotype, inspired us to compare in vitro inducible differentiation and phenotypic changes of GFAP+NNP and glioblastoma cells.