Neural stem cells were suggested to migrate to and invade intracranial gliomas. In the presented studies, interactions of NE-4C embryonic neural stem cells were investigated with C6 and G1261, LL and U87, glioblastorna cells or with primary astrocytes. Glioma-derived humoral factors did not influence the proliferation of stem cells. NE-4C-derived humoral factors did not alter the proliferation of G1261 and U87 cells, but increased the mitotic activity of C6 cells and that of astrocytes. In chimera-aggregates, all types of glioma cells co-aggregated with astrocytes, but most of them segregated from stem cells. Complete intercalation of stem and tumour cells was detected only in chimera-aggregates of G1261 glioma and NE-4C cells. If mixed suspensions of NE-4C and G1261 cells were injected into the brain, stem cells survived and grew inside the tumour mass. NE-4C stem cells, however, did not migrate towards the tumour, if implanted near to G1261 tumours established in the adult mouse forebrain. The observations indicate that not all types of stem cells could be used for targeting all sorts of brain tumours. (c) 2005 Elsevier Ireland Ltd and the Japan Neuroscience Society. All rights reserved.