On the other hand, U87 cells which, when treated with neural stem cell medium, altered their phenotype towards more stem like cells, increasing the levels of CD133 and nestin, and induced highly infiltrative tumours in animals.44 A model has been proposed in which CD133+ cells constitute a non-invading GBM SC population with the potential to switch reversibly between an invasive and stationary phenotype. The gene discussed is PROM1; the disease is glioblastoma.