CDKN2A and glioma: The U251 glioma model is one of the models that is similar to human glioblastoma with regard to infiltrative invasion into the brain parenchyma; considerable foci of necrosis, positive markers of GFAP, S100B, and vimentin (Jacobs et al., 2011); losses of tumor suppressor genes (p53 and PTEN); and deletion of INK4a/ARF (Radaelli et al., 2009).