Therefore, we evaluated the effects of a specific PI3K inhibitor (Ly-294002) (58) in the radioresponse of two telomerase positive high-grade glioma cell lines: CB193 (grade III WHO) a PTEN null one (59,60) and a T98G (grade IV WHO) a PTEN harbouring one (61,62). This evidence concerns the gene PTEN and central nervous system cancer.