TP53 and glioblastoma: DNA damage response is the cornerstone of GBM therapy: both radiotherapy and temozolomide target DNA, causing high levels of DNA damage which overwhelms repair mechanisms leading to the induction of apoptosis via p53 activation (Banin et al., 1998; Canman et al., 1998; Epstein et al., 2001; Turenne et al., 2001; Saito et al., 2002).