TP53 and glioblastoma: However, the majority of studies do not validate p53 as an independent prognostic marker for glioblastoma (Kraus et al., 2001; Simmons et al., 2001; Shiraishi et al., 2002; Rich et al., 2005; Ruano et al., 2009; Weller et al., 2009; Levidou et al., 2010; Rossi et al., 2011).