PTEN and glioblastoma: Several genes have been identified to be associated with tumorigenesis and anaplastic progression of glioblastoma subgroups including, besides the already mentioned p16/Cdkn2/Ink4, EGFR, PTEN, p53, and HDM2 also for example cdk4, cyclin D1, PDGFRα, k-ras, N-myc, gli, c-myc, and myb (Mao and Hamoudi, 2000; Zhu and Parada, 2002).