CDKN2A and glioblastoma: Amongst the huge number of genetic alterations that populate the GBM genomic landscape, five genetic changes dominate: loss of tumour suppressor and aging biomarker (Ink4a), acute renal failure (Arf), cellular tumour antigen p53, or phosphatase and tensin homolog on chromosome 10 (PTEN); and amplification of Epidermal Growth Factor Receptor (EGFR).