Phosphatase and Tensin Homolog (PTEN), which is located on the q arm of chromosome 10 (10q), functions as a negative regulator of the PI3K/Akt/mTOR signalling pathway (Fig. 1C), and is deleted in 90% of primary GBM due to a loss of heterozygosity of chromosome 10 [11, 92] [11, 92]. This evidence concerns the gene PIK3CA and glioblastoma.