PIK3CA and cancer: The PTEN gene, the gene product of which is a negative regulator of PI3-K/Akt/mTOR signaling, and PIK3CA, which encodes a catalytic subunit of PI3-K, are frequently mutated in, depending on the specific cancer, around a third of all tumors [66], loss of PTEN heterozygozity is described in 59% and 76% of glioblastoma and uveal melanoma, respectively [67].