PTEN and brain cancer: For this reason, investigations on the mechanisms reprogramming normal neural progenitors into cancer stem cells are fundamental to decipher the essential logic driving brain cancer development at the genetic, molecular, and cellular levels. PTEN deficiency has proven to be sufficient to reprogramme human neural progenitors into GBM stem cells [113] and its inactivation is very frequent in GBM, occurring through a number of different mechanisms [7, 110, 114].