PTEN and central nervous system cancer: Notably, a majority of primary glioblastoma and established glioma cell lines such as U87-MG and U373-MG carry mutations in the PTEN gene that result in diminished or null expression of the protein [25, 31, 32], leading to aberrant activation of AKT [33], FAK [34–36], and Ras [18, 37, 38] in GBMs.