PTEN and acute lymphoblastic leukemia: Aberrant activation of this signaling pathway in B- and T-ALL can occur by multiple genetic mechanisms, including inactivation of phosphatase and tensin homolog (PTEN), which is a lipid phosphatase that functions as the main negative regulator of the PI3K pathway [31] or more rarely due to gain-of-function mutations in PI3K regulatory and catalytic subunits or in AKT.