Unexpectedly, inhibition of PI3K by LY294002 and NVP-BKM120 was not associated with dephosphorylation of AKT at Ser473, a surrogate marker for inhibition of PI3K activity, in the majority of the ALL-LTCs, whereas AKT dephosphorylation was observed in the control Jurkat cells. Here, PIK3CA is linked to acute lymphoblastic leukemia.