MAPK3 and hairy cell leukemia: Moreover, all p-4E-BP1 positive/p-mTOR negative cases were positive for p-ERK1/2 and all but one for p-AKT, indicating that both p70S6K and 4E-BP1 can be activated by the BRAF/ERK pathway and p-AKT in a large subset of HCL cases.