Particularly low levels of PU.1 expression in patients with APL as compared to other AML subtypes. AML patients were divided into eight subtypes (M0, M1, M2, M3, M4, M5, M6 and M7) according to FAB classification. The expression levels of PU.1 in the eight subtypes were evaluated. The four profiling data sets of AML patients, including GSE1729, StJude, GSE10358 and GSE1159, were combined. The PU.1 level relative to that of GAPDH was calculated as described in the Materials and methods.