PBX1 and acute myeloid leukemia: Consistent with the concomitant up-regulation of p21 expression and the down-regulation of Pbx1 expression, we found that p21 expression (CDKN1A; 202284_s_at in GSE1159) was inversely correlated with Pbx1 expression, but not with Evi-1 expression, in FLT3-ITD+ AML subjects, particularly those with the FAB M1 subtype (r = -0.46, P < 0.01, 212151_at in GSE1159, Fig 8E, top panel), although this correlation was not evident in other AML subgroups.