KLF4 and acute lymphoblastic leukemia: In contrast, both mRNA and protein expression levels of KLF4 were upregulated in T-ALL compared with controls (Figure 1C and D), despite increased expression of miR-2909 in these T-ALL lymphoblasts (Figure 1A), suggesting the possibility of a mutation in either the seed sequence or the 3′UTR region of KLF4 involving the miR-2909 binding site.