SIRT1 protein levels are highly expressed in AML samples harboring activated signaling pathways. (A) Protein expression levels of SIRT1, DBC1, and Actin in cell lysates of primary AML or CML samples, normal BM cells (lane 41), and CD34^pos cells (lanes 42 and 43). (B) SIRT1 protein expression was quantified by densitometric analysis and normalized to Actin expression. Shown are normalized SIRT1 expression levels of FLT3-ITD (n = 16), FLT3-TKD (n = 3), and FLT3-WT (n = 18) AML samples. ***P < .001; ns, not significant; unpaired Student t test. (C-D) Protein expression levels of SIRT1, DBC1, and Actin in human leukemic cell lines (C) and in BA/F3 cells (D) transduced with different oncogenes, as indicated. (E) SIRT1 mRNA expression was determined by real-time quantitative polymerase chain reaction (RQ-PCR) analysis and normalized to glyceraldehyde-3-phosphate dehydrogenase (GAPDH) expression. SIRT1 protein expression was quantified by densitometric analyses and normalized to Actin expression. Shown are mRNA levels relative to SIRT1 protein expression. (F) Shown is the correlation of SIRT1 mRNA and SIRT1 protein expression in FLT3-ITD and RAS-mutated cells (left; ns, not significant) and FLT3-WT and RAS-WT cells (right; P = .033). Black boxes indicate primary patient samples, white boxes indicate cell lines. (G) Log2 transformed mean centered SIRT1 gene expression values (IMAGE clone IMAGE:796114) are plotted for FLT3-ITD (n = 108) vs no ITD AML cases (n = 307).