A putative role for SNAI1 in human AML. (A) Quantitative real-time PCR analysis showing SNAI1 mRNA is expressed ∼12-fold higher in human AML patient samples compared with normal hematopoietic stem and progenitor cells (CD34+, n = 3; AML, n = 6; P < .05 Mann-Whitney nonparametric 1-tailed test). SNAI1 expression is normalized to the expression of the housekeeping gene GUSB. (B) SNAI1 protein expression is higher in AML patient samples compared with healthy CD34+ control cells. The MOLM13 cell line is also shown as a comparison. (C) Western blot analysis showing MOLM13-R, OCI-AML3-R, and THP1-R AML cell lines express SNAI1 protein, whereas HL60-R, NB4-R, and Kasumi-R do not. (D) shRNA-mediated SNAI1 knockdown in OCI-AML3-R and MOLM13-R AML cell lines results in upregulation of the myeloid maturation marker CD11b (red and blue lines) compared with the control shRen.713 shRNA (black line). (E) Quantification of the percentage of CD11b+ cells in shRen.713 infected cells (black bars) compared with shSNAI1 infected cells (red bars). Data are represented as mean + standard error of the mean; n = 3 independent replicates. (F) Wright-Giemsa staining analysis of MOLM13-R cells shows evidence of myeloid differentiation, such as increased cytoplasmic/nuclear ratio and presence of cytoplasmic granules, upon SNAI1 knockdown in shSNAI1.774 and shSNAI1.1577 cells compared with control shRen.713 cells. Kaplan-Meier plots showing that Cre (tamoxifen)–mediated loss of Snai1 in MLL-AF9 (G) and AML-ETO/NRAS–driven (H) AML models leads to a significant reduction in the survival of recipient mice as determined by leukemia growth delay (LGD)52 analysis (AML-ETO, P < .05; MLL-AF9, P < .01). Red lines indicate Snai1fl/fl cells, and black lines indicate Snai1+/+ cells. Dotted lines indicate mice treated with tamoxifen vs solid lines indicated mice treated with vehicle. Data are from 5 recipient mice per cohort, each transplanted with 300 000 (MLL-AF9) or 500 000 (AML-ETO/NRAS) AML cells combined from 2 to 3 primary tumors. *P < .05 Student 2-sided unpaired t test, **P < .01 Mantel-Cox test.