Reduced expression of miR-145 and miR-146a results in myelodysplastic/myeloproliferative features. (A) miRNA tag counts (log₂) are shown for 2 cell lines, one with a chromosome 5q deletion (KG-1a) and one diploid at chromosome 5q (THP-1). (Inset) Relative levels of miR-145 and miR-146a were determined by quantitative PCR in human CD34⁺ cells (n = 3), KG-1a, and THP-1 cells. (B) KG-1a, THP-1, and HL-60 cells were treated with 10μM 5-azacytadine (5-aza) or dimethyl sulfoxide (DMSO) for 48 hours. Expression of miR-145 and miR-146a was evaluated by quantitative reverse transcription PCR and shown relative to DMSO after normalization to 5S. (C) miR-145 (top) and miR-146a (bottom) expression levels are shown for CD34⁺ marrow cells isolated from patients with AML with a NK (n = 54) or deletion of chr 5q (del 5q; n = 4). As controls, CD34⁺ cells were evaluated from nondiseased persons (n = 11). Data are adapted from published microarray data (E-TABM-970 and E-TABM-405). Normalized expression levels are visualized as box-and-whisker plots. (D) HL-60 cells were retrovirally transduced with empty vector (MIG), miR-145, or miR-146a. Transduced cells were isolated by fluorescence-activated cell sorting and analyzed for Annexin V binding after 1 week in culture. Shown is a representative analysis from 2 independent transductions. Gating strategy is provided in supplemental Figure 2. (E) Kaplan-Meier survival curves for mice reconstituted with marrow transduced with vector (n = 11) or miR-145/miR-146a decoy (n = 15) from 3 independent transplants. (F) Hematoxylin and eosin–stained femur (i) and spleen (ii) sections from a myeloproliferative-like diseased mouse. Wright-Giemsa–stained bone marrow cytospins (iii-v) and blood smears (iv) from a bone marrow failure mouse (iii-iv) and a leukemic mouse (v). Spleen image was obtained at time of death from a leukemic mouse (587 mg) and compared with a spleen from a control mouse (100 mg; vi).