In vitro depletion of Hdac3 reduces growth and triggers differentiation in established APL cells. APL blasts from 129SvEv mice were transduced with constitutive pRetroSuper vectors expressing shHdac3 or control shLuc and sorted for GFP positivity, then assessed for (A) depletion of Hdac3 by qRT-PCR. Values are normalized against glyceraldehyde-3-phosphate dehydrogenase and referred to CTRL (shLuc) (n = 2 biological replicates). Data are presented as mean ± SEM. (B) Depletion of HDAC3 by western blot; Vinculin was used as a loading control. Molecular weights of individual proteins are to the left of each blot. (C) Loss of clonogenicity by serial replating assay (data are presented as mean number of colonies counted 7-10 days after seeding 1 × 10⁴ leukemic cells ± SEM (n = 3 independent experiments). Data are presented as mean ± SEM. Statistical analysis was performed with a paired t test. (D) Differentiation by morphologic analysis of the GFP⁺/APL cells, harvested after plating in methylcellulose medium (first methylcellulose): (i) representative cytospins; (ii) percentage of mature and immature cells (×60 magnification, May Grünwald-Giemsa staining, Olympus BX51). The prevalence of mature and immature cells was analyzed morphologically in cytological slides and the absolute percentage of mature cells was reported. Experiments were repeated 3 times (biological triplicate). At least 300 cells were scanned for each case. Statistical analysis was performed with the Fisher exact test.