In vivo Hdac3 depletion reduces tumor burden and/or significantly extends the survival of mice bearing AML or Eµ-Myc lymphoma. MLL-AF9;Nras^G12D AML cells transduced with dox-inducible shRNA constructs (pTRMPV-Neo) were transplanted into CD45.1⁺ mice and shRNA expression was induced 2 days after tumor inoculation by addition of dox to food and drinking water (shRen.713, n = 14; shHdac3.987, n = 12). (A) Tumor burden was assessed by bioluminescent imaging following 8 days of dox treatment. (B) Kaplan-Meier curves for survival analysis of mice bearing transplanted AML tumor with indicated pTRMPV-Neo constructs. Day 0 denotes the beginning of dox treatment. Statistical analysis was undertaken using a log-rank (Mantel-Cox) test. (C) Percentage of shRNA-expressing (Venus⁺/dsRed⁺) tumor cells in the bone marrow remaining at terminal disease stage were analyzed using a Student t test (P < .0001). Eµ-Myc tumor cells (no. 107) were transduced with dox-inducible pTRMPV-Neo with shRNA cassettes targeting Hdac3 (shHdac3.1659, n = 12; shHdac3.201, n = 12) or shScr control (n = 12), FACS-sorted, and transplanted into CD45.1⁺ mice (5 × 10³ cells per mouse). On day 3 postinoculation, mice (n = 6/group) were fed dox in food and water to initiate expression of shRNAs in vivo. Mice were bled and sacrificed on day 10 to assess (D) WBC count, (E) percentage of tumor cells (Venus⁺) in PB by flow cytometry, and (F) spleen size in mice bearing Eµ-Myc lymphoma. Data are presented as mean ± SEM. Two biological experiments were undertaken. Data were analyzed using one-way ANOVAs and appropriate post-hoc tests.