NSAIDs aspirin and sulindac inhibit the growth of primary AML samples in vitro and in vivo. (A) The karyotypes of the AML samples. (B) Twenty thousand cells from AML patients’ BM samples were plated in methylcellulose-based medium and cultured for 14 days. Cell growth was determined by the total cell number after culture. As a comparison, human BM CD34+ cells (STEMCELL Technologies) were cultured under the same condition. (C) Primary AML samples responded to aspirin and sulindac sulfide to various extents. Primary AML cells were plated and cultured as described in (B), except that each well was treated with either DMSO, sulindac sulfide (10 μM),or aspirin (500 μM). The cell growth percentage was determined by comparing the total cell numbers in the drug-treated wells to those in the DMSO-treated wells at the end of culture. In comparison, the growth of human CD34+ cells was unaffected by these 2 drugs. (D-E) Orthotopic xenografts of AML#25 and 1 other AML sample (M4 subtype, Flt3 mutation) in NSG mice. Nimesulide treatment was initiated 1 day after transplantation. After 1 to approximately 3 months (3 months for AML#25 and 6 weeks for M4, Flt3mut AML) the mice were sacrificed and the frequencies of human CD45⁺ and CD45⁺CD34⁺ cells in their BM were determined. Student t test was performed between the control group and the nimesulide-treated group. The comparisons that showed statistical significance (P < .05) were indicated by asterisks. MNC, mononuclear cells; n, the numbers of mice in each group.