Targeting PAK1 inhibits growth and reduces clonogenicity of human acute myeloid leukemia cells. (A) MOLM-13, HL-60, THP-1, and KG1a cells were treated with increasing concentrations of IPA-3. Cell viability was measured by cell counts with trypan blue exclusion every 24 hours. Experiment performed in triplicate (P values are shown for last time point indicated). (B) MOLM-13, HL-60, THP-1, and KG1a cells were treated with increasing concentrations of FRAX-597. Statistics are indicated as in A. A total of 3000 THP-1 or MOLM-13 cells were seeded in methylcellulose containing indicated concentrations of (C) IPA-3 or (D) FRAX-597. (E) Two unique shRNAs targeting human PAK1 were expressed in THP-1 cells. Cell growth was measured by cell counts with trypan blue exclusion. Average of 3 independent experiments. (F) Colony formation analysis of THP-1 cells treated with 2 independent PAK1 knockdown sequences. Average of 2 independent experiments. *P < .05, **P < .01, and ***P < .001 for all experiments.