Merestinib blocks phosphorylation of eIF4E and suppresses growth of primary leukemic progenitors from AML patients. (A) MV4-11 cells, (B) MM6 cells, and (C) AML patient-derived cells (AML-PT) were incubated with merestinib (LY2801653) at final concentrations of either 0.1 or 1 µM for 1 and 4 hours. Cell lysates were resolved by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotted with an antibody against the phosphorylated form of eIF4E on serine 209. The same blots were stripped and reprobed with an antibody against eIF4E. The immunoblots were also probed for HSP90 as a loading control. (D) MV4-11 and (E) MM6 cells were plated in clonogenic assays in methylcellulose with increasing concentrations of merestinib (LY2801653), as indicated. Data are expressed as percentage of colony formation of control vehicle-treated cells, and bar graphs represent means ± standard error (SE) of 5 independent experiments. (F) Dose-dependent suppression of primary leukemic precursors from AML patients by merestinib in clonogenic assays in methylcellulose. Data are expressed as percentage of colony formation of control vehicle-treated cells. Bar graphs represent means ± SE from 5 independent experiments, using cells from 5 different patients with AML. One-way ANOVA analysis followed by Tukey’s test was used to evaluate statistically significant differences: *P < .05, ****P < .0001.