Small molecule inhibitor NSC348884 disrupts NPM1 oligomerization and induces apoptosis in OCI-AML3 cells. (A) HL-60 and OCI-AML3 cells were treated with the indicated concentrations of NSC348884 for 8 hours. After this, total cell lysates were prepared and native gel electrophoresis and immunoblot analysis of NPM1 was performed to assess the disruption of NPM1 oligomerization. The expression levels of β-actin in the lysates served as the loading control. (B) OCI-AML3 cells were treated with the indicated concentrations of NSC348884 for 8 hours. After this, total cell lysates were prepared and native gel electrophoresis and immunoblot analysis of mutant NPM1 was performed to assess the disruption of mutant NPM1 oligomerization. The expression levels of β-actin in the lysates served as the loading control. (C) HL-60, OCI-AML3, and OCI-AML2 cells were treated with indicated concentrations of NSC348884 for 8 hours. After this, total cell lysates were prepared and immunoblot analyses were performed for NPM1, Mt-NPM1 and p53. The expression levels of β-actin in the lysates served as the loading control. (D) HL-60, OCI-AML3, U937, and OCI-AML2 cells were treated with the indicated concentrations of NSC348884 for 24 hours. Then, cells were stained with annexin V and propidium iodide and the percentages of apoptotic cells were determined by flow cytometry. Columns represent the mean of 3 independent experiments; bars represent the SEM.