circMYBL2 knockdown impairs the cytoactivity of FLT3-ITD AML cells, including inhibitor-resistant cells. (A) Effect of circMYBL2 suppression in methylcellulose cultures of FLT3-ITD⁺ AML MOLM-13 cells. (B) Microscopic analysis of Wright-Giemsa–stained cytospin preparations of MOLM-13 and THP-1 cells. Original magnification ×400. Flow cytometric analysis of myeloid differentiation in MOLM-13 and THP-1 cells. The numbers indicate the percentages of cells. (C) Cell viability was measured with a CCK8 assay 48 hours after the addition of quizartinib at the indicated concentration. (D) Western blot measuring p-FLT3 in MOLM-13 or MOLM-13-RQ exposed to quizartinib at the indicated concentration. (E-F) MOLM-13-RQ cells were as sensitive to circMYBL2 knockdown as parental MOLM-13 cells in terms of apoptosis. (G-H) MOLM-13-RQ cells were as sensitive to circMYBL2 knockdown as parental MOLM-13 cells in terms of cell differentiation. (I) MOLM-13-RQ cells were as sensitive to circMYBL2 knockdown as parental MOLM-13 cells in terms of cell proliferation.