Circ-MYBL2 knockdown in leukemia cells harboring the FLT3-ITD mutation increased the number of cells in Sub-G1 and G0/G1 phases and decreased ones in S and G2/M phases, thus substantially impairing the proliferation of these cells, whereas it merely affected the FLT3-nonmutant cells. The gene discussed is MYBL2; the disease is leukemia.