MLLT3 and myeloid leukemia: To investigate whether the CELF2 deletion is functionally relevant to human myeloid leukemia development, we knocked down (KD) the CELF2 expression in MOLM-13 and THP-1 (both contain MLL-AF9 mutation) cell lines (Fig. 2I), and found that CELF2 KD increased the growth of MOLM-13 and THP-1 cells (Fig. 2J), decreased the apoptosis of MOLM-13 and THP-1 cells (Fig. S2B).