ABL1 and leukemia: After K562 and KBM5 leukemia cells were infected with Cas9-GFP/hU6-sgRNA1(BCR1)-mU6-sgRNA2 (cABL1) (Cas9-GFP/dual-BA-sgRNA) viruses, the GFP+ cells were sorted via FACS and used for a targeting efficiency assay.