ATM and B-cell chronic lymphocytic leukemia: HG3 parental cells were transduced to stably express Cas9 protein, and sgRNAs targeting chromosome 11q22.1/11q23.3 were introduced to generate an isogenic HG3 CLL cell line harboring del(11q) (HG3‐del(11q)) of ∼17 Mb size including ATM gene (Figures 2A and 2B).32