AICDA and B-cell chronic lymphocytic leukemia: To experimentally examine the role of AID in developing resistance to idelalisib and ibrutinib, we used CRISPR-Cas9 technology to knock out AID in a human CLL cell line, MEC-1 [24], a human cell line derived from prolymphocytic CLL and previously used as a powerful model to detect AID-dependent genome instability during idelalisib treatment [13,17].