BCR and breast cancer: Although BCR‐ABL expressing cells have functional defects in the CXCR4 signalling axis, imatinib treatment increases CXCR4 expression, and CXCL12 activation improves BM homing and survival of CML stem cells.8, 35 Based on recently published data demonstrating a binding of LASP1 and CXCR4 in breast cancer cells, we investigated the role of LASP1 in the light of this interaction for CML.15 To do so, we generated cell lines with inactivated LASP1 and/or CXCR4 overexpression using a CRISPR/Cas9‐based LASP1 knockout system and a lentivirus‐mediated CXCR4 overexpression in K562 cells.