Identification of negative feedback regulators in response to acute activation of BCR-ABL1 kinase signaling in MLL-AF4 and E2A-PBX1 acute lymphoblastic leukemia

Human B cell lineage acute lymphoblastic leukemia (ALL) cells carrying MLL-AF4 (SEM; BEL) and E2A-PBX1 (697) gene rearrangements were transduced with the mouse ecotropic receptor to permit subsequent entry of retroviral BCR-ABL1 GFP and GFP empty vectors (EV) pseudotyped with murine ecotropic envelope. GFP expression was measured by flow cytometry. Transductions with BCR-ABL1 GFP and GFP empty vectors (EV) were performed in the presence and absence of 2 mmol/l Imatinib (TKI). Washout of Imatinib in one series of experiments is indicated with an arrow. To study gene expression changes in MLL-AF4 and E2A-PBX1 B cell lineage ALL cells that were transduced with empty vectors (EV), BCR-ABL1 GFP in the presence of Imatinib (BCR-ABL1 OFF), washout of Imatinib (BCR-ABL1 ON) and subsequent re-addition of Imatinib, microarray analyses were performed. Three ALL cell lines (SEM, BEL and 696) were tranduced with BCR-ABL1 GFP and GFP empty vectors (EV) in the presence and absence of 2 mmol/l Imatinib, then washout of Imatinib, and then subsequent re-addition of Imatinib