ATF5 inhibits autophagy in BCR-ABL–transformed cells by transcriptional stimulation of mTOR expression. (A) 32D/BCR-ABL or K562 cells treated with either DMSO or rapamycin were monitored for ATF5 and LC3B levels by immunoblot analysis. (B) 32D/BCR-ABL or K562 cells ectopically expressing a GFP-LC3B fusion protein were treated with DMSO, rapamycin, or PP242 and analyzed by fluorescence microscopy. Representative images are shown. (C) qRT-PCR monitoring mTOR mRNA levels in imatinib-treated 32D/BCR-ABL (5μM for 24 hours) and K562 cells (10μM for 48 hours). (D) qRT-PCR monitoring of mTOR expression in human peripheral blood cells isolated from chronic-phase CML patients (n = 3). Cells were treated in the absence or presence of imatinib (10μM for 16 hours). Error bars represent SE. *P < .05. (E) Immunoblot analysis of mTOR levels in K562 cells stably expressing FLAG or FLAG-ATF5, and treated in the absence or presence of imatinib (10μM for 48 hours). Tubulin was monitored as a loading control. (F) Schematic representation of the BCR-ABL/PI3K/AKT/FOXO4/ATF5/mTOR-mediated autophagy-inhibition pathway. Fading of a protein indicates loss of function.