Recently, Bourgeais et al.52 found that the persistent activation of signal transducer and activator of transcription (STAT)5 induced by BCR-ABL promoted ROS production in CML cells by inhibiting catalase (CAT) and glutaredoxin-1 (Glrx1) expression; however, when leukemic cells were cocultured with BM stromal cells to mimic a leukemic niche, CAT and Glrx1 were upregulated, causing downregulation of ROS levels and enhancement of leukemic cell quiescence. The gene discussed is CAT; the disease is chronic myelogenous leukemia, BCR-ABL1 positive.