No abstract

These findings suggest that discontinuation of second- or subsequent-line dasatinib after a sustained DMR of ≥ 1 year is feasible, especially for patients with no history of imatinib resistance. In addition, the natural killer cell count was associated with the TFR.

Leukemia cells in the bone marrow (BM) must meet the biochemical demands of increased cell proliferation and also survive by continually adapting to fluctuations in nutrient and oxygen availability. Thus, targeting metabolic abnormalities in leukemia cells located in the BM is a novel therapeutic approach. In the present study, we investigated the metabolic role of BM adipocytes in supporting the growth of leukemic blasts. Prevention of nutrient starvation-induced apoptosis of leukemic cells by BM adipocytes, as well as the metabolic and molecular mechanisms involved in this process, were investigated using various analytical techniques. In acute monocytic leukemia (AMoL) cells, the prevention of spontaneous apoptosis by BM adipocytes was associated with an increase in fatty acid β-oxidation (FAO) along with the upregulation of PPARγ, FABP4, CD36, and BCL2 genes. In AMoL cells, BM adipocyte co-culture increased adiponectin receptor gene expression and its downstream target stress response kinase AMPK, p38 MAPK with autophagy activation, and upregulated antiapoptotic chaperone heat shock proteins. Inhibition of FAO disrupted metabolic homeostasis, increased reactive oxygen species production, induced the integrated stress response mediator ATF4, and apoptosis in AMoL cells co-cultured with BM adipocytes. Our results suggest that BM adipocytes support AMoL cell survival by regulating their metabolic energy balance, and that the disruption of FAO in BM adipocytes may be an alternative, novel therapeutic strategy for AMoL therapy.

For generation of energy, cancer cells utilize glycolysis more vigorously than oxidative phosphorylation in mitochondria (Warburg effect). We examined the energy metabolism of four leukemia cell lines by using glycolysis inhibitor, 2-deoxy-d-glucose (2-DG) and inhibitor of oxidative phosphorylation, oligomycin. NB4 was relatively sensitive to 2-DG (IC(50): 5.75 mM), consumed more glucose and produced more lactate (waste product of glycolysis) than the three other cell lines. Consequently, NB4 was considered as a "glycolytic" leukemia cell line. Dependency on glycolysis in NB4 was confirmed by the fact that glucose (+) FCS (-) medium showed more growth and survival than glucose (-) FCS (+) medium. Alternatively, THP-1, most resistant to 2-DG (IC(50): 16.14 mM), was most sensitive to oligomycin. Thus, THP-1 was recognized to be dependent on oxidative phosphorylation. In THP-1, glucose (-) FCS (+) medium showed more growth and survival than glucose (+) FCS (-) medium. The dependency of THP-1 on FCS was explained, at least partly, by fatty acid oxidation because inhibitor of fatty acid β-oxidation, etomoxir, augmented the growth suppression of THP-1 by 2-DG. We also examined the mechanisms by which THP-1 was resistant to, and NB4 was sensitive to 2-DG treatment. In THP-1, AMP kinase (AMPK), which is activated when ATP becomes limiting, was rapidly phosphorylated by 2-DG, and expression of Bcl-2 was augmented, which might result in resistance to 2-DG. On the other hand, AMPK phosphorylation and augmentation of Bcl-2 expression by 2-DG were not observed in NB4, which is 2-DG sensitive. These results will facilitate the future leukemia therapy targeting metabolic pathways.