OBJECTIVES: The present study investigates the potential role of hypoxia in maintaining stem cell-like properties and therapeutic resistance in K562 leukemic cell. METHODS: Western blot, flow cytometry and cell viability assays were used to investigate the effects of hypoxia (1% O2) on cell proliferation, drug resistance and expression of the hypoxia inducible factor-2α (HIF-2α), the octamer-binding transcription factor 4 (Oct4), CD133, CD34 and the ATP-binding cassette sub-family G member 2 (ABCG2) as well as Smad2 phosphorylation in the drug resistant cell line K562/DOX and its parental cell line. RESULTS: Hypoxia induced growth inhibition and significantly upregulated HIF-2α, CD133, Oct4, CD34 and ABCG2 expression in the wild type K562 cells (p<0.05). The IC50 of doxorubicin was also enhanced about 2.5-fold in hypoxia. In contrast, the K562/DOX cells, which showed significantly higher ABCG2 expression and IC50 for various drugs, no significant difference in cell proliferation was observed between hypoxia and normoxia. The hypoxia-induced upregulation of HIF-2α, CD133, Oct4, CD34 and ABCG2 expression was significantly lower than in the wild type cells (p<0.05). Moreover, hypoxia induced the phosphorylation of Smad2 and additional treatment with SD-208, an inhibitor of the TGF-β receptor I kinase, resulted in a dose-dependent downregulation of CD133 and Oct4 in the K562/DOX cells. CONCLUSIONS: Hypoxia plays an important role in enhancing the stem cell-like properties and to induce multidrug resistance of leukemia cells. The activation of the TGF-β/Smad2 signaling pathway may be involved in the regulation of this pathophysiological process.
OBJECTIVES: The present study investigates the potential role of hypoxia in maintaining stem cell-like properties and therapeutic resistance in K562 leukemic cell. METHODS: Western blot, flow cytometry and cell viability assays were used to investigate the effects of hypoxia (1% O2) on cell proliferation, drug resistance and expression of the hypoxia inducible factor-2α (HIF-2α), the octamer-binding transcription factor 4 (Oct4), CD133, CD34 and the ATP-binding cassette sub-family G member 2 (ABCG2) as well as Smad2 phosphorylation in the drug resistant cell line K562/DOX and its parental cell line. RESULTS:Hypoxia induced growth inhibition and significantly upregulated HIF-2α, CD133, Oct4, CD34 and ABCG2 expression in the wild type K562 cells (p<0.05). The IC50 of doxorubicin was also enhanced about 2.5-fold in hypoxia. In contrast, the K562/DOX cells, which showed significantly higher ABCG2 expression and IC50 for various drugs, no significant difference in cell proliferation was observed between hypoxia and normoxia. The hypoxia-induced upregulation of HIF-2α, CD133, Oct4, CD34 and ABCG2 expression was significantly lower than in the wild type cells (p<0.05). Moreover, hypoxia induced the phosphorylation of Smad2 and additional treatment with SD-208, an inhibitor of the TGF-β receptor I kinase, resulted in a dose-dependent downregulation of CD133 and Oct4 in the K562/DOX cells. CONCLUSIONS:Hypoxia plays an important role in enhancing the stem cell-like properties and to induce multidrug resistance of leukemia cells. The activation of the TGF-β/Smad2 signaling pathway may be involved in the regulation of this pathophysiological process.
Authors: Charlotte Gauthier; Csilla Ozvegy-Laczka; Gergely Szakacs; Balazs Sarkadi; Attilio Di Pietro Journal: Front Pharmacol Date: 2013-11-07 Impact factor: 5.810
Authors: Chelsea Anorma; Jamila Hedhli; Thomas E Bearrood; Nicholas W Pino; Sarah H Gardner; Hiroshi Inaba; Pamela Zhang; Yanfen Li; Daven Feng; Sara E Dibrell; Kristopher A Kilian; Lawrence W Dobrucki; Timothy M Fan; Jefferson Chan Journal: ACS Cent Sci Date: 2018-07-25 Impact factor: 14.553