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Department of Pediatrics

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Cell Differentiation; Dimethylformamide; Enzyme Induction; Gene Expression Regulation, Neoplastic; Glutathione Peroxidase; Granulocytes; Humans; Leukemia, Myeloid; Leukemia, Promyelocytic, Acute; Membrane Glycoproteins; Monocytes; *NADPH Oxidase; Neoplasm Proteins; Phagocytes; RNA, Messenger; Tetradecanoylphorbol Acetate; Tumor Cells, Cultured


Medical Cell Biology | Medical Genetics | Oncology | Pediatrics


We have used the HL-60 and PLB-985 myeloid leukemia cell lines to examine the regulation of expression of the important intracellular antioxidant enzyme, glutathione peroxidase (GSH-Px), during phagocytic cell differentiation in vitro. Induction of differentiation along the monocytic pathway by phorbol ester results in an approximately twofold rise in enzyme activity and a parallel increase in the rate of 75Se incorporation into immunoprecipitable GSH-Px protein. Induction along the granulocytic pathway by dimethyl formamide (DMF) results in similar changes in steady-state enzyme levels and rates of GSH-Px protein synthesis. Steady-state levels of GSH-Px gene transcripts also increase more than twofold, approximately in parallel with the enzyme levels. Nuclear run-on transcription assays of GSH-Px mRNA synthesis show ratios of induced to uninduced transcript levels of 2.24 and 1.59 with phorbol myristate acetate (PMA) induction and DMF, respectively, in HL-60 cells, and ratios of 1.34 and 3.46 with PMA and DMF, respectively, in PLB-985 cells. Half lives of GSH-Px mRNA are unchanged or slightly shorter after differentiation of HL-60 cells, and slightly longer after induction of PLB-985. Overall, the present studies show that GSH-Px activity rises during in vitro-induced monocytic or granulocytic differentiation of myeloid cell lines and that the increased expression of the cellular GSH-Px gene occurs through complex mechanisms that include transcriptional up-regulation. This pattern contrasts with the nearly complete cotranslational regulation of GSH-Px expression by exogenous selenium.


Blood. 1994 Dec 1;84(11):3902-8.

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