Browsing by keyword "Leukemia, Monocytic, Acute"
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Dexamethasone but not indomethacin inhibits human phagocyte nicotinamide adenine dinucleotide phosphate oxidase activity by down-regulating expression of genes encoding oxidase componentsWe investigated the effects of dexamethasone or indomethacin on the NADPH oxidase activity, cytochrome b558 content, and expression of genes encoding the components gp91-phox and p47-phox of the NADPH oxidase system in the human monocytic THP-1 cell line, differentiated with IFN-gamma and TNF-alpha, alone or in combination, for up to 7 days. IFN-gamma and TNF-alpha, alone or in combination, caused a significant up-regulation of the NADPH oxidase system as reflected by an enhancement of the PMA-stimulated superoxide release, cytochrome b558 content, and expression of gp91-phox and p47-phox genes on both days 2 and 7 of cell culture. Noteworthy was the tremendous synergism between IFN-gamma and TNF-alpha for all studied parameters. Dexamethasone down-regulated the NADPH oxidase system of cytokine-differentiated THP-1 cells as assessed by an inhibition on the PMA-stimulated superoxide release, cytochrome b558 content, and expression of the gp91-phox and p47-phox genes. The nuclear run-on assays indicated that dexamethasone down-regulated the NADPH oxidase system at least in part by inhibiting the transcription of gp91-phox and p47-phox genes. Indomethacin inhibited only the PMA-stimulated superoxide release of THP-1 cells differentiated with IFN-gamma and TNF-alpha during 7 days. None of the other parameters was affected by indomethacin. We conclude that dexamethasone down-regulates the NADPH oxidase system at least in part by inhibiting the expression of genes encoding the gp91-phox and p47-phox components of the NADPH oxidase system.
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Hemophagocytic lymphohistiocytosis with MUNC13-4 gene mutation or reduced natural killer cell function prior to onset of childhood leukemiaHemophagocytic lymphohistiocytosis (HLH) is a rare histiocytic reactive process due to mutations in the perforin, MUNC13-4 or syntaxin 11 genes, or secondary to malignancy, infection or autoimmune disorder. HLH as a preceding diagnosis to leukemia is rare. We report two cases with progression to acute leukemia, one heterozygous for MUNC13-4 and the other with reduced natural killer (NK) cell function and perforin expression. These defects may predispose to a secondary HLH-like presentation of pre-clinical leukemia or confer increased susceptibility to malignancy. HLH patients with genetic mutations or NK cell function abnormalities need monitoring for future malignancy even if the HLH resolves.