Clinical Relevance of Changes of ROS/Peroxiredoxin 1 (Prx1) and Glutathione Peroxidase 1 (Gpx1) Level In AML Primary Cells before and after Induction Chemotherapy

Previously, we had reported that antioxidants (ie, Prx & catalase) were down regulated at the time of diagnosis but those levels were restored to the level of normal individuals as ones achieved CR with signal transduction inhibitors on primary cells of chronic myeloid leukemia(Blood 114: Abstract 1114, 2009). Meanwhile it is plausible that primary cells of acute myeloid leukemia may have different biologies comparing to chronic myeloid leukemia in terms of the regulation of ROS/Prx's and Gpx1. In this study, we investigated the changes of ROS/Prx's and Gpx1 level in the primary cells at the time of diagnosis and at complete remission of AML. In addition, we studied the level of differentiation and changes of ROS/Prx's by ATRA on NB4 cell line simultaneously to study the potential correlation between differentiation and changes of ROS/Prx's and Gpx1.

Pairs of bone marrow sample at the diagnosis and at hematologic remission status of AML patients were evaluated for detection of intracellular ROS using dichlorodihydrofluorescein diacetate (DCFH-DA) and immunoblot assay for the expression of Prx1-6 and Gpx1. We studied the entire process of differentiation by treatment with ATRA on NB4 cell line in vitro in time dependent manner for 4 days. Changes of ROS/Prx's and Gpx1 were evaluated and the level of differentiation was confirmed by Wright's stain simultaneously for 4 days.

In bone marrow samples of AML patients, intracellular ROS levels at the time of diagnosis were significantly higher than those of remission status samples. However, the expression of Prx1 and Gpx1 were increased as well at the time of diagnosis. With induction chemotherapy(3+7), elevated ROS/Prx1 and Gpx1 level came down to the level of normal volunteer bone marrow donors. In NB4 cells, intracellular ROS level were being reduced as time went on after All-trans-retinoic acid (RA) treatment showing progressive differentiation for 4 days. The level of differentiation by RA treatment was confirmed by Wright's stain in time dependent manner. Expression of Prx1 and Gpx1 were decreased after RA treatment by Western blot analysis as well. The activities of NADPH oxidase and Rac1-GTP, which are an essential component of the ROS producing NADPH oxidase, decreased in RA treated NB4 cells as time elapsed compared with control NB4 cells.

Our data suggested that leukemogenesis of acute myeloid leukemia could be related with increased expression of ROS/Prx1 and Gpx1. Elevated level of expression on ROS/Prx1 and Gpx1 were down to the levels of BM of normal individuals as ones achieve complete remission. These findings are quite opposite with the previous observation on CML suggesting different biology in terms of ROS/Prx1 and Gpx1 dysregulation in AML. Interestingly, differentiation processes using RA in NB4 cells were correlated with decreased the expression of Prx1 and Gpx1 in time dependent manner. These data suggest the potential usefulness of differentiation agents(ie, RA and others) in AML treatment via modulation of ROS/Prx1 and Gpx1.

No relevant conflicts of interest to declare.