Oxidative stress in myeloproliferative neoplasms

Abstract

Background: Oxidative stress is an invasive condition with increased reactive oxygen species, now recognized as an important characteristic of malignant disorders as well as their progression. Aims: The aim of this study was to evaluate the role of oxidative stress induced genes and antioxidative enzymes in myeloproliferative neoplasms (MPN): polycythemia vera (PV), essential thrombocythemia (ET) and primary myelofibrosis (PMF). Methods: Using microarray analysis we studied oxidative stress induced gene expression in CD34+ hematopoietic progenitors of MPN patients. An assay for superoxide dismutases (SOD) was based on the ability of SOD to inhibit the autoxidation of epinephrine at alkaline pH. The activity of glutathione reductase (GR) was based on the capacity of GR to catalyze the reduction of oxidized to reduced glutathione using NADPH as a substrate. Glutathione peroxidase activity was assayed following the oxidation of NADPH with t-butylhydroperoxide as a substrate. The antioxidative enzymes activities were determined in red blood cells lyzate. Results: Oxidative stress induced FBJ murine osteosarcoma viral oncogene homolog (FOS) gene expression was highly elevated in ET (3.1 fold) and PV (3.7 fold) comparing to healthy controls. FOS gene expression was higher in JAK2V617F heterozygous PV patients (4.1 fold). Less prominent expression was observed for kelch-like ECH-associated protein 1 (KEAP1) gene in PV (1.6 fold) and PMF (1.8 fold). Regarding ET patients, heme oxygenase 1 (HMOX1) gene was preferentially expressed in JAK2V617F positive ET (2.4 fold), significantly higher than in healthy controls (p<0.05). Also, HMOX1 was significantly more expressed in JAK2V617F homozygous PV patients (2.5 fold), than in healthy controls (p<0.05). In contrary, v-maf musculoaponeurotic fibrosarcoma oncogene homolog F (MAFF) gene was significantly less expressed in JAK2 homozygous PV and PMF than in healthy controls (p<0.01). The levels of superoxide dismutase and glutathione peroxidase were the most abundant in PMF of MPN. The level of glutathione reductase was the highest in PV, not influenced by JAK2V617F mutant allele burden. However in PMF, the level of glutathione reductase was the most increased in JAK2 homozygous PMF and reduced in JAK2 negative patients, in opposite to glutathione peroxidase levels. Summary and Conclusions: Presented oxidative stress induced gene expression demonstrated JAK2 dependence in MPN. The antioxidative enzymes activities were the most prominent in PMF. So, oxidative stress effects both at gene and enzyme levels revealed a variation specific for certain type of MPN.