EHA Library - The official digital education library of European Hematology Association (EHA)

Essential thrombocytemia (ET) is a clonal disorder of the hematopoietic stem cells characterized by excessive myeloid proliferation, with predominant megakaryocytic expansion and a potential of transformation to acute myeloid leukemia. 50 to 60% of ET cases present a JAK2V617F mutation. 5% to 10% of JAK2V16F negative ET patients have MPL mutations at codon 515 and 50% to 70% of ET patients with non-mutated JAK2 and MPL (double-negative) carry mutations at exon 9 of CALR. Genomic instability in ET may be associated with an increased level of reactive oxygen species (ROS) which also leads to DNA damage. Hematopoietic stem cells of JAK2V617F positive murine models have higher ROS levels than found in normal mice (Marty et al, 2013).

To evaluate ROS levels in patients with ET and to observe if JAK2V617F positive cases associate higher ROS levels compared to patients without JAK2V617F mutation.

We studied 23 patients with ET admitted to the Clinic of Hematology, Filantropia City Hospital, Craiova, Romania, diagnosed with ET according to the 2008 revised WHO criteria (informed consent obtained). All analysis were performed after diagnosis and before the start of therapy. The JAK2V617F mutation was detected by allele specific polymerase chain reaction (PCR) testing. ROS levels were detected by flow-cytometry using a Cy Flow Space Sysmex flow-cytometer and a DCFDA Cellular ROS Detection Assay Kit. Studied parameters were compared both to healthy controls and to each other. Exclusion criteria were presence of any condition associated with an increased oxidative status (alcohol consumption, smoking, diabetes mellitus, hyperlipidemia, chronic renal failure, human immunodeficiency, cirrhosis, and active infection), use of antioxidants or iron supplementation. Data analysis was performed using Flow Max software. The differences between the two groups were assessed using the Student T-test and a p-value of less than 0.05 was considered statistically significant.

The study group involved 12 females and 11 males, with a median age of 48 years. All patients had increased ROS levels at diagnosis compared to healthy controls. Eleven patients had JAK2V617F mutation and twelve were JAK2V617F mutation negative. Significantly higher ROS levels were found in JAK2-positive patients compared to JAK2-negative patients.

In our study, patients with ET had increased ROS levels. Cases with JAK2V617F mutation associated higher ROS levels compared to those without JAK2V617F mutation. In our future research, we will focus on the follow-up of these patients for a period of four years and we will try to observe if increased ROS levels enhanced genomic instability and transformation to acute myeloid leukemia.