The treatment of polycythaemia vera: an update in the JAK2 era

Antimalarial drug artemisinin depletes erythrocytes by activating apoptotic pathways in zebrafish

Despite its extraordinary efficacy, administration of the major antimalarial drug artemisinin leads to anemia, and the underlying cellular and molecular mechanisms are not well understood. Here, we report the effects of artemisinin on erythroid development and apoptosis in zebrafish and human cells. By performing a small-molecule screen with zebrafish embryos, we found that artemisinin treatment depleted red blood cells and slightly decreased definitive hematopoietic stem cells, but had no effect on primitive hematopoietic progenitors. RNA-Seq revealed that artemisinin suppressed a cluster of genes in the heme biosynthesis and globin synthesis pathways. Furthermore, artemisinin induced apoptosis in erythrocytes in zebrafish embryos, as assessed by terminal deoxynucleotidyl transferase dUTP nick end labeling assay, and preferentially acted on differentiated erythrocytes by elevating caspase 8 and caspase 9 activity in differentiated human K562 cells. Consistently, artemisinin suppressed the ectopic expression of erythroid genes in jak2aV581F-injected embryos, a zebrafish model for human polycythemia vera in which the bone marrow makes too many red blood cells. Taken together, our data suggested that artemisinin, in addition to killing parasites, has a direct action on differentiated erythrocytes other than definitive hematopoietic stem cells and causes erythroid apoptosis by interfering with the heme biosynthesis pathway in zebrafish and human cells.

Treatment outcome in a cohort of young patients with polycythemia vera

The treatment of polycythemia vera in young adults is challenging, requiring one to run a balance between the increased risk of vascular complications, if left untreated, versus the potential of promoting secondary leukemia/myelodysplasia or cancer, if actively managed with chemotherapy. We report the results of a 20-year retrospective analysis in a cohort of 30 young adults with PV (median age 37 years, range 19-45) treated exclusively with phlebotomy, aspirin and hydroxyurea only in case of vascular complications occurring in the presence of thrombocytosis (platelet count > 600 × 10(9)/L). With this approach, vascular complications were no higher than in other published series, and secondary leukemia/myelodysplasia or cancer was not observed during a follow-up of 14 years.

Polycythemia vera

The diagnostic approach to a patient with polycythemia has been greatly simplified by the introduction of new genetic testing in addition to traditional tests, such as measurement of red cell mass and serum erythropoietin (Epo) level. Clonal erythrocytosis, which is the diagnostic feature of polycythemia vera (PV), is almost always associated with a JAK2 mutation (JAK2V617F or exon 12). Therefore, in a patient with acquired erythrocytosis, it is reasonable to begin the diagnostic work-up with JAK2 mutation analysis to distinguish PV from secondary erythrocytosis. The clinical course of PV is marked by a high incidence of thrombotic complications that represent the main cause of morbidity and mortality in these patients. Blood hyperviscosity as well as platelet and leukocyte quantitative, and qualitative abnormalities play a major role in the pathogenesis of thrombophilia. Prevention of vascular events and minimizing the risk of disease transition into acute leukaemia are the main targets of the whole PV treatment strategy. This can rely on the use of low-dose aspirin in most patients, while the choice of the optimal cytoreductive strategy is based on the individual vascular risk. Phlebotomy is still the preferred treatment in subjects at low risk, while hydroxyurea or pipobroman is usually administered to most elderly subjects or subjects with a previous vascular history. The use of pegylated interferon, imatinib, and JAK2 inhibitors is currently being evaluated.

Absence of hypoalbuminemia despite nephrotic proteinuria in focal segmental glomerulosclerosis secondary to polycythemia vera

In addition to displaying geographic variation, focal segmental glomerulosclerosis (FSGS) has become the commonest cause of the nephrotic syndrome seen in adults in recent years. Secondary FSGS in particular, is observed when glomerular workload is increased. Polycythemia vera (PV) is a hematological disease characterized by abnormal proliferation in the erythroid series. The number of case reports belonging to glomerulonephritis secondary to PV is limited. In the literature, there are few reports of FSGS. One study pointed out that the presence of normoalbuminemia was detected in patients with FSGS secondary to hyperfiltration when there was nephrotic proteinuria. Here, we report a case of FSGS following a course with normoalbuminemia despite nephrotic range proteinuria developing secondary to PV. Our case is the first report in the literature with thes characteristics.