Evolving Therapeutic Options for Polycythemia Vera: Perspectives of the Canadian Myeloproliferative Neoplasms Group

Advances in polycythemia vera and lessons for acute leukemia

The myeloproliferative neoplasms (MPN), polycythemia vera (PV), essential thrombocytosis and primary myelofibrosis, are an unusual group of myeloid neoplasms, which arise in a pluripotent hematopoietic stem cell (HSC) due to gain of function driver mutations in the JAK2, CALR and MPL genes that constitutively activate JAK2, the cognate tyrosine kinase of the type 1 hematopoietic growth factor (HGF) receptors. PV is the ultimate phenotypic expression of constitutive JAK2 activation since it alone of the three MPN is characterized by overproduction of normal red cells, white cells and platelets. Paradoxically, however, although PV is a panmyelopathy involving myeloid, erythroid and megakaryocytic progenitor cells, pluripotent HSC only express a single type of HGF receptor, the thrombopoietin receptor, MPL. In this review, the basis for how a pluripotent HSC with one type of HGF can give rise to three separate types of myeloid cells will be explained and it will be demonstrated that PV is actually a hormone-sensitive disorder, characterized by elevated thrombopoietin levels. Finally, it will be shown that the most common form of acute leukemia in PV is due to the inappropriate use of chemotherapy, including hydroxyurea, which facilitates expansion of DNA-damaged, mutated HSC at the expense of their normal counterparts.

Early Renoprotective Effect of Ruxolitinib in a Rat Model of Diabetic Nephropathy

Diabetic kidney disease (DKD) is still one of the unresolved major complications of diabetes mellitus, which leads ultimately to end-stage renal disease in both type 1 and type 2 diabetes patients. Available drugs that suppress the renin-angiotensin system have partially minimized the disease impact. Yet, there is an unmet need for new therapeutic interventions to protect the kidneys of diabetic patients. In DN, glomerular sclerosis and tubulointerstitial fibrosis are mediated through several pathways, of which JAK/STAT is a key one. The current study explored the potential renoprotective effect of the JAK1/JAK2 inhibitor ruxolitinib (at doses of 0.44, 2.2, and 4.4 mg·kg^-1) compared to that of enalapril at a dose of 10 mg·kg^-1, in a rat model of streptozotocin-induced diabetes mellitus over 8 weeks. The effect of ruxolitinib was assessed by determining urinary albumin/creatinine ratio, serum level of cystatin, and levels of TGF-β1, NF-κB, and TNF-α in renal tissue homogenates by biochemical assays, the glomerular sclerosis and tubulointerstitial fibrosis scores by histological analysis, and fibronectin, TGF-β1, and Vimentin levels by immunohistochemical staining with the respective antibodies. Our results revealed a significant early favorable effect of a two-week ruxolitinib treatment on the renal function, supported by a decline in the proinflammatory biomarkers of DKD. This pre-clinical study suggests that the renoprotective effect of ruxolitinib in the long term should be investigated in animals, as this drug may prove to be a potential option for the treatment of diabetic kidney disease.

Management of Polycythemia Vera: A Survey of Canadian Physician Practice Patterns

BACKGROUND

The 2016 World Health Organization (WHO) revised classification criteria for the diagnosis of polycythemia vera (PV) allows for an earlier detection of masked PV. The literature is scarce about the clinical uptake of new diagnostic algorithms for PV. In a cohort of Canadian hematologists, we aimed to identify how the revised 2016 WHO diagnostic criteria of PV are being incorporated into hematology practice, and if the treatment of PV is comparable to the approaches outlined by the Canadian Myeloproliferative Neoplasm Group.

MATERIALS AND METHODS

A cross-sectional survey of practicing Canadian hematologists/oncologists was distributed to active members of the Canadian Hematology Society using an online survey-distributing website. Univariate and multivariate analysis was performed.

RESULTS

The survey was completed by 86 respondents in total. Only type of practice was associated with respondents offering aspirin to all patients with PV (P = .0009). Respondents who were aware of the Canadian Myeloproliferative Neoplasm Group guidelines were more likely to phlebotomize patients to a target hematocrit of < 45% irrespective of gender (P = .042). Younger practitioners were more likely to use age over 60 years as an indication for initiating cytoreductive therapy (P = .0006). Most (85.3%) respondents would recommend indefinite anticoagulation in patients with PV who developed unprovoked venous thromboembolism.

CONCLUSION

The survey confirmed that heterogeneity of practice in diagnosis and management of PV among Canadian hematologists exists, suggesting that targeted education in specific segments of the PV treatment providers may result in wider adoption of the guidelines and diagnostic criteria.

Myeloproliferative neoplasms (MPNs) - Part 1: An overview of the diagnosis and treatment of the "classical" MPNs

Myeloproliferative neoplasms (MPNs) are rare, yet potentially life-threatening, disorders caused by overproliferation of bone marrow stem cells. The symptom burden experienced by patients with the BCR-ABL1-negative MPNs (also referred to as the classical MPNs, i.e., essential thrombocythemia [ET], polycythemia vera [PV] and myelofibrosis [MF]) can be significant and can negatively impact quality of life (QOL). Since patients with these MPNs can live for several years, thereby requiring long-term treatment and follow-up, nurses play an essential role in communicating with these patients, assessing their symptoms, and educating them on treatments and self-management strategies that can reduce their symptom burden. This article, which is the first of a two-part series, was developed to provide nurses and other healthcare professionals with a review of the diagnosis and treatment of the most common classical MPNs. The second article in this series (also available in this issue) will provide nurses with practical guidance for managing the symptom burden associated with MPNs in order to help enhance the overall health and well-being of patients living with these disorders.