A population-based study published in PNAS has provided new insights into how JAK2 V617F-mutated blood cell clones behave before the development of overt myeloproliferative neoplasms (MPNs).
The JAK2V617F mutation is a well-established driver of MPNs, including polycythemia vera, essential thrombocythemia, and primary myelofibrosis. However, the mutation is also found in some individuals without diagnosed blood cancer, making it difficult to predict who will progress to disease.
To investigate this question, researchers analyzed data from the Danish General Suburban Population Study, focusing on 67 individuals with detectable JAK2 V617F mutations who had repeated measurements over more than a decade. Using a mathematical model, they estimated whether mutated hematopoietic stem cells were expanding, remaining stable, or declining over time.
The results showed substantial variation between individuals. Mutated cells demonstrated a significant growth advantage in 47 of 67 participants, but 12 individuals showed significant clonal decline and eight showed no clear evidence of expansion. These findings suggest that the presence of a JAK2 V617F mutation alone does not guarantee progression toward MPN.
During follow-up, 37 participants were diagnosed with an MPN, while 30 remained classified as having clonal hematopoiesis. Individuals who developed MPN generally had faster clonal growth, but growth rate was not a perfect predictor of disease. Some participants with declining mutation burden still developed MPN, while others with expanding clones remained disease-free.
The study also identified laboratory differences between the groups. Participants who later developed MPN had higher baseline JAK2 V617F allele burden as well as higher leukocyte, neutrophil, platelet, erythrocyte, hemoglobin, and hematocrit values than those who did not progress.
The findings highlight the value of longitudinal molecular monitoring. Repeated measurement of JAK2 V617F allele burden, combined with routine hematology parameters and clinical assessment, may provide more useful information about disease risk than a single test result alone.
The authors suggest that additional factors beyond mutation burden influence whether clonal hematopoiesis progresses to MPN. Identifying these factors could improve risk stratification, support earlier detection of disease progression, and help guide monitoring strategies for individuals with JAK2 V617F-positive clonal hematopoiesis.
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