Quantitative assessment of JAK2 V617F and CALR mutations in Philadelphia negative myeloproliferative neoplasms.

BACKGROUND: Philadelphia negative myeloproliferative neoplasms (MPNs) are characterized by frequent mutations of driver genes including JAK2, CALR and MPL. While the influence of JAK2 V617F mutant allele burden on the clinical phenotype of MPN patients is well-described, the impact of CALR mutant allele burden on clinical features needs further investigation. PATIENTS AND METHODS: Quantitative assessment of JAK2 and CALR mutations was performed on diagnostic DNA samples from 425 essential thrombocythemia (ET) and 227 primary myelofibrosis patients using real-time quantitative PCR and fragment length analysis. Characterization of CALR mutations and detection of MPL mutations were performed by Sanger sequencing. RESULTS: Twelve novel CALR mutations have been identified. ET patients with CALRmut load exceeding the median value exhibited lower hemoglobin values (12.0 vs. 13.6 g/dL), higher LDH levels (510 vs. 351 IU/L) and higher rate of myelofibrotic transformation (19% vs. 5%). The CALRmut load was higher among ET patients presenting with splenomegaly compared to those without splenomegaly (50.0% vs. 43.5%). CONCLUSION: Our study confirms the clinical significance of driver mutational status and JAK2mut load in MPNs; in addition, unravels a novel clinical association between high CALRmut load and a more proliferative phenotype in ET.

[The role of driver and subclonal mutations in pathogenesis of primary myelofibrosis]. / A driver és szubklonális mutációk szerepe a primer mielofibrózis patogenezisében.

Primary myelofibrosis (PMF) is a Philadelphia chromosome negative, clonal myeloproliferative neoplasm characterised by a progressive nature. Morphologically, the bone marrow biopsy shows features of abnormal proliferation of terminally differentiated megakaryocytes and subsequent bone marrow fibrosis. The molecular landscape of PMF includes phenotypic driver mutations (JAK2 V617F, CALR and MPL) which represent major diagnostic criteria, and subclonal mutations that also occur in several other myeloid diseases, but have a prognostic value in disease progression of MF. The most important subclonal mutations affect the genes ASXL1, TET2, IDH1/2, EZH2 and TP53. Triple negative genotype and the high molecular risk genotype and CALR-/ASXL1+ are associated with adverse survival with the latest indicating stem cell transplantation independently of the DIPSS-plus score.