Application of PRV-1 mRNA expression level and JAK2V617F mutation for the differentiating between polycytemia vera and secondary erythrocytosis and assessment of treatment by interferon or hydroxyurea

Low JAK2 V617F Allele Burden in Ph-Negative Chronic Myeloproliferative Neoplasms Is Associated with Additional CALR or MPL Gene Mutations

JAK2 (Janus kinase 2) V617F, CALR (Calreticulin) exon 9, and MPL (receptor for thrombopoietin) exon 10 mutations are associated with the vast majority of Ph-negative chronic myeloproliferative neoplasms (MPNs). These mutations affect sequential stages of proliferative signal transduction and therefore, after the emergence of one type of mutation, other types should not have any selective advantages for clonal expansion. However, simultaneous findings of these mutations have been reported by different investigators in up to 10% of MPN cases. Our study includes DNA samples from 1958 patients with clinical evidence of MPN, admitted to the National Research Center for Hematology for genetic analysis between 2016 and 2019. In 315 of 1402 cases (22.6%), CALR mutations were detected. In 23 of these 315 cases (7.3%), the JAK2 V617F mutation was found in addition to the CALR mutation. In 16 from 24 (69.6%) cases, with combined CALR and JAK2 mutations, V617F allele burden was lower than 1%. A combination of JAK2 V617F with MPL W515L/K was also observed in 1 out of 1348 cases, only. JAK2 allele burden in this case was also lower than 1%. Additional mutations may coexist over the low background of JAK2 V617F allele. Therefore, in cases of detecting MPNs with a low allelic load JAK2 V617F, it may be advisable to search for other molecular markers, primarily mutations in exon 9 of CALR. The load of the combined mutations measured at different time points may indicate that, at least in some cases, these mutations could be represented by different clones of malignant cells.

ESSENTIALS OF THE MOLECuLAR DIAGNOSIS OF ONCOHEMATOLOGICAL DISEASES

Molecular genetic and molecular biology methods enable one to reveal pathogenetic basis of oncohematological diseases, they are particular useful for diagnostic purpouses, to control and evaluate treatment efficiency. In leukemia patients there are two different types of chromosomal anomalities: some of them give rise for chimeric oncogenes, others activate hyperexpression of regulatory genes. It is necessary to take into account this difference in order to proparely develop molecular genetic tests. Molecular tests are more sensitive to compare with other approaches, due to this fact they are especially useful to monitor residual leukemia cells and for early detection of relapse.