Gene and miRNA expression profiles in Polycythemia Vera and Essential Thrombocythemia according to CALR and JAK2 mutations [GEP]

Polycythemia vera (PV) and essential thrombocythemia (ET) are Philadelphia-negative myeloproliferative neoplasms (MPNs) characterized by erythrocytosis and thrombocytosis, respectively. Approximately 95% of PV and 50–70% of ET patients harbour the V617F mutation in the exon 14 of JAK2 gene, while about 20-30% of ET patients carry CALRins5 or CALRdel52 mutations. These ET CARL-mutated subjects show higher platelet count and lower thrombotic risk compared to JAK2-mutated patients. Here we showed that CALR-mutated and JAK2V617F-positive CD34+ cells have different gene and miRNA expression profiles. Indeed, we highlighted several pathways differentially activated between JAK2V617F- and CALR-mutated progenitors, i.e. mTOR, MAPK/PI3K and MYC pathways. Furthermore, we unveiled that the expression of several genes involved in DNA repair, chromatin remodelling, splicing and chromatid cohesion are decreased in CALR-mutated cells. According to the low risk of thrombosis in CALR-mutated patients, we also found the down-regulation of several genes involved in thrombin signalling and platelet activation. As a whole, these data support the model in which CALR-mutated ET could be considered as a distinct disease entity from JAK2V617F-positive MPNs and may provide the molecular basis supporting the different clinical features of these patients. Gene expression profile (GEP) and miRNA expression profile (miEP) were performed starting from the same total RNA of CD34+ cells from 50 MPN patients (1 replicate for each sample). In particular, GEP and miEP were performed on 26 PV and 24 ET (n=17 JAK2V617F-positive ET, n=7 CALR-mutated ET). In addition, 15 bone marrow (BM) samples collected from normal donors were included in the study (GSE53482). These re-analyzed samples have been included in this series for completeness. This series includes only the GEP samples.