miRNAs Expression Pattern in Essential Thrombocythemia and Polycythemia Vera Patients.

Essential Thrombocythemia (ET) and Polycythemia Vera (PV) are myeloproliferative neoplasms (MPN) arising from a multipotent hematopoietic stem cell characterized by an unregulated production of platelets, red cells and white cells alone or in combination, a tendency to clonal evolution and an increased risk of thrombohemorrhagic complications. MicroRNAs (miRNA) are negative regulators of genes involved in cellular proliferation, apoptosis and/or carcinogenesis.

To analyze the expression pattern of miRNA between PV and ET patients and to find distinctive signatures in ET patients according to JAK2V617F and c-MPL mutational status.

Total RNA was extracted from peripheral blood granulocytes of 50 ET patients, 10 PV patients and 10 controls. Median age of patients was 57 years (range, 20-88); males 36%. The JAK2V617F mutation was present in 23 (46%) of 50 ET patients and in all PV patients. MPL mutations were present in 5 (18%) of 27 JAK2V617F negative cases (3 cases MPLW515L, 1 case MPLW515K and 1 case MPLS505N). miRNA expression was profiled in 384 miRNA via Taqman Low Density Array in ABI PRISM 7900. Expression data was normalized with RNU48 and relative quantification was calculated with the 2^–σσCt method. The data were presented as log₁₀ of relative quantity of target miRNA. Median of normal controls was used as calibrator for all samples. Data were analyzed by means of Significant Analysis of MicroArrays (SAM), Prediction Analysis of MicroArrays (PAM) and Class Comparison methods using BRB array tools version 3.7.0 and TIGR multiexperiment viewer version 4.3.

We found a general downregulation of miRNA in ET and PV patients respect to normal controls. A set of 29 miRNA allowed us to discriminate between ET and PV versus normal controls; three of these miRNA were up-regulated and 16 down-regulated in PV and ET vs. normal controls with a >2 fold change and p value <0.01. A distinctive signature of 79 miRNAs differentiated ET, PV and controls and a hierarchical clustering analysis defined miRNA expression profiles of the three particular groups. When we compared miRNA differentially expressed between PV and ET patients, we found nine miRNA, 4 up-regulated and 5 down-regulated in ET with respect to PV patients (p<0.01). Statistical comparisons between ET JAK2V617F-positive and ET JAK2V617F-negative cases showed a distinctive signature of 13 miRNA that allowed us to discriminate between the two groups. In addition, we also found in JAK2V617F cases 19 miRNA differentially expressed between MPL positive and MPL negative patients, with a >2 fold change and p<0.01. Finally, an increased expression of miR-142-5p correlated with JAK2V617F allele burden in ET patients

Our study demonstrates that ET and PV can be defined by specific signatures of miRNA. In ET, some miRNA allow us to discriminate cases according to JAK2V617F mutational status and also between MPL-positive and MPL-negative JAK2V617F-negative patients.

FIS EC07/90791

No relevant conflicts of interest to declare.